A few photos from yesterday.

Cheers!
Ben

However, I started a Facebook page.
https://www.facebook.com/benadrianaudio

Where I put my small thoughts.

I finally got all of Jason Pace’s amps back to him. I also touched up the original KWB prototype. Scott Evans may be right; the Si diodes may be the best sounding. I change my mind all the time, so it’s a good thing I put the diods on sockets.

I finally, finally, finished Steve V’s “Explode” pedal. Steve playes guitar and yells in this wonderfully harsh band called Blacks. The pedal is a fun little fuzz circuit that is being driven with an insane booster. After the fuzz I tried a big muff style tone stack, but with separated bass and treble controls. It works better than I expected. I think Steve will like his one-off pedal.

I have a lot of pedals to build now. I’m a bit overwhelmed. Still, I worked all weekend, I’m making progress, I’m solving problems, and things seem to be falling into place. I hope to just have bigger and better nows as time goes on.

Also, buy a Cartographer record.

Assembled and tested Mike D’s (no not that Mike D.) “mod-wah board” for experimentation on an upcoming filter pedal design.

Brainstormed on Steve V’s “EXPLODE” pedal, a crazy, over the top fuzz-stortion.

Recapped Jason P’s V-4.

Diagnosed Jason P’s YCV-50. Ordered the part. Traynor/Yorkville rules!

Restrung the EGC.

Diagnosed Jason P’s Traynor. Looks like it’s just the wacky standby switch. Now, where do I get one of those?

Tuned up Jon G’s Fuzzy Bunny.

Experimented with the new fuzz circuit.

Worked on Trey P’s Bunnydrive; almost finished!

Pinched the hell out of my finger in a mic stand.

1. “Repaired” an old Digitech dual pedal Chorus/Flanger.
2. Debugged a broken Guv’nor pedal. I have to order a part.
3. Fixed an old benadrian pedal with a broken LED for Howie.
4. Reassembled Jeremy’s Jackson head for sale.

I feel like I did more. Meh.

I’ve not owned a noise gate since the early 90s in my wannabe Helmet days.

I picked up a 1980 MXR Noise Gate Line driver for $40 on ebay about a month ago. Neat. I figure if I don’t like it, I can put it up with a $75 BIN and make a profit.

I plugged it in at full volume. It works great! Much better than my old DOD gate. I was quite surprised.

The “Line Driver” part is hilarious. The final part of the circuit is a 741 opamp buffer. There is an XLR out on the side. However, the XRL hot is just hooked to the 1/4″ out hot connection. The XLR minus and ground are just connected together. That’s just silly. It’s just a high current, unbalanced signal.

It seems to lose a bit of low end and level, but it doesn’t sound bad; nothing you couldn’t EQ out. The bypass isn’t a bypass in the traditional sense. When you turn the pedal off, that just grounds out a part of the gating circuit so that the gate stays full open.

Anyway, I’m surprised by how nice it sounds! but tonight I decided to change a couple caps to see if it would improve the sound.

Replaced the caps noted above with .1uf.  It lets more low end through than it previously did. I didn’t really run the numbers, but it does sound a little better

I now actually like the buffered signal (with the pedal on or off) more than a true bypassed signal.

Cheers!

Earlier in this log you can see my previous mods. I removed the presence control, I turned that knob into a master volume, I cascaded the gain stages, and I left two gain knobs, allowing me to control the gain level leaving both the first and second gain stages. Essentially, I took a JCM800 circuit, hot-rodded it a bit, and corrected all the stuff I didn’t like about it. The result is a crunchy amp with more gain and a much wider range of tones.

During all this work, I noticed that the output transformer was a bit small. Okay, it was more than a bit small; it was smaller than the stock output transformer on my Pro Reverb, which can handle roughly 35 watts. I thought maybe this was the reason the head seemed not very loud, and to squish out earlier than expected on the master volume knob. Many people would like this aspect, since it was a little quieter when saturating. I play in a band with Chris Bolig on drums, who is, whithout a doubt, the loudest drummer I have ever seen, let alone had as a band-mate.

I was hoping a new transformer would give the amp a bit more volume and force. By force I mean that kind of hard to define “whump” that ones feels when say a low palm muted chord is played on an amp with high headroom. Plus, the traynor only had an 8 ohm out. Having 4, 8, and 16 ohm taps would be a great improvement for me. I noticed that Triode Electronics has a very reasonably prices 50 watt Marshall replacement transformer. I was already ordering a tranny to fix my pal Scott’s Alamo amp. What the hell, I grabbed the Marshall tranny.

Today I finally found a big block of unused time. I decided to swap the transformers, and record the before and after.

Here is the mic setup.

And here was how I set the knobs.

And here is how it sounds.
Old Transformer MP3

The first thing I had to do was to pull the chassis. On a Traynor, this is INCREDIBLY easy. Remove four big machined screws, and the top of the amp comes off, exposing the guts. Then there are two more machine screws on each side. With the second set of four removed, the chassis comes out effortlessly. It is so much easier than pretty much every other amp.

So within about 10 or 15 minutes I had the chassis out and the old transformer removed. For a comparison, here is the old transformer next to the new one.

Since the new transformer is significantly bigger, I had to drill holes in the chassis. I would normally shy away from this, but the chassis already had a number of extra holes. This just made me feel better about it. The amp is way past ever doing an immaculate restoration job. Plus, it’s one of the least desirable years of the YBA-1.

Here is the new transformer being mocked up.

And here are the new holes I drilled, as shown by my pointing tools.

The hardest part followed. I had to fit all the new wires into the amp through the one access hole, and then under the circuit board. Plus, the transformer was heavy and it had to be held in place without yet being mounted to do this. I devised a system of setting the chassis vertically and propping the new transformer close to its final position while gently weaving the wires through the inside of the amp. I was a bit too occupied to take photos. I got everything in, bolted the chassis, routed everything, trimmed the wires, and soldered everything in.

Then I had to drill the final hole. There were two speaker outs on the amps already. I had three taps for the impedance options. Rather than putting in a switch, I just added a third speaker jack. Here is the end result.

And here are the jacks from the inside.

So it was all wired up, labeled. The only thing to do now was to put the tubes back in and make sure it worked. I set all the knobs back to where they were, and recorded the same audio bit.
New Transformer MP3

The result: there was a slight difference, but not a ton. However, this was only at that specific volume and gain setting. One thing that does not translate is that if you’re in the room, there is a definite feeling of pushing a bit more air that wasn’t there before. Also, when cranking it up, the power saturation starts later, and the amp is just a touch louder. The low frequencies are a bit more defined, meaning they have more transient response and don’t squish out as much.

For me, I call this a success.

Tech details: Signal chain.

Electrical Guitar Company # 368 – bridge pickup.
Amp.
4-12 with Mesa Black Shadow miked.
57 about 4 inches from the grill.
Metric Halo Mobile IO
Recorded at 44.1/24 then converted to a 192kbps MP3 in Logic

Larger photos here.
http://www.flickr.com/photos/benadrian/sets/72157623098820271/

Today was a nice step, though. I finished two Kowloon Walled Bunny pedals: #005 for a member of the Electrical Audio forum, and #PT2 (prototype 2) for myself! Finally, I own a KWB pedal for Cartographer use.

Here’s number 005

I feel good. It felt like I was working working working to just get back up to parity. It’s nice to be productive again.

Time to order parts!

Feb 25th

My new guitar rules. The one thing that’s throwing me is that it’s a lot louder than my previous man guitar. When I plug straight into the amp, or run it with no pedals, it still distorts too much for my liking. I can’t just turn the amp volume down, because it’s distorting the first gain stage, which comes before the volume knob in the amp’s circuitry. The amp is a pro reverb.

The easiest answer is volume pedal. However, I’d never use it for adjusting volume creatively. Plus, I’d like to avoid adding series resistance, avoid removing resistance to ground, as well as avoid a huge pedal. So I’ve come up with a bunch of overly complicated solutions.

1. Plugging into input 2. Tried it last night. Too much loss, too mushy, too much resistance to ground is removed.

1A. Replace the 68k resistor on input 2 to a higher value, like 250k. Plugging into 2 gives me a bit less of a pad than before, but plugging into 1 gives essentially the same sound. Might work.

1B. Install a pot in the hole of input 2 to replace the 1M resistor to ground, making the input impedance continuously variable.
Would probably work, but kind of silly.

2. Tiny unity buffer box with the ability to cut level, placed at the front or back of the pedal tray. Pull down the volume of the guitar in an active fashion.
Would definitely work, but another powered device to worry about.

3. Change the cathode resistor on the first gain stage from 1.5k to 2.2k, 2.7k, or 3.3k. It will give more headroom and less level out of the first stage. I just turn up a pinch to make up the volume lost on my other guitars.
I like this the most, as I like custom tailoring my amp, but is it overkill?

Thoughts? Other ideas?

Twenty four hours later I posted.

4. solid state rectifier plug in. higher voltage might increase headroom on first gain stage
hmmm.

I was getting pretty confident in my assessment. Oh, how I was so wrong.

Erik Miller of Euthymia Electronics posted this.

You should figure out exactly which amplification stage is causing the problem. My guess is that you’ll find it further down the chain. There is a LOT of headroom in that first stage; you have to hit it really hard before it clips.

You’re welcome to bring the amp over and use one of my ‘scopes if you like.

I was too curious to wait to head over to Erik’s shop, so I did a bit more testing myself.

Okay, Erik is right.

I did the trick where I hook up a coupling cap though a couple jumpers and run various points of the amp out to another amp.

So I pulled the power tubes and ran various points of the amp into a SS power amp and cab. After the first gain stage, clean, after second gain stage, clean, after reverb recovery, clean. Then, after the phase inverter, it’s crunchy. Also, though, there is this hard clipping distortion that happens where there is enough level. It hits a certain point and it sounds like a shitty fuzz. Once it gets under a certain level, the distortion just stops. I hooked it up to the both plates of the phase inverter tube, and it’s a bit worse on the side with the 100k plate load resistor, and a little less on the side with the 82k plate load.

So, I tried a different 12AT7. Still there.
I tried a third 12AT7. Still there.
I swapped the .1 cap in the cathode section of the phase inverter. Still there.
I changed the 1M resistor on the non-input side of the PI and the 100k plate load resistor. Still there.
I changed the bias cap, because it was ancient and needed it. No help but I didn’t expect it.
I changed the .1uf coupling cap on the 100k side after the phase inverter, no change.

One thing I didn’t check was the filter cap that feeds that section. I gave it a full cap job about 5 years ago, did a visual inspection tonight, and prodded it with the chopstick, and it never seemed to add or reduce the distortion.

Things i didn’t get to check. The 82k plate load on half of the phase inverter. The 100 ohm, 22k, or 470 ohm resistors in the long tail section.

To be clear. I hook up to the spot on the board where the .001 coupling cap meets the wire that goes to the tube. No distortion, sounds great. I hook up to where pins 1 and 6 meet the board, distortion on both sides. Definitely not the tube.

Thoughts?

Finally I got over to Erik’s shop…

So Erik and I scoped my amp today.

We were getting some weird blocking distortion and oscillations, so we changed some coupling caps and the resistors on the grids of the power tube.

Here’s the funny part. After about 90 minutes of futzing with a signal generator into a load, I was playing the guitar through a speaker, and heard some bonus noise. We found out that the reverb return tube had a really dirty socket. We hit it with some deoxit and it cleaned it right up.

I was thinking though, I never got the distortion after the reverb send while testing. It was usually much quieter and less compressed when I was taking the line out post-reverb return. However, it was much louder and more squished when taking the post phase inverter line out. That was causing a vibration when the amp head was on top of my test amp, which must have been causing the rude noise earlier in the signal chain.

Anyway, thanks Erik; it was really neat putting the amp on the scope and checking it out!

Okay. I thought it was fixed. Here’s where it gets fun.

just spent a couple hours befuddled by my amp.

Here’s my amp.

http://ampedia.redbeartrading.com/data/schem_layout/pro_reverb_aa165_schem.gif

When Erik and I left, he had put in new coupling caps between the phase inverter plates and the power tube grids. However, he left the leads very long on purpose. Since I had to pull them anyway to clean it up, I decided to do some more testing tonight. So I pulled the coupling caps and power tubes and did some more audio probe testing.

Remember the phase inverter is not connected to the power amp. Essentially, it’s just the preamp.

I hooked up the synth, held down a G with tape, and plugged it in to the amp. When I hooked the audio probe to the plates of the first three gain stages, I got clean signal or a natural mild overdrive. when I hooked up to the plates of the phase inverter, it sounds clean until the volume hits a point, and then it gets kind of a very hard clipped distortion. However, after a couple more numbers on the volume knob, the harsh distortion/static stops. Here’s the funny part. On the plate connected to the 82K plate load, it distorts heavily from about 7-9, but on the side with the 100k plate load resistor, it distorts from about 5-7. So the lower value plate loads is bleeding off more audio signal to ground through the filter cap, making me have to turn the volume higher to get the distortion.

Also, when I turn the volume up on the keyboard, then the distortion happens lower on the volume knob.

So the distortion is frequency dependent, as well as level dependent to something in the phase inverter circuit. However, once it goes past a certain level/voltage, the ugly static/distortion stops. Also, adjusting the tone controls will adjust when the distortion happens.

I wanted to simplify the circuit. I pulled out all the tubes except for the normal channel and the phase inverter. I still got the harsh distortion, and only on the phase inverter plates. Also, I found that if I hoo up to pin 7 grid of the phase inverter, I can hear a similar static. So whatever it is, it’s not on the pin 2 grid signal input, but I pick it up on the other grid of the PI. In addition, it seems in phase on both sides of the phase inverter. So whatever is causing the noise, it’s modulating the current through the PI in phase on both side, and is not coming in from previously in the circuit.

Since the distortion happens at different levels on each plate, and is in phase on both sides of the PI, it gets somewhat cancelled out when running through the power amp and output transformer. I hear the difference when running through the amp in normal operating mode.

I thought maybe there was a problem with the filter cap on the PI section. Perhaps at a certain voltage level it will get weird. I swapped the filter cap, and the problem did not change at all.

My next test is to pull all the tubes except for the PI, find a way to run a loud enough input signal into the grid, and check the output on the plates. I want to make sure it’s a defect in the PI circuit, and not multi-stage interaction.

I’ve heard stories about fender circuit boards becoming semi conductive, or flux on the board acting like a capacitor with other flux on the board. The board is 45 years old, and very warped. I can’t help but want to put a new board in and just prepare my amp for the next 45 years.

So I’m pretty stumped. I can’t help but think that it’s one bad part that fails at a certain frequency or ac voltage. Also, it could be some kind of low frequency oscillation that happens at a certain voltage/frequency, and then intermodulates the audio.

The other idea is to just pull and replace EVERYTHING in PI section (caps, resistors, socket wires, etc.) see if that fixes it. I’d clean the board when everything was pulled as well.

Meh.

And then tonight I have this little experience

onight I decided to try and fix my weirdo amp problem.

I hook my amp up like I had before, with the power tubes pulled and an audio probe hooked into a power amp from the phase inverter. I ran my keyboard into the amp to play the note that would fart out the phase inverter. Guess what? It works fine. I can NOT get the amp to get all weird on me. It was a little disconcerting, actually.

So I put the amp back together and fire it up. There is a loud hum and very low volume. I’m messing with knobs and I smell burning. I look in the back and the power tube closest to the rectifier is bright fucking red!

I turn it off, swap the power tubes, fire it up really quick, and the problem stays with the socket. Something must have happened with the bias supply. I take apart the amp again. I measure the bias. It seems to be fine. I put in my spare tubes. They’re running fine. I prod the new grid stopper and pop, tube goes crazy and the bias has cut out on that tube. Shit, I must have done a cold joint on the resistor.

I re-solder the resistor, and the tube is still ramping up, but there is -16v on the grid instead of -45 (correct) or 0 (the way it was wrong before when I almost had a Chernobyl. I swap the replacement tubes and now the problem follows the tube! I must have damaged my replacement tube while testing the bias. Balls. I put the original tubes in, and it works and sounds great. I put the amp back together and no meltdown. Hooray?

So, let’s see how long this lasts. It really sounds wonderful right now, though.

Did you make it through? I hate and love my amp. Cheers.

On February 5th, after about six months of waiting, my Electrical Guitar Company “Custom 500″ arrived.

Yes that is an aluminum neck and fretboard. In fact the neck goes all the way through the body and the bridge bolts directly into the neck. Here is the guitar with the body removed.

You can see more and hi-res photos here.
http://www.flickr.com/photos/benadrian/sets/72157623243036439/

This is just an amazing instrument. Rather than type a whole new description, I’ll just copy what I wrote to the builder.

—–
The sound is amazing! On tour in late 2007 I played Rich’s all aluminum offset one, and then Colin from Fun Ender’s guitar. The feel wigged me out at first, but after about 10 minutes I just couldn’t put them down. I never played them plugged in, though.

On Saturday I got to plug it in. A few friends who were practicing down the hall came by to check it out. The range of tones available is very diverse. The RW/RP of the pickups is a great bonus. Mainly, though, what everyone noticed what the immediacy of the response. I never got that before when playing the guitars unplugged. The think I’m telling my friends is that it has the attack of a Tele, but the level drops off less for the
sustain. It’s like a Fender response with more sustain, or a Gibson response without the weak, mushy attack . It’s just a totally unique ADSR curve (synth term)

The other thing I told my friends is that it kind of sounds like an angrier, more responsive version of my Ric 360.

The pickups, holy shit! they sound great, yeah, but I had my amp running at full tilt, standing right in front of it, and there was no squeal at all. I couldn’t get microphonic feedback at all. So great!

So yeah, I’m blown away. Fit, finish, sound; I played it all weekend in every little open moment.
—–

So yes, new favorite guitar by far.

I also finally settled on my Cartographer amp setup. I finished the Traynor. I left the tone caps the way they were, but I redid the phase inverter circuit to classic Marshall values. Instead of a 2-12, I managed to grab an inexpensive but good 4-12 from my friend Jeremy. the other amp is half of my old bass amp from Replicator. It looks very intimidating.

That’s the full catchup. Look for more building and repairing soon.