Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Klots on December 15, 2014, 07:44:36 AM
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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? ???
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Was the buzz there before? Do you have the Speedball?
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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..
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Try moving the braided wire against the chassis plate.
Try taking out the stepped attenuator.
-PB
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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.
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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.
(https://www.head-fi.org/image/id/5973004/width/900/height/900/flags/LL)
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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?
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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.
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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.
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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?
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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.
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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?
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Have you tried putting the stock pot back in?
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Have you tried putting the stock pot back in?
Nope, I dont even know where it is :-[
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desolder the wires from your step attenuator and check its fixed resistance and the variable resistance on vol 0 for both channels.
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I think you might have the grounding jumper issue as described elsewhere in this thread.
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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?
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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.
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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.
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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.
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Before you tear everything apart, remove the tube and measure resistance from the center of the RCA jack, to pins 2 or 7 and from the center RCA to ground, for volume positions 0 and 1...John
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If I was just reading this and seeing "when I change tubes I have the problem" then I would say it's a tube pin to socket interface issue. However we are hearing that the problem started when the caps were changed. It isn't intuitive why that would cause the problem, but that was the last event that happened before the problem occured.
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changed all caps back and now only B4 is 62V and B6 is 84V...all other pins are great, but...still the buzz on 0 vol. AND, I found the problem :) It is my 5998 tube. I so remembered that with 5998 it was quiet, but no it is not. Will the speedball change something in the circuit for this tube or is it gonna still buzz when I install speedball? I am gonna still use the 5998 tube, but I just wont turn to 0 volume. Thanks everyone and :-[ :)
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changed all caps back and now only B4 is 62V and B6 is 84V...all other pins are great, but...still the buzz on 0 vol.
Have you a different input tube to try as I seem to recall having some similar discrepancies in my voltage checks which turned out to be due to the 12au7 input tube. After I swapped it for a different one and the voltages measured within a couple of percent of those in the manual .
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Have you a different input tube to try as I seem to recall having some similar discrepancies in my voltage checks which turned out to be due to the 12au7 input tube. After I swapped it for a different one and the voltages measured within a couple of percent of those in the manual .
Seems I was modifying my post when you answered :)
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Maybe the off voltages from the 12au7 effect the operation of the 5998 resulting in the noise? Just thinking out loud and not really knowing what I'm talking about but hey that's how you find stuff out :-\
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Maybe the off voltages from the 12au7 effect the operation of the 5998 resulting in the noise? Just thinking out loud and not really knowing what I'm talking about but hey that's how you find stuff out :-\
I use E80CC tube. But I tested with 12au7 that came with the crack and same sound. So I test that 0 vol thing again when I install speedball (in January or February).. Yes Jamie I that way you can find stuff out :D