Ross Distortion

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

Re: Ross Distortion

Postby snmavronis » 14 Jul 2010, 15:50

I'm curious about my particular Ross R50 Distortion variant since no schematic I've see shows the polarity protection diode and it's unusual to see a tan model made in Taiwan, which are all supposed to be in black boxes. The basic circuits of the Ross Distortion, MXR Distortion+, and gray DOD 250 Overdrive are very similar. As a matter of fact the first Ross Distortions were a dead ringer to the MXR Distortion+ (see image below) complete with exact same PCB layout and script font labeling housed in the same Bud enclosure! It sounds like there was a lot of 'cloning' going on even back then between the pedal companies! So what was the historical order of these 3 pedals - 1. MXR, 2. Ross, 3. DOD?

I'll add the Ross to my pedal chain with my 250 clone and toggle between them later to compare, but by themselves they do almost sound the same. Although surprisingly for a distortion pedal the level output seems to be less as loud in the Ross than the 250 probably from the different level pots used? IDK...

I still want to make photo-exact graphics of all 3 PCB layouts. I'll probably have to draw all 3 'by hand' using GIMP or something. Even though Peps1 made a very very nice copy of the 250 PCB already, it isn't 100% exactly "photo matched" in some small areas and slight angled positions of parts. But it is at least in the upper 90 percentile accurate and probably about as close as you can get to the real thing! We guesstimated the PCB size too while he was researching photos that I helped provide as reference. I'd like to verify the exact board dimensions measured from the real thing though instead of guessing based on skewed and distorted photographs. I'll check with my sources again and request that.

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Re: Ross Distortion

Postby mictester » 14 Jul 2010, 20:07

JOHNO wrote:
snmavronis wrote:I noticed on that page you linked the photo shows larger CTS pots from 1978 and only 2 diodes. I guess after then compared to my picture they used 3 diodes and different 16mm pots

Looking at the schematics at the home wrecker site I noticed the black version has three diodes for asymetrical clipping but, there is no reverse polarity diode drawn on the schematic. In the tan version there are two diodes for symetrical clipping but, no reverse polarity diode drawn on the schematic. But I can't find any gut shot's from a black version to confirm that it had three diodes for clipping. In the pic's I can find one version had two diode and the other had three diodes but one of those diodes was for polarity protection. Maybe there is an error in the schematic? Anyone have any further information?


The published circuit for the black version is wrong! It uses just two silicon diodes for the clipping. The third one is for the reverse polarity protection. As usual it uses the cheapest parts available, and is nothing special at all!
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Re: Ross Distortion

Postby romdos » 15 May 2018, 04:49

I know it's been 8 years, but I just saw your post and I have a black ross from 1981. I'd be willing to send you pics if you still want them.
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Re: Ross Distortion

Postby rs » 18 May 2018, 15:23

Please do post them. :thumbsup
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