Aligning Tape machine using RME DIGICHECK

[skaren]

Hi wise ones,

In the absence of a reliable analogue vu meter would it be possible to use RME DIGICHECK to determine wether the tape machine is outputting the required -1 (setting up the machine for 456 +6) from a 320 nW/m (+5) test tone tape.

Equipment used:
320 nW/m test tone tape.
Studer A80-R 1/4 inch (no VU meters) 7.5 and 15 ips

Lavry Black AD10 - accepts "+4dBu" level signals

RME babyface with DIGICHECK - Default 2-Bar level meter

If it is theoretically possible what should DIGICHECK tell me when the tape machine is indeed outputting -1db?

DIGICHECK is currently showing a reading of about -12db

I only have a shallow understanding of all the terms involved (dBFS, dBu, dBV etc) so go gentle

Any help is much appreciated!

 

[Pip]

Here is a good chart. You can use a volt meter for alignment.

 

[skaren]

Thanks for your reply Pip.

That chart could be very handy.

I originally tried to get a value from the tape machine by using a similar chart and my multimeter but I can't get a reading on it.

This is the one I have https://goo.gl/tZ9NuC

Should it be able to get a Voltage reading from an audio signal? From what I've read some lesser models can't do that specific thing.

 

[Pip]

That should be fine voltage is voltage. Where you have a problem is when it is a very high impedance circuit and you try and read voltage. That is not what should be going on with a standard tape machine output. What are you running out of your tape machine do you have an alignment tape with tones?

The higher the input impedance of your meter the better!

look for a used Fluke Model 8040a that will get you done!

Edit: Yes of course the frequency response ability of the meter is important.

 

[Gold]

This is the one I have https://goo.gl/tZ9NuC

I didn't see the AC voltage frequency range spec in the link.  Some DMM's are only accurate to a few hundred hertz. 

There are a lot of variables in using a sound card. You need to know the relationship between dBu and dBfs. If you know that +4dbu = -18dBfs on the Digicheck meters then you can use the meters. 

I would use the 100 Hz tone because your DMM will likely be accurate there. Check that your DMM AC voltage reading matches what the DIgicheck meters are telling you. Once you know the level relationship between the tape machine output and the Digicheck meters you can use the Digicheck meters reliably.

If you are new to aligning tape machines I'd recommend getting a good vintage AC voltmeter. Something like an HP 400 variant. There are really nice Bruel and Kjaer models too. They don't go for a lot of money and they are nice to use for tape machine aligning.

 

[ruffrecords]

Invest in  a cheap multimeter - the one you have is designed for automobiles and the AC rages are not sensitive enough. Something like this will do:

http://uk.farnell.com/tenma/72-10395/digital-multimeter-handheld-3/dp/2450661

It is auto-ranging and the most sensitive ac range is 4V so you should see the nominal +4dBu from the Studer as 1.23 volts.

Cheers

Ian

 

[skaren]

Thanks you all for your replies.

I think a sensible thing would be to buy a new multimeter.

Thanks for the suggestion of multimeter. However would this one do it: http://goo.gl/fl2ZTm

Next day delivery

 

[ruffrecords]

Thanks you all for your replies.

I think a sensible thing would be to buy a new multimeter.

Thanks for the suggestion of multimeter. However would this one do it: http://goo.gl/fl2ZTm

Next day delivery

That would probably be OK. It has a 2V AC range so you should see your signals OK.

Cheers

Ian

 

[skaren]

Thanks for your reply.

I should hopefully be able to figure out both ways of doing it (multimeter and digicheck).

 

[abbey road d enfer]

Hi wise ones,

In the absence of a reliable analogue vu meter would it be possible to use RME DIGICHECK to determine wether the tape machine is outputting the required -1 (setting up the machine for 456 +6) from a 320 nW/m (+5) test tone tape.

Equipment used:
320 nW/m test tone tape.
Studer A80-R 1/4 inch (no VU meters) 7.5 and 15 ips

Lavry Black AD10 - accepts "+4dBu" level signals

I don't see why you couldn't use the Lavry for this alignment.
First, you expect -1 at the VU-meter, that's +3 dBu (0VU=>+4dBu).
Then the Lavry, with its gain setting in position 13dB, displays a maximum of +11dBu (that's in the manual). So you must align for a reading of -8 on the Lavry's meter.
Admittedly, the Lavry's meter has only 1 dB resolution, but level alignment of a tape recorder is not über accurate either.
The loading of the Studer's output by the Lavry converter is anecdotical.

 

[ricardo]

I didn't see the AC voltage frequency range spec in the link.  Some DMM's are only accurate to a few hundred hertz.

If there isn't a frequency response spec, the DMM is probably meant for 50 & 60Hz only.  Even 100Hz may be dodgy.

There are special rectification methods that are "immune" to hum (??!*) so these are useless for frequency response.

Use an oscilloscope if you haven't got a Fluke  ;D

 

[radardoug]

Just buy a decent ac millivoltmeter and do the job properly! They are cheap on Ebay, good HP's or other brands. Then you can do it at any audio frequency.

 

[Monte McGuire]

Right. Using low frequencies will muddy the issue, since head bumps will add sometimes significant error to any reproduced signal. 1kHz is pretty standard for a lot of reasons.