Phono preamp "sound"

[Rickysa]

I don't listen to much vinyl (yet ) but am curious about a phono preamp's influence on "sound". Having been here for almost a year I've learned that an amp should be auditorily invisible (unless you like the 2nd order harmonics of tubes), and that a preamp should just essentially be a input switch (unless you are using it to "color" your sound).......but.......I built a phono pre (Pearl 3) for fun, and when I dropped the needle just to see if it worked, I raised an eyebrow because the damn thing sounded "clearer" than before. A lot clearer......against my "knowing better" and really zero expectation bias (wink, wink). It was replacing a no-name little box, but I wouldn't have expected a difference?

Anecdotal, I know (with a sample of n=1), but with all the spirited discussions surrounding vinyl (cartridge types/models etc.), I wondered if the preamp could be an influence?

 

[fpitas]

Perhaps the no-name box isn't everything it could be?

 

[Rickysa]

Perhaps the no-name box isn't everything it could be?

Yep, which is essentially my question...I wouldn't have thought something that just boosts a little signal could make that much difference in the chain?

 

[sergeauckland]

Phono stages do affect the sound in several ways:

1)How accurate is the RIAA equalisation? These days there's no excuse for it to be worse than +-1dB, and even tighter tolerances are quite possible with more careful (and therefore a bit more expensive) component selection.

2) If using a MM cartridge, the capacitative loading of the cartridge makes a considerable difference to the frequency response from the cartridge, regardless of the RIAA accuracy. This mostly affects the higher frequencies.

3) Does the RIAA stage have a low frequency roll-off incorporated? Anything below around 25-30Hz is just noise, so best removed. If the matching between cartridge compliance and arm mass is incorrect, then the LF will be even worse affected.

Overall, phono playback is the one area where the biggest audible differences can be found.

S.

 

[fpitas]

Yes, well that is essentially my question...I wouldn't have thought something that just boosts a little signal could make that much difference in the chain?

Definitely. The "all amps sound alike" mantra around here is in reference to some of the best measuring amplifiers that exist. Amir has tried listening to sub-par amps he tested and regretted it

 

[Redacted]

"unless you like the 2nd order harmonics of tubes"..

Devil's advocate - there are tube amps of all types with distortion (i.e. harmonics) that is so low you won't hear it. Just like with transistor amps, it's really when you start to push an amp out of its linear region that you will notice. It depends on design. And a tube amp will also produce odd order harmonics if pushed, like on guitar amps - it's what the "grit" is about.

Also, while your unit may sound great on a blind A-B test, it's measurement results that count!

 

[dualazmak]

To digress slightly from the main topic of this thread, phono preamplifiers are prime examples of audio equipment susceptible to external electromagnetic field (EMF) interference noise, especially when you use MC cartridges. Consequently, they require structural engineering designs that provide adequate shielding against such EMF interference.

I once encountered this issue with a relatively inexpensive phono preamplifier; by DIY installing my custom EMF shielding inside the unit, I was able to significantly reduce the interference. If you would be interested, please visit my post #697 on my project thread.

 

[Rickysa]

Devil's advocate

...I built both a 2A3 SET and a solid state amp (for it's "zero-tubiness") and set up an A/B test when I first started down this rabbit hole to try and learn the difference. I thought insofar as getting a handle on "audio" that would represent two opposite ends of a spectrum. Honestly, I was kinda underwhelmed. That's why I was so surprised when I heard a pretty dramatic difference with this preamp.

 

[geol]

The only approach would be to provide a recording of the two preamps, as is done on all hi-fi forums. That said, since vinyl is, after cylinders and 78 rpm records, the least faithful format, you'll have to take into account the wear and tear on the record between listening sessions.

 

[fpitas]

...I built both a 2A3 SET and a solid state amp (for it's "zero-tubiness") and set up an A/B test when I first started down this rabbit hole to try and learn the difference. I thought insofar as getting a handle on "audio" that would represent two opposite ends of a spectrum. Honestly, I was kinda underwhelmed. That's why I was so surprised when I heard a pretty dramatic difference with this preamp.

SET amps get into a whole other universe. The audiophile explanation is rich 2nd harmonics. I have my reservations. And as noted above, tube distortion is not necessarily 2nd harmonic.

 

[Mnyb]

You also have overload behavior of different phono preamps ? sensitivity to ticks and pops .

 

[fpitas]

You also have overload behavior of different phono preamps ? sensitivity to ticks and pops .

I recall that Amir purposely overloads them in his testing for just that reason.

 

[serendipitydawg]

SPARTAN 16 Moving Magnet Phono Stage by Michael Fidler

Moving magnet phono stage using OPA1642 with mono switch, subsonic filter, low frequency crossfeed and linear power supply

michaelfidler.com

I have this preamp . Its designer is a member here, and some of his other designs have been reviewed here. Hopefully Michael will spot this thread and comment

 

[MaxwellsEq]

I don't listen to much vinyl (yet ) but am curious about a phono preamp's influence on "sound". Having been here for almost a year I've learned that an amp should be auditorily invisible (unless you like the 2nd order harmonics of tubes), and that a preamp should just essentially be a input switch (unless you are using it to "color" your sound).......but.......I built a phono pre (Pearl 3) for fun, and when I dropped the needle just to see if it worked, I raised an eyebrow because the damn thing sounded "clearer" than before. A lot clearer......against my "knowing better" and really zero expectation bias (wink, wink). It was replacing a no-name little box, but I wouldn't have expected a difference?

Anecdotal, I know (with a sample of n=1), but with all the spirited discussions surrounding vinyl (cartridge types/models etc.), I wondered if the preamp could be an influence?

Microphone and phono preamplifiers are certainly an area where difference are measurable and potentially audible.

Compared to the relatively simple line-level preamplifier, the impedance of the cartridge output and the phono preamplifier's input can have a significant impact on frequency response. They also have an impact on both voltage noise and current noise. The gain is high (MM) or very high (MC) which can affect noise behaviour and susceptibility to electromagnetic pickup.

Records are cut with varying degrees of velocity, so a phono preamplifier with insufficient headroom may make surface noise and clicks more prominent and distort with very hot cuts. However, if there's too much headroom, intrinsic noise may be a problem.

RIAA accuracy is harder to achieve than a simple flat frequency response. Low frequency junk below 30Hz should be filtered, but not all phono preamplifiers do this.

Conclusion: I'm never surprised when two phono preamplifiers measure differently. I'm also unsurprised if they sound different.

 

[Cote Dazur]

I dropped the needle just to see if it worked, I raised an eyebrow because the damn thing sounded "clearer" than before. A lot clearer

As mentionned in the posts above, their might be reasons why you could hear a diiference, would those reasons mentionned justifiy "a lot cleaner" indicating a massive devoiation, probably not, that, to me, indicate a major blunder or major anomaly.
I have been playing records for a long time, over 40 years, with both type of cartridge on many different TT using different preamp, and my experience is that the preamp is for all intent and purpose, transparent.

 

[sergeauckland]

As mentionned in the posts above, their might be reasons why you could hear a diiference, would those reasons mentionned justifiy "a lot cleaner" indicating a massive devoiation, probably not, that, to me, indicate a major blunder or major anomaly.
I have been playing records for a long time, over 40 years, with both type of cartridge on many different TT using different preamp, and my experience is that the preamp is for all intent and purpose, transparent.

That's pretty much been my experience. As long as the pre-amp is of 'reasonable' quality, i.e. the noise is, say, -56dB on a 5cm/sec recorded velocity and the RIAA response within 1dB, even 2dB, other limitations of the medium are likely to make a much bigger difference to the sound than the RIAA phono stage. Distortion in a phono stage is unlikely to be anywhere near as bad as the cartridge or possibly the cutting itself. I've never seen any figures for the noise, W&F, RIAA errors and distortion cut into the LP itself, possibly very difficult to separate from the playback.

I have three turntables in regular use, each with a different cartridge and a different phono stage, and couldn't identify any of them by sound.

With the few records where I have duplicates, there's more difference between cuttings (say, UK and USA) and pressings than there is between the turntable systems.

S

 

[Rickysa]

As long as the pre-amp is of 'reasonable' quality

As luck would have it, This is the pre-amp I bought years ago knowing nothing about audio gear. Now I'm even more surprised/confused. The whole "threshold of audible difference" (for lack of a better term) is frustrating to me, and is what landed my here at ASR in the first place. Apparently, I can't even discern distortion worth a hoot

 

[sergeauckland]

As I wrote above in Post #4, Phono stages are one area where there are big differences possible, seemingly contradicted by my post #16 just above. However, I think both are possible, given the wide variety of cartridges, loading conditions and arm mass. Nevertheless, if a turntable system is well set up, with the cartridge well matched to the arm, and the loading conditions correct and with similar stylus profiles and levels of cleanliness, then I doubt there's much audible difference regardless of manufacturers of the system components.

S

 

[MaxwellsEq]

There's more to get wrong in a phono preamplifier than with a line level preamplifier.

For example, electrical noise in a well designed line level preamplifier should be achieved well below our ability to hear it. Whilst voltage noise is the thing to prioritise.

With MC and MM phono preamplifiers, noise is potentially within human audibility range. So with a phono preamplifier it's no longer "it doesn't matter what the noise does because its below audibility", now it's "the noise is potentially audible, what's it doing?"

Since it's all pure analogue noise, we can of course hear signals which are below the noise floor. So a phono preamplifier with a noise of, say, -50dB will still make available sounds below that noise - it isn't a hard cut-off.

The cartridge motor impedance matched with the input resistor in the preamplifier circuit can have an impact on noise behaviour. Most line-level knowledge is about voltage noise, but with the cartridge to preamplifier interface, current noise may become significant.

The hardest thing to balance is overload margin. Whilst there are some very hot cuts, the majority of vinyl is cut many dBs quieter. Clicks have extremely high spikes which can lead to overload, but also sustained ringing and or instability. The obvious fix is to have lots of headroom, but that costs in terms of SNR and it's quite possible that low level noise becomes more obvious.

 

[sergeauckland]

The only thing I would add to the above is that the noise of the phono stage unless heroically bad, is still likely to be below the level of the vinyl itself. Whilst the music is RIAA equalised, vinyl noise isn't, so subject to the bass boost of the RIAA EQ, although hissy noise is suppressed. Nevertheless, if I measure broadband noise on even quiet vinyl in the gaps between tracks, it's rare to have it below -50dB. The 'rumble' tracks on a couple of test LPs measure around -40dB measured broadband, although that's quite impulsive, so very variable.

S.