Studer A807 calibration technique

[Linnovice]

Hi all. I'm in the process of calibrating my A807 MkI. According to the manual the first setting is to match the Internal Level to the corresponding Operating Level. A straight forward checking of levels on a couple of test points on the audio electronics boards.
It follows on to say ‘If the input sensitivity should be higher (e.g. for operation with hifi equipment), the setting of jumper JP1 can be changed.
Position A: input sensitivity -4 to +12dBu (standard)
Position B: input sensitivity -17 to -1dBu
Position C: input sensitivity -30 to -14dBu

It then goes on to describe the Adjustment procedure.

What it does not say is when to change the jumpers. ie. before calibrating the Internal Level or after. Does anyone know the answer?

[jamesperrett]

I'd do this before anything else. What are you feeding it with normally? Input level calibration is important if you are using the meters on a mixing desk to set the level but not so important if you are using the meters on the machine. If you are using the meters on the machine then it is important to ensure that the level they read matches the level sent to tape.

[Linnovice]

Hi James, thanks for the reply.
The deck is fed and feeds a Tascam M30 mixing desk at -10bB (0.3V). But when calibrating I disconnect it from the system and use an audio signal generator set at 1000Hz 0.775V 0dB into a 600ohm load and check levels with a couple of analogue millivolt meters. Pretty standard stuff. The machine has no meters or levelcontrols, all recording/playback adjustments are made at the M30.
The confusion comes when calibrating and hence my original question. If you know the Studer, you initially set an internal input of 1kHz 0.775V 0db by measuring at a test point on the audio board and adjusting with a trimmer. This then has the internal output level matched to it from another test point and trimmer. Again very logical. Problem comes when I move the jumpers to suit the input to the M30. If I set up at the standard level -4 to +17dB it's too hot for the mixer. If I move the jumper then try to set the levels the trimmers can't get the range necessary.
I guess I should set up at the 'standard' level then move the jumpers and ignore the meter readings (which is what I've been doing). Presumably, when I move the jumpers I'm just swapping between groups of resistors and the signal into these resistors doesn't change only the signal out? I'm not an electronics guru as you can tell. Give me a box of spanners and an exploded diagram and I'll take it down to the last star washer. Give me a electronic schematic and I'll scratch my head and watch the sawdust fall :-(.

[jamesperrett]

Originally Posted by Linnovice

Problem comes when I move the jumpers to suit the input to the M30. If I set up at the standard level -4 to +17dB it's too hot for the mixer.

The problem is that you also need to see if there is a corresponding set of jumpers for the output. If you can't attenuate the output using jumpers, you may have to buy/build a suitable attenuator to go between the A807 and the M30. The normal alignment procedure is to set up the playback side of things first with a standard test tape. Once you've set up the playback side, you can start on the record side.

[Linnovice]

Sorry, haven't made that very clear. Yes, there are jumpers on the input and output.
It's not a major problem. I've set up on the standard settings and they are just a bit hotter than the mixer needs. It's just my OCD that likes things to be 'just' right. ��