What Bias Setting Sounds Better A Or B ?

[Neil S]

Can you tell the difference between cool or hot bias, does it really matter?

Have a listen and tell me what track sounds better A or B
All dials on both tracks set to noon accept for Loudness 1 set to 6 and Loudness 2 set to 0 on a 1959 SLP.
Nothing was touched as I had the head off the cabs when I did the bias adjustments.
Both A and B tracks are stereo double tracked, The guitar tone pot was not touched and volume was full for all tracks..
I think you will need to get your golden ears out of that wooden box under the bed for this one

 

[ampmadscientist]

Can you tell the difference between cool or hot bias, does it really matter?

Have a listen and tell me what track sounds better A or B
All dials on both tracks set to noon accept for Loudness 1 set to 6 and Loudness 2 set to 0 on a 1959 SLP.
Nothing was touched as I had the head off the cabs when I did the bias adjustments.
Both A and B tracks are stereo double tracked, The guitar tone pot was not touched and volume was full for all tracks..
I think you will need to get your golden ears out of that wooden box under the bed for this one

Hot bias always sounds better because it increases the sensitivity. But there is a limit to how hot it will go.

The plexi is only going to reach the threshold when it overdrives the power tubes, the volume must be about 7 or higher.

Playing the amp on lower volume (no output tube distortion) is not really a fair demonstration.

does it really matter?

Yes it does matter a lot.

 

[Neil S]

Plexi is only output tube distortion they are distorting now thats why you can hear distortion. There is a fairly big bias difference between the tracks which do you think is the hot one?

 

[El Gringo]

I will vote for A

 

[spacerocker]

I changed my mind several times during the clip - which leads me to conclude that I can't really tell the difference! (even listening though hi-fi speakers...)

I would be interested to hear how different the bias was?

Your transformer clip showed a much bigger difference in sound, which implies it must have been due to the transformers not the bias differences.....

 

[BowerR64]

I couldnt hear a difference but it sounded great. Nice tone

Can you hear a difference, or a feel?

 

[mickeydg5]

The Plexi is reaching for a maximum volume when set at 6.

I run my amplifier's bias towards the hot side --- because I use them at lower volumes. I find it makes more of a difference in that case.
With signal, a high average or more constant high amplitude keeps the operating bias at a higher level. So if you like to play loud then it makes sense to have the idle bias point a bit lower.

Oh but wait, people do not get the bias point meaning. Some do not believe that signal level has anything to do with bias and operation. Oh well.

Anyway I believe ??? was the higher bias setting, not that there was much difference.
I retracted my first answer because I gave more listen. I actually heard more difference in the fretting/playing than in the amplifier/bias. I do not know, maybe I am just crazy.

 

[BowerR64]

You never mentioned that before

 

[marshallmellowed]

I would say that "A" is the hotter bias and "B" is the colder bias. I preferred "B" in the clips (more clarity).

 

[marshallmellowed]

Hot bias always sounds better

Have to disagree with you on that one, it depends on the amp and music style.

 

[mickeydg5]

You never mentioned that before

That I may be crazy.???

 

[sellen]

I prefer B
Was it a bit More "omph" in the Palm muting

 

[Neil S]

Thanks for all your comments.
Both tracks are double tracked so that should smooth out differences in playing a little. The difference in bias is larger than it was in the tranny comparison.

 

[Neil S]

I really don't hear or feel it gets any louder after around 4 but our ears are not good tools for measuring this. Would be interesting to see a volume comparison done one day.

 

[Derek S]

I won't attempt to match A or B with the colder/hot bias settings because in this full mix it was difficult to hear a drastic difference...I'll just say of the two, I liked 'B' better...it's not necessarily because it is (or isn't) more articulate, I just love hearing pick attack, even if it's only chords, just something my ears always tend to notice first, and I liked the pick attack in 'B' all the way through more than A. I'm voting B as the better tone, nevermind what the bias was lol! Nice clip and a fun challenge, thanks for sharing.

 

[Neil S]

We have 7mv difference between A and B tracks. To me I can't hear any great difference, which you think there would be
if upper and lower recommended bias settings had a great effect on tone. I don't believe there is anything wrong with being precise but I think it is not really necessary to worry about great differences in sound quality when it comes to biasing like I use to. Unless of course you amp is biased too far
outside of the recommended settings.

 

[Neil S]

Time to tell everyone what track was what
A was 32ma
B was 39ma

Most liked the hotter bias but the difference is so small that if you biased it a couple of ma either side of the middle of the recommended range you would not gain or loose much.
While keeping in the recommended range the difference is minuscule at most.
I believe my sound would benefit much more from a couple of hours of practice than agonising over a couple of milliamps of bias current, I think its just not worth the trouble. A quick check with the multimeter and away you go.

 

[spacerocker]

Time to tell everyone what track was what
A was 32mv
B was 39mv

Most liked the hotter bias but the difference is so small that if you biased it a couple of mv either side of the middle of the recommended range you would not gain or loose much.
While keeping in the recommended range the difference is minuscule at most.
I believe my sound would benefit much more from a couple of hours of practice than agonising over a couple of millivolts of bias voltage, I think its just not worth the trouble. A quick check with the multimeter and away you go.

Well, I have always maintained that my JVM sounds better biased hotter - but that may be a purely psychological effect! When you have to play, bias then play and listen again 10 mins later it is much harder to compare, and very easy to fool yourself. Either that, or, bias has a greater effect on the JVM (JVMs can be biased notoriously cold from the factoty - circa 30 mV or so?)....Your comparison makes it possible to hear any difference immediately, so it is much harder to fool the ears. This is also helped by the fact that we don't know which is which, so don't have any expectations on a particular result!

I thought "A" sounded better in your comparison - clearer, puchier - but then at other times I favoured B - In fact I think I changed my mind and preferred the "new" sound every time it changed Ha ha!

I think the upshot of this test is that bias makes very little or no difference - at least within the range you used.

 

[charveldan]

The human ear is incapable if detecting Milliamps/volts.

Or for that matter AC/DC resistance, Inductance, Amps/Volts or the flavor of ice cream.

 

[stickyfinger]

Thanks for doing another comparison!
Just seeing this and I like A better.

Also, for clarification, I wouldn't say a 70% bias compared to 55% bias is Hot vs Cold.

Under 40% is Cold and over 70% is Hot IMO. 50%- 70% is in the safe zone and usually sounds better in this range. I like a slight mismatch in tubes around biased 50-60%