Blues Express born, but needs therapy...

[rfgordon]

As an experiment, and partly for a friend, I bought a Weber 5E3 Tweed Deluxe kit. I must say the cabinet is really nice.

Instead of building a straight 5E3, I used the preamp of the Blues Express, since I could do that with two peanuts. I upgraded the PS with a 32/32 cap and two Sprague 20s and added a choke.

I used the volume/tone from the Carmen Ghia. This works pretty well. It really cooks, considering it's a two-knob amp. I have the crossline MV in from the Blues Express schemo, but it's pretty useless in this thing.

Not having to drill out the chassis saved lots of time, but that tweed chassis is a serious pain to work in!

Anyway, the thing is a dynamic monster, but it has a wee bit of 120Hz hum that I can't seem to get rid of. I'm beginning to suspect that the B+ is so close to the signal lines into the 6V6s that it's proximity coupling the noise into it. If any of you have worked in tweed-style chassis, you know what I mean. I used the same grounding scheme as on my other amps--all dead quiet (and aluminum chassis vs steel for this thing). Any ideas? I don't have a scope, so that limits me somewhat.

I need to swap out the coupling caps from the tweed values to the express values, cause the bass is too flabby.

Anyway, I like that circuit--extremely touch/volume control sensitive, but I've got to lick the hum. I'm thinking that I may rebuild it into a longer chassis that'll still fit into the cabinet. With the high gain of the Express, lead dress really matters.

When it gets squared away, I'll try to make some clips.

[sliberty]

Get the chop sticks out and test your theory.

[DerStever]

Rich - I had a hum issue we couldn't figure out - but I took out the power tubes EL34s which were about 6 ma off and replaced them with 2 mongrel (Syl and a JAN) 6V6s which I had laying around - they matched and the hum went away big time. Now for the hiss .......

[rfgordon]

Thanks for your insights. About the only think I haven't done is swap out the filter caps one by one.

However, I found a metal shop yesterday that can bend any kind/shape chassis I want, so I'm gonna rebuild that amp in a different style chassis.

It may have to wait a while, cuz I was in our town's new music store today, and the owner was chomping at the bit to get an amp or two in. He's even agreed to pay to tube up the one's I place in his shop. Between that and my Tone Tubby dealership, it will reduce my build cost quite a bit. And, since I no longer have to accept off the shelf chassis, I can have them made to simplify my cabinet work.

That said, I definitely want to work on the TNT concept: Two Nob Trainwreck. I think it would really rock, especially as an SE amp.

[rfgordon]

OK, it works now! I Puzzed and I puzzed till my puzzler was sore, then I desoldered the ground fo the first cap can (F&T 33/33 multi) and jumpered in two new caps. It fixed the icky big hum. So then I clipped out the MV, since it was pretty much useless.

It's a punchy little monster, that's for sure! The Ghia tone knob is pretty cool--roll it clockwise to trim highs and left to boost mids.

It's still got just a wee bit of 60Hz in it, but I may have to live with that, this being in a steel chassis and all. I'll still try a few other preamp tubes to see if they hum less.

I put a Celestion Vintage 30 in the little cab (there's about a 1/4" clearance between the magnet and the 6V6s!). All in all, a very loud little box.

I know I owe y'all clips from several amps, so I'm gonna try to get the band's recorder next weekend.

So if y'all are looking for a new Trainwreck-inspired machine, I'd recommend this circuit. Just build a Blues Express (the one with only two preamp tubes), use the Carmen Ghia tone/volume controls, and a cathode bias output. Mine is 6V6, but any pair would do. You'd get a different character of crunch from EL84s. Also, I added a choke and extra filter to the regular Tweed Deluxe PS.