Author Topic: calibration tape  (Read 632 times)

Offline kritzingerf

calibration tape
« on: December 03, 2020, 06:14:00 PM »
good afternoon all,

so I need to ask for some assistance here...   I have a number of cassette decks, however, I have noticed that recordings on 1 deck sounds 'different' on another, the voice pitch changed, and the rhythm tempo changed...   this is simply because my decks do not run at the same speeds...   this is a simple enough thing to fix...  apart from 1 thing... I do not know which of my decks are actually running at the correct speed, so I can not make my own calibration tape...

Well, technically I can, and I can use any deck, and make a calibration tape, and then attempt to adjust all my decks to run at that speed, but that does not mean they are running at the correct speed...

now, the question, does anybody HAVE a factory calibration tape that they would be willing to make a copy to sell to me, or have a calibrated deck that we can make a recording on for me to use?   either way I would be extremely grateful.   It would be ideal if you were to live somewhere in Johannesburg, just from a practicality perspective.   the South of Jhb would be even better!

Thanx in advance!

regards

Francois

Online johan.pretorius

Re: calibration tape
« Reply #1 on: December 04, 2020, 06:16:14 AM »
If you cannot find a test tape, here are some suggestions/ideas I've picked up on the Internet over time (copied, not my own wording):

Option #1

Use an app just called frequency generator. Record a 3khz tone on a deck that's known to play at the correct speed, play it back on the deck you are checking or adjusting and use Sound Analyser Free to measure the tone and adjust as needed. Far from perfect I'll admit but proper pre recorded tone tapes ain't cheap and I've not the equipment to measure it more precisely. Results seem close enough that pre recorded tapes sound fine and play at a speed that matches a cd played simultaneously. Hope that helps.

Option #2

If you have a Macbook and a sound card, you can connect your deck and generate 1kHz from the tone generator in garageband and record into one of the blank cassettes. Then play it from the deck and monitor in the EQ from garageband. Check the peak is at 1kHz as per the original signal. You can then adjust the controls inside to match it. This is a very basic way

Download free software called Soundcard oscilloscope on your PC.it has a tone generator and you can also check,adjust azimuth for perfect phase.

Option #3 (use official test tapes)

I still own the TEAC test tapes I had in my audio repair shops. Use a 3Khz tape and a frequency counter. Note: prior to opening the shops I worked for several manufacturers, including Superscope / Marantz. Factory spec on decks from every manufacturers' manuals say +/- at least 2%. The closer it is to the upper limit, the r/p response will slightly improve so most decks new from the box are a tad fast. That makes no difference if you record and play on the same deck as far as speed goes, only when switching to different decks

Any test tape with a stable tone (3kHz is the industry standard) and any frequency counter.
There is no better idle time than Thorens time.

Offline kritzingerf

Re: calibration tape
« Reply #2 on: December 04, 2020, 01:36:09 PM »
Thanx Johan,  I appreciate your response.

My problem is that I do not know which (if any) of my decks run at the correct speed...   so recoding my own tape is not ideal.   It is easy enough to get the tones generated and pushed into a deck, but, if my deck is running at the wrong speed I will be recording the test tone at the wrong speed.  If I play it back on THAT deck, the tone will be correct, but on another it will be off.  So, If I then calibrate using that 'off' frequency, all I am doing is calibrating my other decks to run at the same 'off' speed.   If all else fails, this will be what I have to do. at least all my own decks will be matched, and the cassettes recorded on one will sound fine on another deck...

But first prize is still if someone HAS a deck that is calibrated and running at the correct speed that I could make a recording on.  Even if it is very marginally off, it will be better / closer to correct, I think.   

of course, the bonus prize is if some one has a factory cassette that I can purchase or purchase a copy of...

I still live in hope!

Offline gapco

Re: calibration tape
« Reply #3 on: December 08, 2020, 11:04:21 PM »
Needless to say it's pointless calibrating any machine that has old drive belts,perished capstan rollers,old grease,tired motors,worn playback and erase heads etc...just to get other machines in similar condition to work as the manufacturer intended.



Give me an espresso and nobody gets hurt....

Online johan.pretorius

Re: calibration tape
« Reply #4 on: December 09, 2020, 05:57:44 AM »
My problem is that I do not know which (if any) of my decks run at the correct speed...   so recording my own tape is not ideal. 

Right, I should have pointed that out as well.

Another way to find out whether a deck is running at the correct speed, is to play a prerecorded tape with some piano music. It might not be 100% accurate, but should nonetheless give you some idea.

Hope you find a calibration tape soon!
There is no better idle time than Thorens time.

Online handsome

Re: calibration tape
« Reply #5 on: December 14, 2020, 06:52:33 AM »
Ask if one of the tapeheads here would record a 1kHz tone for you on a deck they have that is correctly adjusted

Online johan.pretorius

Re: calibration tape
« Reply #6 on: December 14, 2020, 08:41:14 AM »
Ask if one of the tapeheads here would record a 1kHz tone for you on a deck they have that is correctly adjusted

Good idea, let me see what I can do.
There is no better idle time than Thorens time.