My Bassman/JTM45

[Blackburn]

Hey all, finally decided to lose my gut shot virginity here, so here goes...

My low volt build with original 5881s and Mullard 5AR4. Preamp is still being tested to taste, in other words, not there yet.

David

[Reeltarded]

Why so clean? You some kinda pervert?

[Colossal]

Yeah, he's freaky..."Doctor" Blackburn, DDS

Looks great David! How do you like those 5881s?

[LeftyStrat]

Looks great to me!

[Blackburn]

I know, I must be kind of sick in the head or something...

Thanks, guys. As for the 5881s, I'm not sure I can make a real assessment while playing it through my Elegante. Something about this thing so far that I'm not digging. I have one ASW Crossroads to go and I'll have two in parallel and can REALLY do this up! The only primary tap I've not used is the 3.4K. I don't know if maybe the speaker or the primary are causing such a grainy, splatty tone with the volume around 11 o'clock and after. 6.6K is cleaner and thicker, but somewhat muddy. 8K is better, but I'm still not satisfied. I need to try the primary that's actually spec'd for these tubes and see if it helps, a la real Bassman.

What I love, this bitch distorts right about where the volume STARTS coming on, with my LP anyway. I am a little heavy handed... I guess the lo volt setup I have is serving my purposes nicely. I've been rolling pre tubes a lot and still want to buy some proper GEs for her. Still trying to figure this one out as it's a pretty fresh build. Let me know what you guys think I could do to alleviate the issues.

[Blackburn]

Oh also forgot to mention, and this is something I plan on changing as soon as I make my next parts order. When I was taking readings when I finished her up, I read about 210v on V1's plate. I wanted it lower, so I changed the 100K resistor for a 220K. Unfortunately, this took me down to just over 140v. My cathode voltage is 1.2v, I think. I don't have any resistors in between 100K and 220K, so I'm gonna stock up on some 150Ks and hope I get between 150v and 170v which puts it just over spec like most of my other pre voltages.

[Reeltarded]

You liked it better before you read the voltages.

I bet.

Have you thrown the 220 back in there to listen?

[Blackburn]

I have that little bugger in there now.

I know what you mean, though.

[M Fowler]

Looks good, you'll probably like KT66 or EL34's in there better.

[Blackburn]

Thanks, Mark. I agree with you. Probably the 66s in here. I've been fantasizing about those for a long, long time. The 34s I'm planning for something else and might even build it into my gutted 5B6 chassis...

A few ideas knocking around up there.

[LeftyStrat]

At least try the EL34's in this circuit. You can mismatch the output impedance to get 3.3k on the primary. This is my favorite configuration.

[Blackburn]

The only reason I'm hesitant is because of the lower filtering compared to JMP50s or Expresses and I think I'll want SS rectification for those, but the biggest reason is I don't have any EL34s. Whenever I cough up some dough for those, they'll be XF2s. Ooh looking forward to that day!

And I do have a 3.4K tap on that OT.

[M Fowler]

You can run both the EL34's and KT66 at 3k4 primary doesn't have to be 6k6 for the KT66's.

[Blackburn]

Yeah I know, Mark. Tomorrow I'm going to wire up the 3.4K tap and see if that helps some of what I'm not digging right now. We'll see.

[M Fowler]

I bet you like it