Right channel noise after installing speedball

ChrisP · 2261

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Offline ChrisP

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on: August 07, 2016, 04:49:41 PM
I just finished installing the speedball upgrade but now there is noise in the right channel. Before the upgrade it was dead silent.

Upon turning on the amp, a barely audible hiss comes on the left channel then, after a few seconds, translates and amplifies to the right channel.

These are my measurements for the boards with the manual recommendation in parentheses:
Small circuit board:
OA 95 (60-90)
IA 175 (170-270)
B-AB 0 (0)
IB 176 (170-270)
OB 79 (60-90)

Large circuit board:
OA 111 (75-100)
OB 121 (75-100)
B+ 177 (170-195)
G 0 (0)

OA and OB are pretty high on the large board and are unequal on both boards. Any way to decrease or remove the hiss?

I want to like the speedball but the silent background on stock crack makes it hard.

Thanks,
Chris
« Last Edit: August 07, 2016, 04:53:45 PM by ChrisP »



Offline ChrisP

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Reply #1 on: August 11, 2016, 08:59:14 AM
Update:
I've reflowed terminals and power terminals and used a different outlet but no dice. I've ordered a new 12au7 but while I'm waiting I'm going to poke around the amp with a stick and cheap headphones to see if it's loose soldering.

Listening to it, the hum starts in the left channel quietly then moves to the right channel but gets louder. Eventually the hum dies down to barely audible levels. After a good few minutes, the left channel is dead silent but there is a little hum in the right.

Any help would be a godsend.



Offline Doc B.

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Reply #2 on: August 11, 2016, 09:49:38 AM
First you were talking about hiss. Now you are talking about hum. Has the noise changed? It's probably the case that the higher gain of the speedballed circuit is bringing up the noise floor from where it was before. In that case you will probably just need to roll tubes until you find one that suits your requirements. But if we can establish which kind of noise it is, I might be able to offer more ideas.

Dan "Doc B." Schmalle
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Offline ChrisP

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Reply #3 on: August 11, 2016, 10:23:03 AM
Sorry bout that, noise hasn't changed. The sound is hard to describe, kind of like a vibrating hum mixed with white noise. Is it normal to have an unbalanced noise floor between the left and right channels?



Offline Paul Birkeland

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Reply #4 on: August 26, 2016, 07:56:00 AM
Your idea to poke around with a chopstick is likely a good one.  While installing the Speedball, you may have disturbed a flaky solder joint in the amp that is now causing you problems. 

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man