Twin Bias settings ?????

Tele · Post by **Tele** » 23 May 2000 1:51 pm

Hi to ya all...

I have a 59 Tweed Twin with 4 5881 tubes which puts out around 80 Watts. I expect it to be cleaner than it is, it goes into distortion around 4-5 on the dial which is quite loud but the distortion could be more harmonic and the amps appears not to have its full power.
Aren't these Fenders fixed-bias ?? What to do?

Andy

Rich Paton · Post by **Rich Paton** » 23 May 2000 2:14 pm

Tele, it needs servicing, before something expensive goes out.
Go here and post your question under the "Fender Amps, Vintage" forum. You'll no doubt enjoy the Fender-oriented sitem, in any case.
http://www.fenderforum.com/

It's a moderated site like this one, so you need to register but that only takes a minute or so.

There are some great amp techs there who will share their expertise. I do tube amps, but that old a model is more their "bag" than my usual work.
Good Luck!

Jay Ganz · Post by **Jay Ganz** » 23 May 2000 2:41 pm

Usually the output tubes are supposed have
about 35ma flowing thru each one. A little
less will "clean up the sound". The negative
voltage that comes from the fixed bias supply
would have to be varied to change this current flow, or other output tubes could be
used. Each tube draws differently. BUT before any of that, make sure your
tubes are alright (obviously). Then voltages
have to be checked thru out the circuit to
make sure they're all within range. When's
the last time you had it serviced?

Donny Hinson · Post by **Donny Hinson** » 24 May 2000 5:24 pm

Make sure it's not just the speakers that are not causing the problem, and then take it to a good tube tech. Being 41 years old, it probably needs a thorough going over!

Tele · Post by **Tele** » 28 May 2000 11:13 pm

Donny,

shame on me - it is just a speaker. I checked it with my amp tech and we played it through a newer 12" EV and it sounded so great.
One of the Jensens sounds real dirty, however it is not blown. I think they are not capeable to handle the power of the 4x 5881 tubes.

Jay Ganz · Post by **Jay Ganz** » 29 May 2000 6:45 am

If they're the correct P12N's that're supposed to be in there, they should handle the power.
What will <font color=red>damage</font> them
is pulling the cord out of your guitar (by accident)with the amp volume up.

Tele · Post by **Tele** » 29 May 2000 9:10 am

unfortunately the speakers are early 60s C12N which should handle the power as well as the P12N but I read that the original 1950s P12N could handle only 30 Watts and that Twins with original Alnico speakers are quite rare.
The Twin sounded great with the ceramic speakers, however since they are not the originals I think I will replace the with JBLs if the cabinet is deep enough. Anyone knows how deep JBL D120F are?