ProCo - You Dirty Rat - exactly, which diodes?

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nooneknows
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Post by nooneknows »

Hi,

some ago I modded a RAT2 putting two 1N34A diodes, whis is, as far as I know, what it is supposed to be in a You Dirty Rat circuit (since I have another stock RAT2 the comparison is easy and I prefer hands down the YDR sound).

BUT, reading around in various forums, the info about the right type of diodes in current production pedals seems a bit confusing. In the official site the YDR is reported to have germanium type diodes but several users opened their pedal and found:

- 1N34A (germanium, I guess around 350-400 mV threshold)
- SH270 (schottky, designed to replace 1N270 germanium type, from the datasheet I've found there is only a max VF of 450mV, typical should be lower)
- BAT41 (schottky, a little lower threshold than SH270)
- (other?)

I bet a SH270 is indistinguishable from a 1N34A in a RAT but I think it would be intersting knowing if the ProCo advert adhere to the real parts used, so, if there are YDR users here, which kind of diodes have you found stock?

thank you

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Post by nooneknows »

(Hey, I wrote this post in the Modern Stompxes forum since I was talking about the actual components type of the real pedal of the original schematics, not about a cheap copy, is the Administrator who moved it here? why?)

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Post by ggbb »

My stock YDR has CDSH270 schottky diodes. I'm not aware of BAT41 being used in YDR - but it wouldn't surprise me (and I haven't really spent time trying to validate YDR diodes). A friend once owned a Vintage RAT (1991 reissue) that had BAT41s stock. I believe this was probably a production mistake caused by mixed up parts (those BAT41s looked exactly like your typical 1N4148 - glass DO-35 and even share the text label "41" in a single line on the body), as opposed to a deliberate substitution because they ran out of 1N4148. The question I always had around that was why they would have any BAT41s present in a RAT production line. We can only guess, but the idea would be supported by the possibility that they were used in YDR production. I believe there was a period when the VR and the Deucetone or YDR were both in production - however this was probably around 2002-2004 which was a few years after the manufacture date of my firend's VR. They may have used BAT41s somewhere else in Pro Co (they make other things besides RATs) - who knows.

Long story short - Pro Co quite obviously do NOT adhere to "germaniums" in the YDR. That's disappointing I suppose - and perhaps legally vulnerable to a false-advertising lawsuit. I expect that a reliable and cost-effective supply of germanium diodes is not obtainable anymore, so they've moved to schottky. I've noted before that they do seem to make part substitutions on occasion or possibility production errors that are let through QA. I would be interested in knowing when they used real germaniums in the Deucetone and YDR, and even the Solo.

Purists would probably argue that while germanium and schottky diodes have similar Vf - when used as a clipping diode they don't sound the same. Based on what I've read, I would tend to agree that they could sound different (capacitance and switching speed are different), but I haven't done a comparison to know for sure. What is certain though is that there's a lot of mojo attributed to germanium in the pedal world, and that "mojo" is not always in and of itself measurable or audible.

All that and still no answer about which diode is "right". :(

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Post by Cub »

ggbb wrote:All that and still no answer about which diode is "right". :(
But a good bit of information nonetheless ! Thank you for that. I'll have a peek inside my SOLO and Juggernaut this weekend to see if I can spot what's going on in there and have a good look at the pot codes as well. Any bit of confirmed information is welcome.
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Post by Cub »

ProCo SOLO
No marking I could find on the pots. It has the good old 3,5mm power jack, not the modern for BOSS style plugs.

On the bottom, there's a VR- sticker with the serial number and "MADE IN U.S.A.", but the top bit where "Vintage Rat" would have been, has been cut off before the sticker was applied. Perhaps they still had a sheet of stickers left after production of the big box reissues seized ?

The chip is an OP07DP from TI with "0AAG81M" on it, should that mean anything.
Turquoise 3PDT swich

Hot: CDHS270 antiparallel with a 1N4148
Melt: red 5mm LED antiparallel with a CDHS270
Burn: red 5mm LED antiparallel with two 1N4148 diodes in series.


ProCo Juggernaut Bass Rat
ER3977 0322 markings on all the pots, I couldn't find out what that means as far as month / year goes. It too has the good old 3,5mm power jack.
A complete "THE RAT RT-" sticker on the bottom. with the serial number and "MADE IN U.S.A."
Chips in both sections are Fairchild LM1458N. The one in the mixer with "V250" on it and V239 on the one in the distortion.
Two blue 3PDT switches.
Two 1N4148 are going antiparallel.

Other notable things are that all 1M resistors are carbon comp and the rest carbon film and something strange is going on with the 2N5458: Gate is where it is supposed to go, Source is in the hole for the Drain and the Drain itself in an added hole just below the one that is now being occupied by the Source. Perhaps it has been repaired at one point ?
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Post by nooneknows »

ggbb wrote:All that and still no answer about which diode is "right". :(

thank you very, much, very interesting anyway

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Post by nooneknows »

Cub wrote:ProCo SOLOHot: CDHS270 antiparallel with a 1N4148
Melt: red 5mm LED antiparallel with a CDHS270
Burn: red 5mm LED antiparallel with two 1N4148 diodes in series.
thx! so again a different combination of diodes is the real difference.

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