Author Topic: Sometime circuits squeal, sometime not  (Read 561 times)

wstimson

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Re: Sometime circuits squeal, sometime not
« Reply #15 on: September 12, 2019, 01:51:01 PM »
Have you tested this phenomenon someplace other than your home?

I ask because I experienced something similar. Sometimes I would get horrible power supply buzz, sometimes it would be fine. I discovered my apartment has such horrible grounding that any time any of the air conditioning units in my "stack" (my room and the two above me) were running, I get power supply noise. If they're off, its fine.

Well, as fine as I ever get, there is so much EMF noise around here that I can barely use wifi 2ft from my router and my wireless headphones go buggy walking across a room....

Given that I live in Arizona, it means I prefer battery power 10.5 months of the year  ;D

Yeah, I live in Phoenix and I can't tell you how many times I've tested a circuit and gotten a TON of weird noise and garbage only to realize I left the soldering iron or the fan turned on.  Switch those off and everything is silent.  Sometimes there's just noisy power, especially if your pedal includes a charge pump.

JackSkellington

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Re: Sometime circuits squeal, sometime not
« Reply #16 on: September 13, 2019, 03:00:57 AM »
I'm beginning to doubt about everything: PSU, my home, my capacitors...

Actually, I told yet but, when I built the circuits of Woolly Mammoth and the Pharaoh Fuzz those was initialli ok, then the Woolly squealed suddenly, then I thought I fixed it with a 47R resistor in line to the 9v, but I tried to jumper it to see the difference and that was ok! So I left the resistor out, but later, one or two days later, it squealed again, and no resistors, diodes or bigger filter caps fixed that.
At the same time Pharaoh Fuzz circuit, that was ok, started to squeal, but a 47R fixed it.
Another thing: after I rewired a Washburn guitar of a friends, this Washburn hums, while my guitars are ok. So my friend brought it from a professional technic, and it was noiseless.

I have to try to test my circuit in another room, but I'm not so optimistic.

But... if I use a resistor in line (I see the original schematic of the SHO released by Zvex with a 100R), a 47uF cap across the ground is already there, can't we be really really sure that is impossible to get this whine? This whine shouldn't be! (Of course if we have a good PSU as I assume is my Boss).

Update: Do you know when people says "it seems to be in the Twilight Zone"? I built in these days a Box Of Rock (three sho in cascade + another one indipendent in the end of the circuit.) and I tested it today. The distortion side works fine, and the SHO stand alone works fine without any whine/squeal. I tried immediately my SHO board, but it squeals. The only schematic difference between the two SHO is a 1N5817 + 82R in line to the 9v and a 100uF instead of a 47uF across the ground. But I did some test with diode and resistor, even in series, without success.
It could be the layout? :o
« Last Edit: September 13, 2019, 04:20:28 AM by JackSkellington »
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alanp

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Re: Sometime circuits squeal, sometime not
« Reply #17 on: September 13, 2019, 10:24:10 AM »
Jack, visit your friend from a decade ago in another town, buy him a beer if you have to, and test your exact setup in his town a town over.
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mjg

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Re: Sometime circuits squeal, sometime not
« Reply #18 on: September 13, 2019, 05:07:02 PM »
After reading this thread, I decided to try a different power supply for the build that has been kicking my butt lately.  It had a terrible drone like hum whenever I connected half the prototype to the other.

Sure enough, new power supply, everything is working fine, no noise.  There you go. 

So it's certainly something to keep in mind when troubleshooting. 

JackSkellington

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Re: Sometime circuits squeal, sometime not
« Reply #19 on: September 14, 2019, 03:48:29 AM »
I don't know about the PSU, having another one is not a bad idea overall, but I'm not sure the main problem is the PSU, the SHO on the Box of Rock board work fine, replicate the power filter doesn't work. I have to say tha my SHO board have a mod, I took off the 100k to the ground and add a Volume output. But the whine doesn't seems depend from the volume output. And it change the pitch acting on the gain pot. Someone got the same issue, reading the Guitar FX tagboard page of the SHO: (But it was a cap problem.)
http://tagboardeffects.blogspot.com/2013/02/zvex-super-hard-on-compact-layout.html

I didn't find any layout that is an exact version of the one I chosen, even if sometime is enough change the value of a pair of resistor and the kind of the diode.  But I would like to try with another one small layout.
« Last Edit: September 14, 2019, 03:51:31 AM by JackSkellington »
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