Thank you for taking the time to help me out here AG...I do appreciate it!analogguru wrote:Sorry that I don´t look at others people schematics - I draw my own.wader2k wrote:analogguru wrote:None of them..........but I'd really like to know which ckt is the venerable gray box that draws so much crazy money on ebay.
as you can see here:
https://cgi.ebay.com/ws/eBayISAPI.dll?V ... :IT&ih=017
it´s an Mxr Distortion+ circuit housed in a Dod-case.
The variations came later.
analogguru
this I knew......but it doesn't help.......
let me rephrase....what value for R4 would I most likely find if I opened up this?
https://cgi.ebay.com/ws/eBayISAPI.dll?V ... :IT&ih=007
8^)
I like to draw my own also.....I do have a BSEET and 25 yrs experience in electronics.......but guitar pedals is a new hobby to me....
Therefore I can´t say what is R4 or R2.
If you opened up this specific unit you must have bought it before.
But if I had the money to buy it, I wouldn't need to build it would I? After all, this is the "haven for free exchange of diy guitar electronics" No?
But there is already a gutshot of the opened unit. From this gutshot I can tell you that it is most likely a 1979 unit, at least from the last weeks of 1978. Only during this period they used the 741´s from RCA in the grey 250.
Now we're getting somewhere.....
Anyway, the feedback resistor was in all units from 1976 to 1979: 1M.
Yup, this I have established
The bias resistor was in 1976 470k, in 77/early 78 510k, the rest of 78 and 79 it was again 470k. With a freeware graphic programm maybe you will be able to recognize the yellow and violet ring in the gutshot.
Thank you, so much!.....and btw.. I'm semi colorblind so I don't trust myself to read colorcodes correctly without a dmm to check.......I wonder why markm's layout and others I have seen indicate 1M for the bias resistor as to my original question? No matter 470k it is.....
BTW, do you have a 741 from RCA ? I think this will have more influence on the sound than the stupid bias resistor - especially when the input coupling cap has a tolerance of 20%, like in this case.
Why yes I do believe I do!......and messing around with the .047uf gain cap will have even greater effect..
analogguru
8^)
Wade
). It feels a bit same like you'd have a wah pedal on middle position. Overall, the 77 version is definetely a good pedal to build for certain solos were you need a tone that's not too bright yet still cuts through great.