Loud buzz on 0 volume [solved]

[Klots]

Hello! I installed 100uf film output caps to my crack and bypass caps to them. And also a bypass cap to last power supply cap. I have valab 23 step attenuator installed. I put my volume to 0 when I first plugged it in after all this stuff and there is a loud buzz, and if I turn volume up  only one step, it is quiet. It is only buzzing on zero volume. Did I do something wrong?  ???

 

[Paul Birkeland]

Was the buzz there before?  Do you have the Speedball? 

 

[Klots]

Was the buzz there before?  Do you have the Speedball?

No there was no buzz before the caps upgrade. I dont have speedball yet (hope it arrives in January). I removed the last power supply bypass cap and it didnt change anything. Then I removed the K72P6 bypass caps for 100uf output caps and still the same buzz. I installed these bypass caps back and nothing changed. So if I turn up the volume just one step there is no hum or buzz etc. And the sound is perfect.

I add a picture too, maybe you can spot something..

 

[Paul Birkeland]

Try moving the braided wire against the chassis plate.

Try taking out the stepped attenuator.

-PB

 

[Klots]

Try moving the braided wire against the chassis plate.

Try taking out the stepped attenuator.

-PB

braided cable is not long enough for that. How removing attenuator helps? I took a wooden stick and only thing that changed the buzz was when I moved the braided cable with it (but it did not go away). Every other wire/component was quiet.

 

[JamieMcC]

Have you put a small jumper wire between the two ground connections to join them all together? The two ground holes need to be connected.

 

[Klots]

Have you put a small jumper wire between the two ground connections to join them all together? They need to be connected.

Yes. I have used the pot almost a year now and everything has worked perfectly. I dont know what went wrong with caps installation 

I will put electrolytic caps back tomorrow, just for test.

There is no difference for connecting film caps? I mean polarity..or should I try to reverse one film cap wires?

 

[serpent68]

I have the exact same problem - loud buzz at startup that disappears with the volume turned up 1 notch.  It started when I changed my input tube to E80CC (I have the speedball).  The buzzing sound is present every time the volume is at 0, otherwise the sound is perfect.

I use the Valab stepped attenuator too.  Somehow I suspect its related to the Valab, but I have not done anything to verify that.  I'm back using 12au7 input tube for now. No such problem with the 12au7.

 

[Doc B]

Yeah, it can get difficult for us to help troubleshoot a kit when the parts used are different than what we supply. It demonstrates some of what is involved in the process of designing and prototyping a new kit.

 

[Klots]

I have the exact same problem - loud buzz at startup that disappears with the volume turned up 1 notch.  It started when I changed my input tube to E80CC (I have the speedball).  The buzzing sound is present every time the volume is at 0, otherwise the sound is perfect.

I use the Valab stepped attenuator too.  Somehow I suspect its related to the Valab, but I have not done anything to verify that.  I'm back using 12au7 input tube for now. No such problem with the 12au7.

Yesterday I got my E80CC tube also, and my crack produces the same buzz with E80CC and 12AU7. Today I will measure resistance and voltages and post them here. Maybe something comes out of them.

You also have caps upgraded or just buzzing with E80CC?

 

[Grainger49]

I don't know if this has been mentioned or if I can keep my mind on track to finish this thought....

Noise at zero volume setting makes me think of a grounding problem at the volume control ground lug.  JUst looking at the finished picture on page 36 of the manual I see one black wire coming from the input RCA jacks.  I see one black wire going to the headphone jack, and from there it appears to get grounded at terminal 12 back at the power supply's final capacitor.

Give those terminals some heat and a tiny bit of solder. 

If this has been mentioned and ruled out, ignore this.

 

[Klots]

I don't know if this has been mentioned or if I can keep my mind on track to finish this thought....

Noise at zero volume setting makes me think of a grounding problem at the volume control ground lug.  JUst looking at the finished picture on page 36 of the manual I see one black wire coming from the input RCA jacks.  I see one black wire going to the headphone jack, and from there it appears to get grounded at terminal 12 back at the power supply's final capacitor.

Give those terminals some heat and a tiny bit of solder. 

If this has been mentioned and ruled out, ignore this.

Will check these out! I did your ground path tour too, all were fine.

Then I did the resistance check also, and everything was as stated in the manual.

And now the voltages...there were problems there with five pins.

My input tube: E80CC
My output tube: 5998

I did all measurements on volume 0 and behind "/" is the value when I turned the volume only 1 step.

T9: 55V/105V

A6: 55V/100V

B1:    40V / 101V
B4: 430V / 95V
B6 : 61V / 105V


So if I am not using vol 0 it seems safe to use, because every voltage is where it should be. Correct?

 

[Codeine]

Have you tried putting the stock pot back in?

 

[Klots]

Have you tried putting the stock pot back in?

Nope, I dont even know where it is  :-[

 

[Codeine]

desolder the wires from your step attenuator and check its fixed resistance and the variable resistance on vol 0 for both channels.

 

[Paul Birkeland]

I think you might have the grounding jumper issue as described elsewhere in this thread.

 

[Klots]

I think you might have the grounding jumper issue as described elsewhere in this thread.

Gr
You mean the jumper on the pot? Why is this jumper only an issue when vol is 0? Shouldn't the Graignger49s ground path testing (sticky thread) reveal it?

 

[Doc B]

You need to return the circuit to the state it was in before the problem started. See if the problem is gone. Then repeat the change you made. If the problem comes back you know that there is some issue with the new part.

 

[Klots]

You need to return the circuit to the state it was in before the problem started. See if the problem is gone. Then repeat the change you made. If the problem comes back you know that there is some issue with the new part.

Ok, then it means I just have to install electrolytic caps again..will test that and everything else today.

 

[serpent68]

Yesterday I got my E80CC tube also, and my crack produces the same buzz with E80CC and 12AU7. Today I will measure resistance and voltages and post them here. Maybe something comes out of them.

You also have caps upgraded or just buzzing with E80CC?

I have Mundorf 100uF film caps fitted together with Speedball from Day 1.  I never have problem when using 12AU7 input tubes.  But when I switch to E80CC or 12BH7, the loud buzzing sound at 0 volume is always there.  Strange to me is that the buzz sound completely disappears when I move away from position 0. There is absolutely no noise, and the sound is very good.