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

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watchnerd

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#1
On the surface, a phono stage would seem to have three pretty straight forward jobs:

1. Implement the RIAA curve

2. Apply gain to amplify the mV signal of the cartridge up to line level of 2V

3. SNR ratio greater than the LP itself, say >70dB

All, of course, while having very low distortion and introducing no sound of its own, AKA straight wire with gain.

I would think this would be a solved problem by now, capable of being implemented by simple op-amps or even perhaps an IC (if anyone could be bothered to make one), with "known good" topologies that would be in the public domain and rampantly copied.

And, yet, we have phono stages costing thousands of dollars, with big toroidal power supplies that reek of engineering overkill for such small signals, and claims of new innovative topologies for a circuit that should have been solved 30+ years ago.

Why?

Can one of you EE or other electronics types explain why all this is needed?

It just seems like complete BS to me.
 

svart-hvitt

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#3
Watchnerd, good question. I would have thought that specs would reflect if the phono stage is good or not.

There is one spec that is often overlooked, though: Head room. Transient capacity is one of those details on which there is less focus in audio reproduction.
 

Sal1950

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#4
On the surface, a phono stage would seem to have three pretty straight forward jobs:

1. Implement the RIAA curve

2. Apply gain to amplify the mV signal of the cartridge up to line level of 2V

3. SNR ratio greater than the LP itself, say >70dB

All, of course, while having very low distortion and introducing no sound of its own, AKA straight wire with gain.

I would think this would be a solved problem by now, capable of being implemented by simple op-amps or even perhaps an IC (if anyone could be bothered to make one), with "known good" topologies that would be in the public domain and rampantly copied.

And, yet, we have phono stages costing thousands of dollars, with big toroidal power supplies that reek of engineering overkill for such small signals, and claims of new innovative topologies for a circuit that should have been solved 30+ years ago.

Why?


It just seems like complete BS to me.
Good question and yes, in the main what todays market is supporting is "complete BS"
Back before Paul McGowan learned he could make a fortune selling ridiculously expensive components he started PS Audio with just such a product.
I ran his PS III phono amp for 30 years till I sold out all things vinyl.
Little jewels like that continue to be made today but of course get no respect and little coverage by high end media. They don't play into the big juggernaut
of todays luxury goods marketing.
Nine Best Phono Preamps
 
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RayDunzl

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#5
Let's see:

upload_2017-9-4_4-29-50.png


Assuming .2millivolt to be the maximum output...
Assuming that is 70dB above almost nothingness at the stylus...

upload_2017-9-4_4-33-19.png


.0002V x .000316 = 6.32 × 10^-8 volts

Hmmm.

I was always bad at converting those. Let's see:

upload_2017-9-4_4-38-7.png


So, the phonostage has to be "quiet" to the point of

.000 (milli) 000 (micro) 063.2 (nano) volts on the input side

... in order to keep noise below the small end of the signal after amplification.

---

Is there any current to work with?

A = 0.0002V / 10 Ohms = 0.00002 A = 20 microamps.

Ok, that's a lot of electrons. 0.00002 Coulomb/s

6.242×10^18 x 0.00002 = something like 1.2484e^14 electrons (124.8 trillion) waving through the wire per second during a strong groove.
 
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watchnerd

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#7
Good question and yes, in the main what todays market is supporting is "complete BS"

Nine Best Phono Preamps
Here's a quick and dirty table of some of those nine best, plus a few more. FWIW, I currently use the Hagerman Cornet 3 (which is entirely tube based except for the PS):
Name |MM Gain |MM SNR |Cost
Behringer PP400 35 68 $25
Emotiva XPS-1 40 96 $179
Hagerman Cornet 3 44 77 $489
Music Hall Mini 35 80 $90
Parasound JC3+ 48 87 $3,000
Parasound Zphono 46 84 $199
Schiit Mani 42 82 $129
Technolink TC-400GL 40 70 $30
Technolink TC-750 40 85 $44
Trichord Dino Mk3 48 ? $539
U-Turn Audio Pluto 36 90 $89

Observations:

1. My current Hagerman Cornet 3 has pretty good specs and a "not too bad" price considering it's tube-based. But, compared to the better SS devices, it's not a bargain, even though it comes in a cheapo white kit case.



2. The TC-400GL is the 2nd cheapest, only $5 more than the Behringer, but with slightly better specs and small enough to be screw-mounted to the underside of a TT. Perhaps good enough for most?



3. The Parasound Zphono vs the JC3+ is an amazing study in contrasts. For $199 you get one of the best specced phono stages on the list:



And for $2800 more you can get the JC3+, which includes much bigger case, more weight, more features, but has only slightly better specs with 2 more dB of MM gain and 3 more dB of better SNR.


Why does a phono stage need to have a bigger power supply than a DAC or CD player?
 

watchnerd

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#8
Watchnerd, good question. I would have thought that specs would reflect if the phono stage is good or not.

There is one spec that is often overlooked, though: Head room. Transient capacity is one of those details on which there is less focus in audio reproduction.
The transient requirements should be less than a DAC or CD player outputting 2V.

For old tech (no R&D to absorb), I strongly believe in paying for components by weight. For $400, I can buy a TEAC UD-301, which is dual mono, balanced XLR, includes a toroidal transformer, and a headphone out. I can't think of any reason a MM phono stage should cost more than $400 from a BOM (bill of materials) perspective.
 

amirm

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#9
Back in the days, phono input was a standard feature on just about any receiver/amplifier. So from pure functionality it doesn't cost much to implement.

The inputs are much more sensitive than standard high-level so keeping them quiet likely costs more. But still not much.
 

Frank Dernie

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#10
On the one hand production volume is low but in the audio market expensive is seen as automatically good. The phono input on my integrated amp is the quietest I have ever used, and probably the most accurate, but even the old noisy ones I have used aren't noisier than the LP background noise.
Accurate RIAA equalisation should be easy, a rumble filter is essential (IMHO) since rumble is raised by 20dB otherwise.
When I was a serious LP listener every amp had the phono stage built in!
 

watchnerd

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#11
Back in the days, phono input was a standard feature on just about any receiver/amplifier. So from pure functionality it doesn't cost much to implement.

The inputs are much more sensitive than standard high-level so keeping them quiet likely costs more. But still not much.
On the one hand production volume is low but in the audio market expensive is seen as automatically good. The phono input on my integrated amp is the quietest I have ever used, and probably the most accurate, but even the old noisy ones I have used aren't noisier than the LP background noise.
Accurate RIAA equalisation should be easy, a rumble filter is essential (IMHO) since rumble is raised by 20dB otherwise.
When I was a serious LP listener every amp had the phono stage built in!
Right, so we've gone from a 'feature' of a receiver that was considered 'good enough' back in the day to a pricey upsell.

Of course economies of scale play a role, but even so, you'd think the old designs could just be copied.

Oh, and FWIW, the new Technics SU-G30 Network Amplifier, with weird tone-generator-impedance-matching and fancy fancy GaN-FETs, includes a phono input (presumably to go with the reissued SL-1200 series):






It converts the analog to digital and seems to do the RIAA curve in software.
 

svart-hvitt

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#12
I guess there really are some differences in phono stages that highly competent people pay for. One thing that drives prices up is obviously features. But take a look at this $10k big box from Millennia, the LOCi, developed for serious archiving, and used by Hollywood studios.

https://www.mil-media.com/LOCi.html
 

Fitzcaraldo215

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#13
When I was a serious LP listener every amp had the phono stage built in!
Yes, but typically just MM, not MC, which ususually has a much lower signal level. MC always seemed to need an external transformer, if not a complete external phono stage for reasonable S/N with the low level signal from MC. Except, my first MC was an Ortofon that had the transformer built into the cartridge. The only problem was it weighted a ton compared to other cartridges, and it was therefore incompatible with "low mass" tone arms.

And, of course, the religion among true, card-carrying audiophiles came to be MC. MM was too inexpensive and required too few add ons, tweaks, etc. No fun in that.
 

Frank Dernie

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#14
Well the enclosure and power supply are the most expensive parts by far, so a separate phono stage will always be much more expensive than including it in the amp.
Most of the amps I owned had MM and MC inputs, but a choice of MC loading adds expense.
I have used low output Ortofon cartridges for decades and have a separate Ortofon transformer and use the MM input since few MC stages have enough gain.
 

svart-hvitt

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#15
A special feature of most phono preamps is the fact that they're unbalanced. Some have unbalanced in, and balanced out, though.

I have never understood the point of running unbalanced. Accept for the fact that balanced may be a bit more work for the engineer and expensive to produce. But given the fact that phono preamps often sell for thousands of dollars, I don't understand why almost all phono preamps are unbalanced. There is some talk about common vs thermal noise, but a well engineered balanced phono stage should have low enough overall noise in any case.
 

Sal1950

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#16
Yes, but typically just MM, not MC, which ususually has a much lower signal level. MC always seemed to need an external transformer, if not a complete external phono stage for reasonable S/N with the low level signal from MC. Except, my first MC was an Ortofon that had the transformer built into the cartridge. The only problem was it weighted a ton compared to other cartridges, and it was therefore incompatible with "low mass" tone arms.

And, of course, the religion among true, card-carrying audiophiles came to be MC. MM was too inexpensive and required too few add ons, tweaks, etc. No fun in that.
For my first voyage into MC I picked up a fav unit of the day, the Marcoff PPA-1 to run with a Supex 900 Super. No worries of power supply noise as the unit was powered by a pair of 9v batteries, true dual mono. :D Ran seemingly indefinitely on those 2 power blocks.
 

Sal1950

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#17
And for $2800 more you can get the JC3+, which includes much bigger case, more weight, more features, but has only slightly better specs with 2 more dB of MM gain and 3 more dB of better SNR.


Why does a phono stage need to have a bigger power supply than a DAC or CD player?
But given the fact that phono preamps often sell for thousands of dollars,
Multi Thousand dollar phono preamps are just a bunch of damn sillyness! A couple hundred bucks should buy you SOTA sound for a pure standalone phono section.
Built into a full preamp it's cost of inclusion should be minimal.
For a simplistic circuit design like phono eq, let the KISS principal rain supreme. ;)
 

watchnerd

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#18
Multi Thousand dollar phono preamps are just a bunch of damn sillyness! A couple hundred bucks should buy you SOTA sound for a pure standalone phono section.
Built into a full preamp it's cost of inclusion should be minimal.
For a simplistic circuit design like phono eq, let the KISS principal rain supreme. ;)
Here is what the Vinyl Anachronist had to say back in 2003, before the vinyl revival had reached the level it has now, 14 years later. I would argue that his $300 price point has come down quite a bit due to increased competition to probably the $150-200 level. But the broad direction seems to be true:

"There are a lot of cheap phono preamps on the market, and they all probably work just fine. Some are the size of a pack of cigarettes and come in a plastic "blister pack" so they can be hung on a peg hook at the local electronics store. Some even lack that little black box and are basically just the innards glued onto a PC board and look like hell. So I'm going to say this once, and although it's not an easy thing to hear, it's the truth. I've listened to dozens of phono preamps in the last few months, and YOU NEED TO SPEND ABOUT $300 ON A PHONO PREAMP BEFORE YOU CAN EVEN START TO APPROACH THE SOUND QUALITY I'VE BEEN TALKING ABOUT.

....$300 seems to be the magic amount that buys you a phono preamp that is significantly better than the one that was probably built into your older receiver or amp, which probably isn't too different than that $24.95 one that's being sold on e-Bay. But to me, $300 isn't that much money when you consider that it takes you and your turntable to the next level, and that suddenly you hear details in your favorite recordings that you've never heard before, and that your whole record collection seems brand spanking new.

Fortunately for you, the $300 price point seems to be a very popular one, with many outstanding companies offering units that are very competent and built to a high standard. Just a few years ago, there were only a couple of phono preamps available at this price, like the one from Creek, and, well, the other one from Creek. Now there are nice units available from companies such as Pro-Ject, Grado, Clearaudio, Musical Fidelity, Graham Slee, Naim, Channel Islands Audio, and many others. Don't ask me, however, which one to buy. Even though there are a lot of very competent, good-sounding phono preamps available at this level, there are no real standouts (there are no real dogs, either). I think that at this price point, most companies execute solid engineering concepts that are tried and true, and they shy away from any exotic concepts that could send the costs reeling out of control. In other words, there's probably only a couple of ways to build a decent phono section for $300, so consequently they all seem to offer about the same sound quality."

More at:

http://www.furious.com/perfect/vinyl43.html
 

svart-hvitt

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#19
Hmmm...seems like people think that unbalanced phono preamps at $300 represent engineering excellence.

What is the science behind this belief? Is the belief in unbalanced boxes at the price of $300 research-driven or is it simply wishful thinking?
 

Cosmik

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#20
....$300 seems to be the magic amount that buys you a phono preamp that is significantly better than the one that was probably built into your older receiver or amp, which probably isn't too different than that $24.95 one that's being sold on e-Bay. But to me, $300 isn't that much money when you consider that it takes you and your turntable to the next level, and that suddenly you hear details in your favorite recordings that you've never heard before, and that your whole record collection seems brand spanking new.
This forum is just losing the science angle completely. This sort of stuff belongs in the bog standard audiophile web sites and magazines.

If there's extra detail to be had, this will show up in the specs and measurements. The price is just marketing and psychology - "Reassuringly expensive", in other words. But sure, you can't trust a $20 item on eBay to be any good.

The audiophile cycle seems to be:
  1. Audiophiles keep raising the bar, spending more and more, until a pathetic little circuit block reaches $300, $1000, $5000....
  2. Someone comes up with a slickly marketed version for $100 that measures the same as the others (which, indeed, it always would have)
  3. Audiophiles whoop with joy. Hey! Someone has come up with a great phono preamp for $100 and it measures the same as one that costs $10,000!
  4. Goto 1.
 
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