Mini Wreck?

[doctord02]

>>From your description, I guess you didn't bypass the cathode resistor on that extra stage, right?

Correct, just a 1.5k cathode resistor to ground. (I believe... could be smaller)

>>When you back off of the guitar volume, how well does it clean up? Is it Wreck like?

Yep, pretty much similar, since the first stage input is exactly like a wreck.

>>How does the Wreck-based version of the amp sound compared to the Extreme?

It's a bit more versitile to my ears. Plus, having a master volume gives you lots of ways to vary the distortion and overdrive. With the pre stage down and/or the guitar rolled back, but the master wide open it's got a great ballsy clean, kinda Hiwatt-like...

It's still cathode biased like the Extreme, so it still has some "give" like a tweed amp, but not quite as squishy... I also used Chris Hurley's Heyboer OT.

It's suprisingly LOUD. The fellow I built it for was suprised that it seems as loud as his Vox AD60VTX combo.

[sliberty]

I'll be using that OT also since mine started life as a P1.

I hadn't decided what to do about a master volume yet. I figured I'd wait until hearing the amp to decide.

My board is all assembled now except for some caps that I am waiting to receive. I may wire it into the chassis tonight. I did the board as an eyelet type - my first. I also have no power supply yet (same reason - caps in the mail). But overall there is not much left to do to complete the build. I'd imagine that I'll finish revision 1 the night the caps arrive. Of course, I'll have to wait until the next day to crank her up.

[slajeune]

Sorry to chime in so late.

I have built a single ended trainwreck designed by David Jones. You can see the details (and small sound clips) here:

http://www.sopht.ca/mambo/index.php?opt ... &Itemid=42

The sound clips are of the ecl86 but it is now with an el84 and it really is a nice aggresive amp. It can do a lot of things (especially with the mods that I added). I am very happy with the amp!

Cheers,
Stephane.

[sliberty]

Thanks for the reply. I checked out the clips and the schematics, and it seems like a cool amp, but what makes this a TrainWreck design? I don't see any resemblence.

[slajeune]

Well,

the first 3 gain stages are the same stages as the Express. So, it's a trainwreck express but single ended.

The modifications I added simply extend the amp.

Cheers,
Stephane.

[sliberty]

OK, now I see. I thought at first that the amp had only 2 triodes (1x12ax7), but now I see that the ECL86 is a triode and an EL84 in one. Interesting.

So, this amp really is quite close to what I am planning. Some of your values around the power tube are different from my initial concept, but they are TBD until I fire her up anyway.

Some questions:

1. Why the 22k resitor on the input?
2. Why the filament reference on the power tube?
3. 5K6 at the grid of the pwoer tube must reduce power tube gain a lot, no?
4. The added DPDT seems to bypass the last stage and reduce the effective cathode resistor on the 2nd stage. Is that how you achieved the Fenderish clean tones? Was the amp so gainy that it needed this option?
5. Did you originally have a TW tone stack and then switch to this config, or was it built this way? If you switched, how did the tonal character change?

Thanks,
Steve

[slajeune]

Some questions:

1. Why the 22k resitor on the input?

That is the value that was on the schematic. You can set this to any value between none-68k.

2. Why the filament reference on the power tube?

This reduces hum injected by the filament.

3. 5K6 at the grid of the pwoer tube must reduce power tube gain a lot, no?

Actually, this should prevent blocking distortion (from my understanding).

4. The added DPDT seems to bypass the last stage and reduce the effective cathode resistor on the 2nd stage. Is that how you achieved the Fenderish clean tones? Was the amp so gainy that it needed this option?

Yes, that's exactly what the DPDT does, it bypasses the third stage. You can control the amp with the gain and with the guitar knob, but with this simple modification, you have something close to a princeton (or harvard). Which is pretty cool! 2 amps for the same price!

5. Did you originally have a TW tone stack and then switch to this config, or was it built this way? If you switched, how did the tonal character change?

The schematic wasn't mine, so I simply used the values as in the schematic. You can play with them and bring them directly inline with the Express values.

Cheers,
Stephane.