trinityamps.com

Hey gang.

Here's a link to a guitars.canada thread with some pics of my JCM800 build. Just finished it this weekend!

http://www.guitarscanada.com/Board/show ... #post74615

Just waiting for the head cab from Coco and she'll be done!

Nice Job emo!!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Thanks man! It's a much better job than my first build...the sIII from earlier this year. I'm planning on re-building that one actually, probably using your new "plexi" layout.

I definitely like using the smaller chassis for the cosmetics but I will say things get a little tight around the power tube sockets with the bulky wires on the Heyboer transformers. Not that I have a problem with over-engineering electrical components, but in this case it was a little painful!

I did have a couple of hiccups when I first fired it up. I had a hum problem that I knew was related to my heater wiring. The heater wires on the Heyboer transformer are HUGE...like 14-gauge stranded with very thick sleeves (bigger than the high voltage secondaries even). Makes it nearly impossible to twist them decently. I had them running directly to V5 at first and the hum was unbearable. Fortunately I'm using a Fender-style 6-volt pilot light that is slaving off the heaters, so I just re-routed it to go to the lamp first & split from there. Fixed it up nicely.

I also wired the input jack wrong (I somehow always manage to mess that up!). Re-wired it and it's fine.

The only thing I'm going to change is the unshielded wire from the lo input to pre-amp volume. I didn't think that very short run - about an inch - would matter but I am getting a bit of buzz from the low input unless the pre volume is dimed. It sounds great other than the buzz. The wire from the pre-volume to V1 is shielded. No issues with the hi input.

I finally got a chance to rip though it for about a couple hours last night. The thing kills, but I'm not sure if I'm going to stick with the KT77's in the power stage...or at least not the JJ's. They're just a little too dark & bottom heavy for my taste in this amp. It's probably partly the natural character of the tubes and because I removed the treble-peaking circuits from the design - they just suck the life out of the amp at lower volumes, and they're basically bypassed when running full song anyway.

Why didn't you use the big transformers?

That's what I get for using a JTM45 sized chassis...no room for bigger iron!

Seriously though, I didn't realize how huge the transformers were gonna be. They weigh a freakin TON. Not that I'm complaining! I don't remember if the old Drakes were that big, but these are the Heyboer clones of those. The PT alone is heavier than my complete sIII including the cabinet!

I'm glad I went with the heavier iron though. With the JJ KT-77's the thing is pulling 444 volts at the plates compared to about 415 for EH EL-34's. I don't know if that's a big deal in real terms, but it sure seems like a lot!

Nice job on the amp!
If you are having two different voltage readings for EL34's and KT77's,you likely are running one set way too hot.They should draw about the same current.
No way should the EL34's drag the B+ down to 415v.You might want to recheck the bias.Those tubes are pretty much alike except for sound.
Depending on which Heyboer set you have,the B+ loaded at the correct bias(about 34ma or so) should be about 440v or thereabouts.
The only way to get it down to 415 is if they are cooking at about 50ma.Not good for your tubes!

Yeah - it was probably just where the bias pot was when I installed it. The 415v on the EL-34's was probably my first reading before I set the bias the first time. I've since swapped tubes a couple of times & re-biased & they all pull about 440 or so. I have the KT-77's back in now & they're pulling just over 440 at about 34ma bias.

very, very sheik
Excellent job on the build

Thanks!

I really should post a more up-to-date pic of the innards. I've made a few small changes & corrected one small error with the pre-amp gain pot wiring to V1.

The wiring's a bit busy around the high voltage side fo things, but it really couldn't be avoided using the JTM45 sized chassis. It was great fun building this one. I bought the chassis naked board & faceplates from Nik Azam & the cabinet from Trinity. All the innards I sourced myself. The result is very gratifying.