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Author Topic: Oscilloscope for RTR Alignment.  (Read 30144 times)

Offline ironbut

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Re: Oscilloscope for RTR Alignment.
« Reply #15 on: July 09, 2009, 10:10:22 AM »
Hi Charles,

I posted a link to some probes for sale on eBay that are made to protect the soundcard while using 'scope software. I'm sure it's pretty easy to make one too but these were only about $20 and come with all the adapters you might need. Like I said, I don't seem to be able to find that thread at the moment but I think it was listed under "soundcard probes" on eBay.

As I've said before, if you plan to use this for anything other than just aligning your heads, bit the bullet and buy the real thing. Spending a few hundred on an old scope that is more than you'll ever need is a lot better than replacing a laptop!
steve koto
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Offline miroslav

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Re: "Software scopes" - BE CAREFUL!!!
« Reply #16 on: July 09, 2009, 10:36:18 AM »
I have nothing against software scopes but PLEASE keep in mind that you are using inputs and outputs to your soundcard that were "designed" to see signal levels from headphones/speakers and microphones.

You go using your PC as a piece of test equipment and you could inadvertently inject who-knows-what into it.  IF you do this please think about PROTECTING the I/O ports somehow.  I haven't done any research on this but someone probably has - like using back-to-back zeners from "hot to ground" to limit the voltages - and maybe even a micro fuse in series with the "hot" leads!  Hopefully there are I/O specs somewhere in your Soundcard literature - if not, ask.

Charles 

Appart from the issue I mentioned in my previous post where the software scope didn't like my 24 bit converters...I wouldn't think there's any real concern...if you have decent soundcards/converters.

The test signals coming from the the deck's outputs are typical Line level signals/voltages, +4dBm to +16dBm...which should work with OK with most soundcards made these days.

Offline microstrip

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Re: Oscilloscope for RTR Alignment.
« Reply #17 on: July 10, 2009, 01:32:02 PM »
I prefer to use an USB audio adapter to avoid damaging the computer if something goes wrong. The EMU tracker PRE (192khz 24 bit) has high impedance inputs with 1Mohm. This is the standard impedance of most oscilloscope inputs and can be used with a normal 10X oscilloscope probe giving an attenuation of 10, extending its range to 20V RMS. I bought some 1/4 phono to RCA and RCA to BNC adapters and connect the probes directly to the  HiZ input.
Francisco

Offline miroslav

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Re: Oscilloscope for RTR Alignment.
« Reply #18 on: July 11, 2009, 11:33:00 AM »
Just found this FREE audio analysis software tool that looks to be just the ticket of anyone not wishing to go the hardware oscilloscope route.

Visual Analyzer

http://www.sillanumsoft.org/

I will be installing the latest version (VA 2009HR) later today on my DAW, and will post back how well it works, but I already installed and earlier version (8.xx) on my XP laptop without issues, and it looks very good so far.

Offline docb

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Re: Oscilloscope for RTR Alignment.
« Reply #19 on: July 11, 2009, 01:35:45 PM »
From their webpage:

Quote
Frequency compensation: one can create/edit a custom frequency response and  add it to the spectrum analyzer spectrum ;

Oooh, that could be a really nice feature for measuring eq curve response...sounds like a very worthwhile piece of software.

Speaking of test equipment for alignment,  I just picked up a Sound Technology 1510A last night that powers up and passes the self test - for a whopping $75. Can you say "screamin' deal?" Thanks to Ed Fallon for spotting it on Craigslist!
Dan "Doc B." Schmalle
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Managing Director - retired, The Tape Project

Offline miroslav

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Re: Oscilloscope for RTR Alignment.
« Reply #20 on: July 11, 2009, 08:29:05 PM »
I'm sure for fulltime bench work, a real good piece of hardware is the ticket, and you don't have to deal with the soundcards or PC...etc.
But since I have the DAW right next to the R2R decks and mixer in my studio...the software version is a good choice for me.

I installed it and tried it out tonight for my Otari R2R alignment?and it works great!
Ran smooth-n-steady, and never crashed, except one time when I clicked on a couple of options while also trying to open a couple of its windows in fast succession while I was running a calibration on the software?s input.
That was a bit much on my part! ;-D
Plus?I never restarted the PC after I installed, though it didn?t ask for it.
But once I restarted, then the software was better at quickly recognizing my soundcards since I have 24 channels of A/D/A split up as 12 input and 12 output pairs?plus the same number of digital I/O channels?so it?s no wonder the software was a bit confused at first.

Anyway?works like a charm for doing the azimuth, plus there are quite a few other analysis tools built in, so it has many more uses.

Not bad for FREE software?though I will donate some $$$ to the guy via PayPal.
He put some serious work into this and it has value for me.

Offline ironbut

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Re: Oscilloscope for RTR Alignment.
« Reply #21 on: July 11, 2009, 10:50:25 PM »

Speaking of test equipment for alignment,  I just picked up a Sound Technology 1510A last night that powers up and passes the self test - for a whopping $75. Can you say "screamin' deal?" Thanks to Ed Fallon for spotting it on Craigslist!

You dog!
I'd love to get my hands on one. I can't believe you found a working one for $75 bucks!
steve koto
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Offline docb

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Re: Oscilloscope for RTR Alignment.
« Reply #22 on: July 12, 2009, 11:33:13 AM »
The guy I got it from had bought an auction lot of gear. He had some sort of budget scope, a CRT tester, a couple of ancient analyzers, mostly kind of useless stuff. Makes me wonder what it was that was in the original lot that made him buy it.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline Studer Fool

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Re: Oscilloscope for RTR Alignment.
« Reply #23 on: July 13, 2009, 08:54:15 AM »
Indeed, "SCREAM'IN DEAL" Dan!  A Sound Technolody ST1510A for $75!

What options if any did it come with? 
What software level is it at? 

I suspect you have a later software level if you passed the seft test, as with earlier versions it was important to set the output level before running self test, where as with the later versions this was worked around so that the self test would pass w/o setting the output level (or you knew this already??).

By the way, our own Charles King (Stellavox) would appear to have amassed some experience with these devices!

-cdw
Christopher D. Wait
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Studer A80-VU & Studer A80-RC (and Doc's lovingly modified Ampex 934 with Seduction Tape Head Preamp Combo!)

Offline ironbut

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Re: Oscilloscope for RTR Alignment.
« Reply #24 on: July 13, 2009, 09:40:05 AM »
Speaking of tape test equipment, has anyone ever seen an Altair T2DS? As far as I can tell, they dwell in the land of unicorns and the "perfect date"!
steve koto
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Offline jcmusic

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Re: Oscilloscope for RTR Alignment.
« Reply #25 on: July 13, 2009, 11:15:54 AM »
Speaking of tape test equipment, has anyone ever seen an Altair T2DS? As far as I can tell, they dwell in the land of unicorns and the "perfect date"!
Please describe the perfect date!!! I must have missed something way back when!!! LOL!!!

Jay
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Offline microstrip

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Re: Oscilloscope for RTR Alignment.
« Reply #26 on: July 13, 2009, 01:00:08 PM »
Apologies for a naive question, but only recently I entered the RTR kingdom with a subscription of the Tapeproject.
I went trough several sites about wow, flutter and scrappe flutter and can now understand what they are. I looked at the specifications of several instruments at Dave Manquen site and Jay McKnight papers. My question now is: what can be measured with these old dedicated instruments that can not be done using a good 24bit 192 kHz USB soundcard with, for example, Spectraplus v5.0 software?
I have been playing with with the demo version and an USB EMU Tracker pre and the specifications are great for RTR tests.
Francisco

Offline ironbut

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Re: Oscilloscope for RTR Alignment.
« Reply #27 on: July 13, 2009, 05:32:02 PM »
It's more of a difference in levels of detail that these instruments can measure. They're both purpose built measurement devices that are more for repairs and pretty extreme tweaking in the case of the Altair. The Sound Tech. would have found a home with someone who might have done studio machine maintenance where getting something done fast and correctly would have been paramount (a recorder down during an expensive session just isn't an option). Having a one box solution would save tons of time.
Any purpose built measurement device avoids the particular noise spectrum that obscures what it's trying to measure too. It's left to concentrate on the range of measurements that are meaningful.
steve koto
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Offline 1audio

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Re: Oscilloscope for RTR Alignment.
« Reply #28 on: August 28, 2009, 11:01:45 PM »
I have an ST1510 and the closest to an Altair in the broader market a Mincom wideband flutter analyzer. For working on tape machines these have lots of benefits over a PC program with the special functions for optimizing bias and tape motion analysis. You can analyze wideband flutter with an fft analyzer but its hard. To get down to 1/2 Hz you need a very large sample and plenty of processing time, and you are looking at close in sidebands of the carrier. The dedicated machinery gets the info much more quickly.

For a scope for this work and one that will be harder to inadvertently damage I would suggest a Tek 5000 series scope from eBay like this http://cgi.ebay.com/Tektronix-5115-Storage-Oscilloscope_W0QQitemZ330354826888QQcmdZViewItemQQptZBI_Oscilloscopes?hash=item4ceaae9e88&_trksid=p3286.c0.m14#ht_500wt_1166 . They can be had for peanuts and the plug in options are endless and cheaper still. Digital scopes have appeal BUT your into analog recording aren't you (or you would not be here) and analog scopes are much better for seeing what comes out of a tape machine that a digital scope. Tape isn't really stable and a digital scope will average the signal making it harder to see.
Demian Martin
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Offline ironbut

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Re: Oscilloscope for RTR Alignment.
« Reply #29 on: August 29, 2009, 12:17:26 PM »
Thanks 1audio (btw we use our real names here). Most of the measurements that I'm interested in making is the flutter in the transport/tape path (at least that's been my focus for a while). I assume that something like a Mincom will use an MRL flutter/speed test tape?

Like you've indicated, software just doesn't cut it when it comes to making these tiny measurements. The AD converter has to be extremely quiet and the higher fequencies become less and less accurate too. When it comes right down to it, I just don't know whether to believe the measurements. I have no problem with doing basic playback head adjustments but outside of that, the software meters aren't well suited to analog signals.
steve koto
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