problem w/cheap converters ?

F

funckyfinger

New member
After reading a thread about recording to VHS I decided to try it. What I found surprised me.It sounded really good. So after that I recorded a song to four different destinations.Fostex MR8(16bit/44.1), computer using Tascam US-122(24bit/44.1),old tape machine, and VHS(HiFi). The mic was an AT4033 and pre DMP3. All four sounded quite different.VHS sounded very realistic,warm and lots of depth,it was my favorite. MR8 sounded good but very 2-D.Tascam US122 lacked depth as well but had very harsh sounding highs.The tape needs not even mentioning,but to be fair it was a cheap 50 dollar radio.

Does this sound like my converters are where I'm running into trouble ? I know this is all very low end stuff but if I'm able to get decent sound to VHS I tend to think my my mic and pre are o.k. and the problem is elsewhere.
 
Are you playing them back all threw the same source? The same a/d converters. Doesn't seem likely because the vhs would be going to analog back into digital and back out to anolog.

So my guess is that you are playing back threw different converters when doing the comparison which will make a difference too.

I think your looking at an educated guess on this one. converters vary both input and output so your converters may be causing you sound problems and a good guess would be that they are not the best. You have to many variables to say for sure though. you're comparing 24 bit to 16 bit in there for one. You would have to find a way to record through the various input converters, yet play them all back through one set of D/A output converters without taking them analog and digital again in the process. I don't know of a way to do that with the vhs.

F.S.
 
Are you playing them back all threw the same source?
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I routed them all to the same mixer using each devices line outs.

You have to many variables to say for sure though
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I hope to redo this test this weekend in more controlled way. This was just a quick test but seems to have opened a can of worms for me.

How did you record onto VHS?
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Just run your signal into the line in on the VCR.


If I could I would record to VHS and then run that into digital but then I would be running through the same conversion I suspect is the problem. :confused:
 
Somehow I couldn't resist testing this. I put a reasonable converter, an RME ADI-8 up against a Tascam CDA500 cassette recorder, and a garden-variety Sony VCR.

The converters were set on 48kHz, using internal converter clock, and levels set to -10dBV so the consumer stuff would be happy (I did test hotter levels, and they didn't like that).

The test file was a burst of white noise (looking at frequency response), then a 1kHz sine wave (harmonic distortion), then a combined 18kHz and 19kHz sine wave (high frequency response and intermodulation distortion).

First I looped the ADI back into itself, using the same unbalanced 12' round-trip RCA cable the cassette boxes would have to use. It performed admirably, with -96dBA noise, less than 0.005% THD (because of the noise, it's tough for me to measure lower), no measurable intermodulation distortion, nice clear high-frequency peaks, and full 20-22kHz frequency response.

The Tascam didn't do so well. This unit can't do double-speed like a Portastudio, but I did use a fresh Maxell II tape. Even so, it checked in with frequency response from 40Hz to 16kHz, 0.4% THD, noticeable intermodulation peaks even with the 1kHz sine wave, and -50/-70dB attenuation on the 18/19kHz peaks which make it practically impossible to measure intermodulation in that test. Noise floor was an unimpressive -57dBA.

With the Sony VCR, it was immediately apparent I had a problem--pretty severe wobble. Reply of the 1kHz sine wave sounded like something out of a horror film. Obviously, a quality VCR (with a new, good quality tape) wouldn't have the same problems I did. However, since this flaw mainly affected the tape speed, I think I was able to infer what the specs would be given a properly operating VCR.

Noise floor, -76dBA. Not noticeable on a mixdown, could be of concern if using for tracking. Frequency response was full 20Hz-22kHz. THD at 1kHz--here is where it gets a little dicey because of the wobble--I think 0.05%, all second order. High frequency sine waves, this is very tough with this unit, I think the 18/19Khz signals themselves are OK, but there are significant, audible aliased peaks at 1kHz and 2kHz.

So, based on that, what are you getting from your VCR (which presumably performs better than mine) that you aren't from cheap converters? Well, I didn't include my Soundblaster in this test, but I've tested it before, and that is probably much worse than your converters. A Soundblaster pretty much has the same results as the Tascam, just not as bad. THD is actually fairly good, good enough anyway, they have little frequency response above 16kHz, and noise a bit lower than the VCR.

So chances are whatever converter you have is outperforming the VCR. However, the VCR is doing something you like, which is probably the small amount of second-order harmonic distortion, a bit of noise to self-dither, and the significant distortion of high-frequency signals. It could be you don't like more accurate high-frequency transients; or maybe some other feature of your monitoring or recording chain makes them sound harsh, so it sounds better to knock them down, fuzz them up, bury them in a bit of benign noise than to leave them as is.

If you like it . . . go with it. I think I would personally save the VCR transfer for mixdown to avoid noise accumulation.
 
Are these HiFi VHS? My recolection is that HiFi' adds a dbx style noise reduction, and that where it got into the most trouble was on hot high freq signals, transients and such. (Maybe this is the nature of the VHS format not the n/r? I only played with the HiFi at the time.)
But the question was if it's sounding better than the digi's, what does that say about the digi.
 
mshilarious, Thanks so much for the info.That is much more in depth than I could have gone.


So chances are whatever converter you have is outperforming the VCR. However, the VCR is doing something you like
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I thought that might be possible. I have been messing around with a tape simulator pluggin and have been able to get results fairly close to the VHS but always at the cost of clarity.I'm using the pluggin that came with Sonar 4 ,perhaps there are better programs.

I'm going to run the VHS signal to digital and see what happens.
 
So I ran the VHS signal to digital. Sounds close to original digital recording, lacks depth with the same harshness to the highs. This would to me confirm that somethings going wrong in the conversion ,yes ?

However, the VCR is doing something you like, which is probably the small amount of second-order harmonic distortion
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Sounds like a job for the msh4. ;)
 
I hope you aren't confusing VHS with analog tape saturation. Hi/FI audio is encoded into the picture data and is read by the spinning heads. It's normally compressed to some extent. The normal audio on VHS is just the same thing that a cassette would be.
 
I hope you aren't confusing VHS with analog tape saturation
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Could be.All I know for sure is the the VHS sounds the best to me. I don't know how the signal is processed by a VCR but it does do someting I really like. I by no means want to start recording to VHS. What I want to try and find out is what I need to do to get my guitar and voice to sound that full and rich in my Sonar program.
 
Farview said:
I hope you aren't confusing VHS with analog tape saturation. Hi/FI audio is encoded into the picture data and is read by the spinning heads. It's normally compressed to some extent. The normal audio on VHS is just the same thing that a cassette would be.
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How can you explain the huge difference in mshilarious's frequency response findings? If the signal is being compressed in the VHS, maybe that explains some of what funckfinger likes about the sound.
 
funckyfinger said:
I by no means want to start recording to VHS.
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I'm sorry but that just made me laugh my ass off. :D

Hey man, if it sounds good roll with it. I don't care if I'm using a Mr. Microphone thru a Beta deck. If it sounds good, why knock it? I guess you just need to figure out how to get it into the digital world without messing it up. I had intentions of trying the vcr thing back in my 4-track days but for some reason or another, I never did. Kind of wish that I had now.

I bet my SECRET dynamic mic would sound killer thru your vcr. :p
 
Try a compressor.

The clarity that you are loosing with the tape simulator is probably what you want. It's just that you can't hear the VCR doing that to your audio (as you twist a knob) so you can't quickly A/B the difference.
 
TravisinFlorida said:
How can you explain the huge difference in mshilarious's frequency response findings? If the signal is being compressed in the VHS, maybe that explains some of what funckfinger likes about the sound.
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I wouldn't extrapolate my findings too far beyond the units I used. I don't know what was going on with that Tascam, but if my Portastudio wasn't in pieces, I bet it would test much better. And I know a decent VCR will outclass the POS I apparently own.

Whether those results go to the nature of the media, I would say for the most part, but +-20% on all figures, at least. But there is also the issue of the analog circuitry that surrounds the media.

I started thinking about how it would be relatively easy for somebody to pop out a killer 2 track VHS mastering box that had a good analog front end and used the whole tape for audio. That is a fat piece of tape. Maybe there is something like that out there that somehow I have totally missed. If not, somebody should start modding dead ADATs to turn them into combination 8 channel summing boxes and analog mastering decks.

No, not me! I don't know anything about that stuff!
 
The tape in a VCR only moves at an inch or a second. It also has the spinning head that reads diagonal stripes across the tape. For digital recording, this works fine. For analog, it would suck giant donkey balls.

Could you imagine the intermodulation distortion from having the head read a strip of tape 29.997 time a second and handing off to another head reading another strip of tape?
 
I started thinking about how it would be relatively easy for somebody to pop out a killer 2 track VHS mastering box that had a good analog front end and used the whole tape for audio. That is a fat piece of tape. Maybe there is something like that out there that somehow I have totally missed. If not, somebody should start modding dead ADATs to turn them into combination 8 channel summing boxes and analog mastering decks
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Someone on gearslutz made mention of someone doing just that. They didn't really give any details. If I had the skills I would be on that right now.
 
funckyfinger said:
Your laughing now. Imagine me walking in a studio with my beat VCR in hand and telling them I had my master VHS I wanted put to CD. :D
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Be sure and tell them it was set for sp (short play).

Farview is making a lot sense but I'd still like to try it myself and see.

Mshilarious, you are just the man to be doing something like this. :D Come on, you know you want to. Think about it. The MSH-VCR deck. It'd be a hit! :D
 
TravisinFlorida said:
Be sure and tell them it was set for sp (short play).

Farview is making a lot sense but I'd still like to try it myself and see.

Mshilarious, you are just the man to be doing something like this. :D Come on, you know you want to. Think about it. The MSH-VCR deck. It'd be a hit! :D
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Yeah, I had it set to SP. If that is 1 ips, then realistically it would have to get sped up, and the tape heads swapped out for something else, before it was a serious audio medium.

Problem is I know nothing about magnetics, and I don't fabricate parts. And farview's comment about diagonal striping is rather apt; the intermodulation distortion I found was pretty bad.

Maybe it could be interesting as a last-ditch analog mixdown medium for dirt cheap archiving, but I would keep the digital originals on archival-grade CDs as a primary storage medium.

When I want lo-fi tape emulation, I can dial it in pretty good on the UAD Roland Space Echo plug.
 
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