I got quite lucky (I think) at an auction a couple of weeks ago and got a lot of three Neutrik RT1-M digital audio test boxes for £99 (including commission and VAT).
It's quite an old design with a slightly quirky instruction set, but very cheap for a fully digital audio tester with IEE-488 interface. And it can't do sweeps.
Its modern enough to do SCPI so Jan Cumps would like it 
.
It's enormously heavy, being housed in a heavy gauge steel 19" rack.case.
The sampling rate is only 48kHz so it's nothing like capable as the modern boxes from Keysight, R & S or Audio Precision.
The operating manual is readily available on the web.
I've only tested one of them but it certainly works for output.
Looks like this on the scope:
I'll need to do a bit more work to check out the input section (might need an actual control programme rather than Hyperterminal ).
But so far it's looking good.
(I just checked up on that big prominent chip on the left hand pcb - the AD569 - its a precision 16 bit DAC, currently available from Digikey for £61 - maybe I should just sell the chips on Ebay (there are two in each RT1-M))
If all three RT1-Ms turn out to work I'll be interested in swapping one !
MK
