Late to the Trainwreck party, gonna build one anyway.

[Matthews Guitars]

Out of sheer idle curiosity, what are the opinions regarding the idea of building an Express with a choke? Because I realized, I have a choke lying around doing nothing at the moment.

Pros and cons of adding a choke to the circuit?

[dorrisant]

I don't think it could hurt unless it alters the voltages.

[dblgun]

It will alter voltages a bit. The choke will have the ability to "store energy" and therefore could have an affect on the amp characteristics. Whether one likes the results is subjective. It really depends on what you are after in the way the amp you are building. Are you after the circuit KF built or one based on one of his with some alterations to tailor it more suited to your liking? Then you need to consider what the specs are on the choke you have laying around. I would stay with the 1k resistor and for that matter the original circuit as a whole, at least initially. That way you have some point of reference to any changes you decide to make going forward.

[Roe]

Out of sheer idle curiosity, what are the opinions regarding the idea of building an Express with a choke? Because I realized, I have a choke lying around doing nothing at the moment.

Pros and cons of adding a choke to the circuit?

it kills the tone and response, if you replace the 1k resistor with a standard choke with around a 110R DC resistance

[Mark]

Well, the lead dress and layout are king. The response is very picky about flux in the appropriate places or you tempt one of two things.

Noisy squealing hell or bland sterility. Be mindful of that.

I have experimented with Express/Liverpool circuits and haven’t found them to be that sensitive. I have heard people finding the first preamp valve being sensitive.

What have you experienced?

[pompeiisneaks]

I built a liverpool, not quite as hardcore as the other two I think but it still has some grind. I didn't have any issues that I recall, it just sounded great

~Phil

[Littlewyan]

Your EL34s will run a lot hotter than they would with the 1K resistor. With that 6.6K OT the screen current draw shoots up a lot and the 1K resistor helps with this somewhat by restricting the current flow. This is why you get a slight sag and compression with the Express due to the large voltage drop (Roughly 100V I think from memory?). The Komet 60 amps use a choke but they also have a slightly lower impedance, 5.2K I think, which probably helps them get away with it a bit. Although I still wonder how EL34s survive in those amps.

[Matthews Guitars]

I've acquired a few vintage correct Vectorbords still in the original packaging, which I'll be using for this build.

Does anybody have the part information on the "flea clips" or turrets, which I'll need to order? I suspect Newark has whatever kind I need.

[martin manning]

Flea Clip Keystone PN 1500: https://www.mouser.com/ProductDetail/Ke ... roCg%3D%3D

[Matthews Guitars]

Thanks. I ordered a few hundred. No harm in having enough for a few extra boards.

[dblgun]

Just a heads up, KF used two types of Vector board. Do you have the early or later used version? The terminals (flea clips) are not the same. One is .062 and the other is .092.

[Matthews Guitars]

.062 I think. The clips fit the boards. However I've got to get some ferric chloride and strip the copper plating off the vectorboards. They're copper clad. That's OK, that strips easily enough.

[Mark]

.062 I think. The clips fit the boards. However I've got to get some ferric chloride and strip the copper plating off the vectorboards. They're copper clad. That's OK, that strips easily enough.

Why not just use Garolite?

It work well.

[Matthews Guitars]

Don't want to. Garolite (fiber) also can absorb moisture and become conductive. Even if you impregnate it with paraffin. Lots of old Fender amps have this issue.

I also want to use boards that are pre-perforated on a grid. So I have what I want to use.

[martin manning]

Garolite (fiber) also can absorb moisture and become conductive. Even if you impregnate it with paraffin. Lots of old Fender amps have this issue.

Garolite is a trade name for glass epoxy resin board material, also referred to as G-10, often seen with NEMA FR-4 fire retardant rating.