Notes from the Bench

September 2, 2013, 3:00 pm

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Notes from the Bench

The postman just brought the proto pcb for a new project. It is a speaker cabinet simulator. I had made one previously but did not like the sound of it, so this is the revised version.

I want a simulator that does not have distortion… almost all of the commercial units have a distortion section that cannot be bypassed so that you just get the speaker cabinet. This unit will be very clean (it’s for recording) so distortion or overdrive will have to be added with a separate pedal.
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Here is a tip for pedal building… look at the inside of the orange pedal in the picture below. Note that when this pedal was powdercoated, there was over-spray and the inside got a heavy dose of the coating.

This coating will insulate the jacks from making a good ground connection on the box, so it is necessary to file, sand or grind away the powdercoating from the areas where you want to make contact with the enclosure, such as around the holes for the jacks.

Save yourself some aggravation, and time spent troubleshooting by grinding off the coating.

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The new power amp for my studio is below. I used a 1590DD cast aluminum box to hold the TA2024 amp pcb that I got on Ebay. The finish on the box was really rough and it took plenty of sanding and a couple of coats of etching primer to get a good smooth surface. Water-slide decals were used on the front and back.

The 15w output is plenty for my studio, and a class D amp will provide a clean sterile sound that I like for mixing.

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Another project that I just completed was a mini-amp in a 1590A box for practicing. This tiny powerhouse can provide up to 5w, but 1w is closer to the practical power for a mostly clean output. I plan on plugging this into a 4×12 cabinet to see what it can do.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

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Voltage Doubler Test

September 7, 2013, 1:14 pm

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I decided to do some tests on the voltage doubler kit to see how it compared to the stock circuit from a datasheet.

I made two voltage doublers using the AMZ pc boards. One was the circuit that I sell in the kit and the other was a standard doubler from the TC1044S datasheet. Under no load, both circuits produced just under 18v output but the voltage drops as you put a load on the charge pump output.

I used two LEDs, each with a current limiting resistor, for a total load of 28 ma, which is a typical load for a couple of average pedals that the doubler would be required to power. With 9.0 volts driving the boards from the bench power supply, the AMZ doubler produced 16.06v and the TC1044S produced 16.18v. This is very close and the slight difference could be due to the fact that different diodes were used on each pcb.

The main advantage was revealed when I looked at the output of the doublers using an oscilloscope to get an idea of the voltage ripple.

The AMZ had 0.14v ripple riding on the DC voltage while the TC1044S had 0.25v ripple. This is a significant difference. Futhermore, the AMZ ripple was a smooth (almost) triangle wave while that from the TC1044S was a sharp angular wave, much like a square wave with a sawtooth tail on it.

Not only is the ripple from the AMZ circuit less, but there are fewer high harmonics in the tri wave than will be present in the sharp ripple wave of the TC1044S, and thereby less noise in your circuit.

AMZ Voltage Doubler PCB

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

SOS page uploaded

September 8, 2013, 8:04 am

≫ Next: 3PDT switches

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I just discovered that the Son-of-Screamer information page had never been uploaded. Yikes!

It is now available online here.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

3PDT switches

November 8, 2013, 4:00 pm

≫ Next: NPD: Seafoam Chorus

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Here are the Standard 3PDT, Pro 3PDT and Premiere 3PDT switches…

I have tested the AMZ 3PDT switch wiring board with all of them to ensure compatibility. It works equally well with any of the three versions.

NPD: Seafoam Chorus

January 18, 2014, 11:19 am

≫ Next: NPD: EXH Soul Food Overdrive

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New Pedal Day! Keeley Seafoam Chorus

More to come as I get some time to play with it.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

NPD: EXH Soul Food Overdrive

January 21, 2014, 4:56 pm

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New Pedal Day! The EHX Soul Food Overdrive.

I spent about 30 minutes looking at the pcb, and as far as I can determine, this pedal does seem to be a Klon Centaur clone. At least it matches the schematics that are posted online, which is my only reference. I couldn’t see the clipping diodes as they are mounted on the back of the pcb, and I did not want to disassemble the pedal.

The box looks to be a zinc casting, and not as sturdy or as finished as the same type enclosure in aluminum. There is also a small switch inside on the 3PDT pcb to change it from true bypass to buffered. Nice touch.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Differential Distortion 2

February 4, 2014, 4:46 am

≫ Next: Little Angel Chorus – NYE

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Ken Willmott published the Differential Distortion design in Popular Electronics, August 1995. He revised the design in 2014 and it is included on the AMZ schematics page with his kind permission. Thanks Ken!

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Little Angel Chorus – NYE

March 19, 2014, 4:56 pm

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Over the holidays just a couple of months past, I laid out a pcb for the Little Angel Chorus. After building it, I found that a few changes were needed to get the most out of it with my rig.

I made an number of mods to the circuit, which I have called the New Year’s Edition to differentiate it from previous versions, since the changes are significant.

The first change, which I incorporated into the prototype pcb, was to use a different startup circuit. I selected a J112 jfet transistor (which is still available in through-hole versions) and used it to set the delay time by way of its ON resistance. A differentiator (R-C) connected to the gate of the fet will pulse briefly when power is applied, and that will pinch off the channel (making it high resistance) long enough for the PT2399 oscillator to start. I’ve only tried it with three different PT2399 chips but it seems to work well enough.

I also eliminated the resistor on the non-inverting input of the first opamp, and connected the pin directly to the bias voltage.

There were a couple of minor problems that I encountered when I started playing the circuit. The LFO made a mild thump as it cycled, and there was not enough depth to the chorus sound. I found myself leaving the Depth control at the max setting.

After a number of attempts to silence the LFO, I finally decided to change the bias resistors (100k and 47k) to 220k for both. This makes the LFO wave more symmetrical and it got rid of the thump. To increase the depth, I decreased the value of the resistor in series with the bias pin of the PT2399 from 33k to 2.2k. This proved to be too low, and I would suggest a starting value of 10k, though I left the 2.2k in my prototype since it did not cause any problem except to reduce the usable range of the Depth control, and I did not want to disassemble the pedal yet again. A few other part values were changed as well, for what I found be minor improvements. Nothing critical.

After making these mods, I found the chorus effect more prominent and the sound was improved (at least with my guitars and amp). The PT2399 is not the best chip for chorus pedals as the delay time is just too long, and there is some variability in the specific delay characteristics from chip to chip, but decent performance can be squeezed out of it if you are willing to tweak the circuit.

Little Angel, New Year’s Edition Schematic

Enjoy!

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

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Tinaja Quest

March 24, 2014, 8:41 am

≫ Next: CLM6000 Replacement

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While searching for a detail about mosfets today, a search link led me to Don Lancaster’s Hardware Hacker archives. I had not been to his site in a long time, and while much of the computer info is outdated, the basic electronics stuff is still golden.

There is a wealth of info there, so check it out at http://www.tinaja.com/

See if you can find the Marcia Swampfelder archives for the lighter side…

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

CLM6000 Replacement

March 24, 2014, 9:38 am

≫ Next: EHX Satisfaction Fuzz

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Several of the classic Craig Anderton projects used the CLM6000 optocoupler, which has become difficult to find. The question then is what to use as a replacement for it. I downloaded the CLM6000 datasheet and then checked the Silonex datasheets to find a similar part.

It turns out that the NSL-32 opto is almost an exact duplicate. It is so close that it is likely to have been originally developed as an alternate to the CLM photo-resistor. Click on the image above for a full size datasheet comparison.

Small Bear sells the Silonex NSL-32 but be sure to get the basic part, and not one of the revised versions with additional suffixes, such as NSL-32R2. You want the basic NSL-32 if you are looking to use it in place of the CLM6000.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

EHX Satisfaction Fuzz

March 24, 2014, 5:33 pm

≫ Next: Buffer & Direct Box

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The Electro-Harmonix Satisfaction Fuzz has been rumored to be a Maestro FZ-1 but after looking at a pcb photo that I saw in one of the guitar forums, it appears to be a Jordan Bosstone. The part numbers are even the same as on the Bosstone schematic I found.

You can’t build one for the price EHX is selling it, so I suggest that you go to your favorite online retailer and buy one. Since it uses through-hole parts on some of the important components, you can even do mods on it without too much trouble.

Check out the demo video: http://youtu.be/WD6BzUqqrsQ

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Buffer & Direct Box

April 20, 2014, 5:28 pm

≫ Next: Install EZ Drummer 2 on Windows XP

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My latest project is a buffer/direct box that I made using surface mount components.

The box is an LMB 101 (from Mouser) and it came already painted gray. For size reference, the width will just barely allow a 9v battery to be placed across the inside, so it is slightly smaller than the Hammond 1590B.

The blue capacitor in the center of the pcb had to be added later because when testing it, I discovered a high frequency oscillation that was superimposed on the audio. Although the datasheet for the IC says that it is unity gain stable, it is not and requires some bandwidth limiting. Trust the datasheets, but verify… especially when using ultra-high speed, ultra-high bandwidth opamps.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Install EZ Drummer 2 on Windows XP

May 21, 2014, 7:40 am

≫ Next: EHX B9 Organ Pedal

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Proceed at your own risk! You need a Microsoft program called orca.msi     Get it here or here.

Install orca and then use it to modify the settings in the EZdrummer2_32bit_install.msi (or EZdrummer2_64bit_install.msi). There are other Msi Editors that can do the same job, but I used Orca.

Load the EZdrummer2 installer into orca and then search for VersionNT>600

VersionNT>600 is only found once in the EZD2 installer. Change that entry to VersionNT>500 and save (only work on a copy of the installer!)

Once the LaunchCondition has been changed to VersionNT>500 EZD2 will install on XP.

I did this last night, authorized my new EZD2 online at Tootrack’s site and then loaded up a Reaper project that already had EZD in it. It worked like a champ.

As soon as you have EZD2 open in your first project, you will need to go to the Menu in the top right of EZD2 and rebuild the database. Also, check Toontrack for upgrades to any extra drum packs you have purchased.

Proceed at your own risk! This worked for me but it may not work for you. Only work on a copy of the installer msi!!! Toontrack will (probably) not provide you with any support for use on XP.

Good luck, Jack

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

EHX B9 Organ Pedal

July 14, 2014, 1:48 pm

≫ Next: FCC Part 15 requirements for pedals

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The EHX B9 organ pedal is an excellent sounding box, but not without problems:
Although it performs audio magic by converting a guitar signal into a quite good imitation of a tonewheel organ, it does require skill to get a convincing sound out of it.

There are several things that you can do to improve the simulation.

1. Play carefully to avoid pitch bends. When you bend a string, it begins to sound like a synth imitation of an organ. Using heavier than normal strings will help in this regard.
2. Put a compressor pedal before the EHX-B9 pedal and turn up the compression to even out the string volumes. This really helps if you have a light picking technique, like me. You won’t miss the dynamic range since most organs only get their dynamics from the volume pedal.
3. Carefully choose your chords. It is easy to span 3 octaves on a guitar neck with a simple bar chord but that’s not a typical sound for an organ. Space the notes close together and use simple chords with fewer notes.
4. Leave the guitar volume cranked up to 10. I have found that a stronger signal makes the B9 track more reliably.
5. Try different pickup selections. Some people say that the bridge pickup works best but on a Tele, the neck pickup seemed to be better.

You won’t be able to plug in this pedal and instantly become Keith Emerson. It takes some work to get the best sound out of it, so try some of these tips and don’t get discouraged!

FCC Part 15 requirements for pedals

July 14, 2014, 1:58 pm

≫ Next: Through-Hole J-Fets

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Over EIGHT years ago, I posted a note over at DIYstompboxes about testing requirements for digital devices, including guitar effects pedals. This subject has come to attention more recently as several manufacturers have been fined large sums of money for not complying with the rules.

Shown above is a label from a recent EHX box with the compliance statement on the back panel.

More reading: http://www.diystompboxes.com/smfforum/index.php?topic=107145.0

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

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Through-Hole J-Fets

July 19, 2014, 7:15 am

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As previously reported, many through-hole jfets have been discontinued and the prices for old stock has gone up 4x to 10x in recent weeks.

Though some online retailers do have old stock of jfets, many of the big suppliers have fewer choices than they did in the past. Pedal parts suppliers, such as Small Bear, have plenty of jfets for diy builders but don’t want to sell bulk to commercial builders.

Mouser, which I use as one of the parts suppliers for many of my projects, has the BF256B in stock in large numbers (over 30,000 as I write this), which is a jfet that can be used in many of the popular circuits, and it is reasonably priced. The only item to watch is that the pin configuration is different, but if you turn the fet around 180 degrees, it will be perfectly aligned with the layouts that I use for the J201 or 2N5457 transistors. Try it in the mini-booster or as a buffer.

Mouser also just started stocking InterFET parts, which source many of the popular jfets (such as the J201) that have been used in pedal projects, however, the prices of the InterFET parts are very high and I cannot recommend them for that reason. Check out Small Bear or Mammoth if you don’t need large numbers of transistors.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

FV-1 Dev Board

October 8, 2014, 5:04 am

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Here is my FV-1 prototype setup.

I folded a piece of aluminum to act as a chassis, then mounted my SPN1001-DEV development board on it. I built one of my dual opamp pc boards and added it as an interface between the guitar input and the digital board. The opamp board can add gain to the guitar signal if needed.

Also, the power jack that I added is configured with center-negative like most guitar fx power adapters (the SPN1001-DEV has the opposite polarity) so when I take the test board over to my pedalboard, any of the pedal power connections will work with it.

The power and signal jacks unplug from the development board in case I need to isolate it for some reason.

All that is left is to clean the front panel and stick on some labels.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Mini vs Mos Distortion

October 17, 2014, 7:03 pm

≫ Next: Good Band Names

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I measured the distortion components of a mini-booster and mosfet boost for comparison.

Argggh! The graph above is not accurate. I was connected to the wrong signal generator and was getting results that were too noisy and distorted! The boosters do much better than the previous graphs indicated.

Check out the updated article in the Lab Notebook.

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

Good Band Names

October 24, 2014, 5:39 pm

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I’ve updated the page of FREE Band Names… check it out if you need a name for your rock-n-roll ensemble!

Good Free Band Names

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.

PNP Power Transistor Closeup

November 26, 2014, 5:39 pm

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This is a PNP power transistor that I have had in storage for years. You can see from the stamp on the metal case top that it was made in the 13th week of 1980.


It says $2.17 on the price tag but I bought a box of dozens of discontinued parts for $5.00 at a local Radio Shack and several of these transistors were in it.

It is more than a little crusty after many years in storage in less than ideal conditions, even though it has been sealed in the blister pack the entire time.

I though it might be interesting to cut off the top of one of these 100 watt PNP power transistors and see what is under the hood.

First, I tried to pry off the top piece with a knife blade but that seemed to be getting nowhere. So then I put the part in a vise and went around the outer rim of the top of the case with a hacksaw. I kept the cut shallow and rotated around the piece as it cut through. The hacksaw blade made short work of it and soon the top dome came off.

It is surprising how thin the wires are that connect the silicon chip to the contact pins. On this transistor, the metal case of the TO-3 package is the collector connection. Sure seems small to dissipate 100w!

Click on the image above to get a large view of the silicon chip. This picture was taken with a Pentax Q10 that had a +2 closeup lens screwed on the filter threads.

The question remains: does it still work? If you look closely at the chip near the left corner, it got dinged by the hacksaw blade and the base-emitter was shorted. I put the device under a magnifying lens and with some careful application of an Xacto blade, I was able to clear the space between the etched sections of the silicon. My Peak transistor tester then registered an hFE of 19, which is more than the minimum hFe of 15 that is specified for the part. So, even considering it is 34 years old, has been lobotomized with a hacksaw, and then microsurgery done to the substrate with a razor, the transistor still works properly and is in spec. Motorola made top notch transistors back in the day!

Copr. 2008 by Jack Orman Visit my site to learn more about guitar effects, download free projects or buy pc boards and germanium transistors.