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Author Topic: Technics flutter measurements with ST1510A  (Read 8732 times)

Offline docb

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Technics flutter measurements with ST1510A
« on: October 20, 2009, 10:18:59 AM »
We just got our Sound Technology 1510A up and running yesterday. One of the first things I wanted to do was verify the flutter spec of a couple of Technics RS1500s. The published spec is .018% and sure enough, that is what we measured on both machines. This is using a 3kHz tone, recording and playing back that tone, weighted JIS standard (RMS) which is what Technics appears to have used for their quote. It was interesting to note that the most prominent deviation (still quite small, and yes we seem to have the "007" spy version of the 1510A that displays a frequency scale) had a period around 3Hz. This seems to correlate with that little hiccup one often sees in the strobe pattern.

« Last Edit: October 20, 2009, 10:21:24 AM by docb »
Dan "Doc B." Schmalle
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Offline ironbut

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Re: Technics flutter measurements with ST1510A
« Reply #1 on: October 20, 2009, 01:15:07 PM »
That's great to hear Doc!
It's particularly interesting that the strobe is accurate enough to pick up that hicup.
 
I picked up a Micom 8300-w a while back but it's sitting in the queue of projects right now (actually, sitting on the dine room table with a few other projects). It needs some cleaning up and I need to make some bnc>rca connectors to use with it.

 I'm fooling around with dampening the motor noise that's transmitted to the headblock right now. I just finished making a contact mic that I can attach to the headblock to make somewhat accurate measurements. Then on to the reversing roller.
I've been searching for the best materials to stuff into cavities on the back of the faceplate to absorb vibrations. I usually just use blu tack type stuff I get from the local hobby supply store and for sheets, the E.A.R. stuff that Percy sells (for the fixed motor housings and those magnetic shielding plates that ring like a freakin bell).
 Any other suggestions?
« Last Edit: October 21, 2009, 11:58:54 AM by ironbut »
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
 HE Audio Jades

Offline docb

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Re: Technics flutter measurements with ST1510A
« Reply #2 on: October 20, 2009, 01:26:05 PM »
For sheet metal I use 3M constrained layer damping tape. Gotta more or less match the mass of the damping material to the mass of the thing to be damped. So for thicker aluminum I suspect a heavier mat might work better. Some of the coolest damping material I have was cooked up by Andy Bartha years ago. He would mix lead shot, maybe #7 or so, with some kind of pourable silicone sealer intended for mobile home rooftops. He made pucks by molding them into muffin tins, but maybe something like that could be buttered into the cavities on the front casting. Or how about stick on lead wheel weights, maybe set in something gooey like undercoating?
Dan "Doc B." Schmalle
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Managing Director - retired, The Tape Project

Offline docb

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Otari flutter measurements with ST1510A coming next
« Reply #3 on: October 20, 2009, 01:28:57 PM »
Shawn is setting up a modded and unmodded Otari this afternoon. We'll report our findings. Factory flutter spec is .06% weighted NAB.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: Technics flutter measurements with ST1510A
« Reply #4 on: October 20, 2009, 02:32:40 PM »
Cool, thanks!
I like the buck shot idea. I'll experiment around with the gazillian caulks and glues I've got. There's a pretty big range of how stiff the material ends up when fully cured. At one end of the spectrum is some stuff called Sikaflex that gets so hard that it can be sanded (but that takes about a month). Another one called Big Stretch which, true to it's name, will stretch to about twice it's original size (I've filled gaps up to 1" for water proofing with this stuff and you can "sculpt" it with a wet putty knife too).
Probably something between those two should work.
steve koto
 Sony scd 777es(R. Kern mods)> Vpi Aires>Dynavector XX-2mkll>Bent mu>CAT ultimate>CJ premeir 140>Magnepan 1.6qr(Jensen xover)Headphone Eddie Current Zana Deux>AT ad2000,HD800 ,Metric Halo ULN-2 (battery powered),
 HE Audio Jades

Offline stellavox

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So how do you like your ST??
« Reply #5 on: October 21, 2009, 05:56:41 AM »
Got the tapes?

Charles

Offline docb

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Re: Technics flutter measurements with ST1510A
« Reply #6 on: October 21, 2009, 10:34:45 AM »
The ST is a nice addition to the lab, particularly a cramped one like ours where an all in one type device saves bench space. We have it on the bench with a Tek TDS420 on top of it and a bench DMM on top of that, a neat little stack. It seems to do some things quite well, like the flutter test at 3K. Probably due to habit I prefer adjusting the playback head azimuth by scope - I think a Lissajous figure gives a little more responsive info than the teeny pips on the line on the ST display. But once that is done adjusting the record head azimuth is very easy to do with the ST. So far our noise measurements seem a little inconsistent. I'm not sure if it is a calibration issue, noise in the lab coming thru, or operator ignorance. We found we had been using a bad cable yesterday and that may have been part of our problem. The frequency response setup is convenient too, although a more modern setup with a laptop could probably do the test to a little higher resolution. We have been using our own tapes for azimuth adjustment and such. If I deem it necessary I will probably order up the MRL tapes.

http://home.comcast.net/~mrltapes/pub211.pdf

We do have one odd issue with the thing. Every once in a while the vernier buttons for setting the ref voltage stop working. It seems that running a self test clears it. We have cleaned contacts and reseated all the cards and checked the ribbon cable that connects the front panel components to the mainframe and it all seems OK. Hopefully it will not happen so often as to require sending it in for service. I think the quote for any repair plus cal was around $1000. I get the impression that the schematics are probably not readily available.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline Studer Fool

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Re: Technics flutter measurements with ST1510A
« Reply #7 on: October 21, 2009, 06:26:41 PM »
Somewhere around here I have a CDROM that I spent too much money for on ebay that has both the Operations manual and the (big) service manual on it.  The scan of the op man. is not great but works (describes the spectrum analyser and the IEEE HP-IB options).  The service manual is much better scan, and handy to have (assemblies and schematics).  I don't know if it's still ever offered on ebay.  Steve Bender has other vintage versions of the manuals available as hard copy.

cdw
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Offline Dave Cawley

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Re: Technics flutter measurements with ST1510A
« Reply #8 on: October 22, 2009, 12:32:14 AM »
I'm not familiar with the ST1510A.  How close in can you see?  I use the HP 3561A FFT analyser, it can show flutter sidebands often as little as 30dB down.  I use it for measuring turntables and tone arms but have just become interested in reel to reel.  I measured an Akai GX625 and although the wow and flutter was within specification, the sidebands were disarmingly worrying.  Not being an expert I can't tell if this is a motor drive problem or a tape path/scrape problem?

Regards

Dave

Offline stellavox

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Re: Technics flutter measurements with ST1510A
« Reply #9 on: October 26, 2009, 04:56:01 PM »
1500 series has some nice features. 

The azimuth test actually tests / measures 4 frequencies (2.8, 5.7, 11.8 and 15.8 Khz) SIMULTANEOUSLY and you can discern phase better than 5 degrees of arc.  The frequency response can be displayed with 10 db per division,  or in "expand" 2 db,  so its very easy to see "flatness" down to a quarter of a dB or so - over the full range of 40hz to 40kHz!  Beats spot tones right out of the gate.  If you have the spectrum analysis option, you can measure the actual level / frequency of the flutter components. - same with noise.  The distortion function works nicely in record - produces a selectable sine wave in 1dB steps that decrease from +20 to -10dB and simultaneously displays either the 2nd or 3rd (you select) harmonic distortion as the level decreases - useful for setting the bias "right on".

Of course to use the level, azimuth and frequency response sweep capability, you need the appropriate test tapes-  which are still available from MRL.  As I indicated in a previous post, they made me up an "all in one" tape with level, Azimuth and frequency sweeps (both NAB and IEC) for 15, 7.5 and 3.75 for not a lot of money.

Charles

Charles