Clean up on Express

[sepulchre]

When you say rolling it off at the control, er, which control? The volume? or the treble?

I mess with the guitar's tone and volume a Lot while playing. My tone control is almost never at 10. Yeah, I like a little darkness if it gets me smooth.

[Richie]

http://www.youtube.com/watch?v=Uc3Xi6aAG80

the Link is Glens tech talk on you tube. I think anyone that owns a wreck type Express clone should watch this,or probably work for other amps to.

Good information on the amp and guitar,and interactions of how they work and sound together,or how he goes about getting the clean to mean tone.

Also he has a great CD out which he mentions there too. I think he has another CD in the works,which hopefully that too will be out soon.

[geetarpicker]

Thanks Richie for the plugs! I put a good word out with a couple folks that have contaced me about that used Express on TGP, that of which I think was one of your build. Nice looking amp, inside and out.

On the amp in here in question, I do recall many years ago working on a customized amp that had a bunch of shielded wire in it. On that amp the wire actually mucked up the tone and clarity quite a bit, and simply removing it all and replacing it with regular non shielded wire was the fix. I'm not sure why, but in some tube circuits shielded wire can cause more problems than it fixes. That said, IMHO the wreck only needs the input lead shield.

[Reeltarded]

I have that same experience with high gain Marshalls. Too much capacitance in all the wrong places, plus some of the life comes from interations of the flux all around the tone circuit. Crosstalk is a tool as much as it is a mess.

[Richie]

Very true. Same with tube shields, sometimes it cures squeals or whistles etc.. some times trying to use them causes the problems.
And depending on the type or brand tube used you can hear the difference with the shield on or off.

Also the way the wire is run/routed/placement from volume pot to tube can also have an effect.

If you have worked on alot of amps, even ones that are exactly the same. Like production 2203s or jcm800s. One amp may not have probelms, nice and quiet etc. The one that looks identicle, might have oscilations and other things going on. When they "should" be the same. They aren't. 18watt trem amps could also have these things happen.

A schematic may tell the info of values and things. But to see an amp how its laid out, and wired can also be a big help. Although seems you can still have to move a lead or 2.

Glen, your most welcome on the plugs..

[sepulchre]

Good evening fellas!

The reason all that coax is in there in the first place is that this amp has gone through three serious rebuilds that moved parts around so much that I felt the coax was needed to keep noise down and/or to prevent oscillation. Now it's not such a . . . (I was going to say trainwreck ) tangled mess and so all that is probably unnecessary and will go.

But I've been reading various threads and saw Glen talking about how the power supply gets pushed when cranked and how that produces the wonderful compression that is a TW trademark. Well, I don't have a standard TW power supply. It's similar but not the same, okay maybe not even so similar. First of all it uses all 47uF caps, and then they're not arranged the same as a TW.

[IMG566]http://i269.photobucket.com/albums/jj55 ... Supply.jpg[/img]

So I'm thinking this won't do the job, eh? Also, the caps are spread across the board, nearest to the sections they feed, sort of like Martin Manning's layout. I could be wrong but that part doesn't seem to me like it should have a great effect on tone. At least I'm hoping it doesn't - I really can't tear the board out and redesign the whole guts at this point. My chassis (and cab) is large but not enough to make a stack of caps like in a standard Express without building another, shorter board. However, I could in time replace the caps with the standard values and rewire them to at least match the schematic. That is unless some of you think this will actually compress as needed. Those fat resistors, 100R & 900R, were originally there to produce some compression, albeit at different values. I tried a few different ones (some the size and shape of dog biscuits) to finally get the voltages and bias right for an Express.

[leadfootdriver]

THat choke is probably what's keeping the amp from sagging. Chokes keep the power stiff.

Try it without the choke, but leave the 900r in there.

[sepulchre]

Well, I got the tubes Reeltarded sent and OMG! It's Great! That 5751 is perfect in the V1 spot, no problems with the distortion now. It cleans up beautifully with the guitar volume. And it still breathes fire when cranked.

It's got a bit of 60Hz hum, even with the guitar unplugged but I think some chopsticking will cure that. However, I'll have to rethink my power supply. I have a couple of resistors in parallel to get the voltage down - one 270R and one 100R. After playing only a few minutes the 100R one got Hot! I might try running it without the voltage drop to see how it sounds.

Anyway, big thanks to Miles for the tubes. He sent a couple of AX7s besides the 5751. Merry Christmas, Bud!

[Reeltarded]

Thank Bob S for the 5751. He added it (among other previously undescribed things) when we did a tube swap that went crazy while I was building Enola Gay.Hah BOOOM!

Goodwill keeps it going! Merry Christmas. Drive the grandkids crazy for me!

[sepulchre]

Will do. I think one of them might want me to build one for him but his Mom would Kill me!

When I get some of the kinks worked out I'll try to make a clip, if I can figure out how to keep from blowing my little H2 up.