Proco - Brat

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

Today I found the first time guts from a Proco Brat:

http://f.hatena.ne.jp/toy_love/20071106041949
http://f.hatena.ne.jp/toy_love/20071106042640
http://f.hatena.ne.jp/toy_love/20071106042538
http://f.hatena.ne.jp/toy_love/20071106042551

After tracing the schematic i was really surprised :shock: :
Neither the drain nor the source have an DC-connection, so the FET seems to be floating - If and how this works nobody really knows.

So my question:
Is there somebody who owns a Proco Brat or Roadkill who can report me about his experience with the FET-switching or can take some photos for comparision ?

thanks in advance,
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Post by polarbearfx »

Looks like it has an input buffer.

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Post by analogguru »

Looks like it has an input buffer.
Yes an input buffer/amplifier....which is also a little bit uncommon, no bypass cap on the source resistor, and maybe the source resistor 5k6 and drain-resistor only 1k ?????

Output is taken from train via electrolytic and gate has 1M pulldown.
FET´s seem to be 2N 5458.

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Post by jakerandall »

I have one of these somewhere. I haven't seen it in years its in a box somewhere. It was a poorly implemented circuit that had potential. I try to figure out some modifications but nothing made it better. I never thought about dropping the buffer, might have helped? The LM308 chip to me is being too taxed, a better chip and some other mods might be nice.

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Post by Dirk_Hendrik »

Am I stupid or just blind? Which schematic are you discussing? :?:
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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Post by JHS »

Proco Brat, schem can be found via Google.
The Brat is a Rat2 with I-buffer and 2 additional diodes in the FB-loop.

JHS

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Post by analogguru »

Am I stupid or just blind? Which schematic are you discussing? :?:
Never heard about the "virtual-imaginary-schematics" which only exists in your head ? :roll:
In hard times of "stalking through booteekers", "intellectual property of stolen designs" and similar things you should look for the Video/DVD "Fahrenheit 451" to learn more about your immediate future.... :lol:
Proco Brat, schem can be found via Google.
The Brat schematic which can be found on the net is only an "Artist´s Impression" and is more distant from reality than many booteeker´s designs from a tubescreamer.

Maybe I will draw a correct Brat-schema when I will find some time.

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Post by bajaman »

Maybe I will draw a correct Brat-schema when I will find some time
That would be nice :D
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Post by soulsonic »

I have a Roadkill that uses that same Brat board. I've been planning to trace it myself since I'm wanting to do a bunch of mods to it. It uses FET switching to be sure and it seemed to work okay - it seemed to be on par with most of the other JFET switching I'd experienced. I was never happy with how the thing sounded - way too thin with very little good sustain. It doesn't sound much like a Rat at all despite the similarities in the circuit. I think it would be very easy to mod one to be exactly like a standard Rat and get the same performance, and it would probably also be easy to mod it into something much more interesting.

I'll post up some good pics of the board if you'd like.
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Post by JHS »

Yesterday I did some research about the BRAT.

Acc. to some DIY-pals it's a stock RAT2 with additional FB loop clipper alà Barber DD. After the buffer for the tone control another buffer had been added to the circuit (maybe to drop the output impedance further to prevent popping on the switch).

If you remove the FB-clippung diodes the BRAT should sound like a stock RAT2.

JHS

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Post by nbabmf »

The Rat was my first pedal ever. It was pretty nasty sounding. I'd like to build one for the sake of nostalgia.

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Post by nbabmf »

Heh... I was the last person to post in this thread, more than 2 years ago!

I have a Roadkill on the way. I plan on making a little more like it's Rat brothers.

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Post by soulsonic »

The biggest difference is that the Brat/Roadkill uses electronic FET switching instead of true bypass.
It should be easy to mod one into being a Rat.
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Post by grantb »

Here's my Brat, or as I like to call it, "the crappiest sounding pedal ever"
Traces
Traces

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Post by grantb »

Sorry not the best pic
BratPCB1B.jpg

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Post by grantb »

Some component values annotated.
BratPCBAnnotatedB.jpg
Thats a 1M in the shadow of the top jack

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Post by nbabmf »

The Roadkill came in the mail yesterday. I took it apart last night by candlelight because the STORM OF 2010 haha took our power out for 10 or 11 hours.

I was pretty excited to see this LM308. There's one less thing I have to desolder and swap out in my quest for raunchy rodent tones.
Image

I got a good laugh out of the writing on the trace side of the board. DETERMINATION IS STRENGTH. FOLLOW YOUR DREAMS. Oh, and would you look at that... Brat, 1996.
Image

Unfortunately, I'm a bit colorblind and the candlelight didn't help... but it looks almost identical to one of the Rat schematics I found here on the interwebs. The primary difference is the two parallel pairs of silicon diodes in the feedback loop. I believe this will be a great platform for mods... and rehousing. That enclosure it came in is ugly, and it could use a new switch.

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Post by RnFR »

i think you can turn over the faceplate on the model. the other side has the sweet hot pink Brat logo. [smilie=a_chuckle.gif]
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Post by grantb »

RnFR wrote:i think you can turn over the faceplate on the model. the other side has the sweet hot pink Brat logo. [smilie=a_chuckle.gif]
Yep. I'm going to house something else in there. I got this pedal for free at a local guitar store by asking for broken pedals for the purpose of using the enclosure. The guy said, "well, this one 'works', but I think you should gut it". :lol:

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Post by JHS »

A basic BRAT-schem can be found on this site.

http://www.happybob.com/rstrand/rat/rat_versions.htm

JHS

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