Hi Steve and Craig,
Thanks for the warm welcome!
Craig, I'm glad to see you're using the B77 Mk.II at the sharp end. Don't let anyone look down their noses at you for using a Revox 77 series machine for live recordings, rather than heavier metal. The legendary TAS-listed BIS LP "La Spagna" with Gregorio Paniagua was recorded on an A77 at 15ips with a pair of Sennheiser mikes and I've never heard anyone complain about the sound quality of that. Oh, and they used 468 tape too. And IEC eq...
To get the best out of the B77 Mk. II, I aligned it for my favourite 468 tape (another instance, like the IEC eq, where I totally agree with the Project guys - I love 468) so that 100mV p-p (35mV RMS) at the record amp inputs gives 0VU on the meters and 355nW/m on the tape. The machine has more than sufficient headroom at 15ips with 468 tape (or other modern studio tapes) to let you use 355nW/m as your reference. The Revox recommended setting of 250nW/m takes into account lower-spec tapes and low-speed machines and is far too conservative for 468 at 15ips. I set up a 4dB overbias drop-off at 10kHz at 0dB. Yes, there's enough headroom in the machine and the tape to run the 10kHz bias alignment at 355nW/m, isn't that great? Good alignment gets you the most bang for your buck, believe me. I used an
MRL calibration tape, part no. 21J403.
As far as mods go, I like to keep them as minimal and as reversible as possible. For the B77, it's very easy to make up an appropriate shorting plug to fit into the input preamp circuit board connector. This will let you feed the inputs straight into the record amp, which only needs 35mV RMS for 0vU as per my alignment - any line source can feed that. You can even make it so you can plug your line source into the front panel mike jacks, which are much handier on location than the rear panel phonos. You no longer have the mike preamp, line preamp, or recording level controls in circuit, so your source needs to have adjustable level, but the VU meters are still in circuit.
We set level by feeding the Revoxes from the adjustable headphone output of the nifty little Schoeps VMS-5U mike M/S matrix/preamp. As a benefit, this lets us set level for both Revoxes at the same time (you need two machines when you're recording live). And of course if you need to take your machine back to original, all you need to do is pull the plugs out and slot in the preamp card. I don't remember the part number for the connectors or the numbers of the pins you need to short together, but if you're interested drop me a personal message and I'll have a look.
As an aside, you can pull off a similar trick with the Nagra IV by feeding your source into the "External Noise Reduction" input rather than the line input. And the Ext. NR input is a voltage input rather than a current input, so no series resistors needed in the connector. Just don't plug that cable into the line input or damage may result - I put some blanking caps on our machines' line input connectors.
As far as switchable NAB/IEC playback EQ is concerned, it shouldn't be too difficult to make a small mod for that (but it will be a pain to have to open the machine to switch...) Let me have a look at the manual, PM me and I'll get back to you.
Now to modify the recording EQ, if you've got a 15ips NAB B77, is another matter. To modify from NAB to IEC, it's easier to modify a record amp board from a low-speed NAB machine. Thankfully there's no shortage of those boards on eBay or elsewhre from people who break unrepairable Revoxes for parts. If you need that done too, let me know.
Thanks Steve for your question about our recordings. We recorded chamber music and small-ensemble classical in a fairly "dead" underground venue. We used an M/S setup with a
Schoeps MK41 supercardioid capsule as the M mike an
MK8 as the S mike. We used a
Schoeps active Y-cable and
M/S hanger to give a very compact and discreet cable-hung stereo mike. We ended up hanging it about 2.5m above the floor, 2m away from the centre of the ensemble, in a room with about 4m ceiling height. The active cable fed a
Schoeps VMS5U preamp/MS matrix, and that fed directly into the recording amp of the Revoxes from its headphone output as described above. We recorded at 15ips with IEC eq on 468 tape. All cable besides the Schoeps active cable was
Van den Hul The Patchway B5.
Hope the above is of use.
With best regards,