A Guide to Piezo Pick-ups (What you don't want to know)



words and photos by: Telegraphy


  One of the greatest inventions in modern times for the sound experimenter is the advent of the Piezoelectric Sensor or Piezo pick-up for short. These little disks of sonic discovery opened up a door to a whole new potential of recording sounds from solid and liquid objects. In the old'en days, if grandpa audio engineer wanted to record with in a violin or under and ocean, he was limited in the placement of and the types of microphones to be used. Non of them really came close to capturing the brilliance in sound as an internally instrument mounted microphone. Having a microphone directly placed on a sound surface  will produce a more brighter sound, Piezo pick-ups are perfect for the job.

 So what are these mysterious microphones and how do they work? In 1880 Pierre and Jacques Curie discovered that by applying mechanical stress on such materials as tourmaline, quartz, topaz, cane sugar and Rochelle salt, they were able to measure a surface charge or voltage on these elements. This is what has become known as the "Piezo Effect". Any crystalline element will in some magnitude, give off an electric charge when stressed. Weather it be physically stressing it, thermally (changing it's temperature) or electrically.

 A Piece of quartz (through scientific experimentation) was found to have the most surface charge then any other element. It's sensitivity to mechanical, thermal and electric stresses made it an excellent candidate for electronically detecting pressure changes in the environment.

 The first real scientific application of the  Piezo Effect was made during world war I, when in 1917  P. Langevin and French co-workers devised an ultra-sonic under water submarine detector. A mosaic of thin quartz crystals was sandwiched between two metal plates. The worlds first "Pick-up" as it can be regarded, had a resonant frequency of 50Kc (that's 50 kHz for all of you kids out there).

                                                                The basic's

 Enough of my history lesson. As someone important so gracefully said, "The only thing we've learned from history is that we never learn from history". Lets investigate closer of how a Piezo Pick-up works. Your typical Piezo element uses a thin wafer of barium titanate and lead zirconate . Now, I'm not a chemist but when it comes to big long names like this,  I go for the short and sweet definition - Piezoceramic. Ahh, that's better. A piezoceramic wafer is sandwiched between a brass base plate and a silver top electrode. The base plate is the mating surface in which the sound energy is passed from the source to the piezoceramic material. The top electrode's job is to electrically connect the piezoceramic to the + hook-up wire. The other - wire is connected to the brass base plate.  Sound pressure hits and vibrates the brass base plate. This sound vibration is transferred to the piezoceramic wafer, where it mechanically stresses it and produces a surface charge proportional to the amplitude of sound pressure. Simply said, sound enters through the brass base plate as a mechanical force and ultimately exits out the silver electrode as electrical energy.

 Now lets get physical! Investigating deeper into the mechanics of these playful Piezo Pick-ups, we find out that the sound energy impresses a longitudinal force upon the piezoceramic wafer. This means the whole disk bends laterally with the sound energy, squeezing and expanding the disk long it's axis. It's better understood view then described in words.

from Wikipedia
 A positive mechanical force will induce a positive electrical charge only on one side of the piezoceramic wafer, as too a negative mechanical force will induce a negative electrical charge only on the other side. This is why Piezo Pick-ups have specific polarities. The alignment of the crystalline atoms all have "Electric Dipole Movements" facing in one direction(much like the poles on a magnet). This direction is based on what material the piezoceramic wafer is made out of.

                                                          Mine's bigger!
             
 Size matters guys! Yes the size of your package makes a difference in performance. Because when it COMES to satisfying your --------EARS? Well what did you think I was talking about? Hee hee. Yes the size of the Piezo Pick-up has a lot to do of how well it responds to different frequencies. The Pick-up's basic constructed is similar to a capacitor. You have two metallic plates sandwiching a ceramic insulator, just like in a capacitor. If you took a capacitor and measured it's "resonate frequency" you will find out that they respond quite well to high frequencies.  This is why most smaller Piezo Pick-up's sound tiny. Not because there cheap or manufacture poorly. They are just responding well to high frequencies. The stiffness of your package (Oh, here I go again). also determines it's natural frequency. As sound pressure pushes against the ceramic wafer, an opposing electrical and mechanical force from within counter acts the lower frequencies but higher ones resonate it with ease. The more the area, the greater the mechanical elasticity, the better it responds to low frequencies. This is a general rule of thumb to abide by when designing your own pick-up system. So to find a nice sounding Pick-up, try using the biggest one as possible. See, size does matter.
                                                     Resistance is futile

 So, now that brings us to the last lesson of the inner workings of these perplexing Piezo Pick-ups. One of the most asked questions of the human race, besides what is the meaning of life, what are the impedance of these devices ? Eeehhhaaaa.......the truth is going to hurt most folks. The nominal impedance of a Piezo Pick-up is high......very high. We are talk'en up to one million Ohms of resistance. Impedance is the measurement of the electrical opposition to audio frequencies. The more opposition - The more impedance. So it is crucial for the output of a pick-up to be properly matched with a different impedance on the input of an amplifier. You want the electrical energy from the Piezo pick-up to flow evenly to the amplifier. The most common and easiest method to match the high impedance of the pick-up to a low impedance input of a amplifier, is to employ a "low pass filter" circuit in between the pick-up and the amplifier. Failure to match properly will result in poor sound quality that will sound tiny. This is one good reason to use a tube amplifier, not just because it sounds better but because of their characteristic high input impedance is perfect for amplifying Piezo pick-ups.

                                                       and now........A cheap pick-up line. 
  In my opinion, you should always use balanced cable to hook up Piezo pick-ups to any other piece of gear. Why? Balanced cable characteristically has lower capacitance per foot then unbalanced shielded coax. Piezo pick-ups are essentially a capacitor with a high resonant frequency. Adding coax with a high characteristic capacitance per foot will only increase our Piezo Pick-up's capacitance and therefor rise the resonant frequency (what we don't want to happen). Plus you gain the benefit of having a balanced system that isn't susceptible to ground loops, radio and electrical interference.

                                                          .....and finally

  So what do you do with a pick-up ? Here are some suggestions of various uses for these profiting Piezo pick-up's:

 1. As a guitar microphone. Experiment positioning them on the body of your acoustic. Closer to the bridge gets you more volume. Away from the bridge achieves a softer warmer sound.

2. The ultimate spy microphone. Jealous of your neighbors? Tape them on the window to hear their complaining about your dog or cat..........or child.

3: Cool body sounds are always a treat for an experimental sound. Stick one in your mouth and sing or burp but don't swallow. After a meal, tape it to your stomach to hear low frequency gulps and rumblings.

4: Can't go without whale sounds from the ocean for your ambient sound track? Well, if your like me and only have a small lake filled with carp, catfish and clams. Through one in with a small sinker attach to it. The water shouldn't harm it - that is if you are recording in the salt water of a ocean. Then I suggest getting some kind of a water proof container, attach the pick-up to the inside wall......the "inside wall" folks, not the outside. Gee's.

5: Attach them to a steal girder of a busy highway overpass and listen to creeks and bumps made by the bridge.

6: A steal radio tower will make whooshing noises on windy days.

7: Record your phone calls pleading to the IRS. Attach them to the receiving end of your phone. Yeah, it's the end closest to your ear.

8:Oh yeah. Use them for your next plate reverb project. http://ionosonderec.blogspot.com/2013/04/diy-plate-reverb.html           

Over The Time Cliff 2015




Eggie teaches us a thing or two.



words and photo by: Telegraphy

  It's back to school with you! As I was driving from work the other day, I stumbled across an abandoned building in Detroit. OH MY. AN ABANDONED BUILDING YOU SAY! IN DETROIT!!! Yes, of course there are a lot of derelict buildings in Detroit. What made this building stick out from the rest was that it was part of the growing phenomena of abandon schools. So I figured what a good place to hopefully catch  a glimpse of Detroit's most mysterious character - Eggie Kishnoshky . Wondering around these empty halls which previously echoed the voices of children on their way to class, I was drawn to one classroom on the third floor. Empty with a few school amenities still left alone from vandals. I set up my camera, awaiting his arrival. After spending more then a few nervous minutes staring at the blackboard, thinking about being robbed at gun point or worst, I took a snap shot of the scene, packed up and left in a hurry. Disappointed about the no-show of Mr. Kishnoshky, I went searching for another place to hopefully catch him.

 Driving around the outskirts of downtown Detroit through old manufacturing communities with their rotting factory's and crumbling bridges and roads, only to be sharply contrasted with newly developed condominiums and lofts sitting beside reclaimed walkways and alleys. So, this got me thinking about the state of Detroit and how it's changing landscape has influenced Ionosonde Recordings.

 In the past two or three years, yours truly have noticed a change in the landscape. Old burnt drug houses have finally made way to the wrecking ball. Vandalized businesses that were left to decay, have now been plowed under. New businesses on the other hand, are setting up shop in places that wore over looked for many years. Yep, things are changing. Just recently, travel publications have took notice and reestablished Detroit as a vacation spot worth visiting. REALLY?

  Getting back to our enigmatic figure. My search for him gained more determination as I wondered into factories and warehouses which were being renovated and transformed into stylish lofts and business space for a new generation of young productive adults. One of these warehouses is situated up above of what was once an old railway. Dug below the ground, this "cut" as it is affectionately called, runs under a hand full of major road-ways. This Dequindre Cut was featured in Ionosonde Recordings popular video Somewhere In Detroit. Sampling imagery of this old railway before, one can see the dramatic change in scenery.
The Dequindre Cut as seen in
"Somewhere In Detroit"

 So the question that arises; "Is Detroit rebounding?" I think the answer to that is written on the chalk board. Our mystifying man of Motown can only give the world subtle hints to what is beyond the horizon for Detroit. But from what I can gather, the younger generation is taking notice of the blank canvas of opportunity which is Detroit. Hum? Starting over, that may be the direction Ionosonde Recordings should be going in. Discovering new sounds - going in a different direction - starting fresh. "Out with the old, in with the new" I think it say's on the chalk board? Ether that or "Eastman was here" I think my vision is going.

 Change is good for both of us and Detroit. After developing the film I used, I was surprised to see Eggie Kishnoshky in front of the blackboard - teaching as you will. Teaching what? Change? Letting go? What ever subject this course is about; we're all paying close attention to our professor because the future depends upon us.

 Writing this last blog entry minutes from twelve midnight, when the calendar year ends and the grandiose machine gun fire starts here in Detroit. I rise my glass of cheap, spiked eggnog with whiskey to a new beginning. Not just for Ionosonde Recordings, but for Detroit and you and as always, I leave you with an image of one of Detroit's most mysterious characters (taken at a warehouse being renovated) . Burying the past in ankle deep snow and presenting the new year with a gift in his hands, Eggie Kishnoshky is just another figment of our imagination that slips through time in a city that's decaying back into sand. Or is it?

   
download "Detroit New Years Eve 2015" here
                    


                                                Solitudes from Detroit
                            
                                                     Telegraphy

Dedicated to the loving memory of my aunt Virginia who passed away Dec 31, 2015 at 3:05 pm
                         (a graceful snow shower
outside my back door signaled her departure)

Build A Vacuum Tube Preamplifier





words and photo by: Telegraphy

  Rise your hand if you think digital sampling is superior in sound quality to analog vacuum tubes
..........anybody? Well for those of you that didn't rise your hands continue reading, all others lower your heads back down in front of your laptops, because today we're going to build a tube microphone pre-amplifier.

  Ah yes, the old debate amongst audio engineers and audiophile's. Does analog sound better than digital. The short answer (if you were to ask the almighty) - Yes it does sound better.  But why?

 Analog is defined as ": Something that is similar to something else in design, origin" which in our case of the "great debate" - analog vacuum tubes are replicating natures sound waves precisely as it is detected by our ear's. Digital on the other hand (keep your heads down laptop people) chops up the smooth natural sound into millions of steps. These steps makes our reproduction sound rough. Just as digital sampling uses "Solid State" devices to detect and reproduce sound. Though they are highly susceptible to distortion; "hollow State" on the other hand (which is referred to as tubes) are much more forgiving towards strong harsh sounds.

 The first vacuum tubes made (around 1902) were actually intended for radio reception and not audio amplification.  It wasn't until 1925 when the Western Electric Co. developed a complete electronic recording system, where by capturing, refining, and amplifying audio. This method employing tubes, revolutionized audio recording. For the first time in history, it was possible to tailor the quality of sound.
 
 Tube preamps are great pieces of gear to have in any home recording studio. There is no better option to obtain high quality audio from low level devices such as microphones and phonographs. So when I built a plate reverb (a low level device) I realized I was in a bind. "How am I going to get enough gain out of this plate reverb and yet still retain excellent audio quality", I thought to myself as I was driving to one of those big ticket item music stores (Ehheemm!! guitar center  ) I've always dreamed of having one of those expensive one or two tube mic preamps that retails for almost a THOUSAND DOLLARS!!! Seriously, if you can show me a capacitor or resistor that cost more then $20, I see no reason why these simple circuits with the minimal amount of components being used, should cost as much as a root canal. Anyways, I digress. Strolling through our un-named music store (hee-hee) I found a rack mounted mic preamp. Now my first though was, "Wow, a rack mounted piece of equipment"
I have a strong proclivity to when it comes to rack gear. It's neat and clean, always where you want it, and it just looks cool.
Looking at the very low, low price on the tag of this mic preamp ($50) How could I not resist. Being un-wise to spotting cheap equipment (They call that being young and stupid) my stupid behind bought myself a Behringer mic2200  Yes, some of you who are familiar with this so-called "tube preamp", can attest to it's crappy noise floor. In fact, others say it has a special knob which is marked "gain" but in reality varies the amount of noise gain. Powerhouse Mega from recordingreview.com forums stated that it only makes a good serving platter. And hey, it works great as a serving plate. My dinner parties turn out great after using the mic 2200 serving platter with auto gain noise knob. My friends are happier, drunker and I almost had a chance to have sex. Thanks Behringer mic2200.

Behringer mic2200 as a serving platter.
  So at this point I've decided to gut the insides of this skin crawling, abomination of a mic preamp and build my own using it's cabinet. So enough about me. Lets learn how to build a vacuum tube preamp. Shall we?
      
The following article is a step by step description of a home built vacuum tube  microphone preamp.
Lets examine the construction of a vacuum tube. As you can see from the cut-a-way view that it is physically hollow. Hence the term "Hollow State". Your basic run of the mill tube has two elements. 1) Cathode  2)Anode. This tube is called a "Diode". It's job in life is to allow current to pass one way and not the other. Much like those gates at the train station you pass though which are eerily similar to cattle fencing at a cattle farm. (It's a conspiracy man!!)  Between these two elements is a space or a vacuum. Tubes work on the principle of charged electron amplification. A small change in electron flow at one end of the tube effects a bigger change in charged electrons on the other end. This electron flow starts at the Cathode, flies through the vacuum and hits the Anode. Now in order for this effect to happen (The Edison Effect) the Cathode needs to be heated to the point where electrons fly off. A filament much like used in incandescent lamps is placed inside of the cathode to heat it up. This is what you see glowing inside of a tube and this is way it takes a few moments for the tube to turn on. Now we have flying electrons coming off of the cathode, it would be nice if we could put'em to good use. Like those holiday meal left-overs. You hate to just through them out - but you don't want to eat another piece of ham or turkey for another year........off load'em on your in-laws!





 The Anode or plate as it's called, is placed some distance from the cathode. Made out of metal or graphite, it is the final element in our tube. Electrons flying off of the cathode are attracted to the plate. The reason why these electrons are attracted to the plate is because of the higher voltage with respect to our cathode. We're talk'en high voltage folks. Nun of this 5 volt digital sissy pules (keep your heads down computer people) At least 200 volts !!

 Now that we have a conducting tube where electrons flow from the cathode to the anode, we can reproduce sounds from it by varying the flow. This is done by placing a third element in between the cathode and plate to act as a check valve. We shall call it - The Farnsworth Circular Modulated Multiplexed Coherer  Radiant Stimulator......just kidding folks, it's simply called a "Grid". It is used to control the electron flow and can be used to  modulate the plate voltage. In other words (our dubious digital dudes) a small signal voltage from a microphone impressed on the grid will vary the electron flow in the same manner and ultimately effect the bigger plate voltage (remember....BIG plate voltage).  Without the grid, we only can use this tube as a simple "current gate" or diode.

  Alright ! We know how a tube works. Now designing a accompanying circuit to make the tube work the way we want is a whole different ball game. Briefly put....

                                              Ionsonde Recordings presents..,..
                                          How to design a vacuum tube circuit.
                                             
( the analog deficient's version)

  This exclusive guide will teach the digital junky in four easy to follow steps, how to design and modify your pre-virtual reality analog vacuum tube microphone pre-amp. Learn how to....calculate bias, plate loading, cathode resistance and much MUCH MORE!!!  We're so confident that you will learn the art of designing a vacuum tube pre-amp's that we gave it a 30 day money back guarantee. If at anytime you feel that you haven't grasped the concept of analog reality, just simply send back your guide and 12ax7 tubes via particle beam transporter too...port 80 ip address 127.0.0.1    



Step 1) Choose your tube. The most common audio tube is the 12ax7. So we will use this one. Now look up the spec's for this tube and you will find a really, really scary looking plotted graph. Yes the  type you dreaded seeing first thing in the morning on the chalkboard in physics class. This graph is a analog computer (Do I have your attention computer people?). Believe it or not this graph, which is called a "load line graph" is able to calculate grid voltage vs plate voltage, grid and cathode bias residences. Basically you can design a complete circuit just by drawing a few straight lines on this ghastly of a graph.
     



Step 2) Choose a plate load resister value. A good starting value is around 100,000 ohms. We will use 150 k ohm. Using simple Ohm's law, we figure out the idle plate current. This means the amount of current draw of our tube at rest - No amplification. Calculations are.... now computer people can follow along using their Windows Calculator application. All others use your abacus or slide rule. 200 volts / 150,000 ohms = 1.33 milliamps. Hey! I see 1.33 milliamps on the right side of this graph! Hey!!! I see 200 volt down at the bottom......Well, draw a line connecting this two points. This is our load line of a 12AX7 tube. That wasn't so bad.     


Step 3) Now that we have formed a plate load line, we can use it to calculate values of other components or figure out different voltages and currents throughout our tube.  Most importantly we will calculate the cathode load resistance but first I have a secret to tell. I think you've noticed all of the animosity toward you computer people. Yes, I'm a little biased to when it comes to digital vs analog. And I'm sorry for all of the joke cracking. Us analog folks love your virtual ways (even though you can only count to 1). Yes I am biased. Biased to covering our next subject which is biasing our tube. It's alright, this will be just as easy as figuring out the loadline.

 Cathode bias - is the voltage present at the cathode which allows the tube to conduct and amplify in a set fashion. Picking any old biasing voltage from the plotted graph would work but our tube would run the chance of distorting our audio signal. We want the best audio quality. To do this, an amplification class known as "Class A" is to be used. Simply put "Class A" amplification in a tube has the best reproduction quality with the least amount of distortion. But, like all things in life there is a trade off. "Class A" isn't very efficient. Yes it's like driving a Bentley because you want to look good but when you want to race that annoying prick with his souped-up ghetto cruiser, blasting heavy base from their rattling trunk lid, your not going to do it! So we will sacrifice speed for class. For a 12AX7, a good all around cathode bias voltage (for Class A, don't forget) is 1.5 volts. Now back to our graph - look up the -1.5 volt curve and place a dot where the plate load line intersects. This is the biasing point. Now pay attention computer people. Draw or read across to the left hand side. You should read 0.5 mA. We have volt and now we have current. Both of these readings can be used just like our calculation of the plate load line. 1.5V/0.0005 A =  3000 ohms. This is the value of the resister off of the cathode. Draw a straight line from 0 volts and 0 mA through the bias point. This is our tube's cathode load line.

Step 4) PUT AWAY YOUR DAMN SLIDE RULER!! We are done. Now it's time to stop number crunching and start constructing.

 OK step back, take a breather. Drink some tea. That intense coarse study in analog computation is like a acid flash back to calculus class in high school. We're all done. Now it is time to have some fun with electronic components, wires and tubes.


The lone 12ax7 with
back lit LED's
Are you kidding me?
The design of this preamp is by Norman L. Koren  His "Spice preamp" is the design I choose for this project. Now, first thing on the list is build a power supply.

 Before I do that - a little bit more ranting about the Behringer mic2200 preamp. After discovering it's eccentricities, I opened up the cabinet only to find one (count'em one)12ax7 tube. I've also notice how the designers included a handy see through window on the front panel mounted just in front of the tube just to show off the fact that this is a "tube preamp". With only one resister and one capacitor on a printed circuit sub board where the tube is mounted, I was a bit concerned. Looking at the schematic diagram, I found a disturbing sight. The one 12ax7 tube in question, was only designed to be used as a cathode follower. What that means (computer people) that it doesn't amplify the audio signal what so ever. All it dose is transform a high impedances down to a low impedances. The amplifying is all done by cheap solid state op-amps. What a joke!


 Tubes as you know, require high voltages. To obtain several hundred volts means we need to build our own power supply. Running to your local radio shack isn't going to help or will it? Radio Shack offers an old school power transformer but it's output voltage is only 12 volts. That's OK, we can get around that. By using two of them connected back to back and using a few diodes and capacitors as "voltage doublers", we can obtain the required 250 volts.
                 
by: dogstar.dantimax.dk
Ripping out the Behringers power supply which only puts out 48 volts (way to low  to power a decent tube) I managed to fit my own built power supply in the space left by the old one. I mounted the two Radio Shack 12 volt power transformers, which are coincidentally enough the right height to fit perfectly inside of the chassis. A small perf board where all the components of the power supply are mounted on, is just to the left.

The old power supply
 Warning:  This supply is capable of producing lethal high voltages. So be cautious when building and testing this power supply. (DO NOT POKE OR PROD WITH A SCREW DRIVER or paper clips for that matter) We know how computer people love using paper clips to hack things.

My own power supply (note the two Radio Shack power transformers)







 "Telegraphy"? "I know how Optimus Prime transforms. Is this the same as the Radio Shack 12 volt transforms?"...........silly computer people..........

  No that isn't how it works. Think of it as a voltage multiplier and divider. Inside of our 12 volt transformer is two coils of wire wound around a central metal core. One coil connects to the house hold mains or 120 volts A.C. This is the input or "Primary winding". The second coil is the output or "Secondary winding". This secondary has a unique property where by however many winding's there are, determines the amount of voltage present. The more winding's - the more voltage. The least amount of winding's - the lower the output voltage will be. It steps up or down the house main voltage, all done by the ratio of primary winding's too secondary winding's. So the first 12 volt transformer; the primary connects to the 120 v house mains and we get 12 v on the secondary where it is sent to a circuit to convert it from 12 volts A.C  too 12 volts D.C.. The second transformer's secondary winding (remember - back to back) is connected to same secondary winding of the first transformer. So through ratio and proportions, the primary voltage of the second transformer goes back up to 120 volts. Hard to follow and strange in design but it works. If it's ugly or atypical and it works - just have faith in it.  So now we have 120 volts A.C. coming out of the primary winding of our second transformer. At this point we can not simply apply that to our tubes. Like a small child  tasting Castoria for the first time, our tubes won't take well to that. They need D.C. voltage. So the power supply is fitted with a circuit that will convert the 120 v A.C. to D.C. (no not the band!..go back to your onion routers) A few silicon diodes does this job perfectly. They only let the alternating current pass through one way to produce a pulsating D.C.. Next some capacitors are needed to filter out the bumps and ridges left by the diodes to turn it into pure D.C.. At this point we have 120 v D.C. Just about enough voltage required for our tubes but we want more power! The voltage can be doubled by using a special circuit called a "voltage doubler". This circuit uses a combination of silicon diodes and capacitors to double the voltage to a higher level. But of course with everything in electronics, there's a trade off. Sure the amount of voltage goes up but that the same time the current handling capability goes down. In other words, our power supply puts out 120 volts D.C. with 500 milliamp current handling capability before using the voltage doubler. After the voltage doubler, the voltage goes up to 240 volts but the current drops down to 250 milliamps.  This means we have to be careful how many tubes we can use with this power supply. 

  With 240 volts ready to use, we can now start on the tube amplifier itself.  As you can see from the schematic diagram below, the pre-amp I decided to build has quite a few components. Most of them are used has ether filtering out high frequencies generated by the pre-amp itself, or used as a feed back network to control the amount of amplification. But keep in mind, the basic theory I covered earlier on how to design a tube using a loadline is the same and can be seen here. You probably noticed by now that there is one input and one output - you've guessed it! This a mono pre-amp. So If you want stereo, you need to build two.



 
 Taking the grand tour of the pre-amp; our first stop(if you please direct your attention to the left, ladies and gentlemen)  is the phono input. R1s, R1g, and C1g make up a filter network, while R1gs is the grid stopping resistor. What is a "Grid Stop Resistor" you should ask? Well, Johny a grid stop resistor works in conjunction with the input filter network to stop any high frequencies parasitic oscillations. Ha, ha! In other words Johny, our tube likes to oscillate on it's own. The grid stop - stops it from self oscillating. As you can see connected to the bottom  and top of the first tube is the familiar cathode bias resistor R1c and plate load resistor R1p. C1m is a negative feed back capacitor. This also controls the amount of amplification and insures the tube doesn't break into self oscillation. (Now if you shall follow me over to the next capacitor. Watch your step, please) C1p is called a coupling  capacitor. It's job is to transfer the amplified audio energy from the first tube, over too the second tubes grid.....continuing on!.... The second tube operates just like the first, it just amplifies the signal even more. (And finally, we conclude our tour with) The third and final tube. This called a"Cathode Follower".  Transforming impedances is the name of it's game. It takes the high  impedance from the plate of the second tube and transforms it to a lower impedance without sacrificing gain. You might notice the output is coming out of the cathode instead of the plate. That's why it's called a cathode follower. The last components are feed back and filtering circuits. (Tours over - please visit our gift shop on your way out)


Point to point wiring.


The traditional way of constructing a tube circuit is to use point to point wiring on a tube socket.  By all means, it's a good time tested method of construction. For a stereo pre-amp your going to need three 12AX7 tubes. Each of them can be mounted horizontally, side by side.
Tube socket brackets 
Neatly mounted.
 To mount those tubes, I had to fabricate my own tube socket brackets. Made out of 1/8 inch thick aluminum sheet. One thing the Behringer engineers did do well is the back connector interface board. Well done!..........but I can't use it. So I ripped it out and reinstalled all the connectors to the back panel.

  Oh yes baby, we're at the home stretch. Now all needs to be done is connect the back connectors to the tubes. Install all three 12AX7's and plug in the A.C. cable for the initial "Smoke Test". Once again, do I have to explain everything computer people......hum. A smoke test is the first time a home built piece of equipment is powered up. If you find no burnt fuses or burnt components after the power switch is turned on - then it's a successful build. Oh, also if anytime during the test you DON'T see any smoke leaving the unit.....Thumbs up dude!!    

            

Un-soldering the connectors
Removing the back interface board.


Useless board removed. 


 As an added touch, I improved upon Behringer lackadaisical attempt to justify a working tube. It's back lighting with a solid state LED's was ridiculous. So I put in an old school incandescent  light bulb. Ah yes, a nice warm light to remind you of the warm sounds that comes out this pre-amp.
Kids, you might want to ask your parents what a incandescent light bulb is.
Real tubes light up.












  Let talk about tubes before I close out. Yes I know, I discussed tube theory up the wazoo earlier but I want to cover what type and where you can find tubes. Remember, you can't go wrong with N.O.S. (new old stock) tubes. They might be dirty, covered in dust or god knows what, but they work almost like the day they were born. I've had great success with these new fangled Russian made 12AX7's tubes. Their easily found on Ebay for as little as $15 each. Another thing to consider when purchasing tubes is when your project requires several of them, always buy "Matched Pairs". These are tubes that have been dynamically measured so that each matched pair conduct evenly between each other.
Well, hope you learned a thing or two about analog electronics. Hey it's fun and you get knocked on your @$$ with high voltage......Just kidding folk's. Be safe out there in the real "analog" world. And if I offended any computer people. I'M SORRY! Your just to easy in the analog world.
                 
Digital? Any idiot can count to "1"
                                              Bob Widlar



I like electron tubes!

iono-20 Requiem




iono-20
Requiem



track listing:

01: Requiem.............................................9:33 min

02: A Solid Liquid....................................9:41 min

03: Stealth Camp.....................................8:35 min

04: In And Out Of A Dream State...........8:33 min


Just in time for Halloween. "Requiem", sounds to bring up the spirits in this transition season. The leaf's are leaving the trees from where they were born, and the day's are getting shorter. This is the time for non-actively, where dreaming gets longer and more lucid. Something about the dark season that brings alternative realities into your sleep. And this is just the beginning.

 Telegraphy summons spirits of dub and techno using colorful sounds and echos in "Requiem"   

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Smoke And Mirrors (Ann Arbor Hash Bash 2015)


words, photo, and video by: Telegraphy


 
The first Saturday of April is usually set aside for us to receive numerous contact buzzes. The wafting smoke clouds at the Ann Arbor Hash Bash  was thicker then usual. This years crowd on the University of Michigan diag, was larger than in past years. All thanks to the celebrity appearance of  cult movie icon Tommy Chong of "Cheech and Chong" fame. The crowd was so smoke saturated that your's truly wasn't able to make it up the steps to where all the speakers were soap boxing. Of coarse as usual John Sinclair made his appearance by jamming with Ann Arbors famed guitarist Laith Al-Saadi.


 I kept sensing that something was different this year. I roamed around the outskirts of this massive crowd, smoke billowing from inside, outside and around the crowd. As the white smoke shimmered in the early Spring sun light, I noticed the lack of Ann Arbors finest. I fact I only saw two police officers the whole time I was there (escorting one young man out of the Monroe Street Fair). But what got me was the fact that young people (eh hem, younger than me ) came out to see their hero dawned in green plastic fake hemp leaves and conveying the same stoner humor as he did in "Cheech and Chong". Yes Tommy Chong enjoying royalty satus, signed photos, albums, received the city of Hazel Park's key to the city (then passing a joint to city leaders) he was followed everywhere by young pot heads. Wow! John Sinclair, move over.

 Besides no cops and Tommy Chong, I was scratching my head figuring out why this years rally seemed awry. After the fan fair of the Hash Bash was slowing down for the day, I made my way to the Monroe Street Fair. Again something didn't seem right. After making my rounds of the venders who were peddling their brand of pot accessories: rolling papers, rollers, pipes, bongs; you name it they had a one stop shop for the eclectic stoner. Even in the back corner, a band of straight business students were selling brownies (non-tainted brownies). Pushing away tufts of smoke like tall weeds in a field, I meander around colorful people who were shoulder to shoulder in groups of small or large smoking circles. Finding my way around, I kept bumping into hippies selling hand crafted jewelry. Displayed in old leather suit cases, they quickly set up shop where ever they could find an open patch of ground (which is nearly impossible). "Huh", I thought to myself as I bumped into yet another peddler. Only this time I thought I was transported into the past. This business savoy man must of been a relative of a 1940's cigarette girl. With a small table strapped on him, this gentleman gave free samples of smoke. Rolling a splif for you. Now that's service.



   At this time the contact buzz had warn off and my sense of logic slowly came back. Leaving to go home I walked passed by Tommy Chongs swank black traveling bus, with included catering chief standing by with bar-b-q'ed goods. In front of his bus was yet another peddler, selling hemp necklaces hung off a single rope strung along the side of a truck. Young girls gather joyously to look at these organic body ware."Well", I said with a assured tone of voice, "Hash Bash is in business - The business of commercialization of weed".

    That's what was different this year.


                                                       

                                                     
               
                                                     
    
                                       

Iono-19 Infernal Convolution

words, cover art and sounds: Telegraphy



01: Infernal Convolution ..........................6:20 min

02: Hearts, Made In Detroit.......................8:49 min

03: When Sounds Are Meaningless...........6:24 min

04: Distorted Reflections ...........................7:04 min



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 "Infernal Convolution" is certainly a release that can lift up a heavy heart with it's melodic synths and echoed drones. Warming us up from a long cold winter season, Telegraphy soothes us in red warm colored splashes of chords deep down to the core. A four track E.P. that starts off with it's titled track which beckons the awakening from the winter hibernation. Curiously familiar melodies, the listener just can't quite put ones finger on. "Hearts, Made In Detroit" and "When Sounds Are Meaningless" has it's own unique qualities that for some reason or another we've all heard before. Closing out with "Distorted Reflections", a dub laden techno track that high-lights Telegraphy's D.I.Y. audio gear know how with heavy metalized sounds of his harmonic reverb.                

Build A Mixing Bowl Harmonic Reverb



Words, photo,and sounds by: Telegraphy

 
Reverberation is the most common and fundamental form of audio effect. This natural occurring effect has audio engineers painstakingly devising better ways to be able to harness natures "audio plug-in". Whether  it's with software or hardware, one thing is certain. Mimicking nature is hard work. With all of today's advanced software reverbs out there, you still can not beat the hardware version.

  A while back I wrote an article describing how to build a D.I.Y. Plate Reverb The response I received from the D.I.Y. community  regarding this article was beyond my wildest dreams. I had no idea there was so much keen interest in hardware based effects out there. That same interest which got me started building the plate reverb, (more recently) persuaded me to take that very same concept and bring it to a whole new level. Taking advantage of a well known side effect all stringed instruments suffer from (wanted or not) a condition known as Sympathetic Resonance would become the foundation of my Mixing Bowl Harmonic Reverb.

 Mixing bowl ? More on that later.

 Before we begin, one has to understand what makes a plate reverb....Well, reverberate. Quoting from D.I.Y. Plate Reverb  
        The concept of a plate reverb is quite simple. An electromagnet, like the one found on a audio speaker, is directly or indirectly coupled to the center of a piece of sheet of metal. Audio from a sound source is fed into this electromagnet (voice coil) which will physically vibrate the piece of sheet metal (plate). These audio vibrations are echoed many times, echos which are in fact persistence of audio. The amount of persistence (reverberation) is determined by  the physical characteristics of the plate. These characteristics many include  length, height, and stiffness of the piece of sheet metal. Once reverberation has been set off in the plate itself, it then needs to be detected. This is accomplish by directly or indirectly coupling microphones to the plate. The micophones pickup the reverberations and sends them back to to be mixed  with the original "dry" audio.
 Now that we know how it works, let's take it to a higher level. Keeping this concept in mind, let's swap the plate with a pair of ordinary kitchen variety salad mixing bowls.......Not satisfied enough? O.K., we'll tie in between them, old used base guitar strings. This will produce some exciting harmonic reverberations. Yes I love excitement. That's why I have my nephew leave lego parts by my bed when I wake up in the morning. Bear foot of course. Exciting !!!  So, why use base strings? The strings act like frequency amplifiers. We can pick and choose what portions of the audio spectrum we want to enhance by way's of using different tuned strings. It works like this... The base strings are acted upon by sympathetic resonance. This condition is best described as when a loud sound directed toward a stringed instrument (ie.guitar or piano) it's strings will vibrate along with that sound. The most familiar exploit is singing into a guitar and hearing it's strings sing back at you.       
                                                                          ***

 The following article is a step by step description of a home built harmonic reverb.   

 Step 1 :

  The cost of building this reverb was around  $100. All materials needed (excluding electronics) were obtained at my local Lowes home hardware store. Electronics on the other hand, were from RadioShack.
materials needed

Some of the parts needed for this project were made in house. Having basic machine shop tools makes a big difference. If your not fortunate to have facilities to make your own parts, don't be afraid to ask your local Ma and Pop hardware store clerk on how they can improvise making parts for you. Why Ma and Pop hardware stores? Because, they have more experience and to put it simply: THEY HAVE TIME TO SERVE YOU!!

  The mixing bowls I purchased at my local Salvation Army second hand store. One thing you can count on at these stores (besides used underwear and soiled bed mattress) is having a great selection of kitchen gear. Perusing through the kitchen isle, a man feels out of place. Woman instinctively know your up to no good - Especially if your tapping each and every single pot and pan with your finger and then bristly putting it up to your ear ( just to hear how they vibrate) . It's just a hint for woman that this man isn't cooking quiche for dinner tonight.
 
The used base strings I "borrowed" from my brother who plays base guitar in his band "Air Base Guitar With No Amp Listening To Deathmetal"  Why base strings? I wanted this reverb to have better resonance down low. The small size of it's construction prohibits lower frequency response. To alleviate this problem, thick strings that resonate well at low frequencies are employed. Yea, we'll get you new strings one day bro. Your not using them now. Right? 

                                                                                  ***

                                                                 Let the construction begin.
 Step 2:  Cutting the perforated angle iron into six 13 inch lengths plus two 9 inch lengths. Bolt them using 1/4-20 nuts and bolts. These measurements are somewhat critical as the points of the triangle has to clear the diameter of our mixing bowls. I this case it's a 8-1/4 inch diameter bowl. As for the three horizontal spreaders; I search high and low for an affordable alternative to which you would find in the metal stock section (they really rob you with highly priced "cheap" metal) So I found myself in the shelving and closet isle, because I have a closet full used close bought at Salvation Army store. And it's messy ! Looking around, I couldn't help but notice the 6 foot metal pipe used for closets. Priced at $9, this was 70% less then what you would find in the metal stock isle. Fantastic !   
Every band has a pyramid on their album.
This should be one of them.

   
 Now before we strap on those mixing bowls to the triangles, we need to punch some holes through the bowls. I used a 3/16 sheet metal punch but you can use the good old fashioned drill. Six evenly spaced holes along the top lip and one big 1/2 hole down in the center of the bowls base. Now before you go and mix someones salad - Tune those base strings  with homemade tuners.

 A 1/2 inch aluminum rod kept rolling under my foot. Thinking it was a safety hazarded, I cut it up into six 1-1/4 inch sections. "There, now I have six safety hazards" " Wait a minute! I can tune base strings with these. Just drill and tape 8-32 screws into them and make a through hole at the other end.    
Holes punched in bowls.
Lashing a base string through the hole at the other end of the tuner and then doing the same at the mixing bowl holes located around the lip. We now have the main component of the Mixing Bowl Harmonic Reverb. You can use as little or as many strings as you choose. Just keep in mind the tension of the strings will have to be spread out around the circumference of the mixing bowls evenly. Equal tension is what we're aiming for. I just inherently went for an even number of six. Because - Well because my brother had six. 





 

The finished tuner




Attached bowl
Pulling it taut!
Step 3: The reverb is starting to come together. Time for us to kick back, have an adult beverage ( under age folks please drink your Ovaltine) Reviewing on what was built :
 1:   Super structure made with perforated angle iron and closet tubing. 
 2:  Homemade tuners made from aluminum rod for tuning the base strings.
 3:  Lashing base strings to tuner and bowl
 4:  DRINK ........Why? Because no good project ever started with a bowl of salad! (no pun intended)


  Now the tuner(s) attaches to the bowl with the 8-32 screw running  through the holes punch around the lip of our mixing bowl. When all of the equally length strings are lashed to the other bowl, it is then time to attach both bowls to the triangles. This is done by using a method my father suggested. Threading hefty nylon cord through the hole drilled in the center of our mixing bowls,the nylon cord is wrapped around a dowel rod to keep it from slipping back out. Use nylon or some other material that's taut and won't stretch as much. It's really annoying having to re-tune your base strings every minute because of a stretchy cord.  

Lovely
   
Now we're getting somewhere
Step 4:  Oh, you might have noticed that both mixing bowls do not look the same......I lied...one of them is a sauce pan. Sorry mom !

 Beyond being a bad boy and not knowing the difference between a fork and a spoon (Spork) , we have something that resembles a Mixing Bowl Harmonic Reverb. After struggling to slip our 32 inch closet metal tubes in place with all of the tension provide by the base strings. It is now time to transition over to making a transducer.

 Around here, we use good old fashioned car speakers as our transducer. Why? Well for one, I'm dirt poor and can't afford a $20 audio surface transducer and second, I have tons a old speakers just laying around (I'm a man - We keep the stupidest things)  So how do you intend on using an old Chrysler car speaker from the 1970's ?  For that I will once again be quoting from D.I.Y. Plate Reverb 

How to disembowel a speaker:
                     
(the ionosonde way)
          
           1: Ripe out cone body. Use hobby knife to cut away cone right down to the dust cover.  "Making first incision"
           2: Cut away dust cover (being careful not to cut into the voice coil or the spider. DOING SO WILL RESULT IN COMPLETE DEATH. ) "nurse Mary, please hand me the forceps".
           3: Using what ever tool at your disposable, cut away speaker basket taking care not to cut away the connection terminals.(I used sheet metal nippers) "this limb needs to be removed, cut off saw nurse Mary"     
           4: Remove terminals leaving the metal mounting tabs( I'll use these as the voice coil mounts) "O.K. sutcher up the patient nurse Mary - My bill will be in the mail"

                                                                         ***
Ah, the Chrysler Deluxe speaker.

1) Cut diaphragm out
2) Trim access.
3) Use sheet metal nippers or what ever is handy to cut housing
away from core.
4) Cut out dust cover
exposing voice coil.
5) Make linking shaft out of dowel rod.
6) Glue in place. Making sure
not to glue voice coil to magnet. BAD!









Attach !















 A few notes about the transducer installation. Depending on how firm your bowls are attached to the super structure, you may need to screw the tip of the linking shaft firmly onto the bowl. Drilling a small hole through the side of the bowl where the linking shaft will rest upon, screw the tip of the shaft through that hole to firmly hold it in place. This firm connection of the linking shaft to the side of the bowl will ensure better prorogation of sound energy into the bowl. Secondly, the 8 ohm impedance of this transducer is to little for mixer boards to handle. So I put in line a step up audio transformer which gives it a better match so more sound energy can flow through.

 Lastly, the pick-up's . Again I shall quote D.I.Y Plate Reverb
Piss...hey you....What if I told you that Radio Shack has had a secrete only known to musicians for many years. You would say to yourself, "Telegraphy your crazy!!", has you search through those pro-audio gear catalog's looking at $100+ acoustic pickups. Well just between you and me (and keep this on the down-low) Radio Shack sells pickups for $4.49 each. They don't label them as such but instead their called Piezo Elements 1500-3000 Hz model: 273 073  The sound quality of this devices are great for the price.
                                                                             ***
   
Taking those $4.49 acoustic pickups (Piezo Elements) out of their packages, I realized that these pickups didn't look like your average piezo element.Well for starters, the elements are buried inside a blast proof, geek proof, flame resistant, and radiation proof  -  black plastic case. To extract this rare element, you need a good sharp hobby knife, a screw driver, and most of all - patience. All you have to do is pry open the top with a screw driver (sounds easy enough. Boy are you in for a treat). Down inside of it's impregnable case is the piezo element. It's almost press fitted down in there, so your going to need a hobby knife to gently pry it loss. 


       
Gluing the pick-ups on opposite sides of the "non-driven bowl" and then running the cabling from both pick-ups and driver transducer to a nice junction box with some 1/4 phone jack plugs. I can finally say it's done. Have another Ovoltine on me!



                                                                               Listen to the Harmonic reverb