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Dynaco mk3 clone hum issue
Dynaco mk3 clone hum issue
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Old 13th January 2013, 01:58 PM   #1
gabdx is offline gabdx  Canada
diyAudio Member
Join Date: Jan 2008
Default Dynaco mk3 clone hum issue

I just finished one of the mk3 clone and let me say the sound is exactly like I wanted. The VTA-octal is a must have.

Now I have unresolved grounding issues... (measured 22mv AC at output and 20-22hertz dominant frequency)

Some information on my build:
1. I didn't put the 0.002uf cap with the center tap of the heaters.
2. I grounded the output tubes to the capacitor bank
3. the case is wood and there is no earth attached from the power outlet to the capacitor bank ground.
4. there is a separate transformer for the bias on the VTA octal, one side of the secondary is connected to the bias and the other to the capacitor bank ground.

What I will do next:
The next step was to disconnect the ground from the speaker binding post and attach it directly to the capacitor bank (-) instead of the VTA board.

Any positive input is appreciated from people who knows tricks and amplifiers. Thanks!

(also posted in the dynaco forum)
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