Noise Reduction in DIY Builds...

[cloudscapes]

- Star grounding on seperate components.

- Ground fills on the second layer of the PCB. With cuts in the fill to "split" noisy parts of the circuit (like clock signals, power, digital, etc) with clean. The "cuts" can be linked through a few traces.

[Elijah-Baley]

[...]
they key help was Elijah-Baley's post, I just did what he suggested, and .. ta-taam.. silence...

__________________________________

my case:
I had just built Jack Orman's booster (AMZ Mosfet Booster), link here: http://www.muzique.com/schem/mosfet.htm, but y'all know it, better than me

I had built it, and loved it...
BUT then I tried it with my brand new XX-cheap wall wart...

and there was this whining... at the pitch of B on the high E string, B4, so to speak...
and it was really frustrating...
cause, you know...

[...]

what I did then:
the same...
100 ohms, ( 100R, just for the searches' sake) and then a 100uF electrolytic...
I didn't even cut the legs of either of them to normal size, cause I really thought of it as a "give this one a goo, too" experiment..

and the whining was gone... totally... at full boost, too...
so, from now, I'll put this small set of whine-elimination before any circuit

thanks a lot to you all & special thanks to you, Elijah-Baley

I'm glad you solved your problem!
Ironically, I built a SHO circuit board (with a volume pot) and I got a whine when I plug the PSU. It doesn't matter if I put in line to the 9v a 47R or a 100R or a diode, or both. I added a 100nF film across the ground, but the whine is stille there. The last thing I should do is to replace the 47uF with a 100uF, then I guess have to change vero layout. Because the weird thing is that I built even a Box of Rock, that is three SHO toghether, plus another one. It works fine, even the last sho section stand alone works fine.

[MrStab]

more crap:

• if you can, avoid attenuating then re-amplifying your signal like the plague. like the plague took ebola out to dinner, got married and had kids.


• avoid using stupid-high-value or carbon-comp resistors for your input bias.


• 100R/100u power filter gives you a low-pass at 15Hz. if you don't like the voltage drop from such a high resistor, and have the space, 47R and 220uF will also give you 15Hz.


• avoid active filters with extremely-narrow Q-factors.


• op-amps have better power supply rejection than discrete transistors.


• if you can afford to kill anything above 5KHz or so, do it. bypass gain stages with small caps.
• For your high-impedance input stage, TLC227* is a fairly-cheap CMOS-input op-amp with 8nV/Hz noise rating. Bear in mind its maximum recommended voltage of +/-7.5V (ie. no 18V supplies without a voltage drop). For all low-impedance parts of the circuit, you can get away with a cheaper BJT op-amp like an NE5532 or something, which have similar noise ratings.
• Don't use the CA3080 for OTA projects - use the LM13700.

sorry if any of that has already been mentioned. here's a related question i've often pondered about:
does op-amp noise rating have any bearing on noise injected into a buffered Vref?

[Elijah-Baley]

Thanks MrStab!

About my SHO, I tried yesterday to replace the 47uF with a 100uF, and it tamed the whine, so I can finish my first 1590A pedal.
I didn't include any resistors in line. I'm wondering if I should use a 47R or 100R anyway.

[MrStab]

what kinda PSU are you using, Elijah? i'm unsure if that's the main issue, as you said your BSIAB works fine, though increasing the cap did tame the whine so... maybe.

you're not using this layout by any chance, are you? the input and output are right next to each other. as others mentioned, that's a no-no, and i would honestly expect that to oscillate.
https://hotbottles.files.wordpress.com/2012/03/zvex-sho-updated-from-zach-schematic-762360.png

[Elijah-Baley]

(It was a Box of Rock, not a BSIAB)
My PSU is an old Boss. I think it's ok, I don't have problem, usually. I built more than 40 pedals, I got this problem with some of the last circuits, but I always solved, escept in one case.
I used this layout: http://tagboardeffects.blogspot.com/2013/02/zvex-super-hard-on-compact-layout.html.

Now, as I mentioned, I have to solve this problem with a circuit out of box of a Woolly Mammoth, that was ok initailly, later it starts to squeal, then it stopped, than it start to squeal again. No matter if I use resistors or diode in line ot the 9v, or bigger cap across the ground. I have to work on it again.

[amptramp]

I have a problem quite often with ground loops from the safety ground of the power supply that feeds the effects and the safety ground of the amplifier.  Quite often there are capacitors to this ground from both the power supply and the amplifier and the ground is taken to different points on the safety ground bus, meaning any current from the capacitors will flow through the impedance of the ground and modulate the other ground.  The idea here may be to remove the capacitance to the safety ground or to provide an isolation transformer for the effects so a safety ground id not needed.  Sometimes batteries are the best answer.

[MrStab]

Once the input signal goes through the 100nF input cap on that layout, Elijah, it's on the trace right next to the output. i wouldn't feel comfortable with that.

i meant your post that said "I never had too much problem of noise or hum, even with high gain pedal: BSIAB...". I just thought i'd refer to it as BSIAB is a notorious troublemaker!

sorry, i don't understand quite what you mean in your last post - i'm a bit of an idiot. do you mean a Wooly Mammoth clone is having squealing problems?

[Elijah-Baley]

Don't worry MrStab.
About the layout I used for the SHO, I got what you mean, but I solved the problem, fortunately.
Perhaps I found always goo dlayout, but casually the last I used it was a bit tricky, it wasn't the schematic, the components valus, but right the layout. I don't know.

My last unsolved squealing problem is the Woolly Mammoth, this layout: https://www.sabrotone.com/?attachment_id=1026

I worked on it without problem changing some parts with sockets, and one day it starts to squeal, then it stopped, and then never stopped to squeal. In a few of days. I tried bigger cap, I guess 330uF, in the power root. As well diodes and resistors.
I don't touch it for about two months.
I should to try again. But that was really tricky. I thought to build it again, or at least try it on the breadboard, at least.

[amptramp]

The problem with transistorized designs is the designer has to accommodate the wide variation in hfe of transistors and if germanium is involved, the variation in leakage currents as well.  You can build a design and test it and have it seemingly be stable and doing what you want but a change in temperature may change the gain sufficiently to make the circuit oscillate.  Add in biasing variations due to part tolerances and you have something that often works but you have to do a lot of calculations to prove it's always going to work.

This is one reason I prefer op amp designs to transistorized designs - if one works, a complete production run will work and all units will behave exactly the same.