Hagen bias help please

T

tonesfoyobones

Well-known member
Happy first time owner of a Diezel Hagen. Mine is an earlier version with EL34's. I bought it from the original owner and he said the power tunes are original. Even though he had another amp that he played more I think it's time for a power tube upgrade.

I've read and seen images of the directions printed on the inside of the amp. I have biased several amps with no issues using a EuroTubes ET “Pro One” Bias Probe. http://www.eurotubes.com/store/pc/bias%20probes.htm

Here is my question:
-Can I follow and use the directions from the EuroTubes site to bias the Hagen or must I use the method mentioned by Diezel on the inside of the amp?
-It says that I need 70mA per pair. I am assuming each tube should be at the very least rated @ 35mA each. Correct?

Thanks in advance for your help.
 
tonesfoyobones":2wswisxg said:
Here is my question:
1-Can I follow and use the directions from the EuroTubes site to bias the Hagen or must I use the method mentioned by Diezel on the inside of the amp?
2-It says that I need 70mA per pair. I am assuming each tube should be at the very least rated @ 35mA each. Correct?

Thanks in advance for your help.
Click to expand...
1 you can follow ET's instructions
2 33-35mA/tube, yes.
 
Awesome! Thank you for replying.

I do have a brand new matched quad of KT77's but was afraid that I could not use them since they are rated @ 34mA. If you are saying that I am safe with 33-35mA then I will give them a try rather than buy another set with a slightly higher rating.

*** When ordering new tubes is it better to have them closer to the + side of 70mA as opposed to say 80mA for a matched pair? Is there a mA limit that I should stay under? If gotten tubes with 43mA ratings in the past for other amps. ***

Again thank you for the reply :thumbsup:
 
I'm a little confused to what you are getting at. I know that there is a variation among tubes of the same brand where some will be hotter than others at the same bias. What my understanding is, is that is really only critical if you have an amp with a fixed bias like a recto and 5150 for example. That is why Mesa has the color code thing going on. My understanding is with an amp that has an adjustable bias, it doesn't really matter, just as long as the tubes are matched to one another. Meaning, your dealer gives you a set that all run around the same bias current with one another to within the same brand to make a matched set. Then, you can change the actual bias with the amp to dial in the 35mv bias rating per tube. So if your dealer gave you a matched quad that runs a little cold, you'd have to turn your bias up a little further to achieve 35mv. Opposite effect if you get a set a little on the hot side.
 
RJF":6fqyd7sx said:
I'm a little confused to what you are getting at. I know that there is a variation among tubes of the same brand where some will be hotter than others at the same bias. What my understanding is, is that is really only critical if you have an amp with a fixed bias like a recto and 5150 for example. That is why Mesa has the color code thing going on. My understanding is with an amp that has an adjustable bias, it doesn't really matter, just as long as the tubes are matched to one another. Meaning, your dealer gives you a set that all run around the same bias current with one another to within the same brand to make a matched set. Then, you can change the actual bias with the amp to dial in the 35mv bias rating per tube. So if your dealer gave you a matched quad that runs a little cold, you'd have to turn your bias up a little further to achieve 35mv. Opposite effect if you get a set a little on the hot side.
Click to expand...

Yes that is to my understanding as well. I was worried that the bias sweep had a small window like some of my Engl's did. From what I gathered there is plenty of sweep on the Hagen trim pot.

Here is another question:
- I am assuming that the tube pairing is 1&4, 2&3 based upon the fuses. Is this correct?

Thanks for helping me out!
 
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