You are here

Log in or register to post comments
deckeda
deckeda's picture
Offline
Last seen: 2 weeks 1 day ago
Joined: Feb 1 2006 - 7:41pm
Options and alternatives for digitizing analog (primarily vinyl) in hi res

Vinyl seems a worthy source for incorporating a higher than 16/44 ADC. High end phono preamps continue to be offered, but apparently there aren't enough of you out there using them or asking to use them to digitize your vinyl.

It seems telling that the phono preamps with A/D converters in them are aimed at the lower end of the spectrum (16/44 resolution only, am I right?)

And so, for people like me who like to use a computer for playback but retain better sound from LPs, pro audio to the rescue. And I don't mind going that route to digitize at say, 24/96 but anything pro audio tends to either be not quite relevant in some way for a home user or underground with respect to being featured in a high end magazine. All of which makes picking one more cumbersome. Especially when it won't be offered at your local audio salon or even online at places that otherwise sell high end toys. Who's gonna be the first here, the chicken or the egg?

I read MF's recent Pure Vinyl August '10 review with great interest, for several reasons.

1) That solution takes advantage of something a computer can apparently do better than most high end phono preamps: provide a correct RIAA curve. If that small revelation didn't provide an eye-opener for you, nothing else will.

2) Included software offers a solution to iTunes' limited/clunky way of addressing the fact that not everything in iTunes will be 16/44 without forcing the user to give up the advantages of using iTunes as a player and database.

3) The software seems to be written by a guy who knows the Mac. I realize not all of you care about that, but given how often a Mac mini (or iMac, or

Mycophile
Mycophile's picture
Offline
Last seen: 1 month 1 hour ago
Joined: Jun 8 2010 - 1:12pm
Re: Options and alternatives for digitizing analog (primarily vi

Don’t limit your choices to just the ADCs / DACs marketed to audiophiles...

A a very good value in an audio interface that will provide excellent results (and used by many Pure Vinyl users) is a TC Electronic Impact Twin audio interface, about $400 from online pro audio dealers, such as audiomidi or zzounds, or Amazon. It may seem crazy to compare inexpensive pro gear with audiophile DACs, but economies of scale in that market (as well as the tremendous R&D budget, and considering that the products have reached a high level of maturity) has resulted in outstanding sounding products at very reasonable prices. Aiming higher you have interfaces from RME, Lynx, Prism, etc.examples of which are listed on the Channel D website (note, Channel D is a Lynx dealer.) The landscape has changed quite a bit in terms of offerings in the last several years, and we try to provide the most current information.

This interface has suitable preamps built-in for low optput moving coil cartridges, as well as high output (such as moving magnet) cartridges, to allow using Pure Vinyl’s RIAA correction.

Another important consideration, for ”live” monitoring, the ADC and DAC must share or be referenced to the same clock, to keep the digital streams synchronized, or else minor differences in clock speed will cause occasional clicks in the monitor output(not in the input / recording, just the monitor). This applies only to real-time monitoring.

By getting a general purpose “audio interface” such as above, one has multiple channels of ADC and DAC synchronized to the
same clock source.

And also let me state, without arguing the reasons, that it is worth using 192 kHz / 24 bit, especially since hard disk storage is so cheap nowadays. (I have been doing vinyl transfers to digital since buying a DAT deck in Japan in 1988, and welcomed the availability of affordable 192/24 audio interfaces starting in 2001).

Regarding digital RIAA correction (which you should try, you will be pleasantly surprised), some audio interfaces such as the Prism Sound Orpheus have onboard DSP with an option for an “RIAA filter.” There are still several advantages to using Pure Vinyl’s RIAA correction, compared to a hardware DSP curve:

1. There is an adjustable (frequency and slope) rumble filter which is invaluable for vinyl playback, to remove low frequency
information which reduces the headroom in recordings and in the power amplifier.

2. If archiving / transferring to digital, you aren't locked into having a pre-corrected recording. The curve can be applied any time later. You also can produce copies using Pure Vinyl with the RIAA curve applied, in a choice of formats (including with sample rate conversion) so need not rely on Pure Vinyl for playback. And see the note below about normalization...

3. You have more choices open to you, such as changing your mind about the rumble filter setting.

4. The RIAA filter in Pure Vinyl is calculated with 64 bits of precision. Hardware DSP chips are limited to 32, 40 or 48 bits. Also, while in the digital domain can make use of Pure Vinyl’s crossover feature, or use signal processing or signal analysis
(AudioUnit) plug-ins.

5. You don't have to be nearly as careful in setting the recording levels: The RIAA filter increases the effective resolution/ word length (AES paper on topic can be downloaded from Channel D), and this can be used to advantage (because it can be integrated with the filter) if any normalization gain is needed. On the other hand, if recording directly to 24 bit with the RIAA curve already applied, normalization will only increase the distortion in the recording.

6. There will be additional options added to Pure Vinyl in the future to take advantage of characteristics of the "flat" transfer. I hope this information is helpful. If you send questions to tech support you will receive personalized answers to your questions. We’ll also be updating our website FAQ on this topic (and computer audio in general) in the next couple of days.
- Rob Robinson, Channel D

deckeda
deckeda's picture
Offline
Last seen: 2 weeks 1 day ago
Joined: Feb 1 2006 - 7:41pm
Re: Options and alternatives for digitizing analog (primarily vi

Thanks for your insight here, Rob! I may indeed have some questions more narrowly related to Pure Vinyl later and will contact your site if so. Until then there are some loose ends in my understanding here.


Quote:
deckeda
deckeda's picture
Offline
Last seen: 2 weeks 1 day ago
Joined: Feb 1 2006 - 7:41pm
Re: Options and alternatives for digitizing analog (primarily vi


Quote:
Mycophile
Mycophile's picture
Offline
Last seen: 1 month 1 hour ago
Joined: Jun 8 2010 - 1:12pm
Re: Options and alternatives for digitizing analog (primarily vi


Quote:
I've glanced at so many of these boxes online over the last week I can't recall which one it was, but the ports and their layout looked the same. So is it a clone of another unit, or is that somewhat common?

Is there anything you might add regarding how jitter is reduced, either coming or going? [I did note on their site something about "JetPLL jitter reduction". I gather that a DAC that utilizes asynchronous USB to reduce jitter isn't an option, since the TC Electronic Impact Twin audio interface doesn't have USB.

I wouldn't draw any inferences from the back panel layout, per se, although the design may have been based on one of their previous models.

Yes, the TC interfaces are connected via FireWire. USB doesn't come into the picture... However you can be assured that all pro interfaces, whether USB, PCI or FireWire, have asynchronous clocking (they "pull" data from the host computer for playback, or "push" it for recording). When monitoring a "live" signal (for example with Pure Vinyl supplying the RIAA correction), the push and pull are coordinated perfectly, because the master clock is in the audio interface. (And note, asynchronous isn't married to USB only.)

Just think of the audio interface / computer combination as analogous to a three-head tape deck, with the signal being recorded to the deck via the "record" head, and monitored via the playback head. With the computer, instead of magnetic tape, we have RAM or hard disk buffering, and connecting it to your analog system is as simple as connecting said tape deck.

Or, as many have done, connect the output directly to the power amplifiers, controlling volume from software, and omit the line stage preamp and use any extra analog inputs of the interface as a virtual line-level preamplifier. (And, to digress a bit: if it applies in your situation, the computer works perfectly with its DVD-R drive as a HD video player in a home theater setup or as a terrestrial HDTV receiver, by adding a USB tuner dongle. Netflix, etc. streaming via Internet connection, nothing more to buy. Connect to monitor via HDMI. Replacing everything except perhaps a Blu-Ray player or SACD transport with two little boxes. Bonus: in case it matters, high WAF.)


Quote:
I have now also read another review [link] in which the author decided to skip any sort of mic preamp and simply use a step-up amp (transformer) for his MC cartridge. Another interesting possibility, and one that would seem to retain the advantages MC carts have when used with step-up transformers.

I was a little bit surprised that his setup delivered excellent results, despite having overall gain on the low side, and not having the perfect match to the step-up output. Obviously, it worked...

Optimally, you would feed the step-up transformer output to a high impedance input (such as the instrument input on something like the Impact Twin), which will supply additional needed gain. Or, just use the microphone preamp inputs without the transformer. As far as loading (of the cartridge, or of the step-up transformer output) you can make an adaptor cable with the proper load resistance / capacitance incorporated into the cable connectors. If that's something you're uncomfortable in tackling, we can custom-build a cable to your specification (load resistance and/or capacitance, with the proper input and output connectors). Or instead, a high end approach would constitute using a Seta Model L phono stage to provide cartridge loading and high quality gain (instead of a microphone preamp, and no adaptor cable needed), plus a Lynx Aurora 8 or Prism Sound Orpheus computer audio interface (for example).

  • X
    Enter your Stereophile.com username.
    Enter the password that accompanies your username.
    Loading