Post by aamicrophones on May 11, 2017 14:43:55 GMT -6
The Altec's had 3 tubes in each module drawing 1.2 amps total to light the filaments X 8 = 9.6 amps X 6.3v = 60.5 watts just from the filament supply.
35ma plate current per module x 8= .28 x 300v for another 84 Watts. That was just too much heat for the inadequate cooling of the original studio.
Here is the schematic for the Gates SA-70 it looks similar to the CA-70 without a part by part comparison it just had more modern 50's tubes I believe.
I racked a couple of these up several years ago for a client. They were designed for AM broadcast and I didn't think they quite had the fidelity of the RCA or the Redd 47.
I thought the low end was a bit lacking compared to the RCA, Redd 47 plus the Altec's and I did re-cap the Gates modules.
My sense is because they were meant for radio announcers the let the low end roll out a bit early than if you were recording music.
I think the transformers were not quite as good as the Altec, Collins and original Western Electric transformers but I never compared them side by side.
We are clearing out my storage room today and tomorrow so all the spare microphone headgrills, shockmounts etc will be moving over to our new facility.
I will finally be able to get to my boxes of old tubes so I will make a list of what old audio tubes I have there.
Cheers, Dave
OOP's that is not the schematic for the Gates I racked at it had EF86 tubes not the 6J7 in the SA-70.
The modules I racked were from a Gates Studioette. I have the schematics in a PDF file but they are too big to post.
Sorry for the confusion.
Cheers, Dave
Well there's one. Plus any parallel between CA-70 and SA-70.
Anyone can send me 6J7's anytime they want!
Eight 459A's would be a good winter addition, I think they are like 35mA 300VDC apiece, with 6W output capability. I got rid of a rack of Langevin 117A's for the same reason, even though they sounded amazing. Eight 6V6's, so like 4 Stalevel turned on at all times.
OOP's This schematic is not the schematic of the Gates tube preamps I racked as it shows a 6J1 tube and the Gates I racked has a 9 pin pentode in the front end so it must have been a model made after the SA-70.
Cheers, Dave