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Trainwreck-Can a Mere Mortal Build One?

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6/22/1999 10:54 AM

Trainwreck-Can a Mere Mortal Build One?

Before anybody asks I don't have a schematic.

Been doing a bit of reading. Mainly in Funk's book where the Trainwrecks are mentioned quite a bit. In his gain scheduling he mentions that the Express is a 1+2 configuration.

1st Gain Stage-Tone Stack--2nd GS--3rd GS---->Driver

In Pittman's book lists the Express tube compliment as 3 7025's, and a pair of EL-34's. It's also pretty common knowledge that Ken Fischer really loves the old Voxes.

Anybody want to take a guess as to the type of cicuit he would use? I'm thinking of something like:

Standard GainStage--Tone Stack--Standard GS--Cathode Follower-->Driver stage

It is also mentioned that the preamp stages don't clip the signal--just boost it to really goose the power section.

Anybody build a circuit like this? Any thoughts/insights?

thanks

bw

PS Can anybody else get into the Trainwreck site, I keep getting a stereo outlet store or something.

6/22/1999 6:26 PM

BWilliamson;

This doens't help much but your post looked lonely :-)

:-)

If you find a Trainwreck schematic I'm sure we'd all love to take a looksy at it! :-)

:-)

I've never seen a Trainwreck schematic to be honest with you and I don't know ANYONE who has one. These may be harder to come by than the Dumble schemtic! (ha, ha)

Perhapes someone here does have one. If they do I'm sure they'll share the info with you.

Best of luck!

Trace

6/22/1999 7:18 PM
SteveR	There is one in Pittman's Tube Amp Book on page 654. It's an AC 30 Top Boost with SS Rectifier. I built a clone of it minus the Vib/Trem using Matchless transformers. It turned out pretty nice. Steve

6/22/1999 11:59 PM

Yeah, I believe that statement about the rarity of the Trainwreck schems. I traded some schems to a guy that claimed to have one but I ended up getting that one out of Pitman's book. I remember a long thread on the old BBS where it was actually a Vox schem--not a Trainwreck. Sorry Steve.

Honestly I'm more interested if anybody has experimented with the type of preamp I surmised.

Thanks for at least showing me some attention.

bw

6/23/1999 0:47 AM

Y'know, I always wondered why it bared such a stricking resemblance to the AC30 circuit. The only real significant change from the ones actually labelled Jennings is the PS. Thanks for straightening me out!

Sorry I can't help out with your quest, although I'm looking at a schematic that I downloaded somewhere from the web that has a similar topology to what you're looking for, but (in breaking the first rule of technical drawing) there is no title or author listed.

The amp basically is as follows:

First Stage -> Tone Stack(&vol) -> Gain Stage -> Gain Stage -> Driver(Split)(&mv)-> PP EL84s

There's no cathode follower, but if you're interested I'll continue searching for more info on this amp.

Steve

6/23/1999 2:08 AM

Re: Preamp considerations

Thanks for the link. I had rumaged across that site quite awhile ago. Had forgotten about it. Interesting. I've found other types of of preamps similiar. All good for comparision.

I don't have enough experience to really figure out what is going on. Using the tube count from Pittman's book of 3 7025's, and knowing there is 3 gain stages. Using Funk's analysis of placement of the stages. I couldn't see them wasting 1/2 a triode following the Fatlady's exaple.

Perhaps the 1st or 3rd stage is paralelled? Too many options.

thanks--keep an eye out

bw

6/23/1999 11:41 AM
BWilliamson	Forget it, I don't even think I'm close with where I was going. Been doing some more reading. One thing I couldn't figure out was what is that switch on the front of the Express. It was mentioned that the Mesa MkI is also a 1+2 configuration. Perhaps he has to seperate 1st stage gain stages and they can be switched between. Thinkin' in that direction now Doh! bw

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