Trainwreck channel in an 18 watt amp?

Mickey_C · Post by **Mickey_C** » Sun Apr 22, 2007 9:06 pm

Has anybody worked on putting a trainwreck type channel in an 18 watt amp?

I searched, didn't find anything. If there's already a thread on this, if you direct me, I'd be most appreciative!

Mickey

dimitris · Post by **dimitris** » Sun Apr 22, 2007 10:22 pm

Hi.Search 18watt forum for T-Rex.
I think that's what you want.
Dimitris

Mickey_C · Post by **Mickey_C** » Sun Apr 22, 2007 11:28 pm

I was afraid somebody might say that.

My search capabilities for that particular forum are currently unavailable.

So, how does T-Rex measure up? Did anybody here build one? Clips?

jelle · Post by **jelle** » Mon Apr 23, 2007 12:07 am

Hi Mickey,

I have build an Express amp into an 18w. It still has the 18w powersupply and a blue bulldog. Sounds very agressive and does come alive with my 4x12 G12m cab but I feel that these amps do not go well with an open back cabinet. Very cool amp and with 18w still very LOUD!!!!! Maybe a bit bluesy for some due to the rectifier tube, The lower value grid stoppers for the EL84's (compared to the 18w) make a huge difference.

I do not have soundfiles, sorry!

I hope this helps,
Jelle

UR12 · Post by **UR12** » Mon Apr 23, 2007 12:21 am

http://homepage.mac.com/geekmacdaddy/FileSharing16.html

Mickey_C · Post by **Mickey_C** » Mon Apr 23, 2007 1:15 am

Thanks for the tips and clips - I found the schematic/layout on the mhuss site!

dartanion · Post by **dartanion** » Mon Apr 23, 2007 4:46 am

Hey Mickey_C,

Good to see you around. I was just about to point you to Mark's website.

You can also take a Liverpool and subtract 2 EL84s!

Mickey_C · Post by **Mickey_C** » Mon Apr 23, 2007 5:55 am

Hey Dartanion,

I saw you blaze through the gear page, spreding the 18 watt DIY gospel in your wake! Nice to see you getting out too. This site is super cool - you don't get any of the spamming for good buddy points (thank god), but you do get the most desirable hush-hush amp builds! Wowsa.

Everytime I hear the TW clips, I drop everything I'm doing, and reach for the drool bucket. I gotta get that sound!

After pouring over this stuff all day, I may just try to wreck a JTM45 from my boneyard! Why? Well, I have a surplus of the trannys for that and 18 and 20 watt marshalls, that's why

Anybody done that yet? Will the JTM45 iron work?

Mickey

dartanion · Post by **dartanion** » Mon Apr 23, 2007 4:49 pm

Hey Mickey_C,

Yeah, the gear page is kind of like Harmony Central in a way, but still more interesting.

18watt has gotten a little stale, and unfriendly in some ways. I figured I would check out what was going on elsewhere.

JTM45 iron should work for a Wreck of some sort. Be creative man

Your chassis designs are some of the coolest that I have seen.

doctord02 · Post by **doctord02** » Mon Apr 23, 2007 5:42 pm

Hi Mickey, good to see you here. JTM45 output iron should be fine. I think the critical part is the PT voltages. If you are building a EL34 Express type amp the magic plate voltage seems to be about 395-405 vdc.

If you are building a EL84 amp, then both the PT and OT iron from a standard 18 watt build should be fine.

Dave
(aka idiotwithasolderingiron over at 18watt)

Mickey_C · Post by **Mickey_C** » Mon Apr 23, 2007 9:51 pm

doctord02 wrote:Hi Mickey, good to see you here. JTM45 output iron should be fine. I think the critical part is the PT voltages. If you are building a EL34 Express type amp the magic plate voltage seems to be about 395-405 vdc.

If you are building a EL84 amp, then both the PT and OT iron from a standard 18 watt build should be fine.

Dave
(aka idiotwithasolderingiron over at 18watt)

Hiya dave!

I have a few of the "Fender sized marshall transformers" from Mercury, and with a full wave rectifier they provide about 405V with a pair of EL34 tubes.

I also have some prefabricated chassis units with 3 octal sockets and 4 novals, which fit the mercury trannys and the Mercury JTM45 OT. The OT can do 3.5K or 7K primary, so now I just need a layout.

I'd kind of like to power scale it, since I have some hybrid turret boards that are perforated on one end, and have the integrated power scaling PCB on the other.

Any recommendations of which layout should I start with?

Mickey

doctord02 · Post by **doctord02** » Wed Apr 25, 2007 7:30 am

Well, this is pretty much the accepted layout:

https://tubeamparchive.com/files/Expres ... rawing.jpg
https://tubeamparchive.com/files/Trainw ... t_REV2.gif
https://tubeamparchive.com/files/express_wiring1.pdf

You may need to flip it depending on your chassis orientation. You know more about power scaling than I so I cant suggest anything there... I would however keep the preamp layout as designed; there are several reports the wire layout is designed to make use of local inductance and coupling to accentuate some things and tone down others. Look thru the Franchesca picture folders for a much better idea of whats going on.

The Express OT was either 5.2K or 6.6K depending on who you believe. I have amps built both ways and both sound good to me. I suggest trying both impedances you have and letting your ears decide.

Good luck and have fun. It's a great sounding circuit.

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Trainwreck channel in an 18 watt amp?

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