Ideal platform for Express clone; experience with 6L6 tubes

[Darkbluemurder]

Hi guys,

I am new to this forum so please forgive me should I ask topics which have already been discussed.

I am considering modifying one of my amps to an Express clone. My preferred choice would be my AB 165 Bassman (which is currently wired as a D 70s clone - basically a very good sounding amp but I have other amps which I will turn into D-clones because they have reverb and channel switching already).

Other candidates could be my butchered JTM-45 (basically good sounding amp but has a bad buzz I could not get rid of) or my also heavily modified 1973 Marshall Lead & Bass amp (an inherently bad sounding amp irrespective of the preamp wiring, tube and OT swaps - the only thing that made it slightly better was the swap of the choke to a Mercury Magnetics choke).

It seems that except for the Lead & Bass none of these amps is well suited to EL 34s due to the increase in heater current. I could use JJ 6V6S but why not use 6L6s?

If anybody tried one of these conversions I would very much appreciate comments on the results.

Thanks and best regards
Darkbluemurder

[MarkB]

I'm in the process of converting an AB165 right now. The board is in and the tubes are wired, but the pots are not wired yet. I'll let you know how it turns out. I'm ordering EL34s to try as well.

[Darkbluemurder]

I also thought about whether most of you had built a clone from scratch or modified existing amps. The reason I am asking is that I am not too good at mechanical work (I can drill holes but hate to do that, and I cannot cut or bend metal). I have experience in basic repairs, changing chokes, output and reverb transformers, power tubes, tube sockets, pots, jacks, cap jobs, modwork (hot-rodded Marshalls, Fenders, D-clones) and I have successfully wired in Hoffman boards in 50W Marshalls. I am yet to replace a power transformer. I am confident I can mod an existing amp to a TWreck style amp. While checking through the various threads it appears that most builders at least used a home made board rather than using the existing board.

Both the AB165 and the Marshalls would have the correct preamp tube complement and a sufficient control layout. I understand the JTM 45 Reissue would even have the "correct" primary of 6k6 (if this amp only hadn't the buzz I cannot get rid of!). In all cases the power amp would only need a few changes. In the AB165 I could even use the Deep switch to add a 470pF treble cap to a hardwired 50pF cap. I could use the Bright switch to change the interstage network from 0.001/56k to 0.002/150k as well (I would use two 0.002 in series and bypass the second to avoid putting B+ on the front plate, and put a 100k in parallel to the 150k to get 60k - close enough to 56k). Wouldn't that make for an Express style preamp and a Liverpool style preamp as well? Is this a good idea and has anybody tried this?

Otherwise I am planning to take it step by step, i.e. first install the general gain stage architecture but keep the grid stoppers and then start to eliminate them one by one until it either gets unstable or too bright. I hear the comments that Trainwrecks are peculiar in this department so I'll take it slow.

Mark, I am looking forward to the results with your AB165, be it 6L6 or EL 34. Good luck with your project!

[MarkB]

I was short two caps for the tone stack, so I just put in an order with AES. I'll get it running with 6L6s, and then order some EL34s. I'm putting a Hiwatt board into my 2xEL84 head at the same time, so I might not finish the Bassman for a couple of weeks.

[Richie]

Although i like the express EL34s much better..
I built an amp a few years ago out of a 4x6L6 dual showman..it turned out as a 2 channel amp. Just used what was on hand in the amp and a few parts thrown in.. and the fender power supply transformers..
Sort of a cross between the fender and express. It turned out great..and would peel the paint off the walls..!!

Just wanted to say they can be built out of donar amps. But i would think alot of the layout in the express is part of the mojo or magic to make these amps turn out like they should.
I've also built an EL84 version or blend between the marshall 18 channel and express channel..

Richie