Pre-Amp Build

[Wntrmute2]

Well, parts have been arriving. Some tubes and transformers. 2C22s on order from Ebay.

 

[BillWojo]

Looks like it will have a well regulated PS. Love the glow of gas regulators.

Billwojo

 

[Wntrmute2]

I forgot to add the schematic. This is courtesy of Paul B.
My plan is to try a hybrid rectifier with a 5R4 tube and to replace the one OD3 with two OA3s for the same voltage drop.
Boy I hate Styrofoam packing peanuts!

 

[paul_b]

I ran into the Cary SLP-98 schematic elsewhere, and this will likely be pretty similar.

 

[Wntrmute2]

Well, that's cool as I have a SLP-98 and am happy with the sound.

 

[paul_b]

I guess it's the 90, but I can't imagine the 98 being tremendously different!

 

[djnagle]

Ok, I might be missing something but where is the 2C22 on you schematic?

 

[paul_b]

A 2C22 is a 6J5 optimized for lower internal capacitances. A 6J5 is more or less a #76 in an octal base.

 

[djnagle]

Ah, I really like the 76 sound in a pre.

 

[djnagle]

I forgot to add the schematic. This is courtesy of Paul B.
My plan is to try a hybrid rectifier with a 5R4 tube and to replace the one OD3 with two OA3s for the same voltage drop.
Boy I hate Styrofoam packing peanuts!
View attachment 27026

Really looking forward to your build Dave. I have a Pete millett low-mu preamp that I can't seem to get the hum out of. My frustration level is making me think I should build a different pre.

You might have heard my millett pre over at Ed's in Rochester hills.

 

[Wntrmute2]

The two 2C22s are supposed to replace the two 6SN7s since they are 1/2 of a 6SN7 I believe.

Something like below. Obviously, it
needs a lot of work. The attenuators are only available in 50K and I'm unsure if I have the diodes and 5R4 hooked up correctly. The transformer has a center tap for the HV windings.

 

[paul_b]

THe cap on the reg tubes should go from regulated +150 to ground.

 

[Wntrmute2]

What kind of resistors for cathodes to grounds? I thought non-inductive wire wound but they seem to be harder to find than I remember.

 

[paul_b]

Metal film.

 

[Wntrmute2]

First layout pictures.

Transformer at back vs transformer in front.

 

[djnagle]

I vote for trannies in back. Wow, that could be taken the wrong way😁

 

[djnagle]

Ok, so 76 in back and 2D22 in front? So you're switching between the two not running the signal through the 2?

 

[Wntrmute2]

No. First thru the #76 then thru the 2C22 as the follower. One each per channel.

 

[djnagle]

Got it. What level of gain are you expecting?

 

[Wntrmute2]

🤷‍♂️