5E8-A Wierd Tone Stack

[Diablo]

I just finished up my 5E8A Tweed Twin and find the tone stack a little odd - it just doesn't seem as useful as my tweed bassman. I added the 47 PF cap across the treble pot (input to wiper) as shown on the layout, although it's not shown on the schematic. The treble control is way too sensitive, just a little on the dial adds a whole lot of treble. Is this just the nature of the beast? Should I clip out the 47 PF cap?

This one was built from a Weber kit with the addition of a Vari-Watt. From descriptions on the net, I was expecting this amp to be very loud. I was surprised that it's really not that loud - I can dime the amp without my wife screaming and running out of the house.

[tubeswell]

Is your treble pot a Linear, or Audio-taper? (I know the Fender schematic doesn't tell you)

[Diablo]

Originally Posted by tubeswell

Is your treble pot a Linear, or Audio-taper? (I know the Fender schematic doesn't tell you)

All the 1 Meg pots are audio-taper. You're right, Fender doesn't list the pot taper on the layout or schematic for the 5E8A. They do list the pot taper on the 5F6A layout....wierd.

[tubeswell]

Maybe try a pot with a more intense taper to stretch out that bunched-up bit? (i.e. go to a 30% taper if you're using a 10% currently etc)

[loudthud]

The 5E8A tone controls are pretty radical. I'm more curious about the volume issue. Do you have a DVM? Does the Vari-Watt seem to work? What range of B+ values do you get?

[Diablo]

Originally Posted by loudthud

The 5E8A tone controls are pretty radical. I'm more curious about the volume issue. Do you have a DVM? Does the Vari-Watt seem to work? What range of B+ values do you get?

I didn't use the dual pot master volume that Skip includes with the Variwatt. He says that most people find they don't need them. The Variwatt does work. The B+ controls in the range of 434 volts down to 12 volts. I've got Shugaung 6l6GC tubes in it and they are biased at 40 mA at idle (434 plate volts). When I dial down the variwatt to 12 volts the bias is 1.7 mA. I'm not sure I'm sold on the tone of the variwatt - it's a little buzzy with the power cranked down and the preamp volume cranked up. The best overdrive tone is with only a little reduction in B+. I have three EH 12AY7 tubes for the preamp, a Shugaung 12AX7 in the PI, and a single RCA 5U4GB for the rectifier. The amp uses the stock Weber 50 watt PT, stock choke, and a Heyboer 18343 multitap OT. The PT and OT are the same ones I have in my Tweed Bassman.

[Diablo]

Originally Posted by Diablo

I'm not sure I'm sold on the tone of the variwatt - it's a little buzzy with the power cranked down and the preamp volume cranked up.

Well I fixed the buzz, and it had nothing to do with the variwatt. It was the three tubes in boxes and 6 other empty tube boxes stored in the back of the amp that were buzzing. I should have known better when I threw them in there, because I had the same problem happen before with a different amp. Now, I'm liking this amp.

[Diablo]

Originally Posted by loudthud

The 5E8A tone controls are pretty radical. I'm more curious about the volume issue. Do you have a DVM? Does the Vari-Watt seem to work? What range of B+ values do you get?

Today I figured out why the volume isn't that loud compared to what folks were saying on the web. I stuck in three 12AX7 tubes instead of the 12AY7 tubes called out in the schematic, and the thing blows me out of the house. With the volume on 2, it's crazy-loud. Since the reissue 57 Tweed Twin comes with the 12AX7 tubes, that explains what most folks are hearing with this amp. I'll probably stick the 12AY7 tubes back in it because I just don't need something this loud, and the volume is a lot more controllable with the 12AY7 tubes. Maybe the "modern players" would prefer the raucus gain of the 12AX7, but I'm a retro kind of guy.