New Trainwreck Inspired 2 channel amp

[UR12]

Hey guys

Just wanted to share a new amp design that I just finished. This is a Trainwreck “Inspired” design. After finishing my Rocket, I was thinking about all of the differences and similarities between the Rocket and the Liverpool. They both share the same power section but are completely different in the preamp department. Obviously they are voiced different. So I came up with an idea to build a two channel amp with one channel Liverpool and one Rocket. I know Ken always stuck with single channel amps but just couldn’t resist giving it a try.

It didn’t turn out as easy as I thought it would. I decided to go with 6GK6 output tubes instead of EL84s. The 6GK6 has basically the same operating characteristics but a different pin out than an EL84. They put out a few more watts and handle a little higher voltage than the EL84. If you look at the two preamp circuits side by side you’ll see that at the input to the PI your channels are out of phase. I decided to go with a different approach and instead of trying to mix the two channels together I would create a design that allowed you to be in Liverpool or Rocket mode only. (No A/B/Y switching here) in other words you aren’t just switching the guitar input between two different preamps. There are 3 relays in this amp that are used to “reconfigure” if you will, the amp for each voicing. The original Liverpool has VTMB and a Presence control. The Rocket has a VTB and Hi Cut control. In Liverpool mode the presence control and it’s associated components are switched into the circuit and the Hi cut control is disconnected. In Rocket mode, the High cut control is switched in and the presence control circuitry is switched out and the tail of the PI is switched to ground. This keeps both modes as accurate as possible to the original amp circuitry.

I have also included a variable Power Level control so the amp can be played at any power level from about 1 watt to 30 watts.

I got to test the amp last night and so far it sounds great. I still need to do some preamp tube swapping and try and tame some relay switching noise but all in all I am very pleased with the results. As soon as I get a few tweeks done and the schematic updated I’ll get it posted here if there is any interest

Here is a few pics.

[bnwitt]

Dana,
great looking work. Will you be sharing your layout and schem? I'm also interested in that power control. It looks easy to implement.
Barry

[UR12]

Barry

Yes I'll be sharing the schemo as soon as I get it finished. The schemo includes the Power control implementation . I am also going to try and get some clips made.

[Drumslinger]

Looks awsome Dana. Looking forward to the clips.

[joe6v6]

Beuatiful work Dana ! , with everything thats going on in there you sure kept everything nice and neat.

JOE

[UR12]

Beuatiful work Dana ! , with everything thats going on in there you sure kept everything nice and neat.

JOE

It helps to have a BIG chassis 7" x 22" x 2.5" This one is the prototype. Maybe we can get Allyn to build one and make it real purty.

[skyboltone]

Really, Really great work and concept mister Hall. I've had to change the nameplate art on my amp because of you!

By the way are your people from around Boston or Western New York? We've got ours traced back to the 1640's in Mass.

Dan Hall

[UR12]

Really, Really great work and concept mister Hall. I've had to change the nameplate art on my amp because of you!

By the way are your people from around Boston or Western New York? We've got ours traced back to the 1640's in Mass.

Dan Hall

Hey Dan

Sorry bout the nameplate

I only have my Hall family traced back to VA about 1800. They came into KY in the 1840s but may very well be descendants of some Halls up in the NY/Mass area. You can checkout my family genealogy webpage at

http://users.zoominternet.net/~jdhall/hall

Lots of info on a few different Hall families in KY

I am distant cousin to Tom T. Hall and his son Dean Hall who plays with that "Redneck woman" and Music Mafia.


My brother "Richie" on this forum is in the process of building the same amp as above except with 4 6V6s. Should be kind of a Express/Rocket sounding amp and I can't wait to hear his.

[Jimy]

Beautiful work. Nice concept and great execution. Looking forward to the clips and, especially, the schem and layout. I'm very curious about the power control. Can you share your impressions? How does the amp sound and feel when scaled back as compared to full voltage? Also, are you scaling just the power section, the whole amp, or...?

[UR12]

Beautiful work. Nice concept and great execution. Looking forward to the clips and, especially, the schem and layout. I'm very curious about the power control. Can you share your impressions? How does the amp sound and feel when scaled back as compared to full voltage? Also, are you scaling just the power section, the whole amp, or...?

According to Powerscaling.com, I guess you really can’t use the term power scaling to describe the circuit I am using as I am not paying for the use of the term. The circuit I am using controls the whole amp and not just the power section. I have tried it other ways and like this way best. (At least for a cathode biased amp) As far as the way it sounds , you still get those singing sustains all the way down to bedroom levels. I don’t care what method you use to reduce the power you will never be able to get it to sound exactly like your amp cranked because you reach a level where the speakers aren’t moving enough and you loose efficiency. Having said that I think this method gets you as close as any and sounds great at lower levels for what it does and tone and feel are still there at levels above 1-5 watts. Just my opinion YMMV.

[Jimy]

OK... um, power modulation then...

Great looking amp. Can't wait to hear it.

[Guy G]

Awesome build..
Would you care to explain how exactly you implemented your variable power board? seems like your method uses less parts than any method I've seen..

[UR12]

Awesome build..
Would you care to explain how exactly you implemented your variable power board? seems like your method uses less parts than any method I've seen..

The circuit I used was derived from a public domain variable power supply. There are only 6 parts on the board (1) mosfet, (3) resistors, (1) zener diode and (1) pot. Basically this is all that is required for a bare bones variable voltage regulator. Some of the other circuits out there include extra parts for current limiting, adjustable sag controls and for scaleing bias voltage on fixed bias amps. All of that isn't really necessary on a small wattage fixed bias amps in my opinion. The circuit works flawlessly and I have had it installed in amps for a couple of years now with no problems. I scale the whole amp and not just the power section. If you just want to scale the power section and not the preamp a couple more diodes would be required. It is a lot easier to design an amp around the circuit than to try and retrofit the circuit into an amp. Have you checked out powerscaling.com?

[Guy G]

Yeah I've checked it, waiting to build the plexi they mentioned. anyway, why scale the whole amp? any advantages?

[Beerman]

Hey Dana. Wanna fit a 240V trannie and send it to me? I'll look after her real good...

But seriously. Has this amp been built to order? Do you think you'll sell it?

Would you be kind enough to post a BOM when you post the schemo and layout?

Love your work, thanks for sharing.