What Bias Setting Sounds Better A Or B ?

[mickeydg5]

As I kind of mentioned before, I kind of play my amplifiers up to half way or a bit lower. It still hits 104-105dB in the room.

Everyone is forgetting about the power tubes themselves. I like cleaner and more powerful. I do not care for early breakup in a power tube.
Some of you are aware of power tube ratings. Well on the scale from 1 to 10 I usually go for the tens. They are cleaner but more powerful and can usually be set at lower idle bias levels if wanted. These tubes are generally more articulate. So when biased hotter at lower level volume settings I feel I get way more as in better presence/chimey highs/solid bass and I know I can hear the difference with as little as 4mA idle variation.

Now if all you want is tube saturation and breakup then go the other route.

 

[Neil S]

This was 7ma and very hard to tell the difference.

 

[mickeydg5]

This was 7ma and very hard to tell the difference.

As I mentioned, two things that matter most are the size of the signal hitting the power stage/volume level and the power tubes themselves.

Your situation makes not much if any difference at all.

 

[Neil S]

And 4ma would be even less.

 

[tschrama]

I think I like A a little better than B and I suspect A to be the high bias en B the lower bias... but... it really doesn't matter much at all... I think I could be very easely fooled between A and B.

 

[mickeydg5]

Your were fooled.

He said B was higher.

 

[charveldan]

My ears detected a 6.899 ma difference.

I have touchy ears ...

 

[mickeydg5]

or

 

[Neil S]

I did an A/B with the ice cream in my ears and you were right, I could not tell the difference.
Although there was a complaint that the volume of ice cream I used made the comparison in valid.

 

[charveldan]

Ben & Jerry #37 Vanilla ...

 

[RickyLee]

Just listened and without looking at comments I went straight to my post.

To my ears i thought I heard some Scorps "Blackout" album tone pumping on A. I think they sound pretty much the same except for that. So my guess is A is hot bias due to the pumping action. Dam, my own post is getting me a bit turned on for some reason . . . .



I should admit that I actually do not hear the pumping or breathing every time. Maybe that is just something else anyway?

But I will keep my answer.

EDIT/ADD: Maybe that pumping/breathing/rising I am referring to actually caused by a low bias due to the lower near cutoff threshold. Our theory experts will let me know on this one.

 

[RickyLee]

OK. Seen your answer. I was expecting a much bigger difference than 7mA when you said hot vs cold. What does 32mA and 39mA translate out to on your amp for % idle?

 

[RickyLee]

I have been going to 60% to 65% proximity if I factor in the cathode current. When I set bias by measuring current across the OT primaries, I just go around 60% or even a touch under, which my Touch Too Much means a couple of mA's lol.

I always try to factor in: Is my mains/wall voltage at the time under load and lower than norm. Like this time of year as it is F ing hot here and I am running my air conditioner. That usually drops my mains from 123VAC-125VAC to 119VAC.

 

[Michael Roe]

Man, this test should have been done on Myth Busters
I will stick with the 35 mA per tube.

Ok, Now on to "Tone Wood".....
I will go first:
YESSSSSSSS IT MAKES A DIFFERENCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Neil S]

I think 39.7 was 70 percent.
The pot maxed out at about 41.

 

[mickeydg5]

Wow, your bias trimmer maxed out at 41mA with those tubes.

Those seem to be some lower output/less mho/weaker tubes. Refer to post #21.

 

[RickyLee]

Wow, your bias trimmer maxed out at 41mA with those tubes.

Those seem to be some lower output/less mho/weaker tubes. Refer to post #21.

So when you use the 10 ratings, does that mean it needs to see a higher negative control grid voltage? Like -50VDC to get 60% idle where softer sets might need -44VDC to get 60% idle?

 

[mickeydg5]

So when you use the 10 ratings, does that mean it needs to see a higher negative control grid voltage? Like -50VDC to get 60% idle where softer sets might need -44VDC to get 60% idle?

No, not exactly. In come cases that does happen.
You can still idle it the same but the higher grade tube should put out differently with greater input signal. More amplitude is more power. Compression/clipping is limiting.

That is why I say listen and do final bias. Several mA here or there does not make much difference in idle bias but if it changes the dynamics then follow your ear.

 

[Dogs of Doom]

A...

 

[Dogs of Doom]

A...

I like A best. Although...

I think it has more to do w/ the overall sound of the doubling sounds better, more full & 3-D. Probably not a good comparison to do a double track/pan effect. But, yeah, A sounds bigger/better...