Do yourself and your OT a favour, solder those speaker cables to the speaker. I very nearly damaged my amp when one vibrated off. I was able to turn the amp off quite quickly in order to investigate further. I'm not sure how long you've got with no load attached but I wouldn't want to test it!

Thanks Mitch, looks promising. The ART I have is a simple passive switch, no tone lost at all, its just not robust enough and i keep getting bad connections.

I'll email RedOnion for a quote for an A/B/Y with isolation transformer then I've got all bases covered

Hywel Harris

Yes I run mine with an a/b/y and its worth doing just for the flexibility of channel swapping. The 'y' is just a blend of the two and I haven't noticed any serious phase effects, though the two channels are out of phase with each other. I also don't notice much of a difference when I flick the phase switch either.

Incidentally   can recommend a good A/B/Y switch?  mine is very cheap and is playing up with a dodgy connection.

Thats pretty much what I had in mind Doc. Started cutting the birch ply this morning.

Aparently you will an oscilliscope to set this properly. Leave it alone if you got it from Nik. If you built a kit take it to a tech!!

Ahh, right oh. Can't do 16" deep on my dovetail jig and would prefer to use all my 4 10" Jensens. I guess I'll just have to cut some front facing port holes and experiment.

Yes. rebias and away you go.

Yes I was referring to the use of a D*ator as a volume control device. Sound like you are using like that.

Must try it.

I know....... but I think we should encourage people to build their own, given a few obvious warnings about killing themselves if they a re stupid

I don't know, I think some people might not have the specialist electronics knowledge but are very practical minded and can work things out.

I do know that the experience has fired my desire to know more. I found this the other day
http://www.freewebs.com/valvewizard1/gainstage.html
and sat for well over an hour today reading it the chapter until my brain was full, will have another go soon.

I've also ordered a couple of Kevin o'Connors books aswell.

I know if I'd just ordered the complete amp I wouldn't be anywhere near as interested in the physics. (maybe it would have saved me from the continual amp GAS though )

Hi Erwin, have you read this thread on TGP?
http://www.thegearpage.net/board/showthread.php?t=600679

And have you tried yours in a similar fashion? When I get a minute I'll try it with my Klein.

spm that was really nice tone and playing. It sounded as though the room volume must have been quite high.

Seriously considering one now. Was going to get a Plexi50 but you made the RockIt sounds so sweet (plus I just love the tone of EL84's)

Pretty much. You wouldn't want to change them until your have familiarised yourself with the amp. Some have stated that the TAD 6L6WGC's are better.

I tried EL34's and didn't detect much of a difference in tone so changed back to 6L6's. Bigger change in tone (well dynamics really) with 6V6's


No don't think so.


25mV to 38mV for 6L6's, not sure about EL34's though they are similar


You might want to experiment with 5751's or 12AY7's in the pre-amp, it does change the dyanmics quite a bit. Currently I've a 5751 in v1 and a 12ax7 in v2, but I have also had 5751 and 12AY7. Not experimented with the PI or NOS yet though.

What you need is called an insert cable where the send goes down one core and the return along another of a twin core mic cable. Ground is common

The attached are from my PA manual. Note that the pair of jacks can be mono.

Like it a lot. SRV cleans would be nice indeed, y'know a little breakup, chimey.

Perhaps we all need to pester Nik about a dual primary for the OT so we can swap to 6v6's and lose the impedance mismatch issues. (I have already mentioned it to him only a couple of days ago!)