Hi All,
I have a Carvin TS100 that I swapped over to JJ 6l6GC's and I'm using it with my Axe FX III guitar modeler.
I biased according to the instructions but at 50mA per side (there's 4 power tubes) it seems very cold.
I have 468vdc B+, so 50mA's is about 55% bias point.
I'm not sure why Carvin wants this so low and my only assumption is to prevent any distortion or addition coloring of sound.
So should the bias be set higher?
2nd question.....although there is nothing wrong with the current fan which is 80x80x25 dc24v, I'd like to find a replacement that's quieter, and has better cooling.
thanks,
dinky
I have a Carvin TS100 that I swapped over to JJ 6l6GC's and I'm using it with my Axe FX III guitar modeler.
I biased according to the instructions but at 50mA per side (there's 4 power tubes) it seems very cold.
I have 468vdc B+, so 50mA's is about 55% bias point.
I'm not sure why Carvin wants this so low and my only assumption is to prevent any distortion or addition coloring of sound.
So should the bias be set higher?
2nd question.....although there is nothing wrong with the current fan which is 80x80x25 dc24v, I'd like to find a replacement that's quieter, and has better cooling.
thanks,
dinky
Max 6l6GC rating is 30W plate, and you have 23W. There's some margin to increase the current, by 10mA or so.
But your tube life may be shorter.
Look for a ball bearing fan with serrations on the blades, but it won't be cheap.
But your tube life may be shorter.
Look for a ball bearing fan with serrations on the blades, but it won't be cheap.
Aside from the fine-tweaks Rayma suggests: "quieter and cooler" really points to a bigger fan. Fan noise is linked to air motion. The quietest fan I ever met was taller than I am.
If you don't have space for a 12" fan, multiple small fans may be an approach.
Thanks guys...
I think I found a comparable fan...not easy finding 24v fans either.
As for the bias, I bumped it up to 63mA per side...according to my calculations, it's about 50% bias...up from 40%.
I think it sounds better.
dinky
I think I found a comparable fan...not easy finding 24v fans either.
As for the bias, I bumped it up to 63mA per side...according to my calculations, it's about 50% bias...up from 40%.
I think it sounds better.
dinky
I agree....today I was increasing the bias and looking at it rise at startup...then slowly after 4-5 minutes settle down to 62-63mA's per side.
The fan is located off center the power tubes (you can see in the pic PRR posted above) and after an hour or so playing, and having the case cover off, The tube under the fan had a temp of about 190.....where as the tube farthest the fan was about 250 deg F....so yeah.....it does need a fan!
Having the cover on would have helped...but I just wanted to make sure everything was OK before sealing her up.
dinky
That's not hot. 121C. Tubes, even cheap domestic receiving tubes, can run much hotter than that. When you get a 3rd degree burn (blister), that's hot enough.