Fender Pugilist Distortion  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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asbestosaurus
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Post by asbestosaurus »

I watched a few demos of this when it came out and thought it was a really cool concept, but was outside of my price range at the time. Luckily, I managed to get a good deal on one second hand. I opened it up out of curiosity, expecting it to be full of SMT. Much to my surprise I was met with a double sided board populated with nice big through-hole parts, made tracing a breeze.

Having looked inside I have to say I'm fairly impressed. The pedal has a separate power board between the 9V barrel jack and the main effect board. I assume this is standard across the line and that it was more economical to separate it than to put it on the main board of every different release. It features a capacitance multiplier circuit to basically eliminate any power supply noise before it reaches the main circuit. Nice touch.
FenderPugilistDistortion0.PNG
The rest of the circuit is pretty much what you'd imagine, reading the advertising. A pre-gain stage with a nice high input impedance and reasonable part values to keep noise down where it counts, plus a bit of high-pass emphasis. Two quite similar 'distortion engines' as per the marketing, one slightly gainier, which can be blended in parallel with or put in series after the lower gain 'engine'. Each of these has a reversed (dark to bright is clockwise) and buffered Rat-style variable frequency low-pass tone control.

In a pleasing bit of due diligence, when switched in series, the signal is routed through an inverting buffer to keep the phase the same at the output.

The blend control and output stage is nothing too complex. It does the job without too much variation in level across the sweep, depending on how the distortions are set. The bass boost does what it says, unlike some which can sound boomy when engaged (or nasty and thin when disengaged), this one leaves your mids thoroughly intact and just shelves up the lower register, I found it fairly subtle with my setup but your mileage may vary.
FenderPugilistDistortion1.PNG
Overall I think it's a very well designed, versatile, and good sounding pedal. At least to me it's maybe not quite worth the full retail price, but I'm not sure how much of that is just because of the fancy name on the front.

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Dr.Detroit
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Post by Dr.Detroit »

That series/parallel blend is very creative. Gets my mind goin' - what about a light fuzz as the first gain stage? etc. etc. Lots to think about.

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arivabox
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Post by arivabox »

it is interesting to see the photo, especially the power board, how the connection is implemented. An interesting move. Great job.

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asbestosaurus
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Post by asbestosaurus »

arivabox wrote: 03 Apr 2022, 02:50 it is interesting to see the photo, especially the power board, how the connection is implemented. An interesting move. Great job.
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Ichabod_Crane
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Post by Ichabod_Crane »

Are the op-amps TL072?

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asbestosaurus
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Post by asbestosaurus »

Ichabod_Crane wrote: 04 Apr 2022, 10:25 Are the op-amps TL072?
Yeah I forgot to mention this, thanks. All of them are TL072CP

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Ichabod_Crane
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Post by Ichabod_Crane »

asbestosaurus wrote: 02 Apr 2022, 05:40 [...]
FenderPugilistDistortion1.PNG
[...]
It's a kind of new power supply section for me. Why does it use that?
My emulator software seems works bad with it, because I get in the output about 0.8v.

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cocnut
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Post by cocnut »

Hi, I've tried to build this power supply and I got ~8.1V on output. Is it right? Simulator also shows ~8.2V :hmmm: I've used 2N3904 and 3906 BJTs and 1N4007 diodes, but it seems to be almost identical with 1N4001 and 4401/4403

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bmxguitarsbmx
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Post by bmxguitarsbmx »

I don't understand this circuit. The NPN part looks like a Capacitance multiplier, which is just an Emitter follower with nicely filtered voltage at the Base. You can make followers in the form of a Sziklai pair, so possibly all these parts could make a "Sziklai Pair Capacitance Multiplier". Anyone understand how this power circuit works?

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stolen
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Post by stolen »

Looks like you could get free extra tones by shorting SW1b, fairly certain it won't oscillate, IC3a gain only goes up to 17 in that mode

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asbestosaurus
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Post by asbestosaurus »

bmxguitarsbmx wrote: 08 Nov 2022, 01:45 I don't understand this circuit. The NPN part looks like a Capacitance multiplier, which is just an Emitter follower with nicely filtered voltage at the Base. You can make followers in the form of a Sziklai pair, so possibly all these parts could make a "Sziklai Pair Capacitance Multiplier". Anyone understand how this power circuit works?
I've since sold it on so I can't quadruple check, but I'm a good 95% sure that the trace was correct. I'm confused by it too but I don't think it's a sziklai arrangement.

One thing I did notice (accidentally haha) is that the effect still works fine with the supply board plugged in backwards, which I don't believe would be the case with a bare cap-multiplier follower.

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bmxguitarsbmx
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Post by bmxguitarsbmx »

Well I'll be durned!

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cocnut
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Post by cocnut »

Have you tried to build it yet? I've tried today and I've used two TL074 opamps. I have some issues. Didn't have too much time to test it well today, but there are my observations:
1. output level is way to high if I turn the level pot to, let's say, 70%+. it is very loud and it starts to squeal if the gain is past 12 o clock.
2. "green led stage" doesnt seem to work and I'm pretty sure I've connected everything well according to the schematic. In blend mode it starts to sound quiet and dirty when the blend knob is set to more than 50%, when I set it to 100% I can hear nothing. Green leds are blinking tho. In series mode its silent too.
3. At first try it sounded little odd, output signal was flat and quiet until I hit the strings pretty hard. Then I built a simple PCB, chnged opamps and it started to work better aside from the issues mentioned above. I didn't use the power supply board, connecting it straight to the 9v supply. I'll try it with the lil board tomorrow.
I think I've tested all caps and they're good. What do you suggest to debug next?

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cocnut
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Post by cocnut »

Also what kind of switches are installed on the original PCB? Standard mts switches are too big for this kind of potentiometers and I'm looking for a replacement as I'm using those pots in my constructions

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Post by Gebrey »

Ichabod_Crane wrote: 05 Apr 2022, 14:42
asbestosaurus wrote: 02 Apr 2022, 05:40 [...]
FenderPugilistDistortion1.PNG
[...]
It's a kind of new power supply section for me. Why does it use that?
My emulator software seems works bad with it, because I get in the output about 0.8v.
Hello Ichabod, can you tell us which software are you using to emulate circuits? Thanks

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Ichabod_Crane
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Post by Ichabod_Crane »

I use Tina TI.

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