Mastering A/B console vinyl signal flow

Hey Folks,

I am designing an insert switcher and mastering console, but it seems like with a couple of "extra" configuration capabilities in the signal flow for routing, it could also be a great vinyl A/B console; accounting for playback and preview heads on a tape deck...

I understand the playback and preview concept, as that it is a delay for the needle and preview for the cutting computer in the lathe to prepare the pitch spacing in the next revolution....

I do know that the typical A/B console has duplicate equipment on the "inserts" that are A/B'ed--alternated during the carving of one song and set up on the alternate switched out set of processors in preparation for the next song...

But the disconnect in my mind, is, wouldn't the cutting computer want the preview to be the same processed signal as the processed playback just that the playback needs to be delayed.... If so, would that then be 4 sets of identical equipment (2 each, one for the preview and one for the playback both to be A/B'ed) if doing things in real-time from the master tape submitted by the client (without dubbing)? 

Or... is the tape with the playback and preview dubbed (after processing) onto the preview/playback machine from a pre-mastering session using the submitted client tape

I guess my real question is what is the process with a typical signal flow for analog vinyl mastering including the signal flow through a console for playback and preview (including monitoring)?

Any thoughts?

Cheers,
-chris

"wouldn't the cutting computer want the preview to be the same processed signal as the processed playback just that the playback needs to be delayed.... If so, would that then be 4 sets of identical equipment (2 each, one for the preview and one for the playback both to be A/B'ed) if doing things in real-time from the master tape submitted by the client"

Absolutely right.  That is what we did back then with 2 sets of everything, including Dolbies.  At least one mastering room I know of had duplicate sets of eq and limiting for the A and B channels: 8 units of processing. 

"delay for the needle and preview for the cutting computer in the lathe to prepare the pitch spacing in the next revolution...."

Yes, pitch spacing.  However, depth control is arguably even more important.

"what is the process with a typical signal flow for analog vinyl mastering including the signal flow through a console for playback and preview (including monitoring)?"

A good place to start might be to review Neumann's mastering console design and then add your own ideas.

Yes, you want eight identical channels for a full A/B path console. Four for each path. Two modulation channels and two preview channels.

These consoles were expensive. On a Neumann SP75 only the EQ's and level adjusters were separate for both paths. The filters, compressor (if it was fitted) and the EE were shared. Same with the later SP79. In those days you weren't supposed to do much processing in mastering.

It was common to make an "EQ'ed cutting master" by recording the processing onto another tape and cutting from that. If you had to run off multiple lacquer sets it was easier to do it that way.

Hey,

Thanks for the insight!  As an electrical engineer, and having grown up with vinyl in the 70's, I find this process fascinating...

Many thanks for the replies and your help!

Cheers,
-chris