Use of a buffer

[Marbles]

Hey guys,

So , I'm building a SD9 and ran into some troubles. I built the bufferless one, since I heard people had results with it. I changed 1 value that was traced from an original, 10uf for the mentioned 22uf.

Since it was suggested in the notes to use a 220n, I did not expect it would be a problem. So.. It worked, but oscillation unbearable. Knifing it, changing IC, rebuilding: No dice.

So I thought: Let's try something else and placed a Boss Reverb in front of it, knowing that was buffered:

Presto, no squeeling.

Can anyone explain why not? :D I wanted to make it true bypass, but not looking forward to start again. Any other remedies for this?

Or is it best to just add like a Klon buffer in the enclosure and be done with it?

[Marbles]

Wait, placing a buffer in the signal makes it still true bypass ofcourse. Geez.

I'm going to say I have to put it before the input, right? I'm sorry, I just am braindead this week.

[balazs.bencs]

Yeah, buffer goes to the input. You could put it before the effect's input, so that you can still have the pedal being true bypass, but when engaged it would be like : guitar->...pedals... -> buffer->effect -> ...more pedals... -> amp

Generally, I think you have an impedance problem, that the buffer solves basically.

Btw I would not worry too much about buffers, I usually think that they do more good than harm. Yes, you can have problems with fuzzes and wah pedals and all that, but in most cases they are pretty useful.

[Marbles]

Thanks a lot!

I'm building it for someone that wants 2 boards. The pedal should be as identical as possible. I'm going to see how much it matters. I'm going to guess his original will have an input and output buffer as well, right?

He uses a looper, so If not in use it will be out of the chain I guess, so no problem with fuzzes.

I can remember I really liked my Klon Clone in the chain, without it doing anything. I'll go this route, thanks!

[balazs.bencs]

yeah, with a looper, it's a no-brainer, cause it is not in the loop at all when it is turned off, but when it is on... then it gets interesting to see, which pedal have issues with a buffer.  

[Marbles]

With the buffer I built still not sounding like it should. So I started building again. I knew that all parts were in place, that's why I didnt put it in the debugging threat (so arrogant, I know), so I checked every resistor: bingo.
No idea what I had in place of the 470r resistor, but it wasn't a 470r. Swapped it and sounds great without a buffer. No squealing.
Thanks for taking the time!