With regards to t he schematic, shouldn't V4 and V5 be "EL34 or 6L6" instead of "EL34 or 6V6"? The 6L6 is a closer match to the4 EL34, and the 6V6 is not rated for the plate voltage present.
EL34s or 6V6GTs for the canonical amps. Good quality 6V6GTs work fine in an Express-style amp provided that they're properly biased. Check vintage data sheets : they were rated at 1 200V pulse for TV applications and work fine at up to 450 V in geetar amps.
They offer slightly less power - but the amp is still LOUD! - with a different sonic presentation, chimier and rounder (less in the mids) and somewhat softer.
I was aware that they could be run in triode mode as deflection amps at 315V with up to 1200V peak output, but didn't realize they would hold up to near 400V in pentode mode, much less 450V.
Most quality small or medium octals can work up to 500 V or so with the right glue, bias and screen supply, then arcing between internal elements, base isolation as well as socket quality become limiting factors.
Have a look at the original datasheets for the 6V6GT and derivatives: all curves are traced up to 500 V.
Jim Kelley ran a quad of Sylvania 6V6GTAs at 480 V in his great sounding amps, and, provided that bias was properly set, they ran hot and happy. So a tad above 400 V in an Express-like amp isn't a problem...
Ron, although I haven't gone through this yet, I just downloaded the files and wanted to thank you for your effort and let you know it is still helping people. One day I will build one of these and I'm sure your work will save me a lot of time and headaches, making the whole process a far more enjoyable experience. Thanks!
fayser wrote:Ron.. it has to be said... this is an incredible piece of work... it's real pick your jaw up of the floor stuff.... well done to you and all the gang on this forum.. this has made it so easy for home enthusiasts like myself to entertain building one of the most revered amps of all time ... my hat is firmly off to you .
Tony
+1+1+1+1
Can't be said too much. super thanks to Ron for the countless hours of original effort and then the pains taking time spent revising these docs for the benefit of others.
AND of course, credit all of those here that helped Ron accumulate all the knowledge required to put this together.
You're all very welcome. Yes, this document is a culmination of all that I learned from the masters here, as well as through the learning curve of doing my actual builds. I don't post much anymore here, life has a way of sucking up even more of my free time!
These documents have not been updated for a couple years, mainly because there appeared to be consensus that they were nearly 100% accurate based on known Wrecks. The BOM probably should be updated as prices and parts availability have surely changed in the past years. But, I don't have the time for it these days and it still serves as a good guide on parts.
I'm going to build that amp. And I will update all prices and availability of parts!
But before, I need to know something. I want my Trainwreck express to work on 6V6 because I've heard that it is better for small venue. I need an amp not TOO loud.
6v6's aren't going to make it much lower in volume. It will however break up a lot sooner. I prefer EL34's myself but that's me. Use an attenuator to lower the volume to usable levels.
Forum Member Sliberty has also used a shared cathode on V1 and a 12AU7 very successfully to lower some gain but he also uses 34's IIRC
The VVR is very good at dropping volume. You won't need an attenuator with a VVR. It is really a matter of taste. Some like the VVR better and some like the Airbrake.....and some like the master volume best. You need to try all of them to know which you are going to prefer
Personally I use an Airbrake BUT I don't use it to the point of bedroom levels. IMO if I can't move that much air I may as well use a headphone amp or a POD
Last edited by HeeBGB on Mon Apr 21, 2014 10:58 pm, edited 5 times in total.