On bias /adjustable fixed

[catnine]

Is it a waste to bias the 6V6GT's, there are JJ's at 60% ?

My 6G2 front end and 5E3 adjustable fixed bias amp has a plate of 405 VDC and the mA for one tube is 18.5 on average put it at close to 60 % of max . I am a bit confused because weber has a area for the bias rite that you put in the plate and it gives you a choice of a 6V6 or 6V6GT and from what I've read the GT is a max IPD of 14 watts.

The amp sounds good and solid bottom which I like . one chart weber has shows 70% for my late VDC at 24.1 and there is below a jim Jones chart showing a plate of 400 VDC and 60% gives 18 mA and a hot 70 % @ 21 mA and cold 50% but lets not go there.

My bias rite is a weber but does not have the plate so I keep the tube in the bias rite just so I can read pin 3 and get the plate without removing the chassis and I know the plate will drop as I raise the mA draw .

Mainly baising hotter say 70% does this bring more breakup of will it keep the bottom end or even bring the bottom out more .

Of course this does depend on the OP tube brand . I have JJ's in there now and have ruby 6V6GTBC coming as well as EH 6V6GT's .

My issue is to retain as much bottom end and keep the touch sensitivity there. This is with strat single coils . There seems to be little talk but reviews on JJ's having a piano type low end sound .

It's all so confusing and I can't A/B tubes so by the time I change and set the bias I can't recall how it sounded .

At one time I had a 77 MM bass amp with old RCA 6V6GTA's and then JJ6V6S and a 71 MM bass amp with the 6AQ5 output tubes and biased about the same and to be quite honest I could not tell much difference so I ask is a lot of this just hype or are we bordering on sales on certain tubes or insanity or is it just me? I am not gigging anymore so it's just here at home now days .

[tubeswell]

70% is optimum for fixed bias to get max power and 'safe' operation.

But nothing wrong with 60% - whatever floats your boat

[Chuck H]

At one time I had a 77 MM bass amp with old RCA 6V6GTA's and then JJ6V6S and a 71 MM bass amp with the 6AQ5 output tubes and biased about the same and to be quite honest I could not tell much difference so I ask is a lot of this just hype or are we bordering on sales on certain tubes or insanity or is it just me? I am not gigging anymore so it's just here at home now days .

Yes, alot of hype out there. Since you have the time ("not gigging anymore'), and you already have tubes coming, why not try the different tubes at different bias points and just decide in a slow, methodical way what sounds best to you.

This is VERY significant because bias, as it relates to guitar amps, is as much about the tone as proper tube operation. Sometimes there is even a tradoff between tube life and preferred tone. So, since you have the tools (adjustable bias and different brands of tubes on order) go with your ears. Take your time about it so you can absorb subtleties. Anything from 15 to 30mA per tube probably won't red plate. Any setting that doesn't light up the plates or cause excessive crossover distortion is acceptible for a guitar amp. But different brands will of course behave different at the same bias settings. IMHO the Weber bias tool on the site is VERY conservative. Believe me, there are no hard rules with this unless your building for the lowest possible distortion. Other than that criteria everything else is fair game...Really. So take your time and listen. You will probably find a brand of tube and bias setting that gives you what you want (or very close to it, it's not a perfect world) with what you have at your disposal.

Chuck

[catnine]

Yes, alot of hype out there. Since you have the time ("not gigging anymore'), and you already have tubes coming, why not try the different tubes at different bias points and just decide in a slow, methodical way what sounds best to you.

This is VERY significant because bias, as it relates to guitar amps, is as much about the tone as proper tube operation. Sometimes there is even a tradoff between tube life and preferred tone. So, since you have the tools (adjustable bias and different brands of tubes on order) go with your ears. Take your time about it so you can absorb subtleties. Anything from 15 to 30mA per tube probably won't red plate. Any setting that doesn't light up the plates or cause excessive crossover distortion is acceptible for a guitar amp. But different brands will of course behave different at the same bias settings. IMHO the Weber bias tool on the site is VERY conservative. Believe me, there are no hard rules with this unless your building for the lowest possible distortion. Other than that criteria everything else is fair game...Really. So take your time and listen. You will probably find a brand of tube and bias setting that gives you what you want (or very close to it, it's not a perfect world) with what you have at your disposal.

Chuck

I am after the lowest distortion with the best bottom end and the best " pick sensitivity" I can get so if I pick a bit harder the amp will react to this . I use heavy strings and by nature pick hard .

I know this is a wildly varied area to enter .

It seems the JJ 6V6's I have have a bit smaller diameter pins than most production tubes and one weber bias rite I got built with the copper tube body fits well but the weber bias rite I got as a kit whcih has the plate voltage wire and a much shorter body of backlight has thicker pins so I don't use it for that very reason.

Don't get me wrong the JJ's at 60 % do sound real good to me it's always that quest for more that keeps me looking for more as always seems to be the case.

I know only that JJ' 6V6's are said to be more like a inbetween of a 6V6 and a 6L6 and this to me so far seems to be somewhat true.

Yes I have time to try out the other tubes and bais mA ratings not to exceed max IDP . I have gone through many speakers in the past and even that makes a lot of difference.

There are many times where these days the internet can render so many opinions and in a sense they influence the way you hear things as opposed to the old days where you changed out a set of 6L6's in a 67 bandmaster or super reverb and all was well . Other than these amps and a few SF champs and a silver tone two twelve with reverb I only have experience with the few home brew copies I have built all basically 6G2 without tremolo builds and a pignose GV-40 and a few pro jrs and one 93 tweed blues deluxe and a tweed 1993 30 watt Peavy which I actually liked better than the 1993 blues deluxe in some ways . Oh I had a few ss amps but they ALL left me bored right off .

So far this 6G2 /5E3 is the best amp tone wise with 6V6's . I had a pair of JJ 6L6's in it but it was too loud for home use but sure sounded great with two 12's .

I guess when the new tubes blow in I will set them at the same bias point as the JJ's and see what they do because after all it is me I have to please and that in not easy . I guess the best bet is to use tubes for aweek and then change them and then I might hear the difference better .

[Chuck H]

Ok, As an aside I will say that if you want max clean headroom, and breakup controlled by pick attack, you should be in the 60% to 70% dissapation range for your idle bias with most tubes. If you experience too much crossover distortion at the lower mA settings then just stick to the 70% dissapation rule of thumb. It works well for what your after at highish plate volts on a 6V6.

No flaming please, I know modern 6V6 tubes will take 400+ volts better than old ones. But the tonal difference is negligable.

Chuck