I've just det the bias in my Stein+ properly (fro 40 to 58mA) and FUCK what a difference!
it's so much warmer, smoother and BETTER sounding now!
it's so much warmer, smoother and BETTER sounding now!
BIAS fucking YEAH! (Krankenstein+)
- Thread starter LSD-Studio
- Start date
58 mA?! Jesus, are you sure? Eurotubes recommends biasing most amps somewhere between 38-44 mA (scroll down on the page), which is where I have my JSX
the + has 6550 tubes which have 42w plate dissipation (compared to 6L6 with 25W or something like that).
the plate voltage is 415V that gives a Range from:
42*500/415 to 42*700/415....so roughly between 50 and 70mA
so even if I'd go with the 35w plate diss he's giving (which isn't correct for my 6550) I would be at about 70%, so still safe
the given range for your amp is correct...nevertheless I'd be really carefull with what Doug tells you about tubes and biasing...just ask someone who's got some knowledge about tubeamps what he thinks about "integrated quads" and changing tubes w/o changing grid-resistors etc
EDIT: the range I calculated above is between 50% and 70%...that's the range most ppl consider being safe for an amp...be careful with the 85% he's mentioning (unless you have the money to replace your tubes every other day)
the plate voltage is 415V that gives a Range from:
42*500/415 to 42*700/415....so roughly between 50 and 70mA
so even if I'd go with the 35w plate diss he's giving (which isn't correct for my 6550) I would be at about 70%, so still safe
the given range for your amp is correct...nevertheless I'd be really carefull with what Doug tells you about tubes and biasing...just ask someone who's got some knowledge about tubeamps what he thinks about "integrated quads" and changing tubes w/o changing grid-resistors etc
EDIT: the range I calculated above is between 50% and 70%...that's the range most ppl consider being safe for an amp...be careful with the 85% he's mentioning (unless you have the money to replace your tubes every other day)
jesterroot4
Member
hmm... i need to learn about this shizz... any useful links? to tell me about it.
all gobbledegoop to me
all gobbledegoop to me
not really....there are great book on the topic though...or wait, this page is good:
http://www.duncanamps.com/
and here's a nice guide to how to bias your amp:
http://www.tube-town.net/diy/bias-setup-e.pdf
jesterroot4
Member
the given range for your amp is correct...nevertheless I'd be really carefull with what Doug tells you about tubes and biasing...just ask someone who's got some knowledge about tubeamps what he thinks about "integrated quads" and changing tubes w/o changing grid-resistors etc
Can you expand on this? Is there a problem with Integrated Quads? I'm running a KT77/6V6 combo in my dual rec and love it. it's been almost a year with no problems.
There should be a test point inside the chasis by the power tubes for you to plug in a multi-meter and a knob to adjust the bias next to that test point. The meter will tell you a rating, usually around 40-something mA with most tube amps from the factory. The lower the mA, the colder the amp, the higher the mA, the hotter it is running...funny how that works. Typically any amp that gets biased a little hotter than factory will have a very desirable effect. I rebiased my JSX, before I sold it, from 42mA to 52mA and it made quite a difference. The amp literally reacted a lot better. Warmer, a little more dynamic, edgier...it was a good change. You don't want to go crazy with the adjustments though. Most bias trim knobs have a slot in the top of them where you would use like a flathead screwdriver to make the adjustment.
~006
~006
both of the 5150 I put the biasmod in came biased more than cold, one was 12mA and one even 8 mA !!!!
here's a nice DIY biasguide:
http://www.tube-town.net/diy/bias-setup-e.pdf
I hope you mean KT77/6L6??
and...why would an amp (like the dual) have a switch for EL34 or 6L6 if one could put any tube in there?
different types of tubes need different grid-resistor values etc to run safely for the tubes, the OT and to give the best results
here's a nice DIY biasguide:
http://www.tube-town.net/diy/bias-setup-e.pdf
I hope you mean KT77/6L6??
and...why would an amp (like the dual) have a switch for EL34 or 6L6 if one could put any tube in there?
different types of tubes need different grid-resistor values etc to run safely for the tubes, the OT and to give the best results
Yeah I noticed that too Lasse, the Recto's have a blatant switch on them for 6L6 or EL34 only. You would have to do some modifications to the board (swap the sockets, resistors, possibly caps, etc.) in order to run something different...but why would you want to anyway? 6L6's in a Mesa pwn...hell even EL34's in a Recto can be kick ass.
~006
~006
Well KT77's are considered (from what I've read) to be a direct replacement for EL34's, so I think that wouldn't be a problem
^correct.
And the integrated quads thing in reference to Bob at Eurotubes is a mix of 2 6L6's and 2 KT88's in a 5150, IIRC.
There was a hubbub about it with Peavey on the Peavey forums, as they recommended it not be done, and Bob disputed it on that forum, with the Peavey people...I think he was banned, and now you see his site reads like a madman hellbent on proving the world (i.e. Peavey) wrong.
Dude's a quack.
And the integrated quads thing in reference to Bob at Eurotubes is a mix of 2 6L6's and 2 KT88's in a 5150, IIRC.
There was a hubbub about it with Peavey on the Peavey forums, as they recommended it not be done, and Bob disputed it on that forum, with the Peavey people...I think he was banned, and now you see his site reads like a madman hellbent on proving the world (i.e. Peavey) wrong.
Dude's a quack.
JoeJackson
Member
::XeS::
Member
Eurotubes says lot of stupid thing. (JJ are the best bla bla bla)
Bias current depends from amp's plate voltage...and each amp has its proper plate voltage (you can find differences comparing 2 jcm800 amps or 2 recto amps)
There is not a range....you have to measure your plate voltage and calculate the right current
Bias current depends from amp's plate voltage...and each amp has its proper plate voltage (you can find differences comparing 2 jcm800 amps or 2 recto amps)
There is not a range....you have to measure your plate voltage and calculate the right current
yes....but the range thing...
of course you have the option of biasing your idlecurrent colder or hotter = range
Emdprodukt
Member of Dude Castle 69
hey lasse, could you do that to my rev, mayabe? where do you buy tubes usually?
we planned to check out each others amp anyway
hey lasse, could you do that to my rev, mayabe? where do you buy tubes usually?
we planned to check out each others amp anyway
sure!
usually I'm buying them here: www.tube-town.de
Nebulous
Daniel
I read about the test points on Eurotubes.com and have jsut confirmed that they are not that accurate, assuming that a bias probe is the accurate way.
I just checked my stock JSX bias at the test points and got a reading of 6mA (!). WIth the bais probe I got a reading of 25mA. Thats a fair difference!
