This is putting a lot of performance pressure on Dave.
Don't push him too hard. His Powers of Procrastination are legendary.
So the 2 track Ampex and the 4 track Concertone play completely different tapes or would the Concertone be able to play both 4 track and 2 track? Down in Ft. Worth at Greg's audio dealer they have somewhat of a museum. The salesman gave us the tour of what they thought was cool enough to hang onto and display in their retail space. I found it pretty interesting and thought it was a worth while pursuit. I also think a museum of this sort is worthy of our (meaning Dave's) support.
So Dave, are you able to identify the tapes and determine what they can be played on?
No pressure ...
Here is the head block of my two track stereo Revox A 700, (in Europe referred to as half track), recorder.
The small head to the left is the erase head. The head in the middle is the record head, and the head to the right the playback head. This allows for off tape monitoring of a tape as it is recorded.
This is the track format.
Now here is the head block of my Brenell Mk 6.
This machine was built especially to my specification. Note there are four tape heads.
Form left to right, 2 (1/2) track erase, 2 (1/2) track record, 2 (1/2) track playback and then that extra head 4 (1/4) track erase. So this machine will record and playback 2 (1/2) track stereo tapes, but can also playback 4 (1/4) track stereo tapes.
This is the track format for 4 (1/4) track stereo tapes.
Then we have the issue of equalization. North America used NAB curves, the UK had CCIR and continental Europe largely DIN. CCIR and DIN curves are close, but NAB very different. All my machines are NAB.
Now speed, reel to reel machines have various speed options. Speeds are 1 7/8 inches per second, speech quality. 3 3/4 ips often used on consumer grade machines, but below Hi-Fi quality, 7 1/2 ips much better quality and what most of us used to use for recording from radio. Most pre recorded reel to reel tapes are 7 1/2 ips 4 (1/4) track stereo. Older ones before RCA invented the 4 (1/4) track stacked stereo head are 2 (1/2) track stereo. These are sought after and sound better than the later four tracks. These are hard to find. At 7 1/2 ips you can not get to 0 db full modulation out to 20 kHz and have to calibrate the machines at -10 db. So there is HF saturation and fall off in HF response.
So for professional recording we all used 15 or even 30 ips2 (1/2) track. At these speeds you can fully modulate a tape to 20 kHz and down to 20 Hz. So you calibrate the machine at 0 db. The problem is that a 10 1/2 NAB tape reel only last 30 min at 15 ips and 15 min at 30 ips. So you have to switch from one machine to the other at the recording session and have the machines very closely calibrated. This is also very expensive. Good master tape was never cheap. I used to switch between my Brenell and Revox A 700
Now we get to the next incompatibility, noise reduction. Reel to reel tapes for pro use can have Dolby A and dbx 1. There were also a few others such as the Telefunken system.
On the consumer end there was Dolby B and dbx 2.
If you go back to the early to mid fifties, the right and left channels were on different heads, so called staggered head stereo. The problem was that there was no agreed head spacing and every manufacturer used a different head spacing! I have one staggered head pre recorded tape in my collection, what I call the museum.
All of this gives the tape collector a wonderful excuse to have a lot of machines!
The machine on the left is 4 (1/4) track stereo. It is a Revox A 77 Mk 4 and has Dolby B available to it. Speeds 7.5 and 3.75 ips.
The next to the is the Brenell Mk 6 2 (1/2) track stereo record and playback plus 4 (1/4) track stereo playback. dbx 2 noise reduction available. Speed 15, 7.5 and 3.75 ips.
The lower machine a 2 (1/2) track Revox A 77 Mk 1. Speed 15 and 7.5 ips. Dolby A noise reduction available.
The machine to the far left is a Revox A77 Mk 2, 2 (1/2) track stereo machine. Speeds 15 and 7.5 ips.
The Revox A 700 2 (1/2) track stereo recorder. dbx 1 noise reduction available. Speeds 15, 7.5 and 3.75 ips.
So that is an excuse (really need) for lots of machines. And you think we have compatibility problems now?
For Dave's machines his Ampex will be 2 (1/2) track stereo 15 and 7.5 ips.
The Concertone will be 4 (1/4) track and have speeds of 7.5 and 3.75 ips and may be 1 7/8 ips.
So I would be certain there are tapes that play on one machine and not the other.