Comments on: RCA OP-6/BA-2 Hybrid Mic Pre Amp: Listening Test/Shootout

By: Raquel Casares Jimenez

Raquel Casares Jimenez — Wed, 04 Nov 2020 04:46:51 +0000

Amazing!
Wonderful work

By: Scott Wolfe

Scott Wolfe — Thu, 27 Feb 2020 13:23:56 +0000

This is a nice write up. How do I find the values for all the caps and resistors. There is no voltage or polarity for the caps needed, and no wattage ratings for the resistors. Also there are a few resistor ratings missing. How do I find this info? Is there a better schematic our there that will help?
Thank you
Scott

By: sho

sho — Mon, 04 Aug 2014 15:45:43 +0000

In reply to chris.

Thank you for your input.
Gee, I better start putting 76 pre together very soon.
You and your site rocks !

By: chris

chris — Sun, 03 Aug 2014 08:55:00 +0000

Hello sho- i actually use the “old 76” preamp on every session that i do at Goldcoast Recorders. It it my standard top-snare mic using an old shure sm56 with a 20db barrel pad attached to the mic. It sounds wonderful. I made the “old 76″‘so long ago that i cannot recall the exact circuit, but in think that it is 1) jensen 115 transformer into 2) 76 tube with 2200 ohm cathode resistor, 100k plate res, 3) volume pot, 4) some sort of configuration of a 6sl7 tube that resolves with a cathode follower, 5) edcor 15k: 600 output trans. C.

By: sho

sho — Sun, 03 Aug 2014 01:50:03 +0000

In reply to chris.

I been interesting in old 8pin tube pre sound as mic pre.
So your OP6 article helped alot, thank you.

6J7, 6SJ7 I love them both, but somehow not cheap in here Japan.
6c5 was used alot in old Gates amps like Sa70
And little cheaper 6J7 or sj, so I use 6C5 reguilarly
Think EMMR knows alot about Gates, he loves Gates seems.

Now I am interesting in 5pin tubes sound, like 76 as mic pre.
Any plan for post sound test of your 76 pre?
That one looks so cool and love to hear the sound.

By: chris

chris — Sat, 02 Aug 2014 20:58:48 +0000

Hi Sho. Wonderful to hear this from you. Nothing could make me happier than somone actually putting this arcane information to good use. I am not familiar with the 6C5; I know the 6C6. The 6C6 is the older 6-pin version of what became the 6J7 aka 1620 aka 6SJ7 aka 5693.

By: sho

sho — Sat, 02 Aug 2014 16:12:02 +0000

Hi Chris, after listening sound here, I build one.
This things sounds great, and loud, great for ribbon.

Used UTC ouncer for input
And used Gates SA-70 first stage (just cause I build sa70 bunch in past)
Other I followed your info, Edcor, Jensen choke.

Little noise problem at first, but now gone. Thank you again for great info.
Thinking about next might be 76>76>6C5 mic pre.

By: RCA M1-12295 PA Amplifier.

RCA M1-12295 PA Amplifier. — Tue, 28 Aug 2012 21:49:35 +0000

[…] was a high output ribbon with a high gain 6j7 pre. I found an audio demo of an RCA OP6 clone at RCA OP-6/BA-2 Hybrid Mic Pre Amp: Listening Test/Shootout | Preservation Sound I heard it and the host said it "moved the room" unlike the other pre he'd compared. I'm […]

By: Evan

Evan — Sun, 15 Apr 2012 01:52:41 +0000

Thanks for putting this listening test and results together – very useful.
I’m still working up to my Altec 1566 project, but some kind of RCA endeavour may be a good follow-up if I succeed on the first outing.
First thing is to get my old Presto Pre’s up and running.. slowly slowly.
Keep up the great work.