What are the more subtle sounding tube preamps?


New member
Username: Mariaevinne

United States

Post Number: 1
Registered: Jul-17
I mean "subtle" as in relatively less tube saturation or color than your average tube-pre. Common sense tells me less tubes as in a single dual-triode, but in reality that may not be the case. I currently have my eye on a CJ Classic. Not sure if that will fit the bill. Any suggestions welcome.

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 18431
Registered: May-04

"Neutrality" is in the mind of the listener, which means "subtle" is there also.

If you feel a pre amp with a measured THD of 0.01% is better than a pre amp with a measured THD of 0.5%, then you have a decision to make which does not directly involve triodes.

If you do not have a clean and clear concept of how live music exists for you, then you are going to be listening to, and for, the colorations and the distortions of the components and speakers. You will not be listening to the musical reproduction values of the entire system.

If you think "imaging" is more important that, say, "timing" or "timbre", you are going to be listening to the artifacts of the system and not to the musical values of the system.

It is not a matter of the configuration of the circuit which makes a component this or that. At one time, many decades ago when "high fidelity" to the source was the one overriding objective for a designer, an audio component under review was deemed "a straight wire with gain". At the time, those words meant the component neither added nor subtracted from the reviewer's concept of musical performance as he - it was always "he" back then - perceived the recording of the original musical performance.

Of course, what the reviewer was listening through - the current system used in conjunction with the component under review - had its limitations so the perception of neither "added" nor "subtracted" elements of music was also somewhat limited by what the whole system was capable of reproducing. At the time, values such as "imaging" and "soundstaging" did not exist in the reviewer's lexicon. Words such as "silvery" and "timbre" had more meaning.


While measured performance of that component has surely been bettered over the decades, it is though still likely that single component would also be rather "musical" today. At the time, for the music lover, there was nothing to else to perceive other tthan the musical performance. Therefore, the words "High Fidelity" (to the source) became shorthand for a good component or a good system.

So, what is "high fidelity" in your mind?

How much value do you place on "musicality"?

How much value do you place on "accuracy"?

IMO both values would have been contained in the concept of "a straight wire with gain". It is the original reviewer's vision of each which then becomes the biggest question and that is always the greatest unknown in the final equation.

IMO you must begin with the fact that every circuit, every single component and every interconnect - to some extent every wire, every dielectric, every plug, jack and solder joint - between circuits and components is a potential source for objective and subjective additions and subtractions. The distance between components and the electrical - and the physical - interactions between components matters when answering a question such as your's. Certainly, with tubes the set up of the system within the listening room is of grave importance, down tocthe support system for each component.

Take for example, the loading of the circuit by the rather necessary volume control found on any control type "pre amp". Using an inexpensive, ubiquitous $10 pot or a cost no object vc will still introduce "an effect" on the circuit due to the electrical loading of the input and the output of the circuits caused not only by the existence of a variable potentiometer but also by each variable setting of the pot Each volume level change will affect the circuit in slightly different ways as each setting represents a subtle shift in the electrical "impedance" seen at the input and the output of the pot.

This is all dictated by Ohm's Law; https://www.google.com/search?q=ohm%27s+law&rlz=1CAACAY_enUS752&oq=ohm%27s+law&a qs=chrome..69i57.3312j0j1&sourceid=chrome&ie=UTF-8

You could therefore say each time you adjust the volume control to another setting, you have somewhat altered the total system settings and therefore the final system performance. What was "neutral" at this point is no longer completely "neutral" at that point due to the electrical interactions of the circuits.

Altering the system settings means the system you had before is not the exact same system you have after the adjustment. To make the system more stable in the sense it performs as designed at every setting on the vc, a designer might introduce a buffer circuit which acts as an electrical blockade on the variables of the vc's constantly changing impedance effects.

Now you've added another circuit (or two if you add both input and output buffers) that will also have some affect on the musical reproduction capacity of the component. Buffers can be either active (a circuit with a "gain" device within them) or passive (no gain device but more individual passive [resistors, caps, coils, etc] devices).

A gain device - let's say a 12AU7 tube - can be run without actual gain beyond about 1dB of effect and have minimal alterations to the perceived sound quality beyond the injection of the "sound of" the type of tube you've selected and the quality of the tube you've selected. Objective test bench measurements will likely not change when the buffered tube circuit has been changed by way of a cheap or a great buffer tube. Subjective performance may - and likely will - change considerably.

However, since every individual component within the circuit has the potential to add or subtract, subjectively - what you perceive, not what you measure - the final musical performance of the system will likely be changed in one or more ways according to your perceptions of the musical reproduction vs the live music event.

All of this, of course, depends as it did ages ago on the listener's personal musical priorities and the transparency of the system within which the pre amp is being used.

What the buffer circuit has done though is to take a known and measurable flaw in the "straight wire with gain" concept and technically made the circuit "better" by minimizing the effects of that technical flaw. Buffers are generally considered to be good additions to a pre amp and most often, when they have been properly executed, they can be beneficial to the overall performance of the system. Their addition to the component however, will alter the final perception of the system's objective and subjective performance.

That would/could make a single dual triode circuit less than desirable or more desirable. The answer is not a matter of whether there is a single dual triode tube or even a bipolar transistor or a FET.

If you should go with a single dual triode though, know that volume controls do not track equally at all positions - making for channel to channel balance errors thus requiring the typical addition of a balance control pot and circuit - and each section of a single dual triode will not perform identically to the other section with the same tube. Add to this the accepted truth that one manufacturer's tube does not "sound like" another manufacturer's tube and all the variables involved in just the one component will make your selection of which single dual triode to insert in the circuit very much a more neutral/less neutral decision.

Just moving between a group of 12AX7's from the same vintage but different manufactures - no NOS tubes - will change the musical perceptions of the listener with each change in which tube is "in circuit". A JJ doesn't "sound like" a Sylvania which doesn't perform (musically) indentical to any other 12AX7. Move between a 12AX7 and a Europen counterpart which is claimed to be "same as" a 12AX7 and you'll likely hear additional changes in performance. An American, a British, a Japanese and a Russian manufactured tube of the same type will each have their own distinct sound quality.

None of this would likely be easily measurable but the question is whether it is "perceivable" by the listener.

Measurably, understand that the instant you fire up a tube it begins to age and deteriorate in measurable ways. Therefore, a new "X" tube and a used "X" tube will be different from each other when both are used in the same circuit. We won't even go into tube microphonics at this point.

Swap out the 12 series tube and in its place adjust the circuit to a 6DJ8 and now you have moved from a tube designed for audio (20-20kHz) to a more linear tube designed for video (5-150kHz). Greater bandwidth beyond the audio frequencies would tend to make you think this is the "better" tube for this application. One issue though is now your circuit configuration - what each tube type needs to operate - has likely changed somewhat so comparing apples to apples isn't as simple as it might first seem.

Add in the same variability between each 6DJ8 as you found in each 12AX7 and you have a plethora of decisions to make as a designer or, if you get down to the micro level of decision making, as a consumer.

A lesson you will learn in audio however - as a consumer, not as an engineer - is greater "accuracy" does not always equate to greater "musicality". Many listeners prefer the known audible distortions and colorations of the 12 series tube over the measured accuracy, within the audio bandwidth, of the 6DJ8. You may be the exact opposte.

This post is quite long now and I've barely scratched the surface of subjective listening. I can certainly go on as I sold high end audio for a lone while and have had this same discussion many times.

What is "neutral", or "subtle", for one listener will probably not be totally so for another. Each listener will have their own "ideas" of how a system should perform. Unfortunately, IMO, most listeners no longer have a concept of how music "exists" for them and they begin to listen to the system and not to the music.

And while it is not wrong to ask a question such as your's, it is also irrelevant to - or, at the least, obscured by - the musical performance of the individual component.

Simplicity in design has its rewards but it also has its drawbacks. Another lesson I tried to give my clients is, if I give you "this" as a benefit, you have to expect I might also take away two other things which are just as beneficial to the total of music reproduction. Audio is not a zero sum game and virtually everything about it is a series of compromises.

CJ has a "house sound" which, ideally, means music as presented through a CJ component will, under "ideal" circumstances, reflect what the designer(s) feel is "the sound (and the perceptions they have) of live music". McIntosh and Audio Research also have house sounds which are true to their components and their designers but not exactly identical to CJ's performance. CJ and Mac are closer to each other than is Audio Research to the other two.

Matching each component in your system to the same "house sound" is the best bet on achieving that manufacturer's ideal. They know the electrical parameters of their components and there should be no rude surprises when you connect a CJ pre amp to a CJ power amp. Of course, there is that pesky element of the interconnects which will introduce another impedance element to which both the pre amp and the power amp will react in an electrical manner.

And, of course, the next question should be, what do you think of CJ's house sound? If you match this pre amp with another manufacturer's power amp, how will that affect the house sound of the CJ pre amp? How will the upstream CJ affect the performance of the downstream power amp?

And, most importantly, no system exists in a vacuum. The room is the single most influential component in the final perception of musicality and system performance overall. It is 1000's and 1000's of times more important than the difference between 0.001% and 0.5% THD.

Move the speakers alone from the short wall to the long wall and you've completely altered the perception of music from the exact same system. Ignore the proper set up for each component and you will have degraded whatever performance had been designed into the component.

Certainly, even the best tubes are somewhat microphonic so you must make adjustments to the fact you are creating pressure waves within the room where your tubes reside. A slight bit of microphony can be heard by many listeners as a longer sustain to each note. Too much microphonics and you quickly cross over into too much sustain. The same effect can be heard by overdriving one tube stage with another tube stage.

A long standing question in high end audio is whether you use long ic's between the power amp and the pre amp to minimize the cable runs between the amp and the speakers or whether you go the other way around. There's a simple electrical answer to that question which depends on the output impedance of the pre amp vs the input impedance of the power amp but that can be a variable which makes, say, an output buffer in your pre amp a more desirable feature despite the certain add/subtract issue of another circuit being thrown into the mix.

None of this really discusses the reason you are hopefully assembling a high fidelity sound system, which is the music.

To that end, I will promise you a shoddily set up system and room will not overcome the additional funds put into the purchase of the "better" components. A decent middle of the road system which is well set up will very likely outperform a more expensive system that is slap dashed together.

Now, none of this still really answers your question and likely confuses any single answer you may be given by someone else. But a really good music reproduction system begins, IMO, with the musical performance of the entire system - including the room - and that is where it ends also.

If you do not have in your head what values exist in a live music performance which you value, then you cannot have any sense of what musical values you have as a priority in your home system.

It all begins with the music and your ability to not listen for the sound of a component, or a single tube, but only to the music.

Contrary to that statement, a really high quality system depends on your ability to focus down to the elemental level and know whether a certain tube type or tube brand is "better" for your musical enjoyment.

You need to develop the ability to listen through the system and to focus only on the music. This will allow you to understand the true effect of a dual triode running both halves together - actually very rare in high end audio - or a dual triode running only one half of each tube and thus requiring two similar (but not identical) tubes - much more common in high end audio.

If all that gobbledegook makes sense to you, we can go further or you can move to someone who will just tell you to buy a single dual triode pre amp. If you continue, know that I cannot tell you exactly which pre amp to own.

The variables of the system - and the room - will dictate which pre amp is better or worse for you and your system (at this moment in time) but not which is exactly the topology of design you should select.

I do not have your ears and I certainly do not have your preconceptions about live music. If you do not listen often to the sound of musicians creating music without amplification, then you and I are on different planets regarding the "sound of music". If you are only familiar with the sound of live music existing within this one venue, then you must make adjustments to the effect on the music of other venues.

That doesn't mean I can't provide useful advice, I've done so on this forum for almost 15 years. But the final decision is yours and yours alone.

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