Thinking about doing a express...questions

[iknowjohnny]

first, is there a particular schematic for a EL34 express that is considered by most as one of the really good ones? second, do these have any preamp drive to speak of or is it almost all output distortion? (compare to a known commercial design if you can) What schematic is thought to be closest to the real TW geetarpicker is using in the clips sticky? What is the best PT ond OT as general consensus goes? (anyone find MC trannys good for these?)

[vibratoking]

It's all here. Check out the files section. Read the extensive discussions. Make an attempt to educate yourself via the data already in this forum. I think you'll find this place a lot friendlier if you do the research yourself and then ask specific questions.

[paulster]

first, is there a particular schematic for a EL34 express that is considered by most as one of the really good ones?

There's only one schematic for the Express. There may have been a grid stopper on the second triode or not, but otherwise they were essentially the same.

The Blue Guitar schematics were based on assumptions, quick peeks and reverse-engineering other, non-Express amps such as the Two Rock model and the Callaham amp.

do these have any preamp drive to speak of or is it almost all output distortion? (compare to a known commercial design if you can)

These are designed such that the PI, power tubes and preamp tubes all hit distortion over a very small range of volume which is what allows you to go from clean to scream by picking dynamics and use of the guitar volume control. The closest commercial design would be the Komet 60 or Concorde, and perhaps one of the 3 Monkeys models which has similar gain staging. There isn't an old reference type amp from Marshall or whoever that you can compare it to because these were never designed with distortion in mind and the newer high-gain amps tend to focus on preamp gain.

What schematic is thought to be closest to the real TW geetarpicker is using in the clips sticky?

See first answer.

What is the best PT ond OT as general consensus goes? (anyone find MC trannys good for these?)

Glen's amp (Orphan Annie) uses Pacific transformers so if that's what you are looking for then get Pacifics. If you like the older, bluesier amps then try to get a Stancor OT.

The Heyboers are pretty much functionally identical to the Pacifics from my experience with them.

It's all here. Check out the files section.

+1

[dartanion]

1. Use the schematic and layouts that Ron Worley put together that are in the files section
2. Yes, significant preamp drive. However, the order in which this happens is power amp > PI > preamp
3. See #1
4. I would say Pacifics, then Heyboer or Edcor. I hear that the MMs are good, but prohibitively expensive.

[redshark]

There's only one schematic for the Express. There may have been a grid stopper on the second triode or not, but otherwise they were essentially the same.

There's actually 2. The other one is the schematic of the express called "Trudy". If you use the search option you will find it. It's almost the same but with more bass and a couple other changes (tweaks).

[paulster]

True. I wouldn't get over-excited by that one though as it's such a minor tweak.

The .002 ceramic across the PVC cap is an easy experiment if you want to try getting a bit more bass but I've always preferred the PVC cap on its own in the Express.

The volume pot change to 500K could be worth it if you want to bring the gain down a little.

That said, Orphan Annie (and most of the Expresses that people have come across) have had the same schematic as Francesca.

[iknowjohnny]

So you can get a decent amount of drive at low levels then i take it. Thats good to know assuming i'm reading you all right. I have been contemplating this for a long time but i haven't really made a decision yet. My last amp turned out like the dream amp i always wanted, tho what i've read about the TW's gain structure and descriptions of the feel and the clips make it hard to resist.

If i begin this i will certainly have a lot more questions !

[paulster]

You don't really get any low levels out of it! It's really loud and clean and then becomes really loud and seriously gainy once you turn up the guitar volume.

At the point the amp gets into distortion territory you've already got the power tubes distorting so they're running flat out at this point. You just go further up the guitar volume dial and the preamp follows suit and adds texture to the distortion tone, so it changes with the guitar volume.

Glen wears earplugs when he shoots video demos if that's anything to go by.

[iknowjohnny]

I think i know what you're gonna say, and this is the deal breaker probably, but if i add a master it won't sound near as good, right? This as i now recall was why i decided to pass or at least put it off last time i looked into it. Not sure i can deal with that because i no longer play out, and while i can turn up somewhat at home, not nearly THAT loud.

[paulster]

A regular pre-PI master will sound crap with this circuit. I know it's a bit of an absolute statement but trust me on this one!

Some people here have reported good success with a post-PI master (and I think there are some clips around) but you will definitely lose the power tube distortion and also the compression in the power supply which helps to even out the volume between clean and scream. The presence control will lose its effectiveness at low levels too because the negative feedback drops right off.

You could consider power scaling and Dana (UR12)'s VVR kit is available for this. Again, people have reported good success with this. Theoretically it'll also suffer from the lack of power supply compression at low levels too, so the clean might be relatively quieter than the scream at low levels compared to flat out, but I've never actually heard that complaint.

Or you could invest in a good attenuator and have something that will work with all your amps. I've played my Express in the dead of night without waking anybody thanks to my Faustine Phantom, and then I can plug in a 100W Marshall or any of my other amps and do exactly the same. But a good attenuator really costs, so you've got to weigh up the pros and cons of all the solutions.

[Big Jim]

I built a plexiglass baffle to go in front of my 4x12 for home use. Helps deal with the volume, but it kind of kills the guitar/speaker/feedback thing.
Very loud amps. Easily will hang with a 50 or even 100 watter.
Jim

[KellyBass]

I've used Dana's VVR in two expresses with great results...none of the fizz I was getting while using an (cheapo) attenuator. A plexi baffle is a great idea as well.

The express is a blast to tweak with. It's very responsive to small changes. Plus, every other amp seems easy after taming one.

[Gibsonman63]

I have only built the one Express, but it from my experience:

Keep it simple and stay with the schematic and layout.
Once it is up and running, get some decent NOS tubes in it before you tweak it.
Play with the coupling capacitors and PI resistors to get the voicing and drive you are looking for.
Find the right speaker and cabinet that works with your amp. A 4x12 cabinet is huge sounding on my amp. A 2x12 is about the right size for most of the stuff I do. 1x12 isn't quite enough for me. The cabinet and speaker combination makes more difference on this amp than any other amp I have owned.

Enjoy rich harmonics and infinite sustain!

[Cliff Schecht]

I really think Ken lifted the 35W rating right from the A-3801 iron rating, which says it's optimized for 35W clean power at +/-1dB frequency response at low distortion levels. The Express can hit that 35W clean mark, but the RMS power increases once you add the extra harmonic content from the distortion in the amp. We say 35W as a more realistic number but as we all know, even the "50W" amps produced by other companies is more of a reference to the power stage setup than it is to the actual power levels. 50W meaning two big-bottle output tubes, 100W being four, etc..