Buffer Noise: spot the source

[mantegna]

Hi everyone, I guess this is my first message on this board but I've been a voracious reader for years! 

I've assembled some switching pedals in the past, but I thought a buffer would have been a simple project to start from with pcb-related material: I realize I was wrong, 'cause even by following each rule on the product's tutorial pages http://diy.musikding.de/index.php/der-buffer.html and trying to build it with each of the 3 transistors given, I couldn't get it to work.

I admit I haven't checked any part before to start assembling them, but the latest trial I came with seems to work and I'm sure all the wiring and pcb populating to be correct: the problem is, as you can hear from the mp3, it's got a signal to noise ratio which is obscene. It's a strange noise, though: could someone help me spotting where is it coming from?

http://www.aronnelson.com/DIYFiles/up/buffer_noise.mp3

[R.G.]

You've heard me do my mantra before. Could you go to the sticky thread "Debugging; what to do when it doesn't work" and follow that. You're part of the way there already. We need to know what the devices and parts are that you have in now, and the DC voltages on the active device.

As an aside, doing PCBs with multiple possible populations to do different  things is an old favorite of mine. But this style of thing is very prone to odd problems if you mix up the versions even slightly. Beyond that, weird hiss sounds are sometimes a symptom of RF oscillation. Even buffers can do it.

[Thecomedian]

Im guessing what has happened is that you either dont or do have a resistor when you should/shouldn't. There's a different parts list for each transistor.

Maybe not. It probably wouldnt work at all if that were so. whenever I have an issue of line noise it usually is a wrongly pinned transistor or a backwards wired jack. In both cases it is very possible to still get audible instrument noise from the circuit.

Another issue is using buffering when you don't really need it. I built a buffer circuit, and it was as if I'd turned up the gain on all the "background" noise that you don't want to hear... finger slide, string touch, etc, while the actual notes of the instrument stayed relatively the same, if a little more clearly defined (saving those mid-high/highs).

If you can validate your circuit as 100% accurate and working parts, it might be a problem somewhere else in the chain/instrument, which hasn't been audibly apparent until the problem got buffered.

Thomas edison learned 100+ ways how NOT to build a lightbulb. The Voss glass water bottle was drawn over 100 times by a calvin klein artist before the final design was accepted.

Once you find the problem, it can go in your note library and you will always have the solution handy if it occurs again. 

[mantegna]

You're perfectly right, R.G., sorry for not having reported Voltages and not having provided "probing results": I was ready to correct this mistake but today the pedal wouldn't even light up. I started checking why and noticed both the diode and the Si transistor had been "fried". I'll build the whole pedal again, as I suspect some resistors to be different from the declared values on the packaging I received, since all the assembling was made following the instructions provided for a Silicon transistor's version. I have to admit I'd have better checked each part before: now that's really something to learn from, I used to trust Germans! 

Thank you both, R.G. and Thecomedian for your support, you've been extremely kind and useful!

[Thecomedian]

Always a good idea to check each component before putting it in. On the off chance you get a single resistor that is completely shorted out, or any other component like that, it'll save a headache to check.  I also like to do a post-build check on all the resistances in the circuit before first turn on, make sure the values and placement in circuit are proper..

[mantegna]

There's so much to learn from you, Thecomedian, and I feel kinda blessed about it: thank you so much again for your tips! 

[Thecomedian]

No problem. We're all here to learn and help each other. Always make sure it makes sense to you, I havent been doing it that long either, but I picked up some things