Analog tape test equip
« on: January 30, 2019, 03:17:33 PM »
Looking for a reasonably priced examples for distortion testers for analog tape calibration.

Is Leader LDM-170/171 suitable ?  suggestions ? not sure if it will do 600 ohms, I think 100K unbalanced for consumer audio equip etc...  http://www.ee.cuhk.edu.hk/~ymfung/ppp/introldm171.pdf

I already know about HP 8903, 331-339A , but too much $$$ , budget is $200 < =

Already have :
Signal Generator ( Leader LAG 120B 600ohm output )
Freq counter ( Tenma ) ,
Scope Tektronix ( 4 ch)   
HP 3400A RMS analog voltmeter 600ohm input
Fluke 187 DMM
MRL test tape

BTW, I see too much old test equipment selling at typical auction for high $ without calibration or knowing internal conditions.  Usually been lying around in some cellar or salvage enviroment for decades unused. For the most part not worth the risk in my opinion. Although there are some exceptions, bought my Tektronix 576 curve tracer for cheap. furthermore,  amp alignment test revealed it to be nearly dead on.

Have a computer based audio interface , but no software for distortion testing ?  Any recommended software for free that will get me by..? 

Some say , REW , not familiar with this . I'll check into this. What is typical layout or setup for distortion measurements?

https://www.roomeqwizard.com/



Any wisdom ? thanks
« Last Edit: January 30, 2019, 07:08:14 PM by electrochronic »
curiousaudioparts at  gmail  dot  com
https://sites.google.com/site/diypartsstore/


Michael Tibes

Re: Analog tape test equip
« Reply #1 on: January 30, 2019, 04:44:09 PM »
Voxengo Span is for free and does a great job for me visualizing the spectrum and the harmonics. One could probably calculate a THD percentage with it, but all I mostly need is the possibility to find a minimum or see the spectral distribution - which works very straight forward and easily.

Michael

Gold

Re: Analog tape test equip
« Reply #2 on: January 30, 2019, 08:55:47 PM »
Why do you need a distortion analyzer to calibrate a tape machine? I know you can set bias by adjusting for least low frequency distortion. That's not the only way to do it though.

Re: Analog tape test equip
« Reply #3 on: January 31, 2019, 02:51:11 PM »
Why do you need a distortion analyzer to calibrate a tape machine? I know you can set bias by adjusting for least low frequency distortion. That's not the only way to do it though.

Service manual suggests this as part of equipment to have in the calibration procedure.
« Last Edit: January 31, 2019, 03:02:35 PM by electrochronic »
curiousaudioparts at  gmail  dot  com
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Audio1Man

Re: Analog tape test equip
« Reply #4 on: January 31, 2019, 03:48:25 PM »
I would also have a WOW & FLUTTER METER to work on Analog Tape machines. How bad is the puck wheel out of round or other parts or the drive motor?

guy_4

Re: Analog tape test equip
« Reply #5 on: January 31, 2019, 05:09:53 PM »
Hello,

Yes, for Tape Recorders serious maintenance you ABSOLUTELY  need a W & F measurement unit !
I have no experience with the Leader brand, but I suppose they are good enough, and you can often find some for cheap on Ebay.

Best,
Guy
"If you think it is expensive to hire a professional, wait until you hire an amateur ! "   Red ADAIR

Gold

Re: Analog tape test equip
« Reply #6 on: February 01, 2019, 09:41:31 PM »
Yes, for Tape Recorders serious maintenance you ABSOLUTELY  need a W & F measurement unit !

I’ve always wanted an EMT 424. Those things are beautiful. I don’t need more projects though.  The Portable One is close enough.

abbey road d enfer

Re: Analog tape test equip
« Reply #7 on: February 02, 2019, 06:46:09 AM »
Is Leader LDM-170/171 suitable ?
I still have one of those. Good enough for tape distortion measurement.

Quote
  not sure if it will do 600 ohms,
I don't get your question. THD is a voltage measurement, no impedance involved.
I think 100K unbalanced for consumer audio equip etc...  http://www.ee.cuhk.edu.hk/~ymfung/ppp/introldm171.pdf

Quote
Have a computer based audio interface , but no software for distortion testing ?  Any recommended software for free that will get me by..? 
RMAA is pretty good for electronic measurements.

Quote
What is typical layout or setup for distortion measurements?
Nothing special, you just inject signal into the input and measure the output of the recorder.

As someone already mentioned, THD measurement is not necessary for routine maintenance.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Analog tape test equip
« Reply #8 on: February 04, 2019, 02:21:41 AM »
You don't say where you are, but the Marconi TF2331 is a decent THD+N meter and night be cheaper than a HP33* but whatever you buy it will probably need looking at,. Anything calibrated and in good working condition will cost more. There is also the Ferrograph RTS2 that was made for testing tape decks and Bell & Howell/Datatape made a device, the TSC1000/2000 that measures 2nd/3rd THD and does other tape related measurement stuff, these were designed for testing computor related tape systems I think, though, not R2R's specifically, I got mine for a fiver .

There are several free bits of software - Soundcard Scope, REW, ARTA and lots of others that can test amps and other bits of kit, but getting them to work isn't straight forward and requires quite a bit of use to get testing right.

Good luck, Andy.

Martin Griffith

Re: Analog tape test equip
« Reply #9 on: April 02, 2019, 04:51:22 PM »
I would also have a WOW & FLUTTER METER to work on Analog Tape machines. How bad is the puck wheel out of round or other parts or the drive motor?
If you feel like building your own, download the service manual of the LA1 from Lindos, it's actually quite a simple W+F circuit

edit : http://www.lindos.co.uk/la1-manual.pdf page 12
« Last Edit: April 02, 2019, 04:55:45 PM by Martin Griffith »


 

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