Ampex atr102 calibration

[thekid777]

Hi,
I have to recalibrate the I/O modules of my atr.(due to recent recapping)
I have a AC voltmeter but don't know what I have to read on it to know if I am at -5dBm...
I just tried to calibrate the input at 1.23 V AC (for the +4dB) with the 1khz tone (coming out from the soundcard , generator inside the sequencer 1Khz sine at 0dB on the master) but I think I made a mistake because when I put music then,the Vu on the atr show me a low level than what should be right.
Thanks for your help..!!!

 

[crow]

Did you measure 1.23V coming out of the soundcard at 1khz?  It's hard for me to tell, but it sounds to me like you may not have your standard levels sorted.  Most sources I've come across recommend adjusting the relative levels of digital and analog equipment so that a 1.23V 1khz sine wave should read 0dbVU on an analog VU meter (such as on a mixer or tape machine) and at -20dbfs on a digital meter (such as in your DAW or a soundcard control panel).  If someone has another perspective or different info, please share!

I hope that's helpful; I may be misunderstanding the issue.  Do you have the manual for the ATR?

 

[QUEEF BAG]

inside the meter cage the electronics i think are to be set at a -5 operating level.

i don't recall what the voltage would be tho...

a smart person is sure to come by eventually.

 

[Biasrocks]

0.4356V RMS = -5dbm (ref 1mW @ 600 ohms)

 

[pucho812]

I think you need to get your conversions correct before you start calibration.

As for what the internal measurements are supposed to be, I would need a manual.  But as far as standards,


1.23/1.228V = +4Dbm

.775V = 0Dbm

in digital we usually measure in DbFS which 0DbFS is maximum amount of signal before you reach digital distortion. If your calibration on your unit is not adjustable, then it will state in the manual what level DbFS is equal to 0Vu/+4. usually you can safe guess at -18DbFS = 0Vu/+4. Pro Tools out of the box is calibrated to that at the factory.. others vary like for example a yamaha 02r is set so -21DbFS = 0Vu/+4.

What are you using for d/a? I am kind of confused as to what you are using for your tone.

anyway you should be able to measure the output with a DMM accross the hot and the cold. Adjust level to 1.228V so you know what's comming out of your D/A. then do a standard tape alignment. and adjust the internals as per the manual of necessary. Just because you recap does not mean the internal operation level is going to be way off... It most likely is though...

 

[thekid777]

Thanks for all your answers!!
It helps me a lot and I see I didn't get my levels right from my da,the tone is coming from the 1296 output.
I have the atr manual but I didn't know about dBm - Volts conversion.

To Biasrocks: when you say 0.4356V Rms it means that I should read 0.4356V AC on the voltmeter?

I have to recalibrate it now because the recap changed the offset and the midrange is quite harsh now..

Thanks again for your help!
Jul.

 

[Biasrocks]

To Biasrocks: when you say 0.4356V Rms it means that I should read 0.4356V AC on the voltmeter?

Yes, between Pins 2 and 3.

Mark

 

[QUEEF BAG]

a little suprised recapping would change the mid range much,

what caps need to be replaced? i thought they were all tants...

 

[gar381]

Lots of tants on the power rails of  ATR100s
I would and have changed them out to Panasonic FCs
as this happened to one of mine from a shorted tant:

GARY

 

[thekid777]

a little suprised recapping would change the mid range much,

what caps need to be replaced? i thought they were all tants...

It's the C25 and C26 that are electrolytics in the I/O.(100uf)


Gary = your picture is really terrific!!I hope to not have the same thing here!!
Thanks for sharing this experience about tants caps...!

 

[thekid777]

I think you need to get your conversions correct before you start calibration.

As for what the internal measurements are supposed to be, I would need a manual.  But as far as standards,


1.23/1.228V = +4Dbm

.775V = 0Dbm

in digital we usually measure in DbFS which 0DbFS is maximum amount of signal before you reach digital distortion. If your calibration on your unit is not adjustable, then it will state in the manual what level DbFS is equal to 0Vu/+4. usually you can safe guess at -18DbFS = 0Vu/+4. Pro Tools out of the box is calibrated to that at the factory.. others vary like for example a yamaha 02r is set so -21DbFS = 0Vu/+4.

What are you using for d/a? I am kind of confused as to what you are using for your tone.

anyway you should be able to measure the output with a DMM accross the hot and the cold. Adjust level to 1.228V so you know what's comming out of your D/A. then do a standard tape alignment. and adjust the internals as per the manual of necessary. Just because you recap does not mean the internal operation level is going to be way off... It most likely is though...

Thanks Mr for this answer,
I am affraid when I check voltage on my DMM I have to put the generator at -14,65 db (nuendo generator sine 1khZ out from the 1296) to get 1,228V AC  :-[
Do you think it's correct?Thanks!

 

[pucho812]

I think you need to get your conversions correct before you start calibration.

As for what the internal measurements are supposed to be, I would need a manual.  But as far as standards,


1.23/1.228V = +4Dbm

.775V = 0Dbm

in digital we usually measure in DbFS which 0DbFS is maximum amount of signal before you reach digital distortion. If your calibration on your unit is not adjustable, then it will state in the manual what level DbFS is equal to 0Vu/+4. usually you can safe guess at -18DbFS = 0Vu/+4. Pro Tools out of the box is calibrated to that at the factory.. others vary like for example a yamaha 02r is set so -21DbFS = 0Vu/+4.

What are you using for d/a? I am kind of confused as to what you are using for your tone.

anyway you should be able to measure the output with a DMM accross the hot and the cold. Adjust level to 1.228V so you know what's comming out of your D/A. then do a standard tape alignment. and adjust the internals as per the manual of necessary. Just because you recap does not mean the internal operation level is going to be way off... It most likely is though...

Thanks Mr for this answer,
I am affraid when I check voltage on my DMM I have to put the generator at -14,65 db (nuendo generator sine 1khZ out from the 1296) to get 1,228V AC  :-[
Do you think it's correct?Thanks!

because it is digital it could totally be correct.  DbFS is a digital meter reading. with 0DbFS being full signal before digital clipping. anything beyond that is completely adjustable and in referencing to analog is up to the manufacture. It's a pain with the digidesign 192 interfaces as the adjustment pots are under a dsub connection in the back FYI.  Just because most systems default at -18DbFS  = 0Vu = 1.228V, etc does not mean anything other then you know  have  a point of reference. Digital is adjustable like that. I have worked with engineers who want -14DbFS = 0Vu, etc and I when working in film and TV they say -20DbFS is 0VU.  It ultimately adjusts headroom level...

 

[thekid777]

Hi,do you know what the Shelf and Eq at the bottom of the card do?
I searched in all the manual but these are a different card version.
Thanks!!

 

[Biasrocks]

Hi,do you know what the Shelf and Eq at the bottom of the card do?
I searched in all the manual but these are a different card version.
Thanks!!

It's an additional record side high end shelving eq. You can use a 5K-7K tone to set that level and the use the EQ to set your 10K level. That's as close as I ever got to making it work. I've also heard suggestions of using full band noise to align that one, but the 5K tone seems to work just fine.

Mark

 

[thekid777]

Thanks a LOT mark!!  8)
Do you know as well if when the masterbias is activated the bias norm on the cards don't need to be adjusted?

 

[Biasrocks]

Master Bias will adjust both channels at once. Bias Norm does that specific channel.

The idea being that once you calibrate bias norm, you can simply use the Master Bias control to do both channels.

I will check each channel (bias norm) every so often to make sure they are still in the ball park.

If your only going to run 15/30ips I would suggest changing over the AUDIO CONTROL card to a two speed setup which allows you to switch between two different tape types easily.

Mark

 

[thekid777]

Hi, I have a resistor that is bad looking and would want to change it,
I looked in the part list from the atr manual and I can see that this resistor (r56) would be a 100 ohm 5% 1/4W.
Can you confirm that you have this resistor on your audio control master bias card?
Mine (which is kind of burned see pic) don't seem to be 1/4W because it's bigger.
Thanks for your help!!

 

[Biasrocks]

Confirmed, it's a 100R 1/4W carbon.

The resistor on your card does not look original, I would say that
there's an old problem somewhere that's causing that guy to burn.

Mark

 

[thekid777]

Thanks! Oh...I hope I could repair this!
Did you replace all the tant caps?!!

 

[Biasrocks]

Did you replace all the tant caps?!!

Yes, completely recapped all the electronics, got rid of all the tants. I can't remember if there's tants in the signal path, I would keep those, but anything power related you're better to off those and replace with a similar value electrolytic.

Exploding tants is not a nice thing.

http://www.groupdiy.com/index.php?topic=16989.msg197772#msg197772

Also, check your bias frequency, mine was horribly off. I had to replace the ceramic cap(s) off the bias generator to get it back to the proper frequency again.

Mark