A "Dummy" Cart For Phono Preamp Noise Testing

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mediatechnology
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by mediatechnology »

Regarding vinyl capture. I still can get in my mind around why would anyone need an a/d with such a low noise, the SNR of a vinyl record is what, like 60 dB? this thing has 129 dB of SNR. What is the logic behind it?
In my situation I'd use it just because I had it.
Most of my clients who are using the COSMOS A/D are doing RAW capture which places higher DR demands on the converter than RIAA-equalized capture.
For most LPs, a 1 kHz 5 cm/s ref should be around -23 dBFS to have any HF headroom. More is needed if there are high level clicks.
But even at a -23 dBFS "0" the 2i2 has more DR than needed.
PS That ULDO-Nacho looks amazing.... the distortion spec is even lower than the SG505.
Thanks. I took Victor's design and made it balanced with a 2180 in the AGC loop. The notch filter is borrowed from janascard.cz
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AnalogJoe
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by AnalogJoe »

mediatechnology wrote: Fri Jan 05, 2024 11:02 am
Regarding vinyl capture. I still can get in my mind around why would anyone need an a/d with such a low noise, the SNR of a vinyl record is what, like 60 dB? this thing has 129 dB of SNR. What is the logic behind it?
In my situation I'd use it just because I had it.
Most of my clients who are using the COSMOS A/D are doing RAW capture which places higher DR demands on the converter than RIAA-equalized capture.
For most LPs, a 1 kHz 5 cm/s ref should be around -23 dBFS to have any HF headroom. More is needed if there are high level clicks.
But even at a -23 dBFS "0" the 2i2 has more DR than needed.
I see, yeah, without the RIAA curve, the low end has much more noise, still, as you say, the 2i2 seems to be much more than what one would ever need.

Is there a specific reason why they are doing a raw capture? They want to have the freedom of choosing between different RIAA EQ 'flavors'? Let me guess, many are using DSP RIAA EQs that "faithfully" reproduce the "true" RIAA curve? Or maybe they are digitizing, and later converting to analog into an ultra-super-duper-special RIAA EQ circuit? I'm telling you, this stuff is getting ridiculous by the minute.
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mediatechnology
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by mediatechnology »

Is there a specific reason why they are doing a raw capture?
Declicking works better.
People declick in the RAW domain then apply RIAA in DSP.

RIAA EQ makes the "hole" punched in the audio by the click longer and interpolation to repair it is spread out over a longer period of time.
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AnalogJoe
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by AnalogJoe »

mediatechnology wrote: Fri Jan 05, 2024 2:44 pm
Is there a specific reason why they are doing a raw capture?
Declicking works better.
People declick in the RAW domain then apply RIAA in DSP.

RIAA EQ makes the "hole" punched in the audio by the click longer and interpolation to repair it is spread out over a longer period of time.
Makes sense, I believe it is a bit of hair splitting, but, I guess I would have to listen to the difference between raw-processed and with RIAA.
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by Gold »

AnalogJoe wrote: Fri Jan 05, 2024 7:24 pmMakes sense, I believe it is a bit of hair splitting, but, I guess I would have to listen to the difference between raw-processed and with RIAA.
I’ve always done declicking to the RIAA de emphasized signal. Processing audio without being able to hear the result until two steps later is a bad idea imo. Despite any technical advantages.
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by Gold »

I bought the Cosmos DAC. The driver software was pretty wonky. It was a while ago but you couldn’t set it up and have it keep settings. The setting it defaults to were useless. It got put on a shelf. If anyone wants it a nominal fee plus shipping and it’s yours.
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mediatechnology
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by mediatechnology »

Gold wrote: Sun Jan 14, 2024 12:52 pm
AnalogJoe wrote: Fri Jan 05, 2024 7:24 pmMakes sense, I believe it is a bit of hair splitting, but, I guess I would have to listen to the difference between raw-processed and with RIAA.
I’ve always done declicking to the RIAA de emphasized signal. Processing audio without being able to hear the result until two steps later is a bad idea imo. Despite any technical advantages.
In the editor or streaming app you can often insert DSP RIAA immediately after declicking and hear both processes working in cascade in real time.

Thats also why the PTS provides analog RIAA so that RAW declicking or RAW capture can be auditioned with EQ applied in real time. It's the premise of the whole gizmo.
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by Gold »

mediatechnology wrote: Sun Jan 14, 2024 2:53 pmIt's the premise of the whole gizmo.
I’ve never been interested in that part of it. I’m still not. It seems like a lot of hoops to jump through for little benefit. I’ve never had a problem with declicking after RIAA.
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mediatechnology
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Re: A "Dummy" Cart For Phono Preamp Noise Testing

Post by mediatechnology »

Flat preamps outsold RIAA boards by more than 2:1 last year so I think its more than a fad for those live streaming vinyl which is quite different from your typical transfer or restoration process.

Many clients use the MiniDSP, where declicking, and then RIAA, are applied in realtime during playback. I've not tried that.

My own experience with the tools I have are that setting up the declicker is a lot easier and the artifacts less.
But what the hell do I know.

The International Association of Sound and Audiovisual Archives (IASA) recommend RAW archiving particularly when the original EQ curve is unknown.

Guidelines on the Production and Preservation of Digital Audio Objects (web edition) https://www.iasa-web.org/tc04/audio-preservation

Sections 5.2 and 5.3 are interesting: https://www.iasa-web.org/tc04/signal-ex ... l-carriers
5.2.6.7 With electrical recordings it is necessary to decide whether to apply an equalisation curve on replay, or to transfer flat.Where the curve is accurately known equalisation may be applied either at the preamplifier prior to making the copy, or applied digitally after making a flat copy. Where doubt remains as to the correct equalisation curve, a flat transfer should be made. Subsequent digital versions may employ whichever curve seems most appropriate, so long as the process is fully documented, and the flat transfer retained as the archival master file.Whether or not equalisation is applied during the initial transfer, it is imperative that noise and distortion from the analogue signal chain (everything between the stylus and analogue-to-digital converter) is kept to an absolute minimum.

5.2.6.8 It is worth noting that a flat transfer will require around 20dB more headroom than one where an equalisation curve has been applied. However, as the potential dynamic range of a 24 bit digital to analogue convertor exceeds that of the original recording, the extra 20dB headroom can be accommodated.

5.2.6.9 Apart from the dynamic range limitations mentioned above, a drawback with transferring electrically recorded discs without de-emphasis is that stylus selection is primarily made through aural assessment of the effectiveness of each styli, and it is more difficult, though not impossible, to make reasonable assessment of the effect of different styli while listening to unequalised audio. An approach taken by some archives is to apply a standard, or house, curve to all recordings of a particular type in order to make stylus selection and other adjustments, and subsequently produce a simultaneous flat and equalised digital copy of the audio. As the exact equalisation is not always known, a flat1 copy has the advantage of allowing future users to apply equalisation as required, and is the preferred approach.

5.2.6.10 There is some debate as to whether noise reduction tools for the removal of audible clicks, hiss etc are more effective when used before an equalisation curve is applied rather than afterwards. The answer very likely varies according to the specific choice of tool and the nature of the job to which it is applied, and in any event will be subject to change as tools continue to evolve. The most important point in this regard is that noise reduction equipment, even fully automated tools with no user-definable parameters, ultimately employs subjective and irreversible processes, and so should not be used in the creation of archival master files.
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