Late to the Trainwreck party, gonna build one anyway.

[Matthews Guitars]

Gotta replace the volume pot. It jumps from zero to HOLY F in hardly any pot movement and then gets even louder.

The amp is so bright overall that I wonder what mistake I've made. I've been looking over it very carefully and just not seeing it.

The treble control is very effective. The bright switches...I hear a click but can't really hear any tonal diference. Using mylar caps, values of 100 and 500 pf,
just like the book says. (Trainwreck Express build guide in the files at this site) Bass and midrange controls have very little effect. Presence seems to work fine,
but I keep it rolled down almost to off because the amp is so bright.

Sorry I didn't post photos during the build process. I can post photos of the more or less completed amp now, though.

I ended up using two different kinds of turrets, one kind on the power board, one different kind on the preamp board. Works OK, not worried about it.

Pretty happy overall, with so few problems considering it's an all new build and I'm not that experienced at building amps yet.

I used Vishay MKT 1813 series caps on the preamp board, and NOS Piher resistors. Oddly I could not find any site that had all the right sizes and values of Yageo 1/2 watt metal film resistors in stock, which was a type I wanted to use. But the Pihers, despite being old stock, are good and on value. I just had to clean the leads.

[Matthews Guitars]

https://marshallforum.com/attachments/i ... pg.160764/
https://marshallforum.com/attachments/i ... pg.160765/
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[Roe]

Gotta replace the volume pot. It jumps from zero to HOLY F in hardly any pot movement and then gets even louder.
...The bright switches...I hear a click but can't really hear any tonal diference.

bright switches should be easy to hear if you do not crank the volume

[Matthews Guitars]

I've gone over the amp very slowly and carefully and found a few little things that needed correcting.

The 50 pf cap between the resistors on the PI will work better when both leads are actually soldered.

Found one or two other not-quite-soldered connections. Now the amp sounds better and is surprisingly stable, but I can make it oscillate if I turn up everything to 10 including the presence.

It's still a bright sounding amp, but definitely within the normal tonal range. Thus, it really works well with my dark sounding horizontal Mesa 2x12 with V30s.

Overall, not many gremlins for a new build. And it does sound great. Ultra aggressive, though. To the point where it doesn't really clean up with a drop of the guitar volume control,
until the volume is turned down so low that there's not much good tone left. I'll be experimenting with various preamp tubes, maybe a lower gain type will help.

I like a heavy natural overdrive, for sure, but I like to be able to clean up the tone at will with the guitar volume as well.

Its basic gain level now is like that of my Marshall 2061 20 watter with a 12 dB gain boost in front. Which will give you screaming lead tones.

[Matthews Guitars]

It LOVES a 12AU7 in V1. This feels like the right tube for it. I still can get plenty of drive but it'll clean up real nice by rolling back the guitar volume control. And it allows me to boost with my Seymour Duncan Pickup Booster for leads, without adding too much gain or noise to the signal chain.

A typical strong 12AX7 is a bit much for V1. Sure don't want to put in a particulary hot example!

[Matthews Guitars]

Kind of a basic question, I know, but I want to hear from more experienced Trainwreck builders and techs.

On this amp, the bass and midrange controls don't do much, except that if I turn down all the tone controls to zero, the amp goes quiet,
so I know the circuits are doing SOMETHING.

I'd like for the tone controls to have more effect. Bass and midrange, that is. The treble control has plenty of effect.

What'd be the best way to go about this?

[Mark]

The effectiveness of the bass and mid controls are effected by the coupling cap (0.002uF) to the third stage. I found the amp had a lot of bass once that cap was significantly larger.
Of course that does great effect the distorted sound of the amp.

I assume that you have checked your wiring?

[Matthews Guitars]

Finding some small "issues" with the wiring have helped to bring everything into focus. The tone controls now operate in an acceptable manner, since I found two or three solder connections that were missing the solder and fixed that issue. And having only one lead of the 50 pf mica cap across the PI plate resistors soldered definitely had a negative effect. That responded well to getting its other lead soldered.

I think I'm done tweaking it. By replacing a few unshielded wires with shielded cable the amp is now unconditionally stable even when dimed to the max and using my most sensitive 12AX7s in it. Except when a guitar is too close to it, but with this thing dimed you shouldn't be within 5 feet of it ANYWAY. It's just too brutally loud.

The hoped for responsiveness to the guitar's volume and tone controls is definitely happening.

Now I can think about a cabinet and cosmetic treatment for it. I've got a KILLER set of curly maple boards that will either be this amp's cabinet, or a cabinet for my Mesa Mark V 90 head.

Following Trainwreck tradition, I may end up with a wood faceplate, hand engraved. And give it a name. Which will be Jacqueline. Tradition also dictates that the front panel should have a wood burned carving on it. Often they are various animals. An Orca. A Donkey. A Blue Whale. A chicken. What to pick......??

[Colossal]

It's just too brutally loud.

This is what they do

[Matthews Guitars]

Yes, it's loud, with EL34s. I understand I can run 6V6s in it as well? Other than a bias adjustment, nothing else is needed?

I'm using the 300V taps on the power transformer, but that PT also has a 260V winding. With a few minutes of work I could swap taps and drop power output but that'd mean a reduction in the amount of power stage overdrive which I think is a critical factor in that tone. However it would also make the amp friendlier to tubes that can't handle as much voltage.

I can't find a vendor for the "correct" indicator lamp called out on the BOM. Would someone here have one they could part with?

[RockinRocket]

Id expect more power amp overdrive with a lower 260v winding. It would change the tone. Get a good attenuator.

[Matthews Guitars]

I have a Marshall Power Brake. I'd say it's a good attenuator, but eventually a Fryette Power Station is going to join my gear collection.

The Power Brake's fan has been useful as a means of helping me to find parasitic oscillations. Turn the attenuation up, start twisting knobs. When the fan starts to spin, I've activated an oscillation that I may not be able to hear.

[Mark]

Yes, it's loud, with EL34s. I understand I can run 6V6s in it as well? Other than a bias adjustment, nothing else is needed?

I'm using the 300V taps on the power transformer, but that PT also has a 260V winding. With a few minutes of work I could swap taps and drop power output but that'd mean a reduction in the amount of power stage overdrive which I think is a critical factor in that tone. However it would also make the amp friendlier to tubes that can't handle as much voltage.

I can't find a vendor for the "correct" indicator lamp called out on the BOM. Would someone here have one they could part with?

I think it’s still going to be loud with 6V6’s. Maybe those yellow jacket things might be a way of quietening it down?

https://www.amplifiedparts.com/tech-art ... dzwyw4e-8b

[Matthews Guitars]

I know how loud 20 watts can be. My 20 watt Marshall 2061 tells me. At full tilt it's 7 dB less than a 100 watt amp. So if the full stack hits 120 dB with a 100 watter, at 20 watts it'll still make 113 which is still quite loud.

I had the option from the start to build this amp with EL84s, but decided to stick with EL34s just because I wanted to. The Yellowjacket converters ARE an option.
I could also install a pair of sockets just for EL84s, parallel wire both sets of output sockets, and run EITHER pair but not both at once. But I'm not going to do that.

[jelle]

Can you post the pics in a way that they can be viewed here?