Terra: A Trainwreck Express build with Stancor A-3801

[mlp-mx6]

I believe they're to shunt flyback voltage from the OT.

[Bruciep07]

EDIT: Doh! mlp-mx6 beat me to it...

Also, a quick question. What is the purpose of the six diodes (D1-D6) in the ampgarage version of the TW Express schematic? I couldn't see any of those diodes actually turning on unless the plates actually somehow managed to drop three diode drops above ground. I guess I haven't really looked at the power stage on a scope yet but does the plate ever actually swing below the cathode on these amps? I assume the diodes are in there for protection (this is the default EE student answer ) but is there something else that I'm not considering?

Exactly that, just there for protection from "flyback" voltages between the output tubes and the output transformer...
Welcome to tag, that's a cool build...

[Ron Worley]

The Express is very sensitive to lead dress and layout.... PTP is a neat idea, but in this amp, messing with KF's recipe is asking for chaos in my estimation....

[Cliff Schecht]

I still find that the presence knob can induce oscillations at the extreme high end of the rotation. At this point I think the best thing to do will be to rebuild a proper Express when I find the money/time to do so. This amp is definitely still playable though and I find that it nails the sound I was after no problem if I keep the presence below about 8 (who needs it that high anyways!). A cleaner build I'm sure will alleviate any necessary bandaids and hum that I'm dealing with but until then, I will gladly deal with a bit of hum and the occasional squeal .

[Bruciep07]

At this point I think the best thing to do will be to rebuild a proper Express when I find the money/time to do so.

selling one of us your other 3801 would help the money issue, hint hint

[guitardude57]

Good job on the build.

Part of our search for tone involves experimenting. So nothing wrong with taking a circuit to another angle. If it works....great. If not, figure out how to tame it. It is great fun and a learning experience.

My build is in a retired integrated stereo tube amp I stripped out. A steel chassis, 7189 tubes, and all point to point....no boards at all. Everything was parts on hand, so no expense.

It sounds fabulous albeit minor oscillation at 3/4 volume and maxed treble. I have it plugged into a 1960A with EVM 12L's and it is way loud. Once the oscillation is nailed......there is absolutely nothing wrong with the tone/sound of this amp under oscillating volume.

I was just amazed at the minimal noise due to the steel chassis.

So I can understand, the purists that want to replicate the original design.
It's all good......but so is taking liberties and pioneering. Right?

So my next one will have an aluminum chassis and use of a 370-0-370 and matching 8R tranny set I have, for some EL34's or maybe 6L6's. I'll try both.

Again, good job.

[Cliff Schecht]

Steel chassis aren't necessarily more prone to noise, it's all about your layout and how you take care of those noise-susceptible stages. I've built a few amps in steel chassis and noise definitely wasn't an issue (weight was though!). If you use your chassis for high current ground returns then I would avoid using non-isolated input jacks, but this holds true for aluminum cases as well.

Also, I fired up Terra today through the 4x12 cab. All I can say is HOLY SHIT this amp came to life! All of my tests so far have been through an ancient 1x12 open back enclosure which makes the Express sound too muddy. But the sound through a 4x12 was, for a lack of better words, breathtaking. The cleans were clear and chimy while the distortion was thick yet well defined. I could see this amp easily cutting through in ANY situation I will put it in. Unfortunately I couldn't play the amp for more than a minute or two as it was incredibly loud and I do have neighbors that work.. The hum coming from the amp at idle was quite low for a high gain build too, especially considering that I was using single coils!

Something else I noticed was that my oscillation problems on the presence pot go away when I use an actual purchased speaker cable (as opposed to the wall-cord that's attached to the ancient cab). Perhaps the extra shielding in the purchased speaker cable is enough to squash those oscillations when the presence is turned past 7 or 8.

[Cliff Schecht]

Finally got to jam with the Express today. She more than held up her own with a drummer, another guitarist and a piano player. And I was being nice and playing through a 1x12 . I don't think I could ask for more from an amp, especially since I can leave all of the effects at home and not worry about being able to get a wide range of sounds. She was nice and quiet too, I was hearing much more noise from my friends Fender solid state amp (especially on the distortion channel)! I've never had an amp cut through the mix so well. My hats off to Ken Fischer and his inspiring design, I can only hope that my future designs can hold a candle to this amp.

[guitardude57]

Cliff, where abouts in Texas are you?

[Zippy]

I was hearing much more noise from my friends Fender solid state amp (especially on the distortion channel)!

Maybe build another amp for your friend?

Which makes me wonder... If your amp cuts through the mix so well, what happens when two people are playing similar amps? If everyone is cutting THROUGH the mix, where is the mix?

[Cliff Schecht]

Cliff, where abouts in Texas are you?

School in Lubbock, originally from Austin.

I was hearing much more noise from my friends Fender solid state amp (especially on the distortion channel)!

Maybe build another amp for your friend?

Which makes me wonder... If your amp cuts through the mix so well, what happens when two people are playing similar amps? If everyone is cutting THROUGH the mix, where is the mix?

The best way to put it is that everybody was able to find their place sonically instead of playing volume wars the whole time. I didn't find myself constantly turning up the volume on the amp to hear myself or bitching at others to turn down, instead everybody sets their levels around me and the drums.

I've been to a lot of jams that didn't go well because somebody decided to bring their 120W 6505+ and a 4x12 cab. My Fender Bassman Reissue (what I was playing at the time) could never compete with an amp like this and I always found myself sneaking over to my amp to turn up the volume. With the 'Wreck, I pretty much just turned on the amp and didn't have to touch it for two hours. But I think I worked my volume control loose on my guitar .

Now how blasphemous is it to throw a good overdrive in front of an Express? I've found that with my Tele, I can get some great sounding cleans and a good sounding distortion but the relatively low output single coils make it hard to grab a bend and sustain it "endlessly". I'm really not looking for anymore crunch or distortion, but I do want just a bit more sustain when I'm trying to make a note sing.

[Ron Worley]

I can't believe an Austinite became a RED RAIDER

Hook 'em baby.... I want some Alabama ASS tomorrow

I'm in DFW, but my oldest is a Longhorn.... gonna move to the Hill Country just as soon as my youngest gets out of High School...

Sorry for the hijack!

[Zippy]

Now how blasphemous is it to throw a good overdrive in front of an Express? I've found that with my Tele, I can get some great sounding cleans and a good sounding distortion but the relatively low output single coils make it hard to grab a bend and sustain it "endlessly".

Just call it "input level compensation" and you're fine.

If it doesn't work, you'll be the first to know. If it does work, hey, you're there!

Expresses for everyone!

[rawnster]

Hook 'em baby.... I want some Alabama ASS tomorrow

Now that's what I call a pipe dream. Roll Tide!

Ok back to thread topic.

[dartanion]

I was hearing much more noise from my friends Fender solid state amp (especially on the distortion channel)!

Maybe build another amp for your friend?

Which makes me wonder... If your amp cuts through the mix so well, what happens when two people are playing similar amps? If everyone is cutting THROUGH the mix, where is the mix?

I'll tell you from experience. Rob, my other guitarist and co-founder of our band, uses a Vapour 20 that I custom built for him to maximize cleans yet still act like a Wreck. I use either a Vapour 30, a Torpedo 30, or a Torpedo 50. So, very similar amps and pedals, and it works really well together. The main thing that you need to cut through is drums and bass. One thing that I make sure of is that we are using different speakers as we use the same 212 cabs for the most part.