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Total Recall Help - mains noise and strange problem with output

Started by Hangingmonkey, March 01, 2016, 02:03:28 PM

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Hangingmonkey

Hi all, Im having some trouble with my total recall build and would really appreciate some guidance.  Ive tested with 3005's and also 3008s.  The voltages provided were done with 3008's.

Theres 2 main issues:

1 – a lot of mains noise in the signal path.  Im using a new EHx branded PSU and the voltage regulator is from mouser.  Ive followed all the values in the BOM with the exception of the 1W 240R which I have subbed with a 1W 220R as my mouser 240R is on backorder.

2- Im getting delay when I probe the BBDs and I have biased as per the document.  (interestingly, with only 1 BBD installed, Pin 3/4 gives me what sounds like the actual signal but I get delay when I probe with both BBDs installed.  Im sure there is a reason for this which someone will hopefully educate me about.

However, the output is a distorted signal (sounds like a ring mod/bitcrusher type noise) which is very quiet with no delay, or maybe there is some delay but is so quiet that I cant tell. 

However, if I attach a 100n cap across the output to the testing rig, this sorts out the problem, ie no distortion on the signal/delay and the volume is louder and the delay repeats sound clean.  (the reason I did this was because when I was probing the signal path, the output was clean when I probed the signal path up to the output compared to hooking up to the testing rig. 
The same happens when the pedal is in bypass, ie vol drop and distortion.

Ive attached some pics and have written my voltages on the voltage sheet in the build doc.  Obviously they are all –ve voltages.  Some of the voltages on 1 of the 4558s look a bit below the expected voltages.

All the parts were from mouser/chromesphere/farnell.  As far as tayda parts, the 4558s, pots and trimmers came from there, I pre-tested the pots/trimmers before soldering

Any ideas.  I really want to get this one working, while Ive built quite a lot of madbean and other projects successfully but Ive always seemed to have had bad luck with the analog delays; I was never really happy with my dirtbag build and aquaboy dlx is in the box of fail so if I get this working, ive checked a significant milestone!

Thanks


Hangingmonkey


joesatch

i'm a noob at this but the sleeve pins maybe try wiring directly to the input/output jacks grounds. Maybe a ground issue

Hangingmonkey

Quote from: joesatch on March 03, 2016, 06:05:11 AM
i'm a noob at this but the sleeve pins maybe try wiring directly to the input/output jacks grounds. Maybe a ground issue

Hey satriani, for a noob thats a top answer and youre spot on.  I thought it would solve issue 1 as i guess I had wired the jack grounds to earth ground rather than signal ground-and it did, issue 1 sorted. 
I wasnt expecting it to solve issue 2 as well but it did!  Thanks a lot.  If anyone has any ideas why it solved issue 2 and why the capacitor helped when i had the grounds wrong, I would be glad to be educated.

Anyway, thanks again satch, much appreciated!

Hangingmonkey


joesatch

Awesome! I built this one too and i love it. I ran into a similar issue as yourself with the grounds. Since the pedal is positive ground it can be funky. Just make sure you isolate the DC jack from the enclosure (i used a plastic jack). Also, take the Bias instructions with a grain of salt, when i followed them my results were nowhere near what the instructions say. I wound up biasing by ear without a probe and it sounds fabulous. Grats on your build ;D