Amp build - Trainwreck Express type amp in a recycled chassis

PeteC

Inspired by Keefy’s posts about Trainwrecks I was inspired to dig out all the Twreck info I acquired many years ago when I was active on Ampgarage and at that time building a Dumble 50watt clone And corresponding with Scot Lerner and a few other guys who were early into reverse engineering the Dumble. 

I had plenty of info on the Express amp but never got round to building one up.   Instead I got sidetracked with making a few plexis after the Dumble ODS type amp was finished.   

So , with curiosity getting the better of me and keen to have a new self built amp to go with the two juniors I have been making, I have set about making a rough and ready Trainwreck Express type amp -  using the famous Francesca as the basic circuit and layout to work from. 

I won’t be sticking rigidly to the original build and parts but will be using the same circuit.   I’ve built lots of amps and know how to trouble shoot issues with lead dress etc.  Some of my quietest amps have looked the messiest in terms of wire runs etc but I know the principles to get an amp sounding good. I am going for 2 x 6v6 output I like 6v6s for their early crunch . 

The donor chassis is from an 80s Pro-Amp Viper which i doubt manny people will remember.  Pro-amp had quite a nice amp called the VSQ65 which I owned for a while, long gone now.....

The circuit board will be eyelets on 2mm Tufnell whale board / phenolic. 

iron is a bit of a challenge cos at the moment although I have a lovely output TX I can use , I only have a couple of spare mains TXs laying around and neither is ideal.  One has a 300-0-300 winding but is only 80-90 ma. And the other is has a 450 - 375 - 0 secondary with no centre tap.  Both TXs have sufficient 6v and 5v windings to do solid state or valve rectifiers etc .     I need to read up Merlin Blencowes excellent book on PSU design and see what I can do to get the B+ in the right ballpark unless anyone has suggestions ? If not I will need to order a new 300-0-300 mains tx. 

The donor chassis up to recently had a 5e3 circuit in it and I’ve removed and kept the deluxe board for future use to build another 5e3 quickly in the future sometime.  

So having printed the board layout to scale it’s time to start drilling the board and staking in the eyelets, before making up the heart of the amp.   Should be fun !   

I know the amp will probably be a bugger to get stable but I am looking forward to seeing how this turns out. 

A few pics of the donor in its deluxe 5e3 state and after gutting , and the removed deluxe board for future use.    

Stay well.   PeteC 

PeteC

Made some progress today.    Eyelet board done and the controls wired with a ground bus.   Got to build the power supply next.  Can’t decide whether to mix things up a bit and go with a valve rectifier instead of solid state for a bit of “sponginess” in the amps response.   

If this circuit in a kind of “make-do” build works well then I will plan a full on replica build next.  

Onwards.......

stay well guys and gals 

MattNovak

I'm far, far away from building my own amps - or even understanding how they really work - but I do love an amp build thread! 

Never played through a Trainwreck either, I've heard they are very dynamic / touch sensitive? My gigging amp for the last 4 years has been a Rosewell Plexi Lite for what its worth..

Winny_Pooh

This is gonna be fun

PeteC

Cheers guys - Yes - the Express is renowned for its touch sensitivity and high gain - but a lot of clones suffer from instability and oscillation. The circuit can be a beast to tame, but Ken Fisher knew exactly what he was doing and built some of the very best guitar amps ever.   I'm hoping this turns ou well.  Ive used this chassis to build and test many different amps - so its riddled with mounting hole and bits and bobs.   It makes it really easy to ry a new amp every so often though.   If they work out well I build up a separate amp properly. Thats how my Park Rocked and "Plexi" 50 copies came about. 

I still need to find a good mains transformer for this express build though...

PhilKing

I was lucky enough to play through one about 5 years ago, when I was still living in New Jersey.  They do sound great, but get very loud.  They are extremely responsive to your playing style.  I'm sure you'll have great fun with it.

PeteC

Yep - very loud @PhilKing !!!

 I am also building an airbrake to use with it for recording in the little studio attached to the house.  Cant risk the cops coming round !!!

PeteC

Parts for the Airbrake just arrived - so at least I can get the attenuator made before the amp is finished. 

PeteC

bit of progress doing the wiring from the main board yesterday - now waiting for some nice TXs to turn up and a Mouser order to arrive with more components.   Really I ought to get back to making some progress on the Juniors ! #easilysidetracked ! 

PeteC

Just about there now.   Just waiting on a mains switch and a couple of bits and pieces then ready to rumble.  

Winny_Pooh

Looking goooooood

PeteC

Finished wiring up and testing the express.  Man this is a LOUD amp !  No oscillation or instability even at max volume so I am pretty pleased with that.  Need to do the panel and cosmetics next and house it in a recycled head cab.   Attenuator next !!    At the moment I am running military 6v6s in it and it sounds great.   Had to adjust the bias circuit to get in the right range for the 6v6s though.  

MattNovak

Amp building is like voodoo to me! I normally have to fault find after wiring up a telecaster, so I can't imagine taking on all that soldering. Looking great, will you post clips?

PeteC

Will do @MattNovak    As soon as I get the attenuator made ( copy of an Airbrake). The amp is too loud for me to crank it at home to get the best from it.  The attenuators will let me get it singing nicely    It’s true what they say about the express circuit.  On 1 on the volume it’s like a 50watt plexi on 7 !!  Some lovely clean tones by tolling off the volume on the guitar.  Can’t wait to crank it up though.    I’m switching between 6v6s and EL34s but think the 34s sound better.  Hard to tell until I can run it wide open tbh. 

greggreg66

This is amazing. I'd love to know more about amps... and how to fix them! I have a Fender tweed Blues Deluxe that's more or less dead, but I don't know how to fix it and when I enquired no-one would fix it. There's basically no volume, you can *just* hear it playing. Apparently the weakest point on these amps is a couple of specific resistors which burn out, but mine seem fine. Visually there's nothing obviously. I have a Pro Junior too which died a while back, popped the hood and a resistor was loose, soldered it back in and was alive again.... no such obvious luck with the Blues Deluxe : (

Your amp build looks awesome

PeteC

I’m sure it will be a simple fix @greggreg66 ; Hang onto it and I’m sure we can sort it out when the lockdown is over 

Keefy

So what happened next?

PeteC

Do you mean with Greg's amp ?   - nothing yet tbh.  but happy to try help after lockdown. 

If you mean with the Express  - its finished and waiting to go into a better head cabinet when I buy some decent Cherry. 

I need to fit a bright switch as well ( apparently a key ingredient for the Express sound ) but its already pretty bright without it.  It will probably boost some freqs though and help the lead sound.    

I A/B'd it with my Plexi 50 clone for as long as I dared to in a built up area,  and its a great amp if you like classic rock tones - the best thing is how you can play the amp from the volume control of the guitar - sparkly cleans through to searing leads with a twist of the volume control, very expressive.  

Keefy

Yes, i meant the Express. What will you do with all those extra holes?

PeteC

When the chassis goes into a cherry cab I plan to make a 2mm thick wooden veneer faceplate - following the same idea used on the original trainwrecks.   The faceplate will cover the unused holes.   

Keefy

PeteC said:

When the chassis goes into a cherry cab I plan to make a 2mm thick wooden veneer faceplate - following the same idea used on the original trainwrecks.   The faceplate will cover the unused holes.   

Like this then: