New Project suggestions

[arielyitus]

Hello everyone,

This is my first post on this forum and I wanted to get started by getting some ideas from you for my new project.

I have built a 5F2A, 5E3 and an 18Watt TMB so far. I really like them all but I have some parts ready to be used in another cool project.

Some time ago I bought a 36 Watt chassis (believe meant for a vht amp) and a PT for a 36 Watt amp as well.

I want a different sounding amp from what I already have, and because of the tube configuration and transformer characteristics I was thinking may be a Trainwreck Liverpool would be a good fit?

Can you guys give me your suggestions?

Thanks a lot

chassis2.jpg

chassis1.jpg

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[pompeiisneaks]

Just knowing that you have a PT for a 36 Watt amp doesn't give enough information on what it could do. We'd need to know the amount of current the main winding and heaters can handle to know how many tubes it can provide for.

Also if the picture you have is the transformer, it has a 5V winding and is drawn with a tube rectifier, do you want/need to use that? if not then those windings don't matter, but if you do, (a liverpool doesn't use one, it uses SS rectification). then that matters somewhat too. I think knowing a bit more of what sound you want would be good. You've done a few builds now that look like you may be ready for a liverpool, so that part shouldn't be a deal breaker.

If you can give more detail on the transformer, that would help, the heaters need to be able to provide current for 4x el84 as well as the 3 preamp tubes.

I've built a liverpool and love it's tone.

~Phil

[arielyitus]

Just knowing that you have a PT for a 36 Watt amp doesn't give enough information on what it could do. We'd need to know the amount of current the main winding and heaters can handle to know how many tubes it can provide for.

Also if the picture you have is the transformer, it has a 5V winding and is drawn with a tube rectifier, do you want/need to use that? if not then those windings don't matter, but if you do, (a liverpool doesn't use one, it uses SS rectification). then that matters somewhat too. I think knowing a bit more of what sound you want would be good. You've done a few builds now that look like you may be ready for a liverpool, so that part shouldn't be a deal breaker.

If you can give more detail on the transformer, that would help, the heaters need to be able to provide current for 4x el84 as well as the 3 preamp tubes.

I've built a liverpool and love it's tone.

~Phil

Hi Phil,

That transformer is meant to be used in a VHT 36 Watt amp which has the following tube compliment:
1x 5U4GB Rectifier Tube
4X EL84
3X 12AX7

I don't know the current ratings for it but I will try to find out.

I would like a more over driven tone, think classic rock but not metal. Dirtiest tone I am looking for would be guns n' roses appetite for destruction kind of tone.

All of the amps I have built have tube rectifiers, it would be OK to have diode rectifier on this one, or may be even a dual rectifier (switch selecting tube/diode)

Thanks a lot for the help

[pompeiisneaks]

Then that does fit the bill. The liverpool uses the same tube complement, and you could definitely do a switchable ss vs tube rectified amp, the only problem being that the liverpool uses 2 40uF caps in parallel meaning it will be 80uF at that first stage which is too much filtering for that tube rectifier and will be hard on it. you 'could' just reduce that first stage down to 40uF, but that could have an impact on the tone of the amp, being a bit less filtered etc.

I'd recommend just sticking with the stock circuit, but that's up to you.

~Phil

[arielyitus]

Then that does fit the bill. The liverpool uses the same tube complement, and you could definitely do a switchable ss vs tube rectified amp, the only problem being that the liverpool uses 2 40uF caps in parallel meaning it will be 80uF at that first stage which is too much filtering for that tube rectifier and will be hard on it. you 'could' just reduce that first stage down to 40uF, but that could have an impact on the tone of the amp, being a bit less filtered etc.

I'd recommend just sticking with the stock circuit, but that's up to you.

~Phil

Thanks, if I go for the Liverpool I think I will stick to SS rectifier.

Is master volume a common mod for this amp? Pre or Post PI?

Also, could you recommend an output transformer?

Are there prebuilt turret boards?

Are the voltages in my PT correct for this project?

Thanks again and sorry for the million questions

[Colossal]

Are the voltages in my PT correct for this project?

You PT is 320-0-320. That is way too hot for a Liverpool and generally* for EL84s (unless you seriously lower the screen voltage).
Solid state rectified (unloaded) 320VAC * 1.414 = 452VDC
If we account for loading, say 180-200mA, that will drop to 400 to 416VDC or so. This is incorrect for a Liverpool.

If you consider tube rectification (as your chassis is a 36W two channel Marshall style layout) a 5Y3GT won't deliver enough current to keep four EL84s cooking in Liverpool territory. That leaves either a 5U4, 5R4, or GZ34 and each will still deliver a fairly high B+, the GZ34 being the highest about 400VDC under load. A 5U4 will dump some voltage so that may be something to consider.

A Liverpool's PT should be about 260-0-260 (unloaded), running solid state rectification.

Is master volume a common mod for this amp? Pre or Post PI?

You can add either or both master volumes but it changes the dynamics of the amp. Trainwreck amps are designed with a high primary impedance for the OT which is intended to produce power tube distortion first, followed by the PI, then preamp.

Also, could you recommend an output transformer?

I would go with a Heyboer, Pacific, or Mercury running 6k6 on the primary for a quad of EL84s.

Are there prebuilt turret boards?

I would look to rjguitars.net. RJ is a member here and a long time supplier to the Trainwreck builder community. Rooster, also a member here, has the period correct NOS signal capacitors for sale in the For Sale section of the forum. Watts Tube Audio does offer Trainwreck and other turret boards but the business appears to be imploding right now, so not advised to do business with them at this time. You can also check with Hoffman, at least for premade turret boards (I don't know about populated).


* by generally I mean your 'typical' EL84 guitar amp (AC30 derivatives etc). There are amps that run EL84s much hotter but they are not typical and have lower screen voltages and utilize OTs with primary impedances to work under these conditions

[arielyitus]

I have seen people drop the B+ voltage with a zener array, do you think I could get it in the ballpark with a few zeners?

[Colossal]

Yes, that is an option too.

[Phil_S]

I'm not fond of the various tricks to reduce B+. You are converting the excess to heat. I don't know how much heat, but you've got a lot of volts to drop, so it sounds like a lot.

I suggest it would be better to find a build that fits that PT, like a pair of 6L6's.

The other way to go, and this is what I'd do, is to build the power supply with a choke input circuit. You can search here for a thread I started several years ago. Someone gave me a PT with high secondary voltage, but not a lot of mA rating. I tested several chokes in a breadboard circuit, all documented in the thread. Generally speaking the rule of thumb, 45% of VAC = VDC with solid state rectification, applies. 640VAC * .45 = 288VDC. That's actually a good spot for a pair of EL84's, provided the required current remains available. I don't recall seeing the mA rating of your PT. Also, remember, this choke will be at the very front end of the power supply, so it needs to be rated for the full amount of current that the total power circuit will draw. I am surprised more people don't look at this as an option. Chokes are not that expensive.

[didit]

Full pre-plate choke is a fine recommendation, and into GZ34 this begins shaping up as a cool Rocket combo. A470 output transformer readily available from various sources.

Best .. Ian