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Old 31st May 2013, 02:40 AM   #1
scrimpu is offline scrimpu  United States
diyAudio Member
Join Date: Jan 2012
Location: Grand Rapids, Mi
Default AC30 problem

I have this homebuilt AC30ish amp.Its 2 channels, 1 is EF86 and the other is 12ax7, Channel 1 is fine but channel 2 has a high pitched hissing sound only when channel 1 volume is at 0, turning it up makes it stop. It also sounds like vol 1 is acting like a tone control for channel 2 if that makes any sense. Vol 1 at 0 makes channel 2 very trebley, turning it up makes the hiss stop and changes the tone of channel 2 and kinda flattens it out. Any ideas on where to look before I tear it all down and rebuild?
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Old 31st May 2013, 06:53 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
What if you tear it down, rebuild, and it does the same thing? Troubleshooting is about finding what is wrong and fixing that. Do you have a scope? You might have a channel oscillating at RF. That often manifests itself as a hum or hiss and thin audio. And correcting that might be more about lead dress and grounding than build errors or bad parts.
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Old 31st May 2013, 02:36 PM   #3
scrimpu is offline scrimpu  United States
diyAudio Member
Join Date: Jan 2012
Location: Grand Rapids, Mi
I have rearranged the grounding a few times and chopsticks reveal nothing. Its all point to point and I don't care for the layout so I am rebuilding this thing.
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