Do tubes make sense in a phono preamp?

[o2so]

Hello,

I bumped into this comment allegedly from David Shaw, from Icon Audio, regarding their PS1 Signature Phono preamp (tube based).

I wanted maximum musical detail, but without emphasizing the imperfections through wear, clicks scratches etc. So I could listen through the vinyl medium, not to it!
It is well known that valve circuits are much more tolerant to overload, they recover much quicker and distort less than transistors. Therefore it follows that valves will deal with the massive transient spikes present in imperfect LPs better than transistors

https://iconaudio.com/ps1-mkii-all-valve-phono-stage-ps1-mkii


I am aware of the generalized opinion (in this forum, at least) that tube-based amplifiers are basically nonsense in terms of sonic quality because they add noise and distortion, and usually have pretty high output impedance which then may mess up the frequency response.

My question is, as per the thread title, do tubes make sense in phono preamps because, as Mr Shaw says, deal better with the imperfections of the vinyl medium?

 

[VMAT4]

For tube amps in general see here. But, if the record has many pops and clicks try cleaning it deeply with a vacuum record cleaner.

 

[Robin L]

Hello,

I bumped into this comment allegedly from David Shaw, from Icon Audio, regarding their PS1 Signature Phono preamp (tube based).

I wanted maximum musical detail, but without emphasizing the imperfections through wear, clicks scratches etc. So I could listen through the vinyl medium, not to it!
It is well known that valve circuits are much more tolerant to overload, they recover much quicker and distort less than transistors. Therefore it follows that valves will deal with the massive transient spikes present in imperfect LPs better than transistors

https://iconaudio.com/ps1-mkii-all-valve-phono-stage-ps1-mkii


I am aware of the generalized opinion (in this forum, at least) that tube-based amplifiers are basically nonsense in terms of sonic quality because they add noise and distortion, and usually have pretty high output impedance which then may mess up the frequency response.

My question is, as per the thread title, do tubes make sense in phono preamps because, as Mr Shaw says, deal better with the imperfections of the vinyl medium?

I understand the notion of trying to find the cure for the awful sound of LPs. Those precious few LPs that sound great set one on a path of attempting to make all LPs sound great, which just ain't gonna happen. There are aspects baked into the recipe that can't be eliminated. If you want "perfect sound" try digital.

That said, I had the best LP playback with a Scott 299B integrated amp. That specific amp did deal with the imperfections of LPs better than anything else I've owned over 50 years.

 

[PaulD]

Hello,

I bumped into this comment allegedly from David Shaw, from Icon Audio, regarding their PS1 Signature Phono preamp (tube based).

I wanted maximum musical detail, but without emphasizing the imperfections through wear, clicks scratches etc. So I could listen through the vinyl medium, not to it!
It is well known that valve circuits are much more tolerant to overload, they recover much quicker and distort less than transistors. Therefore it follows that valves will deal with the massive transient spikes present in imperfect LPs better than transistors

https://iconaudio.com/ps1-mkii-all-valve-phono-stage-ps1-mkii


I am aware of the generalized opinion (in this forum, at least) that tube-based amplifiers are basically nonsense in terms of sonic quality because they add noise and distortion, and usually have pretty high output impedance which then may mess up the frequency response.

My question is, as per the thread title, do tubes make sense in phono preamps because, as Mr Shaw says, deal better with the imperfections of the vinyl medium?

No, Mr. Shaw is talking nonsense.

Any amplifier, with any sort of active devices, can be designed and built to be highly tolerant of overload conditions.

"I wanted maximum musical detail, but without emphasizing the imperfections through wear, clicks scratches etc. So I could listen through the vinyl medium, not to it!" - This is just hifi nonsense, listen through it and not to it - right... it's meaningless in the extreme.

"It is well known that valve circuits are much more tolerant to overload, they recover much quicker and distort less than transistors. Therefore it follows that valves will deal with the massive transient spikes present in imperfect LPs better than transistors" This is just factually wrong, and well proven.

A byproduct of the higher voltage needs for vacuum-tube amplifiers is typically a high overload margin (for small signal circuits like phono preamps), making them tolerant of overload. However, it is just as possible to build high overload margin transistor or FET amplifiers - it's just a bit more expensive than that standard +/- 15V rails that are typical. That there have been poor solid-state designs says more about the designers than the active devices. There are also, to this day, some extremely poor valve amplifier designs.

It is possible to design excellent amplification with all kinds of active devices, it just makes it more challenging, and the engineering tradeoffs more interesting, depending on the devices chosen and the tradeoffs made. It is the implementation that is most significant, not the type of device used.

 

[o2so]

No, Mr. Shaw is talking nonsense.

Any amplifier, with any sort of active devices, can be designed and built to be highly tolerant of overload conditions.

"I wanted maximum musical detail, but without emphasizing the imperfections through wear, clicks scratches etc. So I could listen through the vinyl medium, not to it!" - This is just hifi nonsense, listen through it and not to it - right... it's meaningless in the extreme.

"It is well known that valve circuits are much more tolerant to overload, they recover much quicker and distort less than transistors. Therefore it follows that valves will deal with the massive transient spikes present in imperfect LPs better than transistors" This is just factually wrong, and well proven.

A byproduct of the higher voltage needs for vacuum-tube amplifiers is typically a high overload margin (for small signal circuits like phono preamps), making them tolerant of overload. However, it is just as possible to build high overload margin transistor or FET amplifiers - it's just a bit more expensive than that standard +/- 15V rails that are typical. That there have been poor solid-state designs says more about the designers than the active devices. There are also, to this day, some extremely poor valve amplifier designs.

It is possible to design excellent amplification with all kinds of active devices, it just makes it more challenging, and the engineering tradeoffs more interesting, depending on the devices chosen and the tradeoffs made. It is the implementation that is most significant, not the type of device used.

Thank you for the thorough response. I wonder then if, generally speaking, most modern SS phono preamplifiers are designed to be tolerant of overload, because as you pointed out it is entirely possible to design a SS amp this way, or if in most instances this isn't done because of cost or other practicalities.

 

[PaulD]

Thank you for the thorough response. I wonder then if, generally speaking, most modern SS phono preamplifiers are designed to be tolerant of overload, because as you pointed out it is entirely possible to design a SS amp this way, or if in most instances this isn't done because of cost or other practicalities.

I would suggest that the well designed and engineered SS phono preamplifiers are generally tolerant of overload, and (more importantly) recovery quickly and without misbehaving if they go into overload. Scott Wurcer and SIY are better placed to answer this than I am. There is no reason that a well designed SS phono preamp, using appropriate ICs, would not provide absolutely SOTA performance.

For me, these days I'd be tempted to do the EQ digitally, running the phono output into a pro-level mic preamp (appropriately terminated) and then into a DAC, and doing the RIAA EQ in software. I have no need currently, but if I was starting from scratch I would be VERY interested in that approach. I have tested it and it works well. But I do not have the music collection on black disk to warrant any effort in this regard.

 

[sergeauckland]

Thank you for the thorough response. I wonder then if, generally speaking, most modern SS phono preamplifiers are designed to be tolerant of overload, because as you pointed out it is entirely possible to design a SS amp this way, or if in most instances this isn't done because of cost or other practicalities.

Back in the 'Good Old Days', Shure showed that LPs are often cut with levels up to some 20dB above the nominal 5cm/sec recorded velocity that cartridge output is rated at. Consequently, amplifier phono stages must be capable of at least 20dB of overload margin from whatever cartridge is in use, and a good few modern stages aren't capable of that. On top of that, there is the effect of clicks and pops, which although of very short duration, can easily exceed the 20dB over 5cm/sec that music is cut. As with power amps, the behaviour of the phono stage when overloaded will determine whether the clicks and pops are heard just as a slight click, or a loud bang.

From the measurements I've seen here and elsewhere, many modern SS phono stages feature lower noise, but at the expense of overload margin. It's all very well having an 80dB+ S/N ratio,, but when the S/N ratio of the LP is 60dB at very best, that 80dB is pointless especially if that reduces the overload margin below 25-30dB. I would much rather have a phono stage with a 70dB S/N ratio and a 30dB overload margin than less noise and less margin.

As to why it's not done, hard to say. A low noise opamp running on +-15v, gives a maximum output voltage of about 9v, or about 25dB above 500mV typical output, so adequate, if not exceptional. There really then isn't any excuse for phono amps with less than 20dB overload margin and/or less than 40dB gain on MM.

Again, back in the Good Old Days, the better phono stages, like the Radford, ZD22 & HD250 ran on 50v rails and had a 40dB overload margin. If it was done then, why not now?

S.

 

[o2so]

Back in the 'Good Old Days', Shure showed that LPs are often cut with levels up to some 20dB above the nominal 5cm/sec recorded velocity that cartridge output is rated at. Consequently, amplifier phono stages must be capable of at least 20dB of overload margin from whatever cartridge is in use, and a good few modern stages aren't capable of that. On top of that, there is the effect of clicks and pops, which although of very short duration, can easily exceed the 20dB over 5cm/sec that music is cut. As with power amps, the behaviour of the phono stage when overloaded will determine whether the clicks and pops are heard just as a slight click, or a loud bang.

From the measurements I've seen here and elsewhere, many modern SS phono stages feature lower noise, but at the expense of overload margin. It's all very well having an 80dB+ S/N ratio,, but when the S/N ratio of the LP is 60dB at very best, that 80dB is pointless especially if that reduces the overload margin below 25-30dB. I would much rather have a phono stage with a 70dB S/N ratio and a 30dB overload margin than less noise and less margin.

As to why it's not done, hard to say. A low noise opamp running on +-15v, gives a maximum output voltage of about 9v, or about 25dB above 500mV typical output, so adequate, if not exceptional. There really then isn't any excuse for phono amps with less than 20dB overload margin and/or less than 40dB gain on MM.

Again, back in the Good Old Days, the better phono stages, like the Radford, ZD22 & HD250 ran on 50v rails and had a 40dB overload margin. If it was done then, why not now?

S.

Thank you, this is very helpful. I gather from this that most modern SS phono stages do not provide sufficient overload margin. Is there a way to infer the overload margin from the spec sheet?

 

[PaulD]

This has been covered before:
https://www.audiosciencereview.com/forum/index.php?threads/headroom-in-phono-preamps.6760/
https://www.audiosciencereview.com/...djpre-ii-phono-preamps.3457/page-2#post-83784