Phono Preamp Tube Rush

Sorry to OP for my off topic trip.

No worries. Enjoying the diversion on this horrible day.

Sorry to OP for my off topic trip.

Thanks for the suggestions,

What else do you have in that Vintage System? Inheriting my wealthy uncle's system is how I got hooked.

I visit my friend Bill 15 minutes from Binghamton every spring, we photograph waterfalls with plenty of water.

Last year I pre-arranged with McIntosh, to check out my SS amp MC2250 and SS Preamp C28. I was going to sell them.

dropped off Thursday before noon, picked up Monday afternoon. Good people. btw, that place is HUGE!

Sold em, bought the mx110z tube tuner/preamp and a Cayin A88T Tube amp, wonderful together. I need 16ohm tap, this early Cayin has them, but, bias adjust is inside.

Anyway, McIntosh said no, mx110z too old, no parts, ... They are making me a new mx110z factory box, $55. and shipping it to me free. 

I figure, I'm not ever parting with it, why not have it checked out, probably will need a box.

Audio Classics is a few miles closer to my friend than they are. I'll call them and see what they say.

Elliott - I have a family heirloom MX-110Z in my vintage system. The absolute best places to have that worked on IMO and experience are: Randy Vikan at Elite Audio Techician in WA state. and Audio Classics in NY State. I run a Grado into the 110 phono. I am running Telefunken in the critical areas. The Tuner is as good as the MR85. Have fun :-)

Thanks for clarifying.

I am fundamentally opposed to Moving Coil because of the extra amplification involved. I don't even want to hear a fabulous one, I don't want to go down that rabbit hole.

My Preamp, 55 years old, when direct to the integrated amp's bypass pre-in, then gets all volume from the preamp. In that use, I start to get noise, hum, around 11 o'clock position. It's just above my preferred max. so luckily I stay just below any noise.

I've hosed the internals with contact cleaner, no noises, but hum begins. I've tested my 17 tubes twice, but, to be sure, I ought to try some new ones before I spend some money switching caps .... Oh I'm keeping it, even if it needs spending some money.

Using my preamp into a line input, volume is created elsewhere, no hum from pre-amp even when system cranked. 

So, below my typically desired volume, in any configuration, this 55 year old pre-amp is noiseless. 

btw, The preamps FM Tuner, as they say: with a good signal, is superb.

the tube amp, Cayin AT-88, still sold, is dead quiet. Mine is early version with 16 ohm taps, sadly bias adjust is internal.
........
Still never heard tube rush.
..............
btw, McIntosh does not service these, has no parts, and only referred me to 1 local service shop. He has a 12 week cycle for new work. Says he only needs 2-3 hrs work, probably not mush $ in parts. So, I say, put me in the schedule 4 months from now. No, I can't keep track like that. Bring it here, wait 12 weeks till I get to it.

@elliottbnewcombjr
The "rush" sound from your source components renders roughly the same on both efficient and inefficient speakers - because your efficient speakers are equally sensitive to both the noise to the signal (i.e. signal-to-noise ratio unaffected by speaker efficiency), and you simply set your volume control to the desired signal level (i.e. lower volume to compensate) - the ratio does not change.

With very low output MC cartridges you are reducing the signal without reducing your system’s noise floor (especially that before the volume control, i.e. phono stage), hence the issue - you have to raise the volume to hear same signal level, and thus you relatively amplify the phono stage’s noise level for the same signal level. The ratio gets worse as you go to lower output cartridges. Here is where SUTs can help - to raise your signal without raising noise (ground hums notwithstanding).

With very very efficient speakers as yours, you do have to become concerned about the inherent noise floor of your preamp and amp - i.e. the active gain stages AFTER the volume control. Especially the preamp, since its residual noise is un-attenuated, and amplified by the amp. Preamps that are dead quiet in normal systems may be quite noisy in yours! Generally you try to avoid high gain components with efficient speakers (mine Tannoys are an honest 96dB), but not all high gain components are equal - my ARC Ref 6 preamp has a demonstrably much lower noise floor than other tube preamps at roughly the same gain level (14 dB). It is dead quiet! Very impressive.

dammmmmm audiophiles!!!!!. Please take this out of my mind.

I didn’t know about this, have never heard it, and now it is in my mind that I just haven’t been paying attention. I’ll listen tonight, better not hear anything.

I had my new dual arm tt CRANKED last night. 3 guitarists, Euryhmics, Michael Jackson Thriller, test record musical/imaging tracks, Stereo, Mono, ....

I heard some static between tracks, nothing else. I gotta get a fresh copy of that Eurythmics album, perhaps Valentine’s Day.

Fisher 80Z Mono Blocks; Fisher 500C; Fisher 800 (500c + am); now wonderful McIntosh mx110z (2 MM Phono inputs); My friends never push their system like I do, their speakers are not as efficient as mine, over 100db/1w/1m.
...............................

Is this perhaps related to volume factors?

1. efficient speakers get loud before excess power needed by inefficient speakers, thus the ’rush’ doesn’t occur. Inefficient speakers get you into the 'rush' zone.

2. Low Output MC Cartridges, require more volume than MM cartridges that I use.

3. the combination of inefficient speakers and low output cartridges.

..............................

I change something and if in a couple weeks i want to go to bed at night instead of listening, the change was bad.

An open mind and a test disc w spl meter :-)

Agree completely with the several posts above this one.  I do find the science and psychology of my own perception interesting.  

@lewm   Agreed, that being honest with ourselves is not always the easy path.  I'd rather be happy than right.  Open-mindedness and honesty takes one far in this hobby I'm finding - or in life for that matter.

I have a Herron on order so I certainly appreciate this so far civil thread. Keith has been wonderful to work with and answers the phone.

mulveling

First impressions of tube or component changes can be especially nebulous - because anything that the new component sonically accentuates can easily evoke a new emotional response that we can’t help but latch onto. This can allow us to experience our favorite tracks in a different light, perhaps even noticing parts of the music we hadn’t before. However on extended listening - we may notice the accentuation is really unnatural. We may even go back to our old component and suddenly that "new part" of the music is actually still there, we just hadn’t listened for it before because it wasn’t actually supposed to stand out ...

I agree completely, and that is exactly why I think equipment "shoot-outs" are virtually useless. A component’s true character is revealed over time. Trying to assess it quickly serves no purpose and the result is prone to error.

three-easy, Good for you that you had the intellectual honesty to pay attention.  To complete the experiment, try re-inserting the new tubes after 2-3 weeks using the old set.  See if your impressions remain the same.

First impressions of tube or component changes can be especially nebulous - because anything that the new component sonically accentuates can easily evoke a new emotional response that we can't help but latch onto. This can allow us to experience our favorite tracks in a different light, perhaps even noticing parts of the music we hadn't before. However on extended listening - we may notice the accentuation is really unnatural. We may even go back to our old component and suddenly that "new part" of the music is actually still there, we just hadn't listened for it before because it wasn't actually supposed to stand out, lol. 

Gear or tubes that have a high listening fatigue factor are particularly subject to this phenomenon - and listening to it gets old real quick!

Don't feel bad either, experience can help, but a lot of us (including myself) still fall for this same trap from time to time. 

I played the NOS game with the vtph-2a and came to the same consensus, specially the bloated bass. Decided to stick w stock on this guy - no worries

Ok, 24 hours later and I embarrassingly now need to confess that I'm not preferring the Gold Lions over stock EH's in the Herron.  At first I was smitten with the reduced noise, blacker background, silky smooth mids and extended bass.  I am now realizing that these sonic qualities came at a steep cost of losing the air and wide-open presentation.  Late last night during listening I became keenly aware that the highs were getting rolled off and the bass was actually bloated.  I immediately rolled Keith's stock EHs back in the pre and ahhhh.....everything was so much better.

Interesting lesson here in the psychology of perception.  I was initially seduced by the quiet and a "different" sound, and it took me a bit of time to realize different was far from better.  I have read many times that it's hard to improve on Keith's tube voicing and It'm seeing that now.  I'm still curious about rolling tubes in the Herron but I suspect you need to get into some nice NOS tubes like Tele or Mazda to move the needle any higher.

@dhcod   +1  I think that sums up my perspective as well.

@lewm

I completely agree that not everyone is going to recognize the same or even similar results as me as the change is certainly both system dependent and based on personal tastes. The stock tubes were only 7 months old so they had plenty of tread left. I just thought I’d offer a data point because in general I think you’re hard pressing to get a better sound than what Keith brings into the box from the get-go.

I think it's more about what sound you want than tubes that are worn out. Right out of the box, different tubes make the VTSP-2a sound different, even better in my opinion. Others may be just fine with the stock tube sound. It's a matter of personal taste and also how much time and money you want to invest in listening tests with other tubes.

three-easy, I would expect that different persons would get different results, if each person were to replace the stock tubes with the aftermarket brand you selected, because to a great extent it depends upon the pre-existing condition of the tubes being replaced.  Could it be that your stock tubes were a bit long in the tooth?

That's great news about the Gold Lions. Now that you know that you can improve the VTPH-2a with different tubes, It may be a interesting  experiment to grab a pair of smooth plate Telefunkens from ebay and see if the improvement in sound quality is worth the extra noise. It was for me. In my VTPH-2a, they just did a better job of presenting the music, more soundstage depth, more of a feeling of hands on instruments, truer vocals. Still great dynamics. But a little more noise. 

^ that’s good to know sir - ty! 

So curiosity got the best of me and I decided to try replacing the original EH 12AX7 1st gain stage tubes in my Herron VTPHA2A just to see if I could reduce the noise floor a tad.  I went with Gold Lion reissue ECC83/12AX7 tubes from Upscale Audio - ordering the quietest option they provide.  My expectations for improvement (over an already gorgeous sonic presentation in Keith's stock tubes) weren't particularly high but I was pleasantly surprised when I immediately realized a notable difference.  Tube rush, and still only at very high volumes, was reduced probably a few dB but even more surprisingly the sound character changed for the better as well - the Gold Lions delivering a very smooth, more richly dynamic presentation that's been improving further over the 10-12 hrs I have on them now.  Just thought I'd share the experience with anyone interested.

SUT is the easiest way to get low noise input.  Works very well. 

I'm thinking all-tube may be possible using a pentode into a load of 10k or less.  Then again, microphonics will become the new problem... 

All tube phono with low output MC is probably impossible to get really low noise.
Low gain tube phono + SUT has been what I've used for the past 8 years. 
Cary PH302 has low 38dB MM stage and I'm currently using with Cinemag 1131 on 26dB (1:20) setting. I'm using vintage NOS tubes. Super quiet and dynamic with the Denon 103R.

It’s all relative. There will always be phonostage hiss, whether tube or solid state. The goal is to get it quiet enough such that it is lower than silent groove noise. How much SNR is enough?

I just tested my system (Piccolo2 - Cornet3 - Tuba) at full volume into an HP400 AC meter. The difference between a silent groove (my best is the Hi-Fi News Analog Test LP) and the tonearm up is 9dB. Perhaps not numerically impressive, but it’s like night and day listening-wise. The uncorrelated groove noise sounds way louder.

Forgot to mention, this is with a Dynavector 20XL MC cart (0.3mV) into 100 ohm loading...

Interestingly, changing from my Herron VTSP-1/166 to a Lamm LL2.1 made a big difference, and not because the Lamm itself is quieter because it isn't. Could it be something with input impedance?

@lewm 

I appreciate the detailed explanation!  I was unaware of the Manley hybrid design.

three-easy, Manley, in the Chinook and in my Steelhead, use a hybrid cascode at the phono input.  "Hybrid", because the cascode is built out of a transistor (probably a JFET) and a tube (the 6922/6DJ8).  That is quite a bit different from using a 12AX7 all by itself to supply all needed gain.  A cascode per se will give you more gain and a wide bandwidth, plus shielding from input capacitance (because the JFET drives the 6922 via its cathode), compared to any single tube used in common cathode mode.  The trade-off is high output impedance of a cascode. The 6922 is well suited to this topology, because it has high transconductance, needed to take advantage of the drive from the JFET, rather than a high gain factor, in contrast to the 12AX7. 12AX7 has relatively low transconductance and very high gain.  You'd not use a 12AX7 in a cascode. Nor would you use a 6DJ8 by itself for the high gain needed at a phono input.

I had brought up the question earlier in the thread about why not use a 6922 instead of the 12AX7.  You definitely could get enough phono gain with the 6922 and this is commonly used in the Manley phono pre's (for example).  Now would the overall sound quality be as good in the overall circuit design compared to what Herron achieves in the VTPH-2A?...I have no idea.  I use the Herron VTPH-2A and am happy with it.  I may try a coupe of Roger's SLN tubes in the 1st gain stage soon and see if it makes a notable difference but either way I'm perfectly good with the Herron. ;-)

I far prefer tube-based circuits to solid state, for sound quality, but all tubes do have a finite life span, and as the end draws near, they become noisier, until they reach a final common pathway of being noisy.  This malady will affect SLN tubes as well as non-select samples.  The variable is time from new to noisy, which is impossible to predict for a given sample of a new tube, but I would agree that for a tube that starts out SLN, perhaps (on average, but there are no guarantees) the time to its becoming noisy will be longer than for a non-select tube.  But the point I was trying to make earlier is that circuit design also has a lot to do with "noise" one perceives over the speaker.  For one example, ARC stuff was always known for driving tubes very hard, near their recommended limits for voltage and current.  In the old days, this led to short lifespan. Circuit layout also has an effect.  What tubes are chosen for a given task also has an effect.  Someone wondered why Herron(?) didn't choose to use a 6DJ8 instead of a 12AX7 in its phono stage; the simple reason is you could never get enough phono gain out of a 6DJ8, used as Herron uses the 12AX7.  The 12AX7 is a standard choice used in common cathode mode for the input of an MM phono stage; all the gain is done at the input before RIAA, as Hagtech mentioned.

Harry, you did not read the thread carefully enough. I mentioned them way in the beginning.

Mike

This is a topic I’ve been following for awhile. Although I’m not an EE, I do know I hear what I believe is tube rush from my Aesthetix Rhea eclipse phono pre. I’ve tried to ensure good connections from the cartridge all the way to the pre. I also found I had some RFI or EMI from a google mesh wireless extender that was positioned too close to my TT/cartridge.

But I can say unequivocally that going to ultra low noise 12AX7 NOS tubes (amperex) in V1 and switching from 6922 to 7308 ultra low noise amperex made a big difference. It did not eliminate but the rush but it is now very tolerable. And with the low-noise telefunkens in the other tube slots, a very very enjoyable sound. 

I've just skimmed the thread and so may have  missed it, but nobody has mentioned low noise tubes.  I have found the NOS JAN-Phillips 7981's sold by The Tube Store to be substantially below stock tubes in my Brown Audio Lab headamp.  I also own a Counterpoint SA-2 headamp, and in that unit tubes are paralleled to achieve the same effect.

Tubes are inherently tweakier than solid state.  You can have tubes that have gone a bit 'microphonic' that need to be weeded out as a first step.  Power up the phono stage with the cover off and the volume at midrange, and very gently tap each tube with a pencil eraser and see what comes out of the speakers - a bad tube will be pretty obvious and I've had bad ones even in brand new batches.

Gain mismatches with a low output moving coil cartridge into a tube phono stage running at almost full volume are likely to give you some noise. If you listen to rock music with limited dynamic range that still may work for you, but on music with greater dynamic range you are likely to hear noise.  Consider the SUT that several have suggested - they work quite well - as long as you set the impedance correctly, assuming that it is adjustable on your unit.

And unlike solid state gear, you have a whole new set of non-soldered contacts that can get dirty and make unreliable contact and will need cleaning (usually every few years)  I'll leave the cleaning procedure and materials to someone else to explain.

Get the contacts right, and the tubes non-microphonic and the gain correct and it still may be a noisy pre-preamp for your system.  Which is why I run a solid state phono pre in my main system, which otherwise uses all tube amplification.  If you get a tube phono stage operating well for you, don't get upgraditis and get something else - you may well regret it.  I have had a tube phono stage in my second system (which ironically is otherwise all solid state) for some time and it is quiet and really quite good (CJ Premier 15). I have no intention of changing it any time soon.

Yes, MC carts with lower ESR will produce less noise.

RIAA networks contribute noise, but it's not usually a problem, as the networks are implemented after one or two stages of gain.  Ten nanovolts of noise at the input of a phonostage has a lot more impact than ten nanovolts added somewhere in the middle.

You have to look at the entire picture here (as you hinted).  Every single component adds noise.  

the only reason I raised the issue of Johnson noise was in response to a question about whether any tube-based phono stages are quiet enough for hiss to be inaudible when one’s ear is placed against the speaker, while a record is not being played. And my response was to the effect that for typical combinations of system gains, sensitivities, and volume control settings theoretical limitations might come into play which could make that impossible, or close to it.

*If* the phono section has sufficient overload margin yet still has plenty of gain (60dB) and a stepup transformer, you can get so much output out of the phono section that the noise floor of the line section will obscure that of the phono section- such that switching between Aux inputs and phono will not have an audible change to the noise floor even with your ear pressed to the loudspeaker drivers. I've demonstrated exactly this at shows.

If Johnson noise is a problem you can narrow the bandwidth of your cartridge to 100 Hz (stick chewing gum behind the cantilever I guess)
or dunk your cartridge in liquid nitrogen before you play a side:) 
Seriously, this is all academic because there is not a darn thing (reasonably) that you can do about it and I hate math.

Do I conclude from the talk about Johnson noise that (1) MM cartridges with their inherently much higher internal resistance and much much greater inductance will be noisier than MC types?

What matters, of course, is signal-to-noise ratio, and of course the greater amount of Johnson noise that would be generated by the greater amount of resistance in a MM cartridge occurs in conjunction with a greater amount of signal.

And (2) what about all those high value Rs often used in an RIAA network, again, IF one is obsessive about Johnson noise?

I’m not especially familiar with the internal designs of phono stages, but I would expect that quality designs typically apply a significant amount of gain "ahead" of the RIAA equalization circuitry. Resulting in much better S/N ratio relative to Johnson noise generated by that circuitry than if the output of the cartridge was applied directly to it.

Also, keep in mind that Johnson noise that can be generated by a high value resistor may or may not matter depending on the impedances and configuration of the associated circuitry. For example, as Hagtech and the Sound Devices paper I linked to both indicated, shorting a high impedance input will essentially nullify the effects of Johnson noise that would otherwise be introduced by that high impedance.

Finally, of course, the RIAA network rolls off everything above 1 kHz to some degree, which encompasses 95% of the spectrum that is nominally audible.

In any event, the only reason I raised the issue of Johnson noise was in response to a question about whether any tube-based phono stages are quiet enough for hiss to be inaudible when one’s ear is placed against the speaker, while a record is not being played. And my response was to the effect that for typical combinations of system gains, sensitivities, and volume control settings theoretical limitations might come into play which could make that impossible, or close to it.

Best regards,
-- Al

Almarg and Hagtech, Do I conclude from the talk about Johnson noise that (1) MM cartridges with their inherently much higher internal resistance and much much greater inductance will be noisier than MC types?  (But of course the noise that accompanies the greater gain needed for a typical MC vs an MM would swamp Johnson noise in most cases.)  And (2) what about all those high value Rs often used in an RIAA network, again, IF one is obsessive about Johnson noise?
I've never measured the R across the secondary of a typical SUT but I would never have imagined it could be as high as 3900 ohms.  Surprising.  I am not an SUT kind of guy, either.

Most LOMC cartridges have bandwidth well past 20KHz- most have no worries going to 40KHz.

Hi Ralph,

Yes, I realize that. But what I was attempting to calculate was an approximate figure of the amount of Johnson noise (aka thermal noise) attributable to the cartridge’s resistance **that might be audible** while a record is not being played.

@hagtech, thanks for confirming that the ESR (equivalent series resistance) of a cartridge can be used for purposes of that calculation.

Best,
-- Al

I then extrapolated from that number to the result corresponding to the 12 ohm resistance of my cartridge, over a 20 kHz bandwidth:

@almarg Most LOMC cartridges have bandwidth well past 20KHz- most have no worries going to 40KHz.

if executed in the balanced domain you get a maximum of 6dB less noise

Actually, that's not true. With balanced amplification you get 6dB more signal gain, but you also get 6dB more differential noise gain. Overall SNR is the same.  

IME you get the same gain- not 6dB more. We might have to straighten out our terms here- it might be that we are talking about the same thing.

Lewm, according to the meter I have yes with peaks just slightly over 110 dB. (I had ear protection on at the time:) God knows how accurate the meter is. I think more remarkable is that this is with ESLs (using subwoofers from 125 Hz down). From 10 row center the last NIN concert I went to hit 120 dB (I also had hearing protection on) Getting the meter into the concert was a bit rough. Had to take the battery cover off and show that it was working while everyone behind was getting pissed. Anyway, the loudest I ever play it on rare occasions is 105 dB usually with concert videos. Most of my listening with Rock and Jazz is at 95 dB. Don't forget to warm up your ears first! 
I love your Steelhead, almost bought one but right now I am looking at Phono amps with balanced outputs and inputs. Coming from where Manley does you would think they would do that. 
We live in a house I have been building since 1993. 
In regard to the SLN tubes the only thing I can say is that with the system set at 95 db I can not here anything with my ear right against the speaker over the background noise of the house. With the volume maxed out I can just make out a hum, again ear against the speaker. The Tubes are now 6 years old. I have no idea if this is noisier than when they were new but even if they do get noisier with age I suspect a SLN tube will always be quieter than a LN or standard tube of the same age and make.

if executed in the balanced domain you get a maximum of 6dB less noise

Actually, that's not true.  With balanced amplification you get 6dB more signal gain, but you also get 6dB more differential noise gain.  Overall SNR is the same.  

The benefit of balanced amplification is rejection of common mode noise such as power supply crud, and crap injected on both + and - inputs together (sometimes hum).  You get a better amplifier with higher overall performance, but noise floor from a differential source such as the resistance of a cartridge is the same.  

@lewm - Sorry I wasn't more clear.  Yes, I meant thermal noise from input resistance. 

The SUT in question had 3900 ohms on the secondary (thin wire), which generated quite a bit of noise, much more than I get from my JFET-based headamp.

And yes, you can use the ESR of a cartridge to perform a baseline minimum noise floor calculation.  You then have added noise (aka noise factor in the RF world) from the amplification (which you can break down by stage).  The first stage is by far the most important.  That's why I use special low noise matched JFETs for MC front-end.

Another good test for "tube rush" is to compare noise level between open and shorted inputs.  Most of the noise you hear open is from the 47k loading resistor.  Shorted, you hear the amplifier and tube rush.  

I might wonder whether one can model a phono cartridge based solely on its internal resistance, in that calculation.

@lewm, that’s a good point. But the inductance of my cartridge is spec’d as 25 uH at 1 kHz. If we assume its inductance is also around 25 uH at 20 kHz, its inductive reactance at 20 kHz would only be about 3 ohms. And it would be progressively less than that at lower frequencies, of course. So it would appear that the cartridge’s impedance is primarily resistive throughout the audible frequency range.

Best regards,
-- Al

Thanks. I can’t argue with your logic, and won’t.I might wonder whether one can model a phono cartridge based solely on its internal resistance, in that calculation.  But I have no better idea.

Almarg, What formula did you use to calculate the Johnson noise of a phono cartridge?

@lewm

Hi Lew,

I performed that calculation in two different ways, and got the same result both ways:

Method 1: The section of the Wikipedia writeup on Johnson noise that is sub-titled "Noise Voltage and Power" contains an equation for rms noise voltage which makes clear that rms noise voltage over a given bandwidth at a given temperature is proportional to the square root of the product of that bandwidth and the resistance which is responsible for the noise. That section also states as follows:

For a 1 kΩ resistor at room temperature and a 10 kHz bandwidth, the RMS noise voltage is 400 nV.[6]

Footnote 6 indicates that a more exact result is about 403.6 nanovolts, or 0.4036 uV (microvolts).

I then extrapolated from that number to the result corresponding to the 12 ohm resistance of my cartridge, over a 20 kHz bandwidth:

0.4036 x [square root [(12 ohms/1000 ohms) x (20 kHz/10 kHz)]] = 0.0625 uV

0.0625 uV is 78 db less than the 500 uV rating of my cartridge, since:

20 x log(0.0625/500) = -78 db

Method 2: I started with the following paper, although it pertains to microphone amplifiers:

https://www.sounddevices.com/microphone-preamp-noise/

The paper states that:

The noise generated by a 10k ohm resistor (based on the thermal noise formula above) is around 1.8 uV (-114 dBV).

I assumed they were referring to a 20 kHz bandwidth, or at least to something of that order of magnitude. I then extrapolated from the 1.8 uV/10K numbers to the 12 ohm resistance of my cartridge in a manner similar to Method 1 above, and after converting to db relative to the 500 uV rating of my cartridge I got the same 78 db result.

Best regards,
-- Al

Whether or not you have "tube rush", in my opinion, is much more a function of the topology of the phono circuit than it is a matter of buying super low noise tubes. RAM and Kevin are completely reputable, but any tube will become noisier as it ages, and such aging can occur at different rates for different samples of the same tube type. So even SLN tubes are only SLN on the day they were measured. And one SLN may become only LN, for example, in a matter of several hours of use, while another may remain SLN for a much longer period.
I own both an Atma-sphere MP1 and a Manley Steelhead. The MP1 uses a dual differential cascode input voltage amplifier in the phono section, and the Steelhead uses a hybrid (solid state and tube) version of a cascode. (It’s single-ended.) Neither of these devices ever produces any tube rush at useable settings of the attenuator. The Steelhead, in fact, is silent for practical purposes (meaning you may hear a very faint noise at the sitting position if you are not playing an LP, with the volume control cranked all the way over).
It seems to me that phono stages deriving most of phono gain from the use of 12AX7 tubes at the input might be more likely to exhibit noise at high volume control settings.

Almarg, What formula did you use to calculate the Johnson noise of a phono cartridge? I was prompted by your earlier post to do some reading on it, too, and I would have guessed the noise of a phono cartridge per se would be much lower than what you quote. but I am not sure what are the correct values to plug into any of several equations I found on the internet.
Mijostyn, You can really achieve 110db SPL in your home audio system? I hope you don’t live in an apartment.

daveyf 11-11-2019
Anyone here actually own a tube phono stage that is so quiet that when you place your ear right up against the speaker and the phono stage is active...and at some mild gain, but with no music playing ( or even at no gain) they hear absolutely no tube noise/rush ( dead silence)...I doubt it.

I’m doubtful that is even theoretically possible with typical combinations of system gains, sensitivities, and volume control settings, even if a solid state phono stage is used.

Out of curiosity I did some quick calculations of the Johnson noise that would be produced by the resistance of my phono cartridge itself. As I mentioned earlier I use an AT-ART9, which is rated to produce 0.5 mv under the standard test conditions and has a specified resistance of 12 ohms.

I calculated that at room temperature and over a 20 kHz bandwidth the 12 ohm resistance would result in Johnson noise that is about 78 db below the cartridge’s rated output. If we assume for example that the volume control is set such that the cartridge’s rated output results in an SPL of 90 db at the listening position (which I think is a reasonable ballpark assumption), it would mean that the cartridge itself would be producing 12 db of noise at the listening position, within that 20 kHz bandwidth. That would almost certainly be inaudible at the listening position, of course, even when a record is not being played, due to the combination of RIAA equalization, A-weighting, ambient noise in the room, etc. But I would by no means assume that to be the case if the listener’s ear is placed up against the speaker, even if the phono stage, cabling, and the rest of the system add zero noise. My understanding is that an SPL of about 0 db is considered to be the nominal threshold of audibility, and 12 db at the listening position would correspond to a much higher volume right next to the speaker.

Regards,
-- Al