Ssssh, is your tube preamp really that quiet?

No all-tube phono section is perfectly quiet. But a lot has to do with what cartridges it can work with and whether it has an SUT or not.

If we use an SUT with our preamp the noise is not an issue with any cartridge. If no SUT then when you turn up the volume some hiss is audible.

A surprising number of manufacturers that are otherwise all-tube will use a semiconductor as the first stage of gain.

The real issue has to do with the surface noise on the LP. If the phono section is louder than the surface of the LP then you have a problem. If not, if the surface noise of the LP is the dominant background noise, you have no worries.

Are you saying that without an SUT, all tube phono preamps will solicit some tube hiss when the gain is turned up and no music is playing?

Actually, all phono sections make noise. Tube units tend to make more, thus SUTs are more commonly used with tube phono sections.

I personally find that tubes are more musical, so even though its harder to make them be quiet, I much prefer them to solid state phono sections.

Manley Steelhead into Manley NeoClassic 250 monoblocks: dead quiet

This is an example of a phono section that employs a semiconductor at its input, IOW, it is not all-tube.

Ralph, is it possible to make a tubed phono section without a SUT that is noiseless?

No. All circuits make noise (tube or solid state), the question is how much? You can get a tube phono section to be pretty quiet assuming the tubes are good (our phono section is good to about 0.2mV); anyone saying that their all-tube phono section is 'dead quiet', that sort of thing is not telling the whole story!

If you are using a low output MC cartridge without a stepup transformer, there is going to be a limit as to how low output you can work with from the cartridge. For us that point is at about 0.2mV (0.2 millivolts), where if the preamp has good tubes in it, the phono noise will be below the surface noise of the LP.

What I have found over the years is that everyone has different tolerance levels for noise. Some people are upset when they have the volume up way high, and then lift the arm off the record, and hear all this noise. But you know what? All phono sections that are all-tube are going to do that.

If you run an SUT (its an option in our preamps) you can get the noise floor down to a point where it is near the same level as the line stage. That's pretty quiet! But if you turn the volume up real high, the noise is still there. What is happening is the transformer boosts the cartridge level so much that you just don't have to have the volume control up that high yet its playing at a very high level. So it makes the illusion that the phono section is silent. But no phono section is actually silent- they all make noise!

Phd, your hiss is coming from your line section, not the phono.

Jwpstayman, your preamp makes hiss but not at the levels you play with the cartridge you use. All preamps make hiss- its a fact of life.

Phd, all active circuitry makes noise. Transformers are passive devices and don't make noise, but there is a price paid for their use as well. IOW there is no free lunch.

IOW there is no curse :)

I see the words 'dead silent' used a lot. I know that is not the case; as I mentioned before different people have different tolerances for noise.

For those who think their all-tube system is dead silent on phono try this little test. Leave the tonearm on the tonearm rest. Set the source to phono and turn up the volume all the way. If you can then say that even with your ear pressed to the drivers of your loudspeakers that there is no hiss whatsoever then you have a good case for 'dead silent'. I think you will find though that you have no need to press your ear to the drivers- the noise will be quite evident.

Yes, Charles1dad, you and I are of the same opinion in that regard.

Hello Charles, the same thing happened to me although it was a different solid state preamp that I started with.

We can get such good gain numbers with the use of stepup transformers that at normal listening levels, you can't hear the phono noise over that of the line section and amplifiers regardless of the loudspeaker. But I have yet to find a stepup transformer that conveys the music as well the tubes do running directly.

Over the years we have experimented with semiconductors as well- super linear FETs and bipolar devices, and we have tried OP Amps as well. Try as I might, I can't get them to sound as musical as the tubes- I hear the same problems with the semiconductors in our stuff as I hear in the competition. So for the time being anyway, we are sticking with the tubes. They just work.

FWIW the Ref 3 is a line stage. This thread is about phono sections.

It is. Usually line stage noise is negligible unless you have speakers with high efficiency- 96 db or so and you may have to think about it. When loudspeakers get up to 104 or more, quite often the amplifier noise can be an issue too.

With most line sections the position of the volume control has little to no effect on noise. But I do know of some where the volume control is post-gain stage (the Dude, for example); such line sections are affected by the volume control position.

Why would a volume control (attenuator) after the gain stage affect the level of noise? Wouldn't that be true only of a volume control that is before the gain stage? Or have I somehow got this backwards in my head? I sense that I still have much to learn!

You do have this backwards. Think about the volume control as a valve of sorts that lets the sound through the circuit. The circuit is going to make a fixed amount of noise. So if the volume control precedes the line stage it will have little effect on the noise of the line section. If it occurs after the line section the noise will be reduced as you reduce the setting of the control.

The reason the latter is not done more often is that there is a price paid for having the volume control be the last thing the signal sees in the preamp- and that is that it can raise the output impedance substantially, and make the preamp highly susceptible to artifacts in the interconnect cable.

So to allow the preamp to drive longer cables without artifact, and to be able to make bass easier into transistor amplifiers, most designers put the volume control at the input of the line section (which has the additional advantage of preventing overload of the line section by a strong input signal).

Does this help your understanding?