So I have been given free reign to gut a Blues Jr and do whatever I want with it

[mort]

The plan is to throw out all the boards but use the PT, OT, tubes, speaker and verb tank. Reverb is a must in this situation.

It will need to use a diode rectifier since the PT doesn't have 5v taps. Was thinking of doing something along the lines of an AC15 or Matchless Lightning, sans tube recto. Any other suggestions welcomed. It will be a backline amp for a blues jam night so I can literally do whatever I want as long as it has reverb. What would be your inclination to build in this scenario?

[mozz]

I'd leave it stock and do some mods, BillM website has the info. I changed the stock OT for a buddys amp with the TO20B with some tone stack mods and he loves it, gets more play than all his other amps.

[tubeswell]

If its for a blues amp and you're keeping the BJ PT and OT, then I vote for something with 6V6s that keeps cleanish up to about 7/10ths on the volume dial, like a PR or DR

[Mick Bailey]

You don't need a 5v tap to use a tube rectifier in a small amp; an indirectly heated 6.3v tube such as an EZ81 can be powered off the regular heater supply, just how Vox does it in the original AC15.

[dchang0]

I was asked to add a one-tube reverb to a Blues Jr. I used the very-common 12AX7 circuit commonly found on the web. We kept everything else stock, and the customer loved the result. It too gets more play than his other amps.

[mort]

In this case the amp has a problem that I cannot figure out (maybe the board is bad?) and he has two other Blues Jr's so having a different flavor available on stage is very much welcomed. It's also a good thing to get something with my name on it up there to be played and seen every week

Still considering what to put in it. I do like 6v6's so a PR is a possibility.... I'm doing it practically pro bono so trying to keep from having to buy too many parts, but this guy does a ton for the local music community so I won't mind too much if I do end up spending a little money on it. Hmmm decisions decisions

[dchang0]

Ah, yeah, if it's un-repairable, might as well gut it.

One small amp I have always wanted to build is the Gibson GA-1RVT. It's got reverb AND tremolo in a circuit small enough to stuff into a 5F1 Champ. I have not heard any recordings of it, however, so it may not actually sound all that good. There are larger Gibson circuits you might be interested in building that seem to be well-regarded (and there are recordings of these). This route would be the "bragging rights for a rare circuit and rare tone" approach.

If I were to build another amp from scratch, I would probably build just the clean Normal channel from a JMI-era VOX AC15 (with EF86 in pentode mode). I'd do all the tricks to reduce tube microphonics including suspension-mounting the tube socket, etc. It's not a complex circuit but sounds amazing from quiet to dimed. This would probably be the cheapest route. You might also consider building a clone of the newer AC15HW1X (but this has no magic-sounding EF86).

An extension of this idea is to build the AC15 Normal channel and add the ability to switch between Top Boost, EF86 as pentode, EF86 as triode, AC30-style 12AX7 as first preamp stage. He would get all the JMI-era VOX sounds in one amp. You should be able to easily add a one-tube reverb to any AC15 build.

Another from-scratch build I'd like to do is a push-pull design based on the 6BM8. That idea's been discussed at length on this forum somewhere, and the 6BM8 is known to sound amazing.

I'm not a fan of the PR. I built one as my first build and liked it, but not enough to play it much. It was too boring--none of its features were all that good. Kind of a Jack-of-all-trades, master of none amp.

[copperheadroads]

Great suggestions so far , 6v6 would be my first thing to do .& the reverb on the BJ is it tube driven ?

[dchang0]

Stock reverb is not tube driven.

[danman]

I recently gutted a Tweed Blues Jr and built a Princeton 6g2 in it. Turned out very nice and I like the fact that it uses a 12" speaker instead of the usual 10".

[mort]

Ah, yeah, if it's un-repairable, might as well gut it.

One small amp I have always wanted to build is the Gibson GA-1RVT. It's got reverb AND tremolo in a circuit small enough to stuff into a 5F1 Champ. I have not heard any recordings of it, however, so it may not actually sound all that good. There are larger Gibson circuits you might be interested in building that seem to be well-regarded (and there are recordings of these). This route would be the "bragging rights for a rare circuit and rare tone" approach.

If I were to build another amp from scratch, I would probably build just the clean Normal channel from a JMI-era VOX AC15 (with EF86 in pentode mode). I'd do all the tricks to reduce tube microphonics including suspension-mounting the tube socket, etc. It's not a complex circuit but sounds amazing from quiet to dimed. This would probably be the cheapest route. You might also consider building a clone of the newer AC15HW1X (but this has no magic-sounding EF86).

An extension of this idea is to build the AC15 Normal channel and add the ability to switch between Top Boost, EF86 as pentode, EF86 as triode, AC30-style 12AX7 as first preamp stage. He would get all the JMI-era VOX sounds in one amp. You should be able to easily add a one-tube reverb to any AC15 build.

Another from-scratch build I'd like to do is a push-pull design based on the 6BM8. That idea's been discussed at length on this forum somewhere, and the 6BM8 is known to sound amazing.

I'm not a fan of the PR. I built one as my first build and liked it, but not enough to play it much. It was too boring--none of its features were all that good. Kind of a Jack-of-all-trades, master of none amp.

I've built a couple of copies of the early Ac15 circuit w/ ef86. I LOVED the ef86 channel and hated the bright channel. But just the single channel ef86 with reverb might be the ticket. And with a master volume it could still get all the guts of the pentode front end and not piss off the owners of the small club. Hmmmmmmmmmmmmmmm

[mort]

Question: do you think an EF86 AC15 channel would sound drastically different with a diode rectifier vs an EZ81? or will it just be a little tighter sounding?

[dchang0]

I have not tried a diode rectifier in a JMI-era AC15 circuit myself.

This thread may help you decide:
https://www.thegearpage.net/board/in...-ac15s.884179/

I too did not like the newer AC15 models' tone, but there are other factors that may be more prominent.

[tedmich]

Question: do you think an EF86 AC15 channel would sound drastically different with a diode rectifier vs an EZ81? or will it just be a little tighter sounding?

Korg didn't think so and used a SS rectifier in their AC15's for a very long time I believe.

[mort]

What about omitting the choke and using a resistor in its place? Big difference or small difference?