Calibration Problem

[ASRHTB]

Hello,
I have restored my Akai GX-600DB. It works just fine except for calibration. I have tried to calibrate it with the audition's tone generator. When I calibrate it according to high speed works well, but when I try to use it at low speed, all calibration goes away... I expect calibration should work at both speeds. So, I have calibrated the device according to slow speed, and it works fine, but when switching to high speed, all goes away...

Can someone explain how to calibrate the device without test tape, which I do not have?

Note: 1000hz sin for record side calibration, 700hz sin for playback calibration.

 

[oldvinyldude]

You have likely heard it before-here and elsewhere. One cannot calibrate without a calibration tape. I don't have them either-so mine remain uncalibrated.

 

[ASRHTB]

You have likely heard it before-here and elsewhere. One cannot calibrate without a calibration tape. I don't have them either-so mine remain uncalibrated.

Yes, I heard that this is only an assumption . I have asked my friend to record a tape for me with his calibrated recorder. Maybe I can calibrate it then. Thank you for your help. It was a great help to me.

 

[ASRHTB]

You have likely heard it before-here and elsewhere. One cannot calibrate without a calibration tape. I don't have them either-so mine remain uncalibrated.

Another thing I want to ask is that the datasheet says 0.775v scotch 221 700hz test tape. Is 0.775 V means amplitude/volume level at 77 % and Is there any special thing with the scotch 221?

also, I found at eBay calibration tape, is this good enough?

 

[oldvinyldude]

I know just enough to be dangerous-keep that in mind. I hope someone more knowledgeable will weigh in.....

.775v is the level of signal that should result when the calibration tape is played. Calibration always starts with playback level adjustment. Play the tape and adjust your meters to indicate 0db on their scale. You can use other calibration tapes, if they were recorded at different flux levels, by making corresponding corrections in where your meters read.

Again-I hope someone will let us know if the above is correct-I probably have it wrong!

The tape in the link may be good, but I have no experience with that company\seller. I also don't read other languages (I gather you are located in Europe).

MRL Magnetics is the real deal here in the US.
Genlabs has a good reputation. They are in Europe.

In looking at the SM, I don't see any separate adjustments for other than 7.5ips. Most consumer decks did have adjustments for each speed-but yours does not. Seems you have to pick one and only use the deck at that speed. Playback of tapes recorded at different speeds might be decent, but recording-you can only pick one speed for alignment.

 

[ASRHTB]

I know just enough to be dangerous-keep that in mind. I hope someone more knowledgeable will weigh in.....

.775v is the level of signal that should result when the calibration tape is played. Calibration always starts with playback level adjustment. Play the tape and adjust your meters to indicate 0db on their scale. You can use other calibration tapes, if they were recorded at different flux levels, by making corresponding corrections in where your meters read.

Again-I hope someone will let us know if the above is correct-I probably have it wrong!

The tape in the link may be good, but I have no experience with that company\seller. I also don't read other languages (I gather you are located in Europe).

MRL Magnetics is the real deal here in the US.
Genlabs has a good reputation. They are in Europe.

In looking at the SM, I don't see any separate adjustments for other than 7.5ips. Most consumer decks did have adjustments for each speed-but yours does not. Seems you have to pick one and only use the deck at that speed. Playback of tapes recorded at different speeds might be decent, but recording-you can only pick one speed for alignment.

Thank you for the explanation.

 

[ASRHTB]

@oldvinyldude, hello again. In the service manual there are recording adjustment at page 18 says put 1000hz sin wave to line in and adjust VU meters around zero DB by using 20 kb Semi-fixed resistors. On page 21 says put 1000 Hz sin and arrange VU meters around -20 DB by using Tc1 70p. And than says arrange similar Arrangement for 10k Hz. You might see the frequency adjustment here:



at the page 21 says. So I have confused. I do arranged with tc1 to -20 DB for 1000hz, but when I supply 10khz should I change same tc1 position?