Pedal Mod – BBE AM64

Circuit board
This is what science looks like when it is about to rock out

This one is really simple.

The BBE AM64 is a distortion pedal for guitar.  Yep.

I love overdrive pedals, particularly medium-gain ones, that let you control the amount of crunch with your picking or the volume knob/pdeal.

I love fuzz pedals, particularly the insanely gain-y ones where you hit the button and hold on for dear life.

I’ve never been a fan of distortion-distortion pedals, because they’ve always seemed like a kind of boring middle ground. Like the porridge that Goldilocks chose, and we all know that she just played the same damn pentatonic licks over and over until the bears ate her or whatever.  Not sure on that–I didn’t read the book, because I knew it would just spoil the movie.

Anyway, what?  Oh, yes–distortion pedals.  Right. They have no real sensitivity to them, but they are also not crazy.  That seemed pretty boring.

I just didn’t get it at all until I had to switch quickly between singing and playing guitar parts and soloing in the same song. Then I understood the value of just pushing a button and automatically getting That One Sound for Just This Bit of the Song.

Which brings us to…

 

The Pedal – BBE AM64

I happened upon this wonderfully cheap example of just how well production pedals CAN be made, did a bit of reading up, and it seemed really dumb not to get it.  I think these things sold for well under $100 in their heyday, and then ended up getting cleared out at something like $30 a year or two ago.

For that, you got:

  • A metal box (with a heavy plastic bottom, which is quite solid).
  •  Mechanical true-bypass switching, using one of them blue 3pdt switches just like the big kids use.
  • Box film capacitors.  Really.
  • Full-sized Alpha pots.  Really.
  • Cleanly made board with all human-fixable (no SMC) parts.

This is a long way from sucking.  It’s really how everyone should be doing it, PARTICULARLY folks who charge more than $30 for pedals.

The pedal has three knobs:

  • Level is the output level
  • Tone is the tone control
  • Gain is how much crunch you get

There is no useful clean setting on the stock pedal. If you turn the gain all the way down, and the level all the way up, you’ll end up quieter with the pedal on than with it off. With the gain up at all, you start to clip.  Yep, it’s a distortion pedal, and that’s what you’d expect it to do.

The circuit is based around a TL072 op-amp, and uses a pair of LEDs for clipping.  Sometimes I like LEDs for clipping–I’ve used them in a couple of other mods I have done–but in this case, the result was pretty fizzly.  I tried the pedal with a few guitars, and found:

  • It’s kind of OK with humbuckers, but I don’t use them much
  • On a Strat with regular passive pickups, it’s meh.  Works fine on the bridge pickup, if you really jack up the gain on the pedal, but almost everything can do that trick.  Boring in other positions, and notes fizz as they decay.
  • Surprisingly good on my Tele-ish guitar.  It’s got a P90 in the neck, and got along pretty well with this pedal
  • Quite unpleasant with my Strat with Lace Sensors.  No sir, I did not like it.  The fizziness was really pronounced, and there was nowhere to set the tone on the pedal that wasn’t either a cloud of low mid or a piece of piano wire in your eye.

The Mod

I did about the simplest thing I could do:  I swapped one of the clipping LEDs for a 1n4148.

That seems to have sorted things out nicely.  The disto is now thicker and finer-grained, which lets the notes have more body and the sustain makes more sense.

i figured that this would be a good first step.  This pedal is a good candidate for putting in a socket and some switches and trying out a bunch of op-amp and diode combos.  It might also benefit from some messing with the tone stack, as the stock set up has too much range.  There are simply too many places you can turn the tone knob that sound awful.

But for now,  this one change has made it a fine punch-it-and-go pedal for all those times you just can’t say with flowers.

Overall, this might be the best platform for distortion modding , because the base pedal is very well-made, most of the parts you’d want are already in the pedal, and the stock configuration sounds far worse than it should.  I’d certainly pick up another one or two if I got them at the same price.

4 Replies to “Pedal Mod – BBE AM64”

  1. Thank you, THANK YOU, for this post. For modding this pedal, and then sharing. I bought this pedal, one of the first pedals I’ve ever owned. kinda liked it, kinda didn’t. it was dirt cheap on ebay, and I’m a sucker for racing stripes and red on black. much like you, not a big fan of distortion but I love fuzz! Fuzz not Fizz. After playing with it for a couple years, I was wondering what to do with it. ditch it, re-sell it, learn to like it? I was wondering if I could mod this pedal (hell, if I could mod ANY pedal – as I never tried to mod one before). After googling “BBE AM64” and “mod”, I was surprised and beyond excited when I found your blog. So I bought the diode you prescribed, got frustrated trying to de-solder (still no good at it) for about an hour, and eventually ended up succeeding at this – my first pedal mod, and I am quite pleased. Turned a $30 pedal into a $100-sounding pedal.And something I like and actually use! Thanks again!

  2. HEY! Sorry it took me so long to get to this comment. I kinda fell off the planet for a while.

    Thanks for reading the blog, and I’m glad it was useful. As for your de-soldering problems, it’s not unusual to need a bit of practice at that stuff. In a lot of cases, it’s harder to take the old parts off than it is to put the new ones in. This is particularly the case if the manufacturer has used lead-free solder, which has a higher melting point than the old stuff.

    If this is something you’re going to do a lot, you might want to get some practice. Just find some old piece of electronics that was going to get junked, and remove all the parts from the boards. After about 10 shots at this, you’ll probably get pretty smooth at it.

  3. Hello,
    I saw you post about the bbe am 64. you seem super knowledgeable about the circuit. I just wanted to know about the high pass and low pass filtering. I feel that I want to add a switch between the high pass and low pass filters, where I can get a little more bass and or maybe change the way the tone knob gets very shrill after 9’oclock, raising the value of the cap? I see that someone noted c8 could add bass and c2 removes it, Im just not sure. I also have switches for the diodes to switch between leds and 1n4148 symmetrical and asymmetrical.

    My AM64 has a reasonable decay, very comparable to my clone of Suhr Riot. The gain of these 2 circuits are not that far (only about 3 dB more for the Riot at the mid-hump), which is not that surprising since the Riot is also a modified Guv’nor.

    What pedal did you compare it with?

    Some easy mods would be to:

    – Socket the IC and experiment.

    – For more bass, add 33n or 47n in parallel of C8. For even more, just swap C8 for a 220n, but it might get muddy.

    – For less bass and a mid scoop, change C2 for 220n (or add 100n in parallel). It sounds VERY aggressive and metal!

    – To get rid of some top end, rise C7 to 1n.

    I just wanted to see if you could help me out thank you

  4. Sorry–I drifted off to another part of the 1nertweebs for a while there. I am probably back now.

    You’re getting waaay above my meager skills here, but I’ll take a run at the things I DO know:

    First, keep in mind that I just wanted my AM64 to do ONE thing: I stomp on it, and it goes to full-stupid distortion. No nuance, and I wasn’t looking for it to be really versatile or have a lot of settings, so I stopped once it did what I wanted. There’s a lot more in this pedal I am not taking advantage of, but I’ve also used it live exactly once (to play some Chixdiggit covers!). I can pretty much guarantee that your mileage WILL vary..

    – I’d go with what you read about the caps that add and remove bass. Worst thing that could come out of trying it is that you don’t hear anything you like and then you can just put things back as they were.

    – That’s a very cool idea with the switchable clipping diodes. If you want to make a versatile pedal, that’s a good way to do it.

    – I compared the pedal to

  5. a stock SD-1
  6. an SD-1 I modded (removed mid-hump cap, put in an LED, which cleaned it up a bit. This meant it’s even less of a distortion and more of an overdrive)
  7. (both SD-1s were in conjunction with an overdriven amp)

  8. A modded LA Metal pedal, which is my daily-overdriver
  9. Channel-switching on my amps with and without clean boost pedals
  10. Somewhere I think I still have a recording of a thee-way test of the pedals, and I will see if I can find it.

    I think you would probably get more RANGE of sounds with all the other mods than with changing ICs. What I mean is that, changing the IC will change the BASIC sound of the pedal, but changing the caps and diodes will let you adjust those basic sounds more. But of course, the coolest is to do it all!

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