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Discussion Starter #1
Good day peeps. So I finally got my new tubes in for my Traynor. I wanted to try something different than the sovteks that were all across the board previously so I ordered jj ecc83/12ax7 pre amp and tung sol 6L6 STR power. The manual says to set the bias to 75 mV and the lowest that I could set the voltage was 77. Is this going to be an issue? Will it burn out my tubes prematurely? Will it damage anything in the amp? It does not make the banshee in a blender noise anymore and it sounds good, but I only ran it for about ten minutes because I am not sure about the voltage being a bit higher.
 

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Can't help, but watching with interest. I haven't changed the tubes in mine yet
 

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my understanding with mine (YCS50) was, the bias they 'suggest' is on the colder side...I can't see 2mV being a big deal
 

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Traynor measures the bias across a 2 ohm resistor at the cathodes of the tubes. So doing the math, that translates to 37.5 ma per tube. Your 77mV translates to 38.5ma a very small amount of current. Traynor doesn't list the actual plate (high) voltage for the tubes, but I doubt it is over 450VDC. So even at the higher current you are well under the maximum dissipation of the tube.
You will be fine.
 

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Discussion Starter #5
Ok thanks for the info guys. Another question then. @ezcomes said the bias they suggest is on the colder side. Does this mean that the tubes can handle a higher voltage? What is the result of running a higher voltage when I set my bias? What would happen if there was 85 mV instead of the 77 I currently have?
 

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Does it sound bad? Coldest possible bias you can get without negatively affecting your tone will give you longest life from your tubes.
They have designed it for what they believe is the best compromise between tone and tube life.
Do you run at high power? If not, your dirty sound is coming from the preamp. Most bigger power amps get the dirty sound from the preamp and bias the power section quite cold. 5150 runs a lot colder than that traynor.
 

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Discussion Starter #7
It sounds pretty good from Thursday nights test run. I run it on the 25 watt setting in the studio, with channel 1 (clean) at about 8 out of ten and channel 2 at 8 with gain at about 7. The master volume is just under half.

So from what I am understanding, higher bias will give a richer tone? It makes the tubes “work” harder?
 

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It sounds pretty good from Thursday nights test run. I run it on the 25 watt setting in the studio, with channel 1 (clean) at about 8 out of ten and channel 2 at 8 with gain at about 7. The master volume is just under half.

So from what I am understanding, higher bias will give a richer tone? It makes the tubes “work” harder?
Did you bias at the 25 watt setting? Because I believe their 'power scaling' probably changes the HV of the power tubes, and thus how the tubes bias.

I think you should bias at the full power setting.
 

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So from what I am understanding, higher bias will give a richer tone? It makes the tubes “work” harder?
1) No, it is not a given that hotter bias will give better tone. Sometimes it works out that way though. It depends on how cold it was biased to begin with. Bias is one of the most over-rated factors as a contributor to tone. Many of the classic amps never even had bias adjustments, and the ones that did were often never adjusted. It's kind of like wondering if turning up the idle speed on your car engine will make it go faster.

2) Yes, hotter bias will make the tubes "work" harder to give basically the same tone.

* In both cases above I'm referring to biasing hotter than the factory setting.
 

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Discussion Starter #10
Did you bias at the 25 watt setting? Because I believe their 'power scaling' probably changes the HV of the power tubes, and thus how the tubes bias.

I think you should bias at the full power setting.
I followed Traynors recommended procedure and biased on 90 Watt after I let it warm up.

It's kind of like wondering if turning up the idle speed on your car engine will make it go faster.

2) Yes, hotter bias will make the tubes "work" harder to give basically the same tone.

* In both cases above I'm referring to biasing hotter than the factory setting.
After reading this I went and did some research on how tubes actually interact. It is still clear as mud to me, but at least the mud is a bit thinner and I have the most basic idea what they do. From what I got was the bias voltage setting is the power through the tubes at idle, the same thing that you said in your first point. The bias does not necessarily change tone, but how hot the tubes run when there is no signal going through them.
 

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I tried to set bias today on a newly acquired amp. I don’t think the amp was ever used much and had quite the layer of dust. While wiping with a microfibre towel I am certain that the bias pot got moved.
I did as much technical reading as the old brain could tolerate and set the bias to around 32 ma. The amp was set up with the ability to read each tube individually (cool idea). You can actually see how well the EL 34 tubes are paired, or drifted.
I made the mistake of setting bias on half power, and played for a half hour, quite excited about throwing switches of circuits, chokes vs. resistor, half power vs. full, gain vs. PIMV, etc.
I rechecked bias and realized my mistake. I reset bias at full power to 32-3ma and checked the half power bias. Half power bias was about 4-5 ma higher and gain distortion comes in much earlier. It is still quite a loud amp, irregardless of power setting. Use of an attenuator is a must. The very large power transformer is warm in contrast to the output transformer.
Lots to learn, and maybe a new amp day when I get my act together.
I have never set bias before, and I think I did it right.
 
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