Shouldn't a Phono Stage Be Like a DAC? Why so expensive?

[March Audio]

I haven't seen such a one-in-all package.

The problem with phono signals is the extremely low voltage and impedance. So what you'd need, is a preamp that magnifies the incoming signal to a level that off-the shelf analog to digital converters handle.

There are some flat amplifiers for use with the tiny phono signals, for example Channel D and the aforementioned Violectric PPA V600. The flat signal can be manipulated after AD conversion.

I think this is the ideal chain:

Cartridge => flat preamp => AD converter => digital RIAA and DSP => DAC

This electric chain should, I guess, be of low noise in order for the DSP to be specifically targeted at correcting noise from the vinyl disc instead of trying to correct chain induced noise.

As Dallas has already mentioned, just try a good mic preamp.

 

[watchnerd]

I just found this gem, which is John Atkinson measuring the Devialet [Duh-vey-uh-lay, right?] phono section, this from the older Premier, which is an ADC / DSP based feature. The current version has a few more configuration features (more EQ choices, preconfigs for popular cartridges) than the one reviewed here:

https://www.stereophile.com/content/devialet-d-premier-da-integrated-amplifier-phono-stage

Some interesting bits stand out:

"To choose the gain appropriate for your cartridge, you move the Max Level slider on the Configurator. For MM, setting this to "5.0mV" gave a measured gain at the Preamp output jacks of 45.3dB (45dB is specified); setting it to "10.0mV" gave 39.5dB (39dB specified). For MC, setting this to "500µV" gave a measured gain of 62.5dB. Which gain you choose will be critical, as you need to avoid overloading the D-Premier's A/D converter. With the MM input set to "5.0mV," a 1kHz tone at 5mV resulted in a digital-domain signal at –2.18dBFS. For my Linn Arkiv B MC cartridge, I had to set the Max Level to "1500µV"; with typical LPs, this resulted in digital peaks of around –3dBFS."

In terms of measured quality:

"The channels are superbly well matched, and the de-emphasis is perfect up to 10kHz, better even that that of the Liberty B2B-1, which was the best I had measured until now."

"Channel separation (not shown) was good, at >80dB below 1kHz, and noise was very low in MM and MC modes. The overload margin was good, at an even 17dB across the audioband in MC mode (set to "500µV") and 20dB in MM mode (set to "10.0mV"). One peculiarity: At 20kHz, some sort of soft limiting seemed to be in effect; I couldn't get the input to overload. Distortion was low, at typically 0.06%, and dominated by the subjectively benign second harmonic (fig.4), though this digital-domain spectrum does reveal some low-level, higher-order harmonics. Intermodulation distortion was also low (fig.5)."

Subjectively, he says:

"As for the sound of the D-Premier when used to play LPs, it was clean, clean, clean—not in the sense of sterile, but in the sense that there was very little coming between the music and me...Back in the day, I used to time how long I could hear the decay of the reverb, and it was the rare playback system that let me get past 2 seconds or so. The Devialet's resolution and low noise revealed a full 3 seconds' worth of reverberation.

The inevitable ticks and pops on my old LPs also seemed more tidily handled, less sonically obtrusive, by the D-Premier than by a conventional analog phono preamp, the Liberty B2B-1, feeding the Ayre Acoustics QA-9 A/D converter"

So it would seem that a DSP-based phono stage has the potential to exceed even high quality analog phono stages ($1800 for the Liberty B2B-1).

 

[Frank Dernie]

That would be my experience of Devialet too.
The fundamental characteristics I felt were clean and clear with no harshness with a firm deep bass with no boom (I use the 1976 RIAA curve, not the 195os one which has no sub-sonic roll off and boosts rumble).
Despite getting excellent reviews the Devialet is not very high end fashionista. Digital is the biggest barrier, since the high end press and enthusiasts are resolutely anti or lukewarm. All in one is another, for many the more, the bigger and the heavier the boxes the more high end. Not being a fashionable brand is another IMO. In my travels for work I bought magazines all over, and the most popular brands in each country seemed to be those supported by the best and biggest advertising.
FWIW I started with a D-Premier before on line configuration was activated, you told your dealer what inputs and settings you wanted and they emailed a configuration file - though the default configuration makes it like any typical integrated amp so a specific configuration is not essential. I bought a second amp later and configured the pair as dual mono. I had this pair updated to 800 spec, which in retrospect was a waste of money for me. It added a lot more DSP capability for future developments and added a USB input, which I don't use, but lost the HDMI input, which I did. Then, in a fit of irrational extravagance, I traded them in for the Original d'Atelier limited edition, mainly for the colour...

 

[watchnerd]

That would be my experience of Devialet too.
The fundamental characteristics I felt were clean and clear with no harshness with a firm deep bass with no boom (I use the 1976 RIAA curve, not the 195os one which has no sub-sonic roll off and boosts rumble).
Despite getting excellent reviews the Devialet is not very high end fashionista. Digital is the biggest barrier, since the high end press and enthusiasts are resolutely anti or lukewarm. All in one is another, for many the more, the bigger and the heavier the boxes the more high end. Not being a fashionable brand is another IMO. In my travels for work I bought magazines all over, and the most popular brands in each country seemed to be those supported by the best and biggest advertising.
FWIW I started with a D-Premier before on line configuration was activated, you told your dealer what inputs and settings you wanted and they emailed a configuration file - though the default configuration makes it like any typical integrated amp so a specific configuration is not essential. I bought a second amp later and configured the pair as dual mono. I had this pair updated to 800 spec, which in retrospect was a waste of money for me. It added a lot more DSP capability for future developments and added a USB input, which I don't use, but lost the HDMI input, which I did. Then, in a fit of irrational extravagance, I traded them in for the Original d'Atelier limited edition, mainly for the colour...

You can get used pre-Pro versions of the Expert 200 for ~$4k. At that price it's worth having just as a super flexible Swiss Army knife software definable preamp.

 

[Frank Dernie]

You can get used pre-Pro versions of the Expert 200 for ~$4k. At that price it's worth having just as a super flexible Swiss Army knife software definable preamp.

Pointless using it as a preamp IMO

 

[svart-hvitt]

I just found this gem, which is John Atkinson measuring the Devialet [Duh-vey-uh-lay, right?] phono section, this from the older Premier, which is an ADC / DSP based feature. The current version has a few more configuration features (more EQ choices, preconfigs for popular cartridges) than the one reviewed here:

https://www.stereophile.com/content/devialet-d-premier-da-integrated-amplifier-phono-stage

Some interesting bits stand out:

"To choose the gain appropriate for your cartridge, you move the Max Level slider on the Configurator. For MM, setting this to "5.0mV" gave a measured gain at the Preamp output jacks of 45.3dB (45dB is specified); setting it to "10.0mV" gave 39.5dB (39dB specified). For MC, setting this to "500µV" gave a measured gain of 62.5dB. Which gain you choose will be critical, as you need to avoid overloading the D-Premier's A/D converter. With the MM input set to "5.0mV," a 1kHz tone at 5mV resulted in a digital-domain signal at –2.18dBFS. For my Linn Arkiv B MC cartridge, I had to set the Max Level to "1500µV"; with typical LPs, this resulted in digital peaks of around –3dBFS."

In terms of measured quality:

"The channels are superbly well matched, and the de-emphasis is perfect up to 10kHz, better even that that of the Liberty B2B-1, which was the best I had measured until now."

"Channel separation (not shown) was good, at >80dB below 1kHz, and noise was very low in MM and MC modes. The overload margin was good, at an even 17dB across the audioband in MC mode (set to "500µV") and 20dB in MM mode (set to "10.0mV"). One peculiarity: At 20kHz, some sort of soft limiting seemed to be in effect; I couldn't get the input to overload. Distortion was low, at typically 0.06%, and dominated by the subjectively benign second harmonic (fig.4), though this digital-domain spectrum does reveal some low-level, higher-order harmonics. Intermodulation distortion was also low (fig.5)."

Subjectively, he says:

"As for the sound of the D-Premier when used to play LPs, it was clean, clean, clean—not in the sense of sterile, but in the sense that there was very little coming between the music and me...Back in the day, I used to time how long I could hear the decay of the reverb, and it was the rare playback system that let me get past 2 seconds or so. The Devialet's resolution and low noise revealed a full 3 seconds' worth of reverberation.

The inevitable ticks and pops on my old LPs also seemed more tidily handled, less sonically obtrusive, by the D-Premier than by a conventional analog phono preamp, the Liberty B2B-1, feeding the Ayre Acoustics QA-9 A/D converter"

So it would seem that a DSP-based phono stage has the potential to exceed even high quality analog phono stages ($1800 for the Liberty B2B-1).

Indeed, for the undogmatic audio enthusiast with a specifications oriented leaning digital signal processing is a great tool.

I still think, however, for DSP to be flexible and SOTA, it needs to be carried out in a computer, Windows or Mac based. Adequate software could take out all the unwanted noise, according to user's preferences.

The question is: What would this mean for latency? Could a PC be connected to the phono chain without (too much) latency for real-time playback?

 

[RayDunzl]

Indeed, for the undogmatic audio enthusiast with a specifications oriented leaning digital signal processing is a great tool.

That's me!

 

[Cosmik]

Indeed, for the undogmatic audio enthusiast with a specifications oriented leaning digital signal processing is a great tool.

I still think, however, for DSP to be flexible and SOTA, it needs to be carried out in a computer, Windows or Mac based. Adequate software could take out all the unwanted noise, according to user's preferences.

The question is: What would this mean for latency? Could a PC be connected to the phono chain without (too much) latency for real-time playback?

Since when has vinyl been real time..? My DSP-based system has about 0.4s latency but unless trying to use it with video it is not much of a problem.

 

[svart-hvitt]

Since when has vinyl been real time..? My DSP-based system has about 0.4s latency but unless trying to use it with video it is not much of a problem.

What makes your DSP so slow? Mine has about 4 ms of latency.

On a second thought, I think DSP in PC based playback introduces only slight, hardly relevant latency.

 

[March Audio]

What makes your DSP so slow? Mine has about 4 ms of latency.

On a second thought, I think DSP in PC based playback introduces only slight, hardly relevant latency.

Depends on the dsp you are performing. If filtering the delay depends on the type of filtering employed. IIR can have very short delays, FIR delay will be dependant on the number of taps and sample rate.

My speaker XO FIR filtering takes around .74 seconds. Massive problem for video, zero problem for music playback as realtime is not required.

 

[FrantzM]

That's me!

me too!

 

[Cosmik]

What makes your DSP so slow?

Not exactly a function of "slowness" - it still has the same throughput - but FIR filtering introduces latency as BE718 says above.

 

[watchnerd]

Pointless using it as a preamp IMO

Was thinking with active speakers.

 

[RayDunzl]

My miniDSP has 6144 taps @ 48kHz so as much as 6144/48000 = 128ms but if the filter is centered, then 64ms delay. I've not measured it.

PC solutions aren't so tap-limited and can have big delays depending on configuration.

I might barely notice it with video, but the AV sync seems a bit variable anyway, and I'm not bothered, unless watching a musician perform.

I guess it's no worse than being 64 feet (or so) from a live musician. Opera glasses, anyone?

 

[Frank Dernie]

Indeed, for the undogmatic audio enthusiast with a specifications oriented leaning digital signal processing is a great tool.

I still think, however, for DSP to be flexible and SOTA, it needs to be carried out in a computer, Windows or Mac based. Adequate software could take out all the unwanted noise, according to user's preferences.

The question is: What would this mean for latency? Could a PC be connected to the phono chain without (too much) latency for real-time playback?

I disagree. The maths is not complex and anyway a specialist DSP programme can easily be better than a universal computer for its own specific tasks

 

[watchnerd]

I disagree. The maths is not complex and anyway a specialist DSP programme can easily be better than a universal computer for its own specific tasks

Right. The phono EQ curve is not very complex.

 

[svart-hvitt]

Right. The phono EQ curve is not very complex.

I was not primarily thinking about curve corrections. DSP could be used to remove unintended noise during playback. That's where the "bigger", more flexible computer comes in.

 

[watchnerd]

I was not primarily thinking about curve corrections. DSP could be used to remove unintended noise during playback. That's where the "bigger", more flexible computer comes in.

Do you mean like pops and ticks? Groove noise? I'm not sure what noise you're thinking of.

 

[svart-hvitt]

Do you mean like pops and ticks? Groove noise? I'm not sure what noise you're thinking of.

Yes, that "kind" of noise. Using "intelligent" software to tailor the playback to your needs and taste after being corrected for distortion that probably wasn't meant to be. This is what for example archival projects do, manually, but I guess "intelligent" software could work pretty well.

Please note, I am not aware of software that does automatically this during playback.

 

[watchnerd]

Yes, that "kind" of noise. Using "intelligent" software to tailor the playback to your needs and taste after being corrected for distortion that probably wasn't meant to be. This is what for example archival projects do, manually, but I guess "intelligent" software could work pretty well.

Please note, I am not aware of software that does automatically this during playback.

For archiving rarities, it's a good post-production exercise for preservation.

For consumer playback -- buy better vinyl!

95% of my vinyl is >180g, recent pressings that have hardly any pops and ticks (unless my static management is bad).