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DT25 Tube Bias


kawititnow
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Hey everyone,

 

This is my first time swapping out tubes. I ordered a matched set of EL34's with 24-hour burn in.

 

I put the new tubes in, let it sit in standby for a few minutes, took it off of standby. I measured the bias on V2 and adjusted to 25 mV, I then measured V3 and was reading 35mV. I adjusted it to 25mV and then measured V2 again and it was 15mV.

 

So basically I have a 10mV difference between the 2.

I assume this is not normal. Any way to adjust them independently?

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Hey everyone,

 

This is my first time swapping out tubes. I ordered a matched set of EL34's with 24-hour burn in.

 

I put the new tubes in, let it sit in standby for a few minutes, took it off of standby. I measured the bias on V2 and adjusted to 25 mV, I then measured V3 and was reading 35mV. I adjusted it to 25mV and then measured V2 again and it was 15mV.

 

So basically I have a 10mV difference between the 2.

I assume this is not normal. Any way to adjust them independently?

 

As far as I know there is no way to adjust them independently. I did the same thing you did when I had an issue with sound fading off after 15 minutes of play which culminated into no sound all together. All the fuses checked good so I ordered an ultra matched set of EH's and after making the bias setting had 4mV difference and I thought that was abnormal. I was thinking the tubes should read the same but I suppose they don't most of the time.

 

I'm not sure what the bias was new since I wasn't equipped to check it. I had another problem anyway which Line 6 fixed.

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I hope they are EH brand EL84's. These amps are not forgiving of modifications.

They might come highly recommended for general use, but are they, when it comes

to a DT amp?

 

These are hybrid amps (analog and digital sections), so you can't do tube swaps like we use

to do in the 1960's and 70's, on an all analog tube amp.

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  • 1 month later...

So just for future reference, how do you check the bias voltages on a DT25?

 

Craig

 

 

If and ONLY if you have previous experience and skills working on tube amps you might find this link helpful.  Voltages in there can kill you so be careful.

 

http://line6.com/supportarchivenew/thread/75238/

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