Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: John on September 25, 2011, 11:55:49 am

Title: Proofread schematic?
Post by: John on September 25, 2011, 11:55:49 am

Hi fellas, I've been thinking about building a simple PP using the 6SL7 in stead of 12ax7, mostly out of curiousity. This is what I came up with, and was wondering if you'd be kind enough to proofread it for me before I start. ANY comments *duck* are welcome. I give credit to Geezer and Tubenit for the preamp stage, and I'm trying the Moonlight tone stack. Trying for less knobs n stuff on this one.

I used the 470R cathode resistor for the 6V6's, but that may be way off base... haven't done the math yet, and I'm just assuming B+ right now. Thanks for your help!

Title: Re: Proofread schematic?
Post by: sluckey on September 25, 2011, 12:59:28 pm

You need a blocking cap between V2-6 and that 470K that's headed to the tone stack. I've never seen the 5 volt recto filament fused before??? And 2 amps is probably toooo close to the actual current draw of that 5Y3. If your B+ node A voltage is really 300V you'll probably want a 250Ω resistor under the 6V6s.

Title: Re: Proofread schematic?
Post by: John on September 25, 2011, 05:06:46 pm

Sluckey, thanks!

I copied the design from the HoSo in regards to the V2-6; should I put the cap before the 470k instead of parallel with it?

The fuses idea I got from the Immortal Amp Mod articles. And of course you're right, the 5Y3 draws 2A heater current, so I'm guessing a 3A fuse would be better. I thought it was a lot of fuses too, actually.  :laugh:

And I also realized that the 470Rk is what's in the Champ-only one tube instead of 2, so that 470 is way wrong regardless.

Thanks again!

Title: Re: Proofread schematic?
Post by: John on September 26, 2011, 07:49:07 am

Okay, changed the K resistor to 250, and actually took out the 470K coming off V2-6, and put in a 500 p cap. Also, read Merlin's article on fuses, took out the heater fuse, but added fuses going to the rect. plates.

Just wait till you get to proof read my layout .  :icon_biggrin:

Title: Re: Proofread schematic?
Post by: sluckey on September 26, 2011, 08:22:06 am

Quote

and put in a 500 p cap

How did you determine that value? Seems small to me but I've never used that TS before.

Title: Re: Proofread schematic?
Post by: John on September 26, 2011, 09:37:43 am

Oh, just a wild guess! I'm sure I'll be tinkering with a lot of the values along the way.

I bet I should use something like a .022?