Since nobody seems to have done this before and I was sick in bed for a week recently, I used that time to trace the schematics of the SansAmp PSA-1. One "tiny" part is missing and that's the "mystery" circuit inside the black box used for the CRUNCH and DRIVE. I assume it's based around yet another 072 dual opamp since there are +5V/-5V going into the black box. Anybody with an x-ray?
I did not trace the digital part as that's rather boring. In the end there are only 5 control lines that go to the analog part, two go to the 4053 analog multiplexer of which one switches the bypass signal and the other seems unused. The other three control the four 100k DS1267 dual digital potentiometers which are daisy chained together so that only three control signals are needed.
http://www.freestompboxes.org/viewtopic.php?f=7&p=247415#p247412
user
DimebuGG at freestompboxes.org made a nice PDF from my crude sketches and added a "guess" for the gooped up section:
http://www.freestompboxes.org/viewtopic.php?p=247791&sid=f9471fc5a58c04a4964a57049c687f59#p247791
5 comments:
Nice one! Have you identified the portion that refers to the speaker sim? Would be great to bypass the speaker sim like they do in the character series pedals. I performed that mod on a Joyo American Sound and it really came alive.
regards
This is awesome, thank a lot! Unfortunately it is probably everything except where I have a problem. My PSA 1 has a problem with holding it's settings. Settings are correctly stored in each bank and while they don't get lost something makes one or more settings slide off. It changes the tone and one of the change-LED's start flashing. I can select the bank again and the tone is back but the problem is that while it can sometimes hold the setting for 30 minutes it often happens within a second. I once played a gig with fluctuating line voltage which caused it originally but I would super appreciative of ANY ideas about what I can do, what I should check, what I might want to try replacing or anything else you can think of really.
Thanks a lot in advance :-)
By the way - yeah sure, I can do the X-ray of the "black box". But I need to know what I am looking for - can you recognize just from the internal circuittry?
Hi Poul, thanks for offering your help. The author of this blog is not very responsive these days, but I'm sure the community would be very happy to see the internals of the black box.
Apparently it's not possible to see the component values on x-ray, so what we are looking for is the topoloy of the circuit. That already would be very helpful.
Alex.
Hi guys, just a saw all the comments here, somehow I didn't get notified :) xray images would be cool!
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