My 12xxx Done - Pics! - Soundclips

[roylfuchs]

Hey Wdelaney, can you recommend some preamp tubes for my amp? Right now I'm running all JJ's. I did the exact scheme that you have. I installed the resonance mod from Mark Cameron last weekend and it really brings out the bottom end. I also finally got the loop scheme from Larry as well, but I need to look at that for a bit to understand it.

[Hydesg]

hi,
may i know if the rest of the power section to the layout you posted is the same as the 12000 series ?

would you recommend using sozos in this build?

[ACDCG400]

Definitely, never use anything else!

[wdelaney72]

Yes, I like the Sozo's, and outside of the added gain stages, this is a stock 12xxx.

I did some tweaking last week, with the following changes:
1) Removed the Cathode bypass cap on v2
2) Used 10K resistors on the cathodes of the added gain stages.
3) Replaced the one .0022 output coupler to .022.

Definitely tamed a lot of the fizz and sizzle. I like it much better this way.

[roylfuchs]

How's about tubes for your preamp section, any suggestions? How about pick-ups? I'm thinking something with a little less output, like a screamin demon or alnico II pro. I'm using a Tom Anderson H3 and it is too hot IMO.

[axeman]

It works. It's quiet. I absolutely love it. It rocks. Many thanks to George, Mark, Steve, Dan, Bainzy, Larry, and everyone else here on the site for their knowledge.

Stock 12xxx layout, except
1) shared cathode (yes it shows split, but the .68 is not connected)
2) 300 uF on V2 cathode

Marstran OIT Dagnal clone, Shuguang power tubes V1 RFT, V2 Tesla, V3 RCA Command 5751.

The switchable gain stage is setup like Banzy's mod, but I'm using both sides of the extra tube, in effect adding 2 stages. Values there are out from preamp pot into 470K resistor, out from tube into 100K resistor with .0022 coupling cap. Into 470K_1000pF / 470K voltage divider. Through a 470K resistor into 2nd half of tube. Out 100K resistor with .022 coupling cap into MV pot. The rest feeds into v2 and is stock from there.

I had posted this a while back, but I did change a few things and I had a bad output tube socket causing a lot of hum.

Next up, my '67 build (how's that PT comin' Brian?) and a head case for this bad boy.

I'll work on getting some sound clips later in the summer when I have acces to some recording equipment.

Please excuse the bullet holes on the rear of the chassis... some ideas are great on paper.... then when you actually start doing stuff you realize it's more hassle than it's worth. Besides this was an experiment and an educational amp!

hi can you please place instructions for the triple stand by switch on the 68 1200

Thanks

[wdelaney72]

http://forum.metroamp.com/viewtopic.php ... ht=voltage

[frenchie]

where can i get one of those nice double pec pots ??? i mean easily......

[wdelaney72]

$33.05 US !!!!!!

http://search.digikey.com/scripts/DkSea ... 1051S28-ND

[hotguit]

Hi
I read carefully this thread, very interesting.
I modded my 1987 in order to have an extra gain stage without adding an additional tube (like in Rockstah pic) but just cascading the two stock stags (V1A and V1B).
The result is not bad too me (maybe a little bit too harsh and with less gain than i need at medium /high MV level but all in all a good tone)
Now i'd like to try adding a tube like the layout posted here on this thread but i have some question:
1 does the general gain ammount increase?
2 if it does, how much?
3 even at medium/high MV settings?
3 Is it possible to obtain a clean sound yet?
I have also a big problem with my amp: F.M. intereferences at medium/high gain setting; what can i do?
Thank you for your help.
Hot

[wdelaney72]

This layout does have the ability to play clean. I found that the harshness can be tamed by raising the cathode resistor on the added stage. Up it 10K with no bypass cap. Makes a huge difference.

You could also take out the bypass cap on V2. I like that for stock 12xxx EVH tone, but not in this higher gain mode.

[hotguit]

Hi Walter
i've some question about your mod.
Some time ago i made the Bainzy mod on my 1987 using only a triode of the added tube; it sounded horrible so now i made the Cas. mod (or the so called caswell mod) posted by Rockstah but i'd like to have more gain and sustain.
Well, did you follow exactly the layout for your mod? I mean did you follow teh exact R/C value for cathodes? or did you chabge 'em?
How did you name the tube? V1 is the first stock tube or is the added tube? (just to understand which tube you are talking about)
And don't you think could be of help putting a volume pot between the added tube and V1B?
As i'm very interested in this mod i hope you can help me in understanding it a little more.
bye
Thank you
Hot (Peter from Italy, so forgive my poor english)

[wdelaney72]

For this amp I used Bainzy's mod for the switching piece and placement of added tube but w/ different values.

While Caswell's exact layout is still unknown, many agree (including me) that the first thiing he did was convert to 2203 (which has 4 stages) and add one more gain stage inbetween the 2nd and 3rd stage.

Start with a stock 2203 layout and prior to hitting the 470K-470pF resistor that feeds V2a, add another gain stage. You'd first hit a voltage divider of somekind (start with 470k-470pF / 470K and tweak to personal taste). Start with an unbypassed 10K resistor for new tube's cathode and tweak to taste. Go out of the added tube into the usual 100k / .022 coupler and then feed the stock 470K-470pF mixer resistor feeding V2a.

I tried this recently and liked it better than this one...

[hotguit]

Thank you Walter.
I'll try this mod.
Haven't you got any layout of this mod (the one you described i mean)
It would help a lot.
bye
and thank you again
Peter

[Gee Donner]

Walter,

Did you see this picture? To me it looks like the roumor is confirmed that the new gain stage is right before V2. Like you say. But it is not a 2203 spec (according to what I can see). I think it is a cascaded 1959, because you see the cathode caps for both standard v1a and v1b are in there still.

Then it looks like he is going from this through a 470K/500pf 470K voltage devider. through a 0.022 to someting to the new stage or what do you think?

///G