mini wrecks...

[riscado]

Let's say you wanted to build a trainwreck inspired amp, but keep the package smaller (yet maintaining the push-pull ouput), so you would go for a 2x6V6 (either cathode or fixed bias) or a 2xel84 and use a 15w OT iron...

the preamp can essentially be the same, although maybe plate voltages will have to be adjusted accordingly right? What more would you take into consideration when building one of these smaller amps? How would the filtering values change when compared to the bigger amps for example? Any sugested values?

thanks

[brownnote]

It works great on the 18W Lite platform; 14"x6"x2.5"...either el84/liverpool 6V6/express...it's a little tight to build, but no noise problems. Filtering is about the same topology, but a little lighter values.
Single turret board for preamp and power supply.
Using 18W type iron.

That's one way to go anyway...makes for a nice compact little screamer

[LeftyStrat]

If you want to go even lower in output, you can use something like the Moonlight or uTube amp power sections. Both use a 6SN7/12SN7 as the output tube for a total output of one watt. Still pretty loud, and if not loud enough, you can always add a post-transformer line out.

I'm currently working on a small amp like this, using one of the EH transformers back-to-back with a 12 vac wall wart available from diystompboxes or hoffman amps.

I am using the uTube power amp, but I scrapped the PI in favor of a 12ax7 type PI, but now it is just a matter of getting the balance of gain at each stage right.

There is also a schematic floating around here that uses a 12au7 for the output stage. It uses a concertina PI, and I haven't heard clips.

A lot of the clips of miniwrecks I have heard have good distortion for rhythm style playing, but I haven't heard the blossoming sustain for lead tones like a real wreck. That doesn't mean they don't have it, I just haven't heard any clips that demonstrate it.

I suspect that a long-tailed pair is part of the TW mojo. I would love to be proven wrong, so if anyone has clips of a miniwreck (whether single-ended or non-LTP) that does the lead harmonic blooming feedback thing, I'd love to hear them.

Of course, at some point the lack of push from a low powered amp is going to inhibit the feedback thing, but from my regular Express, I still seem to get a good amount of controlled feedback even at lower volumes (which is still pretty loud).

[Richie]

uR12 is building a light version liverpool combo. I'll be building a 2x6v6 express combo 2x12. In the marshall 18 2x12 cab.

[riscado]

What I'd mostly like to obtain from this smallish amp is the ability that wrecks seem to have to move into feedback even when played clean (after playing a chord they seem to haul with feedback).

I'll be using a real close approximation of the real amp, so a long tail PI will be used...

What would you guys choose if using 6V6's? Cathode or fixed bias?

Richie I'll be following yours' and Dana's build very closely as I'm quite curious regarding the results...

What do you think of hammond 125E iron for the OT of these projects?

thanks

[mlp-mx6]

I built one in a Fender Blues Jr. chassis. It sounded GREAT (imho). I drilled out the "Fat" switch square hole and made that a Bright switch. Voltages were spot-on for a Liverpool-style with 2 EL84s. The main hassle was having to make a board to hold the tube sockets, as those were board-mounted in the original circuit also. With it being in a combo cab, I REALLY had to search to find non-microphonic preamp tubes.

[riscado]

Richie will the 2x6V6 combo be fixed or cathode bias?

[Richie]

mine will not be cathode biased. it will be like a mini express..

[riscado]

Ok Dana is doing the el84 cathode biased version, you're doing the 6V6 fixed biased version, maybe I should try the cathode biased 6V6 and share the results later on...

I was thinking of using a 125E hammond for the OT, could you guys tell me which OT you'll be using?

thanks

[UR12]

Ok Dana is doing the el84 cathode biased version, you're doing the 6V6 fixed biased version, maybe I should try the cathode biased 6V6 and share the results later on...

I was thinking of using a 125E hammond for the OT, could you guys tell me which OT you'll be using?

thanks

Not sure about Richie but I'm using a 10.5k Heyboer tranny I had wound to the same physical specs as the 18watt Marshall tranny