Liverpool Amp - Xtra Small Platform

[RJ Guitars]

I had the chance to do a little more soldering... it almost felt like cheating it was so easy to get to the terminals on the pots. I went with the traditional Wreck spec solid core wire with soft PVC insulation... the magic is all in the color!

[dorrisant]

Looks great, rj!!!

Do you have any of the TXs left for sale?

Tony

[dorrisant]

Looks great, rj!!!

Do you have any of the TXs left for sale?

Tony

[RJ Guitars]

Looks great, rj!!!

Do you have any of the TXs left for sale?

Tony

Hey Tony, I have a bunch of power transformers and not so many output transformers. I don't want to go with too much of a lightweight OT on this build because I expect to get around 8 watts max from this build. I really like OEM Fender Pro Junior OT because they are rated at 15 watts but are not too big and they are also pretty cheap. If I could find a slightly smaller unit with similar specs except rated for 10 watts, I'd be pleased...

[RJ Guitars]

Another update photo - I put the pots on the inside of the chassis and then added the preamp board... so far no ugly surprises.

I ordered the knobs off EBAY - they are shipping from Hong Kong so I should have the amp done by the time they get here.

I gotta start thinking about a cabinet for it. I'll not sure whether to go for the mini Wreck in cherry or go for a combo cabinet... I don't have a cabinet this small so anybody wanting to trade some fine woodwork for some amp parts - send me an email.

[dorrisant]

Looks great, rj... I PMd you.

[RJ Guitars]

I soldered a bit more. I finished up the power tube wiring and also the presence circuit. It's a bit tight around that 7 pin socket but I think it's all in there and nothing looking like trouble so far... we'll see?

[RJ Guitars]

It's alive and doing quite well. I tried to make a quick recording but it was a little too loud and overloaded the camera audio circuit... I'll put it on the list for sound clips.

It sounds very Liverpoolish... aggressive and as expected it's pretty loud. It started right up with no issues. It would seem that miniaturizing the package size didn't cause any catastrophic issues.

I'll get some voltage measurements and post those . I'll get onto some other priorities that are waiting on me but continue refining this in the near future.

If you've never heard EL95 output tubes they are a great sounding tube. I'll try a few other output tube options including the 6AN5 tube and see if there are any other that sound good.

Clips coming soon...

[ChrisM]

I like the heater wiring, neat and no close to the other tube elements/wires! Just how Merlin describes it in his preamp book.

[RJ Guitars]

I like the heater wiring, neat and no close to the other tube elements/wires! Just how Merlin describes it in his preamp book.

Yes, as you can tell I do look to Merlin occasionally for an idea. I knew that everything with this amp was going to be a bit crowded so I also chose the 20ga teflon coated wire for the heaters so I could get all the power I needed through the wire with the minimum outside diameter.

[M Fowler]

Very cool rj, tight environment in those chassis.

I have a few of your chassis like that sitting around.

[RJ Guitars]

Yes this chassis is 11 inches across and I think it could be done a little more comfortably in a 12 inch chassis. At these voltages I need a bit bigger size of filter caps to operate in the safe zone.

Ultimately, this means you could build a 2 hole output Liverpool or Express in a little combo amp like a Champ or other similar sized cabinet. Also anytime I pack in components real tight and reduce the footprint it tells if I should expect problems if I attempt to build a PCB board version. If it works with turrets I usually find it works even better with a PCB board... because this gets rid of a lot of excess metal and the wire runs are more precisely controlled... I'm not sure if I'd go ahead with a mini Wreck offering but this idea tests the concept.

If anybody feels like they want this amp lemme know... I have a plan to finish or sell all the half finished projects I've got laid out.... I don't really need another amp and I'd love to sell this one before I get caught up in making another cabinet and finishing it.

[RJ Guitars]

The knobs came in so I put them on and I had to find a pair of booster glasses just to see the screw slot well enough to tighten them down - little bitty rascals for sure.

I wanted to try some other output tubes so I rewired the power tranny in the original Wreck style half wave rectifier mode so i could drop the B+. I was getting 320 volts to the first cap which was only rated at 250V so I new I needed to do something a little different anyway. Now I have a max B+ of 180 volts which ultimately comes down to about 70 volts on the plate of the first preamp stage. To my surprise, it still sounded good and was still pretty loud... gives you an idea of how far down in voltage you have to go for a power scaling unit to do it's thing.

The EL95s still sound awesome. I then tried some 6AN5 tubes... they also sounded awesome and the clean to mean thing worked well. Finally I tried some 9001 "acorn" sized tubes. They sounded kinda cool but there is almost no headroom. Tube distortion at Bedroom levels - kinda cool! There are a ton of options for 7 pin output tubes and they are generally dirt cheap.

[jelle]

Awesome project! What signal caps did you use?

[Gibsonman63]

That would make an awesome little grab and go amplifier.