Re: S800 Support Thread
« Reply #760 on: July 10, 2018, 06:01:15 PM »
Hi Peter,

Thanks for your reply. Will try what you suggest and follow-up. Thank you!

BTW, was there a chance not too long ago at a 500 series for this EQ? I thought I saw a post in this thread a few pages back, not sure if it made it to the White Market or if it did and I missed it...

Thanks,
Chris
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR


peterc

Re: S800 Support Thread
« Reply #761 on: July 11, 2018, 03:59:44 AM »
Hi Chris

I did make a 500 series prototype which still sits in my rack, but no more that that unfortunately
If opportunity doesn't knock, build a door.

Re: S800 Support Thread
« Reply #762 on: July 13, 2018, 02:29:29 AM »
Update:

I took out the toroidal, flipped it around in various orientations, outside the chassis, etc. Yet I still have the hum.  :(

Seems to me that the hum is in and around the LMF and HMF, in the lower portions of the sweep (i.e., LMF ~100Hz up to about 1/3 rotation in the range, and similarly for HMF ~1k). Anyone else experience this? Is it the pots? BTW, LF and HF are quiet as a church mouse...

What would be my next step?

Chris
« Last Edit: July 13, 2018, 03:19:40 AM by fazeka »
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

Le Roux

Re: S800 Support Thread
« Reply #763 on: July 15, 2018, 03:42:08 PM »
My build

I had buzz/hum on all channels, which after a few hours of being on, disappeared?

Anyways...
« Last Edit: July 15, 2018, 05:10:58 PM by Le Roux »

Re: S800 Support Thread
« Reply #764 on: July 17, 2018, 03:27:47 PM »
I had buzz/hum on all channels, which after a few hours of being on, disappeared?
What's the reasoning for this? It doesn't seem possible that it can be attributed to anything with the build if it just sat there turned on and the hum just "disappeared" ?!?...

:o

For mine, I have the Small Bear Electronics (Alpha 16mm, solder terminals) pots wired up to the PCBs. When the LMF and HMF freq. sweep pots are kept away from the others, the hum goes down significantly.  :D However, when these are mounted to the front panel (i.e., within the vicinity of the other pots), the hum returns... I even tried shielded cable for these pots (telescoping the braided shield on the pot side of the cable, connected the shield on the other side of the cable to the star ground point) and no help. :( I'm really scratching my head here, it's quite maddening!  >:(

Does the hum having anything to do with these pots being dual-ganged? Or is it attributable to (that part of) the circuit? Capacitive coupling?

Chris
« Last Edit: July 17, 2018, 04:09:35 PM by fazeka »
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

Le Roux

Re: S800 Support Thread
« Reply #765 on: July 17, 2018, 07:11:18 PM »
Seriously, I had a hum/buzz on all boards outside of the case and when I installed it, was still there.

All of a sudden, it was gone!
No idea why!!! As long as it don’t come back!

I used AML parts kit.
It’s a log pot?? Or rev log?
Is small bear matching what’s required?
Only thing that comes to my mind!
I hear ya on frustration
Had a project or two I gave up on cause I can’t spend all day everyday  figuring out why it doesn’t work!
There’s music to be recorded!!

 

Re: S800 Support Thread
« Reply #766 on: July 21, 2018, 06:16:42 PM »
What's the reasoning for this? It doesn't seem possible that it can be attributed to anything with the build if it just sat there turned on and the hum just "disappeared" ?!?...

:o

For mine, I have the Small Bear Electronics (Alpha 16mm, solder terminals) pots wired up to the PCBs. When the LMF and HMF freq. sweep pots are kept away from the others, the hum goes down significantly.  :D However, when these are mounted to the front panel (i.e., within the vicinity of the other pots), the hum returns... I even tried shielded cable for these pots (telescoping the braided shield on the pot side of the cable, connected the shield on the other side of the cable to the star ground point) and no help. :( I'm really scratching my head here, it's quite maddening!  >:(

Does the hum having anything to do with these pots being dual-ganged? Or is it attributable to (that part of) the circuit? Capacitive coupling?

Chris

Maybe if you record the sound and upload it somewhere so we can hear it and maybe someone can tell where it could be coming from. From what I've read, whether the pot is on the board or wired the issue persists and wire and shielded wire didn't make a difference.

Maybe its a grounding issue?? Does anyone know how the inputs and outputs should be wired correctly? I would love to know that because I think I may have done mine wrong. I know the power ground should go to the chassis star ground.

peterc

Re: S800 Support Thread
« Reply #767 on: July 22, 2018, 07:21:21 AM »
HI Chris

This is a bit of a head scratcher.

What I would do next is to eliminate the long wires to the Mid pots. Desolder the wires at the PCB and add in a pair of resistors on the pads to simulate the mid position of the pot.

Is the front panel grounded? Try removing the pots from the front panel to break a possible earth loop.

What are the + and - rails looking like? Any AC or hum on them? Check with a scope for best results.

Peter
If opportunity doesn't knock, build a door.

Re: S800 Support Thread
« Reply #768 on: July 23, 2018, 12:43:49 AM »
Maybe if you record the sound and upload it somewhere so we can hear it and maybe someone can tell where it could be coming from.
I can do that at some point. Peter has since posted something to try, so will give that a go first to see if it resolves...

From what I've read, whether the pot is on the board or wired the issue persists and wire and shielded wire didn't make a difference.
Not quite; the smallbear electronics pots can't be attached directly to board as they have solder lugs (was trying to go for a different panel layout than the stock Colin @ Audio Maintenance/Omeg pots. When the  LMF & HMF frequency sweep pots are wired to the board but kept away from (i.e., not attached to) the panel, hum/buzz is nearly non-existent. When attached to the front panel, in close proximity to the other pots, the hum/buzz is present. When EQ is switched out, there is no hum/buzz regardless if the pots are attached to the front panel or not. Shielded wire did not make a difference here.

Maybe its a grounding issue??
Surely.  ;) But I am wracking my brain trying to resolve...
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

Re: S800 Support Thread
« Reply #769 on: July 23, 2018, 01:12:48 AM »
What I would do next is to eliminate the long wires to the Mid pots. Desolder the wires at the PCB and add in a pair of resistors on the pads to simulate the mid position of the pot.
Thank very much Peter for the suggestions. What I did was remove the LMF and HMF frequency sweep pots and the hum goes away, that's why I think it's isolated to that part of the circuit. I can try the resistors...

Is the front panel grounded? Try removing the pots from the front panel to break a possible earth loop.
Using a VOM and checking front panel for continuity to star ground, I get none.

If I'm understanding you, I think I already did this essentially when I stated above that when the pots are not installed on the panel (i.e., "floating/dangling" on their wired connections to the PCB), there is virtually no hum/buzz... The one thing that is odd is that the other pots don't have this issue and they are mounted on the front panel.

What are the + and - rails looking like? Any AC or hum on them? Check with a scope for best results.
I will check and revert back.

Ultimately, what I am thinking is something in the wiring between one gang and the other on these pots is what I believe to be causing the hum. I have each of these gangs wired to the PCB as three wires, twisted. When these two groups of three wires (essentially, representing each gang) are pushed apart (I didn't twist the 3 + 3, it's getting kinda bulky/tight in there with these short lengths of wire), the hum drops down a lot. When these two groups of three wires are pushed close together, the hum goes up and is consistent with the aforementioned hum problem.

Again, is there anything specific in the circuit design that is causing this to happen? Or is it with the pots? I mean, most everyone else is using the Colin @ Audio Maintenance/Omeg pots that attach to the PCB directly so maybe explains why no one else has this hum? But I do remember a few wiring pots to the PCB and they never complained of hum... So, thinking either the issue is with these (cheap) Alpha pots or with the way I have them wired to the PCB causing some kind of coupling between the gang wiring... ??
« Last Edit: July 23, 2018, 01:16:08 AM by fazeka »
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR


Re: S800 Support Thread
« Reply #770 on: July 25, 2018, 02:17:24 PM »
I had the same issue a few months back, as long as the pots weren't close together there was not an issue. I am using the omega pots from AML Kit. I thought maybe it was the pots too but before buying new pots I thought I would try different wiring. Maybe the wire i was using, so I tried shielded cable. That did not help. I also add a second mnat power board (still 1 toroid) so that 4 EQ boards go to one board and the other 4 go to another board. That didn't help.

I thought maybe my grounding was wrong (I can't remember how I had it) but I changed it to go from the mnat power to the chassis. that didn't help. Input and outputs ground goes to a terminal block to the chassis. That didn't help either.

What stopped it for a while was was when I mounted it to the front panel, it magically went away for a while. I think its back now on one channel, I might be bugging out but I thought I heard it again yesterday after reading this thread again.

I am double checking now.

Re: S800 Support Thread
« Reply #771 on: July 28, 2018, 02:00:54 PM »
Ok so its definitely back and its in the LMF and HMF on channel 3 as it is sweepable on those pots. funny enough it only happens in bypass. When the eq is in no noise. Really odd.

Can anyone help with this?

Re: S800 Support Thread
« Reply #772 on: July 28, 2018, 05:24:58 PM »
Hi,

I don't suspect the problem being these pots... I think it is something about the circuit. Though, I am not very savvy in theory to explain. My best guess the noise (hum/buzz) is due to some kind of coupling...

If I could mount these LMF and HMF pots in another plane relative to the PCB and/or the other potentiometers, I'd be done as there is no (or very greatly diminished) noise (hum/buzz) upon doing so, as I stated earlier. Of course, this is not practical as it would mean having these controls accessible via the top or sides of the unit which, needless to say, complicates their usage in a rack-mountable device! ;D

It is odd that you are encountering noise/hum/buzz with these when the EQ is switched out. I would suspect the issue would only arise with the EQ engaged... I don't mean to offend but are you certain the in/out switch is wired correctly?

Cheers!
Chris
"Kind of like going into Safeway at 4 in the morning and chugging a beer in the produce section; been there, done that." - CJ

"We're not making an atomic bomb, just cooking a few electrons." - PRR

Re: S800 Support Thread
« Reply #773 on: July 31, 2018, 02:11:30 PM »
Hi,

I don't suspect the problem being these pots... I think it is something about the circuit. Though, I am not very savvy in theory to explain. My best guess the noise (hum/buzz) is due to some kind of coupling...

If I could mount these LMF and HMF pots in another plane relative to the PCB and/or the other potentiometers, I'd be done as there is no (or very greatly diminished) noise (hum/buzz) upon doing so, as I stated earlier. Of course, this is not practical as it would mean having these controls accessible via the top or sides of the unit which, needless to say, complicates their usage in a rack-mountable device! ;D

It is odd that you are encountering noise/hum/buzz with these when the EQ is switched out. I would suspect the issue would only arise with the EQ engaged... I don't mean to offend but are you certain the in/out switch is wired correctly?

Cheers!
Chris

No offense taken, 100% with you that this could be user error from my end as I'm not an expert builder (I do things well but not an expert )  but the bypass is definitely wired correctly. when it is engaged I can eq any signal that goes to that channel. a little goes a long way with this thing.  I'm going to look at the diagram again and see if I can figure out what components are dedicated to the LMF and HMF.


On a side note  - Does anyone have a mouser bom they can share with me? I have a few spare boards that I am thinking of building to test and see if I get the same issue. maybe even replace the ones I have issues with.

JW

Re: S800 Support Thread New
« Reply #774 on: September 16, 2018, 02:59:48 PM »
Question 1. (edit: never mind)

Question 2. If wiring up multiple boards, does each board's signal ground need to make a homerun back to the power supply ground, or can we daisy chain them together and then to the power supply ground?
« Last Edit: September 16, 2018, 06:07:42 PM by JW »


 

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