Sort Of Newbie!

[The Ballzz]

Hi Folks,
I've been a member for a while, but don't post much, as it's difficult to communicate, having no good way to draw schematics & layouts. I can, however, at least share a couple pics of my first "from Scratch" build. This a a near duplicate of a Marshall JCM800/2203 preamp using a 10 watt 2 X 6AQ5/EL90 power section.



Thanks For Looking,
Gene

[xtian]

Nice! And how does she sound?

[The Ballzz]

Nice! And how does she sound?

Sounds fantastic. There is just something special about these 6AQ5 tubes that seems to give the illusion of regaining the loss of air movement of the speakers when dropping down from 50 or 100 watts to only 10 watts. It's really pretty cool! The pics were from before the amp was finalized. You may notice some funny stuff in the cathode bias area. This was an attempt at utilizing a scheme developed somewhere by a guy called Da Geezer, for dropping apparent volume by kind "floating" the ground of the cathode bias caps, or something to that effect, details of which I don't recall. The volume drop was not substantial enough to bother keeping it.
Thanks,
Gene

[gktamps]

Very nice! I have a pile of 6AQ5s, and I've wanted to use some in a build. I see the label on your OT - what PT did you use, and what voltages is it putting out?

Cheers,

Greg

[Leo_Gnardo]

Looks fantastic! I've been thinking of doing the 6AQ5 version of a JTM45 for a while. One of these days when I got some extra $$$.

[Phil_S]

Yes, I've got a pile of 6AQ5's, too. They are good for all sorts of amps. You just need to keep the B+ around 300 or less.

[eniam rognab]

my first tube amp used a single 6AQ5 cathode biased. i very much enjoy the sound of it!

thanks for sharing your build

[The Ballzz]

Looks fantastic! I've been thinking of doing the 6AQ5 version of a JTM45 for a while. One of these days when I got some extra $$$.

It's funny that you mention that. This amp was first laid out generally as a 1959, but with only one input and 2 volume pots to blend the 2 halves of the first 12AX7 just as if you had a 4 input jumpered. There simply was not enough gain for my needs, so it only required a few component swaps and lead swaps to make it the 2203.
The power transformer is a Classictone 40-18085:

http://www.classictone.net/40-18085.html

but the same transformer is also available as a lay down style 40-18027 if you prefer:

http://www.classictone.net/40-18027.html

I used the 550v/275v-275v taps.
This amp was built from schematics and layouts designed by Terry Shaffer of GR AMPS along with a lot of help and tutelage from Terry. I can answer "some" questions, but I believe it would be unethical for me to share some of his deeper secrets and magic tricks he developed to get the best out of these tubes. Terry does some excellent work and here is a link to his site:

http://www.gramplifiers.com

Thanks 4 The Compliments,
Gene

[matt h]

(deleted)

[The Ballzz]

Yes Indeedy,
Those God awful 7 pin sockets that are readily available are a royal pain to deal with! On the plus side, Terry has been fortunate and wise enough to stock up on a hoard of much better units that are sized as a standard 9 pin, with better terminals/lugs and bigger holes for the wire. Unfortunately, I used the God awful ones and darned near went "POSTAL" in the process! The next build will acquire some good ones from Terry and will have no knobs/pots, just an on/off and standby. After measuring all of my optimum settings, I will simply use fixed voltage dividers in place of the pots. Especially with a low watt amp as this, once it's dialed in the pots will never move and my volume will be what it will be! If it's not loud enough, that's what they make PA's for and why I always mic my rig. If it's a tad too loud, well, that's what a good attenuator is for. This is my current rig. The amp on top is 10 watts. It drives 2 of the speakers (dry only) and also the Lexicon effects unit from a speaker level DI and that effects unit drives the bottom MG 100 (effects return in, which bypasses the whole preamp) to drive the other 2 speakers (wet only) and this is by far the best sounding way to do time based effects that I've ever found. I do actually use the digital verb and chorus/flanger of the MG as it sounds pretty good and using it does not require use of the preamp.
Just Thought I'd Share,
Gene