anyone ever built a tube mixer similar to the RCA Living Stereo type??

[ncdrawl]

I am lusting after one, me being a sound engineer , audiophile, and tube lover..

anyone got schematics or anyone care to build one or advise?

Hollow State, interested in you particularly..

ncd

[HollowState]

Me? I'm not familiar with the Living Stereo mixer. But years ago I built a dual channel (stereo) mixer with three inputs each. I used the first cascade stage (line input) from the Ampex 351 recorder found here for each of the six inputs. It was for use with low impedance mikes and the input transformers were UTC HA-100Xs. Although A-11s, or similar, would have worked just as well. These were a lot cheaper back in the late 60's and I happened to already have them. Today, perhaps Lundahls or the Ampex octal plug-in types would be more economical.

I used unregulated, but well filtered, DC for the filaments, shock mounted tube sockets and Alan Bradley 2W pots on the output of each channel for summing along with a larger output capacitor to preserve base. This was for field recording and was always next to the recorder so no low impedance output (transformer) was needed. Your needs might be different.

Victor

[ncdrawl]

do you still have that mixer?

[HollowState]

Originally posted by ncdrawl
do you still have that mixer?

That's an interesting question. The reason being I thought I did. Sometime in the past I went looking for it and couldn't find it. Then later I tried finding it again and still could not. I know I never sold it or took it apart for the transformers. At some point I wondered if it was left at someone's home where I was recording with it. But that was a long time ago from a faded memory. If I still have it, it's hiding.

It was housed in a wooden cabinet (19x7x10) that was covered in black vinyl with chrome corners and had six HH Smith skirted knobs across the front panel. I wish I knew where it was 'cause it's a long lost old friend.

Victor

[kevinkr]

Originally posted by ncdrawl
I am lusting after one, me being a sound engineer , audiophile, and tube lover..

anyone got schematics or anyone care to build one or advise?

Hollow State, interested in you particularly..

ncd

Was there one? I have always understood that the early recordings were either 2 or 3 channel and went directly from the mics to mic pre-amplifiers to recorder electronics with no mixing of any sort involved.

Post recording mix down from 3 channel to 2 channel stereo was probably accomplished with a very simple mixing set up that summed the center into the left/right channels or may even have been ignored in some cases? Reportedly the center channel was used for producing the mono recordings as well.

It would be really nice to know exactly what was done and at what point in the recording process...

[kevinkr]

I am just getting into live recording, and while I am unlikely to copy vintage designs for my electronics I am also curious.. Old Ampex gear generally had quite good microphone pre-amplifiers.

I'm thinking more along of the lines of transformer coupled I/O with tubes like the D3A or 5842 providing the required mic gain.. Have not thought about mixing yet..

[HollowState]

Originally posted by kevinkr

Was there one? I have always understood that the early recordings were either 2 or 3 channel and went directly from the mics to mic pre-amplifiers to recorder electronics with no mixing of any sort involved.

That's what I thought too. I've never heard of a "Living Stereo" mixer.

Originally posted by kevinkr
I am just getting into live recording, and while I am unlikely to copy vintage designs for my electronics I am also curious.. Old Ampex gear generally had quite good microphone pre-amplifiers.

When I was in my twenties I was really into Ampex tape machines. Because of this, that is the way I chose to go for my purpose built mixer to record local bands and musician friends. If I were to do it over again I'd probably use different tubes this time around, but would keep the high quality input transformers. (I know a little bit more now) I hand built two transports (plus electronics) back then not being able to even afford used units. All I needed to buy was the stainless skim plate for physical layout, some UMC (Beau) motors, a puck wheel and an empty head assembly for Nortronics heads.

The Ampex tube electronics go for really crazy money on fee-bay these days as mike preamps. But most of the electronics in them becomes wasted. And they're filled with carbon comp resistors, old foil capacitors and 12AX7/12AU7 tubes that have been frowned upon by the DIY nay-sayers. Yet these electronics produced some of the most valued recordings.

[cerrem]

From a few things I remember...
The controls were constant impedance, L-PAD style, thus not disturbing the loading....
They also used a transformer to blend the Center-Channel into the L and R sides.... It was done with a Phase shifting transformer to avoid cancellations....
Webster Hall in NYC was one of the famous locations for RCA recordings in the 1950's and early 1960's.....
I had a professor who had worked for RCA in those days....He designed vacuum tubes mostly improved them and was also involved with recording...pretty amazing...

Chris

[kevinkr]

Originally posted by cerrem
From a few things I remember...
The controls were constant impedance, L-PAD style, thus not disturbing the loading....
They also used a transformer to blend the Center-Channel into the L and R sides.... It was done with a Phase shifting transformer to avoid cancellations....
Webster Hall in NYC was one of the famous locations for RCA recordings in the 1950's and early 1960's.....
I had a professor who had worked for RCA in those days....He designed vacuum tubes mostly improved them and was also involved with recording...pretty amazing...

Chris

Does sound quite interesting!

IMO I suspect what we think of as a modern mixing board arrived about the same time as the first 8 track studio recorders. (Very late 1960s - early 1970s) Earlier affairs driving 4 track recorders seem to have been quite primitive by today's standards..

[kstagger]

the only vintage RCA mixer circuit I can think of is this one (page 23)
http://www.pmillett.com/file_downloads/RCA_HiFi.pdf

allows you to sum two channels. And a hat-tip for Pete Millet for posting so many books and manuals.