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Otl tube amp without volume pot, possible?

post #1 of 7
Thread Starter 
Hi, I have a diy tube amp that I didnt build myself. I will attach a picture.

Problem is that the channel balance is uneven at low to medium volume and only at max is it okay. So I bought an external volume control that works great.

Still I fear its not perfect. The left side is perhaps a tiny bit more "full".
Therefore I am considering removing the pot completely and simply use the external volume controller. Is this possible and is it difficult? Could it be something else and not the pot?

Thanks in advance! I appreciate all the help I can get.

-Rune
post #2 of 7
Thread Starter 
post #3 of 7

Replacing the pot might be an easier option.  To remove it set the volume level you want, then measure the pot to find the resistance from the input to the output and ground, then replace the pot with suitable resistors = permanent volume level.

post #4 of 7
Thread Starter 
Thanks for your quick answer. I would have thought that I didnt need resistors when I have an external volume control. Or do resistors / volume pots serve other purposes than limiting the volume? I apologice for my ignorance smily_headphones1.gif
post #5 of 7

No not really, however i wouldn't be surprised if the amp starts to clip or distort the signal at full volume, i was just playing it safe by adding some attenuation to the input.

 

If you do wire it that way just remember never to plug/unplug audio inputs with speakers or headphones connected as those tiny bumps will be amplified into very loud thumps.  Personally i wouldn't be comfortable with it running that way, i would fit a stepped attenuator instead of a volume pot.

 

Thinking about your original issue, you could try measuring the resistance of the pot on both channels to see if it is causing your imbalance issue.

post #6 of 7
Thread Starter 

I get your point - thank you! You imply that if I choose to install resistors they should be similar to that of the old volume control? Can it be beneficial to choose a resistor that goes well with a specific headphone (HD600) - is that a thing??

post #7 of 7

Please study high voltage electronics safety before beginning work on this amp. 

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