Re: Bias problem



Pete wrote:

With JJ6l6gc i had 470 plate, -44 bias on pin 5, 42.5 mA for about 19.74
watts static and it sounds kick ass with a stock 6100 setup.
What tube are you referring to in the above? I have always been under the impession
that in order to run EL34's in a 6100 you HAD to modify the bias circuit.
Is this true or just horse shit?

I've seen reports from others who have been able to get them in range without a modification to the circuit. I'm not sure about mine as I haven't had it from new and I originally took it to someone to convert but I believe he just set the bias from what he said later and the fact that he didn't change the screen grid resistors. With 6L6/5881s, the maximum negative bias potential gives around 15W static dissipation and I've can get EL34s in range easily. I found 6L6/5881s sound better at around 22W static and EL34s at around 15W.

I'm using Harma '5881's at the moment, the early button base cold war era valve before the Sovtek label was put on them. They even have the Russian part number on them in Cyrilic writing. These are military stock and sound better than the later Sovtek '5881's. They're a good valve for heavy metal but don't sound as complex as other valves. They do respond well at low volumes, though, and it's easy to tell that the 6100LM was designed around this valve as other types make it difficult to get the balance right between overpowering bass and not sounding full enough.

When I replace the KT66s I tried with some Tung Sol 5881s at the weekend, I'll be interested to see how they sound.
.



Relevant Pages

  • Re: Biasing JJ E34L valves
    ... that gets you to an approximate "hotter" bias setting, ... I don't like the sound of EL34s biased hot. ... It seems the confusion has arisen because the Groove Tubes ... version is intended to be a 30W valve, ...
    (alt.guitar.amps)
  • Re: iPod trouble - can anyone help?
    ... with the valve stuff. ... I'm talking about a musician buying an instrument that makes the sound ... This is what they are not are: valve audio amplifiers ... But what does it matter - they are both valid as musicians. ...
    (uk.comp.sys.mac)
  • Re: iPod trouble - can anyone help?
    ... that is the way 'audio buffs' see these things. ... specific sound, they are cost, maintainability, size, reliability etc. ... distortion, and all sorts. ... The same goes for valve amps. ...
    (uk.comp.sys.mac)
  • Re: Fender deLuxe Hot Rod ,2002
    ... from a valve amp, I think that very much depends on what you're putting ... clipping, and inherent 2nd harmonic distortion, all contribute to a sound ... that is particularly suited to a guitar. ... "There is little if anything better sounding than a Fender Strat ...
    (sci.electronics.repair)
  • Re: One for the bottleheads
    ... >> I would agree that at least some designers may be unaware of this, ... I spent some time at one point, in making and trying some valve circuits. ... but unsatisfactory as they made the sound poorer. ... said that speakers that "make a trumpet sound more like a trumpet" also ...
    (uk.rec.audio)