a to d and d to a

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a to d and d to a

Postby rob » Fri Nov 12, 2010 7:50 am

Hi,
want to simplify the a/v in the kitchen/dining area. The CRT has to go and as have 2 computers there was going to use them as tv and audio source. Also want to start digitising some vinyl. There's lots of USB DACs around from $100 to 3k but not much in the other direction other than software which means doing it inside the computer @ 16 bit. Have found the Terratec (link below) which is USB 24/192 a/d & d/a plus 5.1 plus phantom power and you name it for $299. Sounds cheap - anyone tried it - does it sound any good? Anyone have any suggestions, advice or recommendations re digitising vinyl? Are computers that noisy? Is there any point going 24 bit with cheap hardware as I already have some software.
Cheers,
Rob


http://www.terratec.net/en/products/faq ... 19871.html
rob
 
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Re: a to d and d to a

Postby DVDdoug » Fri Nov 12, 2010 6:37 pm

Since this doesn't have anything to do with speakers, you'll probably get better answers on another forum, like maybe HydrogenAudio.org.

The folks at HydrogenAudio do a lot of blind ABX testing, and it turns-out that there is no audible benefit to high-resolution audio... 44.1kHz, 16-bit is good enough. Of course, this is very controversial, and you'll get lots of disagreement from the "audiophile" community, but many of these audiophiles don't trust blind testing. (I don't trust sighted testing... If those super-expensive speakers cables only sound better than standard speaker wire when you know which one you're listening to... Maybe your'e fooling yourself! :D )

The main problem with CDs (16/44.1) is dynamic compression and "loudness wars" which results in CDs that are not taking full advantage of the 16-bit dynamic range. (And, they are 2-channels only. ;) ) I have a collection of concert DVDs with 5.1 channel Dolby. These can sound amazing, even though they are 48kHz Dolby AC3, which is lossy compression (like MP3 & AAC).

And, your built-in soundcard/soundchip may also be good enough. About the only "spec" I worry about is noise. (I noticed that you mentioned noise too.) Most soundcards have low distortion and (fairly) flat frequency response, so if you don't hear noise, your soundcard is probably adequate.

I usually worry a little more about the ADC than the DAC. I'm not sure if that's justified or not, but I think it's easier to build a good low-noise DAC than it is to build a good low-noise ADC. 24-bits is probably* helpful when recording live, because you can use some of those extra bits for headroom to prevent clipping. And, when recording from microphones you really need something better than a regular soundcard, because you need a good low-impedance balanced mic preamp (and good microphones, of course).

With vinyl, the vinyl itself is the limiting factor. (Due to the noise floor, vinyl has less than 16-bits of dynamic range.) Here is a HydrogenAudio thread about "cleaning-up" vinyl transfers. I use a program called Wave Repair to remove the "snap", "crackle", and "pop", and then I'll usually try some regular noise reduction filtering and/or noisegating, and sometimes some EQ for old dull-sounding recordings.

* I know of at least one expert who says that room noise is always the limiting factor, and that 16-bits of dynamic range is more than enough for live recording.
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Re: a to d and d to a

Postby rob » Fri Nov 12, 2010 10:16 pm

Hi and thanks,
I'm grateful for your common sense, considered reply.
I've looked through a few forums but, not knowing the participants, its hard know if they are speaking from experience or from a spec sheet, or have a vested interest. Dealers catalogues all make the same claims and post links to e-zines which all make the same claims. I've been sifting through BS for the past few evenings, so thanks for switching the lights back on, it was the sort of reply I was hoping for.
I've read about the sounds wars and 16 vs 24 bit but thought the sample rate was still relevant so will look at Hydrogen Audio when I get a moment. It sounds like the simplest approach is to stop looking at pretty boxes with yellow caps inside and try the computer I already have to see whether its good enough.

Cheers,
Rob
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Re: a to d and d to a

Postby llung » Mon Nov 15, 2010 3:27 am

rob wrote:Hi,
want to simplify the a/v in the kitchen/dining area. The CRT has to go and as have 2 computers there was going to use them as tv and audio source. Also want to start digitising some vinyl. There's lots of USB DACs around from $100 to 3k but not much in the other direction other than software which means doing it inside the computer @ 16 bit. Have found the Terratec (link below) which is USB 24/192 a/d & d/a plus 5.1 plus phantom power and you name it for $299. Sounds cheap - anyone tried it - does it sound any good? Anyone have any suggestions, advice or recommendations re digitising vinyl? Are computers that noisy? Is there any point going 24 bit with cheap hardware as I already have some software.
Cheers,
Rob


http://www.terratec.net/en/products/faq ... 19871.html


Rob,

I digitized all of my LPs a few years ago. The setup was pretty simple - I built a standalone phone preamp, connected to an old Turtle Beach Fiji sound card (ISA bus!) running Windows 98. This is my LAUD system and the Fiji is an excellent card - if not a little old. For post processing, I use Sound Forge to chop entire album sides into tracks. I did not do any post processing - every pop and tick remains. Most pop removers are low pass filters and I figured the LPs with pops were bad enough to begin with that I didn't want to alter them any further. But to each his own.

Your real limitation is going to be the vinyl itself. Even the best kept vinyl has poor S/N despite the claims of the vinyl fanatics. I don't recall the exact numbers but the noise floor on all my recordings was not something to write home about - no matter how good or bad they were to begin with.

The other thing you need is a good RIAA preamp. An old stereo receiver with a phono connection would work but building your own that is decently true to the RIAA curve is easy and cheap - google it.

The 24 bit issue really isn't much of an issue IMHO. If you had a full 24 bits system with 24 bit ENOB (effective number of bits), your system would be sensitive in the microvolt range. And since we're talking LPs with relatively poor S/N, all you have is wasted bits. The Terratec device you looked at pretty much reflects a very good quality consumer ADC. Note that the best S/N given is 114 dB or about 19 bits ENOB. Is this better than 16 bits? Probably. Will you hear a difference? Not likely if you record at the right input level. Is it 24 bits (144 dB S/N) ? No.

If your PC already has a sound card with a line-in connection, just go ahead and use that with your stereo. If you like the results, you're all set. If you think it's not good enough, then perhaps something the Terratec device would be better.

good luck
-lou
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Re: a to d and d to a

Postby rob » Mon Nov 15, 2010 8:35 pm

Thanks Lou,
spent a grand or so on the analogue end of my system a few years ago and have been enjoying it immensely. I want to try to preserve the sound of the vinyl as much as the music - otherwise I would just buy a CD. Like you, pops and surface noise don't bother me so I'm not that interested in buying expensive software to fix it.
I did digitise an album a few months back with an iMac and Toast5 and it seemed a bit hard.
I know the best TT's manage about 70db and vinyl is closer to 50 but had read about higher sampling frequencies being beneficial and was concerned about the 20 cent DACs in consumer computers being inadequate, hence the initial search. A mate had good results with M-audio but I was concerned about it being a PCI card, so your comments are reassuring. Anyway, will perform some more serious tests and burn CDs to listen. See how it goes.
Thanks for the reply.
Rob
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Re: a to d and d to a

Postby DVDdoug » Mon Nov 15, 2010 9:04 pm

llung wrote:Most pop removers are low pass filters and I figured the LPs with pops were bad enough to begin with that I didn't want to alter them any further. But to each his own.
Yes! To each his own... Some people want to accurately capture the vinyl sound.

But FYI - Wave Repair (in the manual mode) only "touches" the file where you highlight the defects. So if your'e lucky and you only have one or two pops on the record, only a few milliseconds will be altered. In fact, when you save the changes, it's really fast because it only re-writes the changed bytes.

Wave Repair has a handful of repair options. (It has a low pass filter, but that's not one of the "normal" repair techniques.) The one that seems to works best on most defects is to copy the few-preceeding milliseconds of sound over the defect, or you can copy from one channel to the other if the defect exists on only one channel. Most of the time, the repaired audio is "perfect" (to my ears). You can't always transparently remove all of the defects, and you can get some artifacts.... In some cases it sounds better with the defect left as-is.

The downside is that there's usually more than one or two defects, and it usually takes me a full day, or a full weekend to fix-up an LP. So... I usually buy the CD if it's available! :D

rob wrote: pops and surface noise don't bother me so I'm not that interested in buying expensive software to fix it.
Wave Repair is only $30 USD, but it is time consuming to use. So, if your not bothered it's not worth the trouble.
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Re: a to d and d to a

Postby llung » Mon Nov 15, 2010 9:25 pm

rob wrote:Thanks Lou,
spent a grand or so on the analogue end of my system a few years ago and have been enjoying it immensely. I want to try to preserve the sound of the vinyl as much as the music - otherwise I would just buy a CD. Like you, pops and surface noise don't bother me so I'm not that interested in buying expensive software to fix it.
I did digitise an album a few months back with an iMac and Toast5 and it seemed a bit hard.
I know the best TT's manage about 70db and vinyl is closer to 50 but had read about higher sampling frequencies being beneficial and was concerned about the 20 cent DACs in consumer computers being inadequate, hence the initial search. A mate had good results with M-audio but I was concerned about it being a PCI card, so your comments are reassuring. Anyway, will perform some more serious tests and burn CDs to listen. See how it goes.
Thanks for the reply.
Rob


Hi Rob,

The higher sampling rate (like 96KHz) raises the nyquist frequency and thus the bandwidth of the analog signal you can capture accurately for playback. In theory a 44.1KHz sampling rate will capture 22.05KHz audio which is more than enough for audible sound. Raising this to 48 KHz (with 96KHz sampling rate) won't hurt. But since your source is vinyl, you're already limited on the high end by the nature of the medium. Also, if you plan to eventually convert these recordings to CD, you'll need to downsample to 44.1KHz which introduces another set of digital artifacts since the sampling rates are not multiples of one another.

M-audio also has USB devices if you prefer those over a PCI card. As far as I know, they are well regarded (but I've never used one myself).
good luck

-lou
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Re: a to d and d to a

Postby rob » Wed Nov 17, 2010 10:20 am

Thanks to you both for the advice,
I do have a PC in the garage for Speaker Workshop but am mostly on Mac and (initially) would be using it for digitising. No reason why I could not transfer it to PC for noise reduction, so Wave Repair could be a useful and inexpensive tool and PC might prove a cheaper option in the long run should I buy hardware.
I guess I misunderstand higher sample rates as I thought that more samples meant a truer rendition of the original waveform as well as a higher cut off frequency.
I have A/B'ed CD's and vinyl and preferred the vinyl rendition but only on a few samples and never as a "naive subject" or "blind" - so hardly conclusive. Having read many heated vinyl vs CD arguments my rational mind concludes the CD was either re-mastered with little care for the end result, that the tape was degraded at the time of re-mastering or that I'm kidding myself. I do believe that "burn-in" on electronic equipment is more likely happening in the listener's brain so, perhaps my investment in analogue parts is driving my perception. Don't really care either way as I'm enjoying the outcome and am passive ie: not producing music for others.
I do hear more HF content on vinyl than CD's and sometimes feel my ears are blocked when listening to digital. I wonder if this could be due to HF hash on the record (surface noise) or the noise floor (or un flat response) of the RIAA pre-amp which is fooling me. Maybe its the smoother roll off of HF on vinyl which sounds more natural - maybe the ceremony of dropping the needle? Who knows? OTOH am very cynical about this cable nonsense.
Anyway, just wanting to digitise it faithfully.
Next step is try what I have.
Cheers
rob
 
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Re: a to d and d to a

Postby Chromedome2000 » Mon Nov 22, 2010 1:28 pm

This may be a bit off-topic but if you have some scratched CD's or DVD's, your local video rental store may have a machine to polish the scratches out. I've taken several unplayable discs over the past couple of years to our local rental store and had them polish them with excellent results. They charged $1.50 per disc, an amount I find reasonable to restore them to near pristine condition. They won't, however, polish Blu-Ray discs as they have a much thinner protective layer than CD's or DVD's. The store manager told me the machine cost them $4000.00 (!) so buying one for yourself is probably out of the question.
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