Issue when both EL84 tubes are inserted [Solved]

a 3W single ended EL84 amp for home, work & school

Issue when both EL84 tubes are inserted [Solved]

Postby dsound » Thu Aug 22, 2013 9:22 am

I finished piecing the amp together and it powers on! (lol) The issue occurs when I have both EL84 tubes inserted, when both are inserted, there is a high-pitched hum that is audible without any headphones/speakers plugged in. When I insert Headphones, the high-pitched-hum (from both channels) plays through the headphones and is very loud.

The strange part is this high-pitched hum completely disappears when either one of the EL84 tubes is removed. Music plays fine, no issues

I've checked all my solder-points and they seem good but there's obviously something that I'm missing. Thanks for any help you can offer!
Last edited by dsound on Fri Aug 23, 2013 5:49 pm, edited 1 time in total.
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Re: Issue when both EL84 tubes are inserted

Postby Shannon Parks » Thu Aug 22, 2013 10:57 am

Email me some big internal pix, or post them. See if it gets stable with J8 removed (the feedback). If stable, then take voltages and post those, too.

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Re: Issue when both EL84 tubes are inserted

Postby dsound » Thu Aug 22, 2013 2:05 pm

separks wrote:Email me some big internal pix, or post them. See if it gets stable with J8 removed (the feedback). If stable, then take voltages and post those, too.

Shannon


Thanks for the advice!
I will take voltages + pics tonight. I was able to quickly unplug J8 though and it seemed to stabilize the amp.
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Re: Issue when both EL84 tubes are inserted

Postby dsound » Fri Aug 23, 2013 10:56 am

Problem solved! Turns out it was an issue with the wiring to the speaker-taps. Beautiful music playing through both channels now. Thanks for making such a great product!
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Re: Issue when both EL84 tubes are inserted

Postby Shannon Parks » Sun Aug 25, 2013 5:08 am

dsound wrote:Problem solved! Turns out it was an issue with the wiring to the speaker-taps. Beautiful music playing through both channels now. Thanks for making such a great product!


Excellent!

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