Is the Accuphase C-47 the phono pre-amp to beat for measurements?

[GXAlan]

I'm of the mindset that phono preamps don't really need a lot of SINAD since your limitation is in the medium itself. I am perfectly satisfied with my Luxman LXV-OT10 but I am curious from a "if I win the lottery" standpoint what the best phono pre-amp could actually achieve.

The Accuphase C-47 seems to have incredible performance if I am reading the marketing correctly.

If I look at that -155 dBV means that it has a 0.018 microV for MC and 0.158 microV for MM? So for MC, at 0.5mV, the 1 kHz THD is 0.0009% or -101 dB.

And for MM, it's 0.0005% for THD, or -106 dB?

And since noise is so low, your SINAD for MC is still ~100 dB? Looking at my own input shorted measurements of my phono preamp, I am 75 microV rms noise and 49 microV if A-weighted but even if you estimated an unweighted value, it would still beat anything measured here to date?

Accuphase Laboratory, Inc.　C-47

www.accuphase.com

If you look at the internals, it doesn't look "impossible" to replicate.

 

[Balle Clorin]

I love Accuphase and have a A-48, but I would rather use a Parks Audio Waxwing , it would provide a better overall control over the quirks and imperfections of Vinyl, and the set up of a TT and cartridge..
So buy a C-47 for display and hide the Waxwing ..

 

[AaronJ]

I'm concerned about the fact that they're only using "low noise power supplies" instead of "ultra low noise power supplies." Joking aside, Accuphase makes beautiful gear and I agree that it's what I'd have if I won the lottery. I actually worked at a company where 48 people won the Powerball for $175M back in 2012 but sadly was not involved. It was mostly custodial staff among the winners so I was happy for them.

What do you reckon this would cost someone to build without the gorgeous casework and Accuphase mark up?

edit: never mind, the diagram conflicts with the text below on page 4. They are using power supplies of the ultra-low noise variety.

 

[undeakyetonde]

• High-accuracy phono equalizer with RIAA deviation of only ±0.3 dB

Is this high-accuracy?

 

[morillon]

not really, standart....+-0.05db ...yes

 

[ivanj]

A friend with a P.E. measured a C-37 several years ago and told me it 'it is the closest thing (ed: phono preamp?) I have measured that resembles a straight wire with gain."

I'd reckon the C-47 is better still. I have one on loan, own a Waxwing and the MC Pro from Mr. Fidler.

I can't measure them but I can give my impressions FWIW.

 

[GXAlan]

I can't measure them but I can give my impressions FWIW.

Sure. Have you tried blind testing where someone else switches the phono stage? Are there any obvious differences like noise, or overload on pops/clicks?

 

[ivanj]

Sure. Have you tried blind testing where someone else switches the phono stage? Are there any obvious differences like noise, or overload on pops/clicks?

I've found that Accuphase separates measure (and sound) better than their specs. Time will tell. I don't have a blind switching test bed. I'm wondering is the balanced input on the C-47 makes a difference?

When I put a new component in the system I usually ask my wife if she can tell the difference. Sometimes she volunteers, even from another room without being cued or prompted, 'what did you do? it sounds better.' (no it is not volume related.)

Sorry very unscientific but life and symphonic performances are like that. Appearances should be left appearances.

 

[restorer-john]

@GXAlan Do you have this preamp or are you just dreaming?

I've got a Accuphase C-11 here from 1991. S/N 90dBA for a 4mV (MM) input at 1kHz.

The C-47 would obliterate anything tested on ASR even if it was close to claimed spec.

 

[GXAlan]

Just dreaming

 

[Skeeter]

I'm of the mindset that phono preamps don't really need a lot of SINAD since your limitation is in the medium itself. I am perfectly satisfied with my Luxman LXV-OT10 but I am curious from a "if I win the lottery" standpoint what the best phono pre-amp could actually achieve.

The Accuphase C-47 seems to have incredible performance if I am reading the marketing correctly.

View attachment 390531

If I look at that -155 dBV means that it has a 0.018 microV for MC and 0.158 microV for MM? So for MC, at 0.5mV, the 1 kHz THD is 0.0009% or -101 dB.

View attachment 390532

And for MM, it's 0.0005% for THD, or -106 dB?
View attachment 390536

And since noise is so low, your SINAD for MC is still ~100 dB? Looking at my own input shorted measurements of my phono preamp, I am 75 microV rms noise and 49 microV if A-weighted but even if you estimated an unweighted value, it would still beat anything measured here to date?

View attachment 390537

Accuphase Laboratory, Inc.　C-47

www.accuphase.com

If you look at the internals, it doesn't look "impossible" to replicate.
View attachment 390538

The reason these figures appear to be so fantastic is they’ve quoted noise in dBV so the noise reference 500uV (a typical MC test level) is 66 dB better than reality. A SNR of 71 dB (unweighted) is about the very best you can expect on MC. On the MM side, the typical reference is 5 mV, so subtract 46 dB off the above spec to arrive at the SNR. However, it’s clear the MM figures do not include the input source thernal noise and any input noise current. This will mean even after accounting for the dBV to dBr adjustment, the MM SNR will be overstated by at least 10-12dB. On MM inputs, using a JFET input amplifier (the best device for MM), the theoretical best case SNR is 76.5 dB