Modding the Mids in a Twin

David Mullis · Post by **David Mullis** » 3 Jan 2003 7:05 pm

Hey I read on another Twin thread about replacing the slope resistor in a Twin to make it better suited for steel. I'm pretty good with electronics, but I've never been inside a Twin, or any other Tube amp for that matter. Could someone steer me in the right driection on this? It sounds like it would be pretty easy to do, but I want to make sure I replace the right resistor.

Thanks
David

Gino Iorfida · Post by **Gino Iorfida** » 4 Jan 2003 12:13 am

Well, it IS a very simple change, HOWEVER, the innards of tube amps are not the safest thing to be poking around in, even with the amp unplugged. The filter caps in the amp can still retain enough lethal voltage to well, paralyze you, do nerve damage to your pickin' hand, and possibly kill you.

The change, however would be swapping the slope resistor in the tone stack, as well as the caps for the bass/mid controls to give the notch in and about the 2khz zone, which is the sweet spot for steel. at most $5-$10 worth of parts, and about a half hour job at most by a good tech... if you dont want to kick up the $$ right away, next time you have the amp in the shop for a retube and gettin the bias set, have them mod it for you...

Secondly, if you do have an older twin, it may be a good time to have the amp given the once over by a good tech, to make sure all the caps are fresh, the resistors are in spec and to give her a good cleaning... and oh yea, to make sure you ahve a 3-wire grounded plug/cable in the amp...

Email me and I'll be willing to help get ya on the right track though etc.[This message was edited by Gino Iorfida on 04 January 2003 at 12:14 AM.]

David Mullis · Post by **David Mullis** » 4 Jan 2003 6:51 pm

Thanks Gino, sounds a little intimidating. I guess tube amps are not as friendly as the SS stuff I've modified before. I'll email you for a list of what needs to be done. We have a really good tube amp guy in this neck of the woods. However, I don't know if he's ever modified any twins for use with steel.

Ken Fox · Post by **Ken Fox** » 5 Jan 2003 12:41 pm

David, a handwired tube amp is a lot easier to work on than a PC board amp. Just discharge the B+ and go for it! Unplug the amp, then turn on the standby switch and attach a jumper from chassis to pin one of the first preamp tube, tube #V1. That will drain your B+ throught he 100K ohm plate load resistor in less than 30 seconds.
You can find a schematic and a board layout at:
http://www.ampwares.com/ffg/index.html

David Mullis · Post by **David Mullis** » 5 Jan 2003 3:02 pm

Thanks Ken, I bought this am from a mutual friend of ours. I use to have to old Tremolux head that you have.

Nick Reed · Post by **Nick Reed** » 12 Jan 2003 5:16 pm

I gigged with my new Twin Reverb for the first time last night. (It a '65 re-issue) I ran my pro-fex through it for delay. All I can say is WOW!
I like it better than either my Peavey Nashville 400 or Nashville 1000. I'm hooked on Fender Amps. BTW, I realize most everyone else here in Nashville will disagree with me on this one. But I like it and think the Fender Twin is best suited for my ears. NR [This message was edited by Nick Reed on 12 January 2003 at 05:18 PM.]

David Decker · Post by **David Decker** » 13 Jan 2003 8:38 am

Gino do you know the parts that need changed, and what the new values are?