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Posted By: bridgman Digital stuff - 07/31/17 04:50 AM
1. From the D to the A...

So back in Oct 2014 I posted the following...

Thanks Boomzilla. Was about to try the CD3 tube buffer, but made the mistake of staring at my system for a while trying to figure out what upgrades I would probably want to do in the future. I decided that supporting some kind of digital sources would probably be the next step, so instead of the CD3 I ordered a TubeDac-11 from Grant Fidelity (basically a DAC/pre-amp with tube buffer on the output).

Figured that would also let me use a digital connect for the CD carousel, which I remember sounding just a tiny bit better than the analog (with levels at least casually matched).

The unit arrived as expected, I unpacked it, and set it aside until I had time to play with it. Somehow got it in my head that I would have to move it (and an audio system) down into the basement near a computer before I could do anything with it, but last night I was staring at the electronics in the living room (including the Adcom power amp) and realized I could hook it up as a pre-amp any time I wanted.

Started by disconnecting the Adcom and playing the system (MP5HP mains) through the power amp in the HK 3270. Once again even with best efforts level matching the Adcom still sounded better than the HK 3270's power amp even at volume levels where the extra power should not be a factor. Shook my head and carried on.

First step was hooking the CD carousel's RCA outputs to one of the analog inputs on the Tubedac, hooking line out (the SS outputs, not the tube buffered outputs) to the Adcom, and confirming that the thing actually worked. Seemed to work fine, sound was pretty similar to HK pre-amp stage... maybe a tiny bit better, didn't seem to be worse anyways.

Next step was switching in the tube buffer. Definitely sounded different but not in a way I could describe easily, and it'll take more time than I have right now to figure that out. I did think the tube output sounded "nicer" but feel like I might be losing a bit of clarity or imaging as well.

Last step was hooking up an SPDIF cable from the CD player to the DAC and switching between analog and digital inputs with the source selector. The two inputs seemed about as "different "as I remember from switching between them on my AVR although at first glance the analog seemed more detailed than the digital. Didn't even think about level matching at the time though.

Anyways, I've left the system hooked up like that for now (CD via SPDIF into Tubedac-11 then tube buffer outputs into Adcom) and am listening to that for a while until I have time to play with switching back and forth.

Downside of the new setup is that I lose phono (the tubedac, being relatively modern, does not have a phono input) but that's OK because (a) when I don't have time to tinker with equipment I usually don't have time to play vinyl anyways, and (b) I have pretty much given up on finding room in the living room for an LP rack, so thinking hard about moving phono and LPs down to the basement (which is where the hypothetical third system comes in).

If I'm not going to have a turntable or LPs in the living room, that means I need to think about getting back into LP ripping now that I have a turntable that doesn't suck. Which leads me...

2. And from the A back to the D

I'm probably going to want to keep the receiver in the living room (for FM stereo when the signal strength gods smile on me) which means I'm eventually going to need a phono pre-amp downstairs. There seem to be two main options for LP ripping (other than the turntables with built-in ADCs)- phono pre-amps with built-in ADC and line-level ADCs used for affordable digital recording, generally from musical instruments & microphones.

The phono pre-amps with ADC all seem to be 16-bit, while there are a few line-level ADCs in a similar price range with 24-bit capture. General consensus seems to be that >16 bit resolution doesn't make a noticeable difference on playback, but it is desirable for capture because it eliminates the need for super-accurate level adjustment to avoid clipping the ADC (levels too high) or losing a non-trivial portion of the 16-bit resolution (levels too low).

There is also a suggestion that 24-bit is superior for post-processing, but it's not clear whether the benefit there comes from capturing in 24-bit or whether converting to 24-bit before processing accomplishes much the same. I suspect the former (more precision tends to help with noise analysis IIRC) but not sure.

My recollection from previous LP ripping experiments (there was just the one, really) was that there was enough difference in recording levels among my LPs that a single "set it and forget it" level was not practical, but I also seem to remember that the outliers were relatively rare so there's a good chance that most of my LPs could be captured with a single input level. Software also seems to be better these days, eg tools to run through a file and normalize the levels before playback / burning. I don't remember having that back in the dark ages.

So anyways, I'm kinda leaning towards the Rega Fono Mini A2D. There are similar units from NAD and Pro-ject but all three seem to be limited to 16-bit and only the Rega has continuous level adjustment. Some of the units include Windows/Mac SW but I'm likely to end up using Linux anyways so not much benefit there.

Has anyone experimented with LP ripping recently and found something much better that isn't much more expensive ?
Posted By: bridgman Re: Digital stuff - 07/31/17 07:34 AM
Missed the key question... I remember how bad some of the early CDs sounded until the record companies got the low pass filtering figured out... but I don't remember if that ended up being dependent on having very high order "brickwall" filters available.

I can't imagine that a $200 box has a really high order lowpass filter in it (there only seem to be a few parts) so if we're sampling at 44 KHz then it brickwallseems there is a good chance of some aliasing happening. I guess maybe that's where the 48 KHz sampling option comes in - only a bit higher than 44 but maybe enough to keep 1/2 the frequency far enough away from whatever cutoff frequencies were typically used in LP mastering (I heard -3dB between 16-20 KHz) to let a cheap low pass filter make sure nothing gets aliased back down into the audible range.

Might have to put this back on the "no time to think about it" heap. It does seem that there are quite a few inexpensive 24bit/96 KHz ADCs available if you go with line level so more options than I first thought.
Posted By: bridgman Re: Digital stuff - 07/31/17 03:52 PM
Wish the edit window was longer... initially I was more concerned about 16 vs 24 bit but am starting to think that sampling at 96 KHz and low-pass filtering in SW before down-converting to 44 KHz might be worth it as well.

That would still mean I need a separate phono pre-amp as well... bleah.
Posted By: bridgman Re: Digital stuff - 08/09/17 04:46 PM
Quick bump... I can't be the only one with a basement full of LPs looking to rip them, can I ?
Posted By: MatManhasgone Re: Digital stuff - 08/09/17 06:31 PM
I gave up trying to get as good a quality recording from my old LP's as I have on a factory CD. I think there is no audible difference between 16 and 24 bit, and anything over the 44KHz is just taking up more disk space than you are ever going to hear.

Post production, I have no idea as to what is current and what works. I remember doing that sort of stuff a good 20 years ago and have since replaced just about everything on vinyl that was worth keeping.
Posted By: CV Re: Digital stuff - 08/10/17 04:52 AM
Originally Posted By bridgman
Quick bump... I can't be the only one with a basement full of LPs looking to rip them, can I ?

I don't have a basement full, but I do have a small collection. There are only a handful of tracks I need to rip, though. When I do, it's not going to be anything very involved. I imagine I'll just buy or borrow one of the USB turntables. I can't really justify spending a lot. Rasputina is about to release an album on vinyl only, so that's my real kick in the pants.
Posted By: bridgman Re: Digital stuff - 08/13/17 04:31 AM
OK, thanks to MatMan's advice in the other thread the rest of this fell into place.

I had read too many posts along the lines of "recording your LPs at 16/44.1 will work fine, it's just that you are going to end up recording them all again later" to feel comfortable buying into a 16/44.1 ADC, so the next phono+ADC up was the Furutech ADL GT40/GT40a (a or alpha is the new version intro'ed a couple of years ago). The GT40 shows up used for a decent price, the DAC, headphone amp and ADC are all very well regarded, but the phono stage always seems to come across as the weak link in reviews.

(comments about the phono stage reminded me of the Feng Shui analysis of my new house, which could be neatly summarized with one word... "regrettable")

The GT40a seems to have an improved phono stage (although it was hard to be sure) but bought new they get expensive if I'm only planning to use it for LP ripping. If you use more of the functionality they still seem like a good deal though.

So what to do ? There seemed to be no shortage of well-regarded ADC/DAC's at a good price once I learned the magic term "audio interface", although it was a bit tough at first translating pro audio terminology back into something I understood.

Once I figured out that the 1/4" TRS phone jacks were being used for mono balanced signals (differential) rather than stereo things started to make a bit more sense, and after I realized the interfaces were designed so you could use a TS plug to input/output a normal consumer audio signal (unbalanced RCA) they seemed like a pretty good solution except that they didn't give me an solution for the phono stage portion of the LP ripping chain.

Then it hit me... this was no different from recording cassette tapes with favorite songs (in lieu of the TEAC 3340 I really really wanted but could never afford), and I already had a perfectly good receiver (the HK 3270) with tape monitor jacks, 2 sets in fact. After an abortive test using an LP I hadn't played in years, I concluded that the phono stage in my receiver would be good enough for now, and that I could hook the audio interface in just like a tape deck.

(the test was phono into the receiver, Rec Out from receiver to Line In on the TubeDAC hooked up as pre-amp... once I used an LP I was familiar with, it sounded just fine)

With that in place, all I needed was the right audio interface. I do pretty much everything except timesheets in Linux these days, so the Roland Quad-Capture was out for now (I was looking for easy, not another heroic struggle) and the leaders seemed to be M-Audio M-Track2/2M and Scarlett 2i2. The M-Audio units seemed a bit more attractive in pretty much every way including price, but the Scarlett 2i2 seemed like the most used on Linux so I wussed out and ordered one of those plus two 1/4" TS to RCA stereo cables.

(TS = Tip/Sleeve, what we think of as mono, while TSR = Tip/Sleeve/Ring which we think of as stereo... but in pro audio Tip is one side of a differential pair ("hot"), Ring is the other side of the pair ("cold") and Sleeve is the actual ground)

I won't have any time to play with this for a week or two so ordered from Amazon with Cheapskate Shipping... will update when it comes in and I get the first album ripped.

Regarding the whole 24/96 vs 16/44 thing, after a lot of reading I concluded that (a) doing the initial recording at 24/96 is worth it, (b) opinions about 24/96 vs 16/44 playback seem to depend on the quality of the algorithm used for sample rate conversion.

For the moment the plan is to capture at 24/96, keep everything at 24/96 initially so I can go back and split into tracks and do noise reduction, then revisit the decision when I start running out of storage.

EDIT - hey, I guess if I added a decent microphone this would give me a good solution for running room analysis software, although I suppose the mic in on the built-in sound chip would probably have done the job already.
Posted By: bridgman Re: Digital stuff - 08/13/17 07:56 PM
More surprises... most of the recommended mics for REW are USB these days. Makes sense I guess, although using an external interface for the audio out (driving your system & speakers) rather than built-in audio still seems to be recommended.
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