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Author Topic: HOW TO USE THE CALIBRATION TAPE  (Read 8830 times)

mep

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HOW TO USE THE CALIBRATION TAPE
« on: September 01, 2009, 12:55:44 pm »
Maybe I missed it, but I sure did look.  Are there any instructions on how to use the calibration tape?  The Otari MX-55 manual says they assume you want everything calibrated to +4dBm and gives instructions on how to do that using the calibration tape.  Is that the right answer?  I received 6 tapes yesterday, and so far all I have done is set my machine's flux to 250 and set the equalization to IEC and let 'er rip.  Judging by the Otari VU meters reading the playback head with the 3 tapes I have played so far, all appears right in the world.  I also have really good readings on my Ampex 350 VU meters.

Offline docb

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #1 on: September 01, 2009, 03:28:35 pm »
We did a brief instruction in past newsletters, which are not very easy to find:

Part One
http://www.tapeproject.com/August2007/August2007.htm

Part two
http://campaign-archive.com/?u=4f23616eda4b05232b75ece4e&id=1J2ghkjcZI&e=71aa28f943
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

mep

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #2 on: September 02, 2009, 09:14:33 am »
Thanks Doc, I appreciate the links.  What is not clear to me is that if I end up having to tweak my deck in order to get 0 on the VU meters at all the different frequencies, will that only effect the IEC playback or will it have changed my NAB playback as well?  For the here and now, when I make a recording and play it back, I believe it is very accurate to the source.  And this is true using various different tape formulations.  I would hate to make any adjustments that would change something for the worse when I play back tapes I have already made.  Any thoughts on this would be appreciated.

Offline ironbut

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #3 on: September 02, 2009, 10:58:54 am »
How the calibration effects all playback on a machine depends on the machine itself and whether you're using the internal playback electronics of that machine or not.

If you're using the stock playback electronics of any machine, you should check first to see if you have settings for IEC and NAB or just IEC or (quite often) just NAB. If you have a switch that allows you to choose between these two different playback equalization curves then that switch is connecting one of two circuits (either active or passive). So when you do adjustments to one circuit, it doesn't effect the other. Some machines have an actual circuit board that has to be exchanged to switch from IEC to NAB. Others with microprocessor controls can be switched with the touch of a button.
In any case, NAB and IEC are different enough that a second circuit is needed.
steve koto
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mep

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #4 on: September 02, 2009, 11:16:10 am »
My Otari MX-55 has a switch for IEC or NAB.  The manual doesn't address performing calibrations for each standard which made me wonder if I adjusted the calibration for IEC if it would somehow affect the NAB settings.  Since I don't see where there are different trim pots to adjust for IEC vice NAB settings, I can't help but think if you change those settings it will affect both IEC and NAB.

Offline docb

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #5 on: September 02, 2009, 11:42:25 am »
If our tape is used for physical head alignment only and the IEC playback EQ setting is used that head adjustment will be valid for either EQ. If you are using the tone tape to tweak some adjustments like trimpots in the EQ circuit you really should have a tone tape for each EQ you are interested in.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #6 on: September 02, 2009, 11:45:14 am »
All the setting may not be adjustable. You may just have fixed resistors for some or all of the eq. The only way to be sure is to switch from one to the other and see what goes in and out of the circuit. The NAB should have a high frequency and a low frequency filter while the IEC just has a high frequency filter.
Also, if you're happy with the sound of both Eq's, there's no reason that you have to tweak this unless you change heads or something.
steve koto
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mep

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #7 on: September 02, 2009, 01:26:21 pm »
OK, here is the deal.  I joined the TP under the limited subscription deal and I have received all 6 of my tapes.  I thought the purpose of the calibration tape was to set up your deck so that it will be set as closely as possible to the deck that actually made the tape in terms of playback levels at discrete points across the audio band for the type of tape used as well as azimuth alignment of the playback head.

I haven?t made my way through all 6 tapes yet as I just received them on Monday night.  So far, I am very pleased with what I am hearing.  I can?t imagine the midrange or high end being any better than what I am hearing right now nor the bass on TP-08 and TP-09.  My favorite tape so far is TP-09.  When Mose Allison sings Seventh Son, it sounds like you are there watching him sing. The acoustic bass throughout TP-09 just sounds right.  It always surprises me how much bass energy comes from an upright acoustic bass.  I have only listened to Side A of TP-03 and TP-05 and I haven?t heard any bass drum whacks yet that knocked me over if there is supposed to be any (and don?t get me wrong, there is bottom end there and I am not complaining-I am just not familiar with either one of these albums).  If there is some extreme bottom end on side A of either TP-03 or TP-05, please tell me which cut to listen for.  And I am only saying this as I want to understand if I am missing something which would dictate the necessity of going through the calibration process.   The bottom end on TP-09 sounds fantastic.  Ditto for TP-08.  The top end punch on TP-05 is amazing.

The bottom line is that my deck sounds so good with recordings I make and playback and so far with the TP tapes that I am loathe to change anything, especially if changes I make on the IEC side would cause changes on the NAB side.  When I looked at the calibration procedure in the manual for the MX-55, I saw nothing to indicate there are different trim pots for IEC and NAB although it seems there should be.  Maybe I overlooked it and I will study it again.  Part of being an audiophile is being slightly neurotic.  You would hate to think there is possibly more on these tapes than what you are hearing if you only did some tweaking.   Based on what I am hearing so far, it?s hard to imagine it could get much better.

Offline docb

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Re: HOW TO USE THE CALIBRATION TAPE
« Reply #8 on: September 02, 2009, 01:46:58 pm »
Mark, it will do no harm to put the tone tape on and see what the response is. Without doing this we can't really advise on what your machine's frequency performance is. Just put the tone tape on, set the playback eq to IEC, adjust the level controls so the VU meters read 0dB on the first 1kHz tone on both channels, and then let us know what dB you read for each of the following tones of 10kHz, 15kHz, 90 Hz, 60 Hz and 30 Hz. If there are any frequencies that are reading higher or lower than 0dB tell us how much and we can advise on what might be done to improve the machine's performance.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project