What does tube equipment sound like?

[KeithL]

I wanted to come back to this one because it's important.

If you'd asked that question thirty or forty years ago, the answer would have been simple: There is no such thing as "what a tube is supposed to sound like". The ideal hi-fi component would be "a straight wire with gain" - and so would have no sound of its own. Ideally, therefore, the ideal piece of tube equipment would sound exactly like it wasn't there. If you hear something distinctive about how a piece of equipment sounds, then what you are hearing is its failure to achieve this goal.

The history of tube equipment (until recently) was a march in this direction:
First there were only triodes - they had lots of distortion but were a lot better than, well, nothing.
Then came tetrodes and pentodes - extra grids for control and feedback - lower distortion.
And push-pull - two tubes arranged in an ingenious way so most of the distortion cancelled out - lower distortion.
And ultralinear - a cool way to connect extra windings on the transformer to tube grids - and, you guessed it, lower distortion.
And all sorts of other circuits like cascodes.
And, of course, feedback appeared earlier along the way.

Notice the trend here?
Lower distortion; less "characteristic sound"; more like "a straight wire with gain".

Ideally, the perfect piece of high-fidelity gear would sound like nothing at all - and you wouldn't hear the difference between "tube nothing at all" and "solid state nothing at all".

So, how did it get so f%$#@&ing complicated?

Well, early on, a few common types of distortion dominated everything. You had THD (total harmonic distortion); IMD (intermodulation distortion); and noise. These were pretty easy to measure, and those measurements pretty well "predicted" how something would sound... more or less. Things with more distortion sounded worse.

Unfortunately, when solid state came along, this turned out to no longer be true. Pretty well all decent solid state equipment was way better than the best tube equipment in terms of those numbers, but some of it still didn't sound very good. Thus started the idea that there was something magical about tubes. The reality was more prosaic; solid state equipment had a tendency to other (and different) common types of distortion. Since the tests were designed in the days of tube equipment, they didn't measure all the stuff that was important for solid state equipment, and so didn't do a very good job of describing how it would sound. [I'll bet they never thought to do emissions tests on horses either, or have a Model T checked for colic.] However, this all got figured out eventually (but it was after tube equipment was all but forgotten; its numerous disadvantages far outweighing any complications about measuring things). Now we can measure either one or both and get a very accurate idea of what it will sound like... but the mystique - and the idea that there's some magical difference that transcends the measurements - is far too well entrenched to die.

To get back to the question; according to the original definition of high-fidelity, the perfect tube preamp or amp would be indistinguishable from the perfect solid state equivalent - because neither one would have any sound of its own. HOWEVER, the original unavoidable defects of tube equipment have become wound up with the benefits in the collective unconscious mystique-mind of the tube loving public (I made that up; sounds cool doesn't it .

Suddenly, Now that tubes are "cool" in their own right, the characteristic colorations that make them sound different than solid state equipment have magically changed from flaws to being "desirable". (It's a bit like someone saying that riding a horse just wouldn't be the same without the slight smell of horseshit that comes with it.)

OK, I'll stop being a condescending smartass now, but my point is that tubes are "supposed" to sound like whatever people who like tubes want and expect them to sound like. A tube preamp or amplifier could be designed to sound exactly like its solid state equivalent, but then why would anybody bother to buy it? [OK, it would be very difficult to design a tube power amp with a high damping factor, but it could be done. Making a very low distortion tube preamp is relatively easy, and I'll bet you couldn't tell it from a good solid state preamp blindfolded.....]

The real distinction is between tubes that deliver a subtle hint of tube coloration (like fine wine) and those that pour it on so thick that you can barely make out the music (like Mad Dog). Personally, if any, I'd prefer the sort that add just a tinge of midrange warmth and shimmer, but I can't stand the kind that makes you feel like someone poured honey in your ears (and I won't even nag about whether that "airy and floating in space" imaging is accurate to the original, or if the amp is "making it up"; who cares if it sounds good?). Unfortunately, though, this means that there really isn't any definitive "right" or "wrong". Hey, some people actually like the taste of Mad Dog, and I personally do agree that cheap tequila makes a better Margarita than good tequila (because the good stuff gets lost under the sour mix). 

My underneath-it-all point is that the amount of "tube sound" you end up with IS almost entirely a design choice. Whether you prefer to think about whether it was "designed to sound that way" or "wasn't designed not to sound that way", it is mostly a matter of design. (I suppose there are some bad designers who get carried along with the flaws and don't have a choice... but I hope they're in the minority )

Jun 10, 2013 19:58:54 GMT -5 danr said:

Interesting topic Keith. I honestly don't "know" what a tube is suppose to sound like, so I am not sure my limited experience with tube gear is indicative or not. Here's all I know. I heard some sort of Sonic Frontiers tube amp driving B&W Silver Sigs. I would describe it as velvety & seductive, with great imaging that seemed to float in space. Again, I don't know if this was real tube sound or purposely engineered to sound that way.

I do know that at the right price, I would try some Emo tube gear for music, but there is no way I'll be selling my XPRs any time soon. In fact, they're gonna have to pry my XPRs from my cold dead hands.

For me, if your tube gear sounds like what I heard, I feel like Emo tube product will be a nice change of pace and a "hobby" for me.

[KeithL]

Thank you....

The whole idea of "tube rolling" is a relatively new thing. In the old days, tube numbers were considered to be "generic"; any 12AX7 was the same as any other. It was kind of like the soda brands: some manufacturers claimed theirs were better, and nobody much took them seriously. (Some variations like 12AX7A and 12AX7B had differences - but not necessarily ones that matter for audio applications.)

The fact is that tube numbers were intended to be standard. A 12AX7 is supposed to be the same as any other 12AX7. The differences between them are electrically trivial, and are mostly due to slight differences in electrical characteristics like the capacitances between electrodes and the emissivity of the cathode (think of the differences between brands of incandescent light bulbs). While there were always certain brands known for being slightly quieter, or slightly less prone to microphonics (going "boing" when you tap them), by and large all brands cost about the same and nobody especially thought one sounded better than another. Recently, however, a sort of cult has sprung up about certain specific brands and types of certain tubes - and things like the plate color and getter shape. I suppose it's no different than the idea that grapes grown on certain hills make better wine, but I find it sort of offensive (the idea that someone would pay $100 for a certain brand and plate shape of 12AX7 when, originally, it would have come out of the same $5 bin as all the rest, and the storekeeper would have given you whatever one was on top of the pile).

The reality is that some specific brands and variations of certain tubes will sound subtly different when used in certain equipment (that happens to be sensitive to the slight electrical variations between them). With other equipment they'll all sound about the same. The problem with the whole cult thing is that the associations are really sort of random; a tube that sounds one way in one piece of equipment may sound entirely different in another brand or model of equipment. Sure, try a dozen different tubes and see if they sound different; if they do, then use the one you like; but, unless you know that a particular variation will sound a certain way in the particular unit you have, you may as well try $5 ones as $500 ones - you are just as likely to find a lucky good match (and, at $5 each, you can try a lot more of them before going broke). DO NOT assume that the "Telefunken 1942 long grey plate 12AU7" that they're asking $200 for will sound wonderful in your headphone preamp because some reviewer thought it sounded "too wonderful for words" in his amp - which isn't even the same model. [Back when those NOS tubes were just plain New, they all cost $5, or maybe the one with the fancy writing was half a buck more.]

You should also know that some tubes are interchangeable and others are not.

One important thing *SPECIFICALLY TO DO WITH OUR VACUUM TUBE AMPLIFIER COMPANY PRODUCTS* is that some of our amps use tubes that are *NOT* interchangeable. For example, our little Black Magic (20 watts per channel) uses the MIL-SPEC version of the output tubes. Regular ones aren't rated for the same high operating voltage as the MIL-SPEC ones, and they may well burn out if you try to use them - which could damage the tubes or the amp. ALWAYS check with the instructions (or the manufacturer) to make sure which tubes it's OK to roll, and what with (there are also some tubes which may or may not be interchangeable in a certain unit depending on how the sockets are wired). 

As far as biasing the tubes, the best advice I can give is to follow the manufacturer's instructions (everybody handles bias differently). Most preamps, and even some power amps, are "self biased" or "auto-biased", which means that the bias takes care of itself. Others have specific procedures that you must follow to get the bias adjusted correctly (mostly output tubes in power amps). Likewise, in some equipment, certain tubes should be matched in terms of gain or bias requirements - but, again, each piece of equipment is different so the best advice I can give there is "read the directions" - or ask.

Incidentally, you won't get a shock if you turn the amp off first (and try to avoid touching the metal pins just in case); glass is an insulator

DO be careful about letting the tubes cool down first though - some of them get VERY hot.

The differences you can expect from rolling tubes really depend on the equipment. Typically you may hear tighter or less well controlled bass, more or less high end, clearer or less clear high end, and slight changes in overall frequency balance. You also may hear a difference in the amount of noise, and in the way the noise that is there sounds. As I said before, it depends on the equipment involved - with some equipment you may not hear much change at all; with other equipment the changes will be quite noticeable. (Usually the changes are more or less subtle.) Also note that tubes DO change sound as they age. Unlike with solid state equipment, where "burn in" is mostly a myth, tubes do change sound over the first fifty or a hundred hours of use, and then more gradually as they age.

Jun 12, 2013 14:04:07 GMT -5 paintedklown said:

Keith, this has been one of the most educational threads I have ever read in regards to audio, and certainly THE most educational thread I have ever read about tube gear.

Thank you for your input and contribution, it has been an invaluable "primer" on tube gear for me.

Like many other guys that are relatively new to the hobby, I have always seen tube gear as mysterious pieces of equipment reserved only for the ultra wealthy "golden eared" audiophile.

I will admit, that I am still very nervous with the idea of buying tube gear, and then attempting to swap the tubes myself (tube rolling), due to not wanting to fry anything, or get an electric shock!

However, along with this fear, also comes the biggest fascination that tube gear carries for me, the fun of tube rolling to find the sound that works best for you, your system, your room, your listening habits, etc.

I have heard that swapping tubes, in even modestly priced tube gear, can have a great effect on the sound.

Can you please dive into tube rolling a bit? Maybe talk about the process of swapping the tubes, properly biasing them, and what sort of results we can expect from this.

Thanks.

EDIT: I want to note here that I have never heard any tube audio gear in my life, not even so much as a tube buffer. I have heard (and own) a tube guitar amp (Epiphone Valve Jr.) and a tube based mic pre (ART Tube MP), both of which are ultra low cost pieces used for recording.

[monkumonku]

Jun 23, 2013 23:50:08 GMT -5 KeithL said:

Thank you....

The whole idea of "tube rolling" is a relatively new thing. In the old days, tube numbers were considered to be "generic"; any 12AX7 was the same as any other. It was kind of like the soda brands: some manufacturers claimed theirs were better, and nobody much took them seriously. (Some variations like 12AX7A and 12AX7B had differences - but not necessarily ones that matter for audio applications.)

The fact is that tube numbers were intended to be standard. A 12AX7 is supposed to be the same as any other 12AX7. The differences between them are electrically trivial, and are mostly due to slight differences in electrical characteristics like the capacitances between electrodes and the emissivity of the cathode (think of the differences between brands of incandescent light bulbs). While there were always certain brands known for being slightly quieter, or slightly less prone to microphonics (going "boing" when you tap them), by and large all brands cost about the same and nobody especially thought one sounded better than another. Recently, however, a sort of cult has sprung up about certain specific brands and types of certain tubes - and things like the plate color and getter shape. I suppose it's no different than the idea that grapes grown on certain hills make better wine, but I find it sort of offensive (the idea that someone would pay $100 for a certain brand and plate shape of 12AX7 when, originally, it would have come out of the same $5 bin as all the rest, and the storekeeper would have given you whatever one was on top of the pile).

The reality is that some specific brands and variations of certain tubes will sound subtly different when used in certain equipment (that happens to be sensitive to the slight electrical variations between them). With other equipment they'll all sound about the same. The problem with the whole cult thing is that the associations are really sort of random; a tube that sounds one way in one piece of equipment may sound entirely different in another brand or model of equipment. Sure, try a dozen different tubes and see if they sound different; if they do, then use the one you like; but, unless you know that a particular variation will sound a certain way in the particular unit you have, you may as well try $5 ones as $500 ones - you are just as likely to find a lucky good match (and, at $5 each, you can try a lot more of them before going broke). DO NOT assume that the "Telefunken 1942 long grey plate 12AU7" that they're asking $200 for will sound wonderful in your headphone preamp because some reviewer thought it sounded "too wonderful for words" in his amp - which isn't even the same model. [Back when those NOS tubes were just plain New, they all cost $5, or maybe the one with the fancy writing was half a buck more.]

You should also know that some tubes are interchangeable and others are not.

One important thing *SPECIFICALLY TO DO WITH OUR VACUUM TUBE AMPLIFIER COMPANY PRODUCTS* is that some of our amps use tubes that are *NOT* interchangeable. For example, our little Black Magic (20 watts per channel) uses the MIL-SPEC version of the output tubes. Regular ones aren't rated for the same high operating voltage as the MIL-SPEC ones, and they may well burn out if you try to use them - which could damage the tubes or the amp. ALWAYS check with the instructions (or the manufacturer) to make sure which tubes it's OK to roll, and what with (there are also some tubes which may or may not be interchangeable in a certain unit depending on how the sockets are wired). 

As far as biasing the tubes, the best advice I can give is to follow the manufacturer's instructions (everybody handles bias differently). Most preamps, and even some power amps, are "self biased" or "auto-biased", which means that the bias takes care of itself. Others have specific procedures that you must follow to get the bias adjusted correctly (mostly output tubes in power amps). Likewise, in some equipment, certain tubes should be matched in terms of gain or bias requirements - but, again, each piece of equipment is different so the best advice I can give there is "read the directions" - or ask.

Incidentally, you won't get a shock if you turn the amp off first (and try to avoid touching the metal pins just in case); glass is an insulator

DO be careful about letting the tubes cool down first though - some of them get VERY hot.

The differences you can expect from rolling tubes really depend on the equipment. Typically you may hear tighter or less well controlled bass, more or less high end, clearer or less clear high end, and slight changes in overall frequency balance. You also may hear a difference in the amount of noise, and in the way the noise that is there sounds. As I said before, it depends on the equipment involved - with some equipment you may not hear much change at all; with other equipment the changes will be quite noticeable. (Usually the changes are more or less subtle.) Also note that tubes DO change sound as they age. Unlike with solid state equipment, where "burn in" is mostly a myth, tubes do change sound over the first fifty or a hundred hours of use, and then more gradually as they age.

Thank you for your enlightening and informative posts! I think no matter what, human nature is to create differences and then compare/rank, even if no practical or even absolute differences exist. That was interesting what you wrote about how tubes were supposed to be all the same and you just took what was on top of the pile.

The analogy to grapes was a good one, too. It is true, some areas are acknowledged to be better for growing wine grapes than others, and also for particular kinds of grapes. Bordeaux for Cabernet Sauvignon and Merlot; Burgundy for Pinot Noir and Chardonnay, for example. You have to start with good grapes to make good wine. But once the grapes are harvested, then it depends on how they are treated. Some wines are so manipulated that they really do not reflect the region or "terroir" of where they originated but are fashioned to meet the tastes of the masses (for example, lots of oak, or a buttery character or this or that). A great deal depends on the skill of the winemaker. After that, it depends on how the bottle is treated and also, the tastes of the buyers because the same wine is not going to be perceived equally by everyone.

It's no different with audio gear. People are so into what DAC or what other part (capacitor, resistor, transformer, etc.) is used in a particular piece of gear. True, you have to have something of good quality to begin with as you can't make good stuff from junk, but so much of it depends on the engineer. That's why I get tired of reading posts from people who second-guess Emo about the parts that are used in their gear, or talk about how they can do some magical mod to it to make it 200% better. The parts are only part of the equation, and perhaps the minor part. The engineering/design is what matters.

But no matter what is produced, and no matter how similar item A is to item B, people will always find a way to differentiate A from B so that they can brag or pontificate about how one is better than the other.

[emovac]

I'm late to the thread, but this was very educational indeed. One thing I might add: if you going to get serious on the tube equipment, pick up a tester. Some tube dealers have been known to send out marginal tubes, especially in the NOS. They work, but not like they're new (or even close to it).

I had an AH! Njoe Tjoeb 4000 player that used tubes (great player until the power supply crapped out!) and a very nice custom tube buffer. Both used 6DJ8 class tubes, which can be interchanged with military spec 6922 or 7308. One great cheap substitute for the quasi-expensive 6DJ8, is the 7 volt 7DJ8. Works great at about half the price of the 6DJ8.

[reed]

What about OTL [output transformerless] tube amps? With OTLs you actually hear the tubes, not output transformers. I'm owned a couple of Atma-sphere OTL amps ... most organic sound I've ever heard. As previously mentioned, how about SET [single ended triode] amps? The sound of a 2A3 or a 6C33-C triode is spectacular.

[earwaxxer]

The cheapest way to find out what tubes sound like is to get a Bottlehead Quickie kit. Sure you have to built it, but for $99 its pretty awesome. I modded the crap out of mine and have several hundred invested in it, but the signature sound is the same. SET preamp. Battery powered. What I can describe as a 'real' sound to the music. It has the dynamics you expect from real sound. Along with the 'sizzle' etc. Hard to describe. All I can say is, when I take the tubes out the sound is still very 'good'. Just not very 'interesting'.

[garbulky]

I've read this entire thread - which was very informative but nobody (any tube users chime in please) has been able to tell me in detail what tube's sound like. I would like to know. And I understand they sound different, but any descriptions of a particular amp in a system would I think help people that would actually like to know. Maybe even a track referenced.
I heard a VTL tube amp, it was quite a beast - 120 watts and according to our resident B'zilla it sounded closer to solid state than most tubes do. I heard a reduction in bass but it had a smooth sound and there was a "gloss" to it. In treble it was subdued and laid back. A nice amp that was easy to listen to. I didn't have a chance to explore it much but that's what I got from a few minutes. Interestingly no kind of "bloom" was heard that I could attribute to it.

[hemster]

Sept 19, 2013 0:54:32 GMT -5 garbulky said:

I've read this entire thread - which was very informative but nobody (any tube users chime in please) has been able to tell me in detail what tube's sound like. I would like to know. And I understand they sound different, but any descriptions of a particular amp in a system would I think help people that would actually like to know. Maybe even a track referenced.
I heard a VTL tube amp, it was quite a beast - 120 watts and according to our resident B'zilla it sounded closer to solid state than most tubes do. I heard a reduction in bass but it had a smooth sound and there was a "gloss" to it. In treble it was subdued and laid back. A nice amp that was easy to listen to. I didn't have a chance to explore it much but that's what I got from a few minutes. Interestingly no kind of "bloom" was heard that I could attribute to it.

All you'll get is opinions - and they're like ars noses, we all have one!

Some tube amps sound very clean and mellow, others sound warm whereas some others sound very similar to solid state amps. Some preamps sound worse than solid state.  No amount of superlatives will suffice - you really need to listen to some tube gear for yourself.

Even if someone posts how they think their tube gear sounds in their system, it may very well sound different to you. 

I recently had the privilege to audition an old Conrad Johnson PV-15 tube preamp with rolled 6C4 tubes (from the 1960s!) and I thought it sounded very nice.. with vocals and most rock. However when playing some Spirogyra it sounded worse to me than a  Marantz SC-7S1 solid state preamp!

[KeithL]

Let me start by saying that I've never heard a "serious" OTL amplifier (I've heard a few "little experimental ones"), so a lot of this is based on engineering theory. Basically, tubes themselves have a very wide frequency response (often wider than transistors), and a rather high operating impedance (which makes them NOT well matched to modern low impedance dynamic speakers). This is why all OTL designs need rows and rows of tubes (they're all in parallel to lower the output impedance; a job normally accomplished by the output transformer in other designs). Even with dozens of tubes in parallel, the output impedance will still be quite high, which means you'll have a low (poor) damping factor; the only way to fix (assuming you want to) that will be to add lots of gain and lots of feedback. Other than this, the main differences between tube and solid state amps are mostly due to the drawbacks of using output transformers, which an OTL design does NOT have.

Personally, I'm not sure what you mean by "organic". From Atma-Sphere's spec pages, their amps seem to have VERY low damping factors. The ones I looked at had damping factors of 1 and 4 respectively; halve those values for a 4 ohm speaker. Most modern solid state designs have damping factors in the high hundreds - ours are all rated 500 or higher. Damping factor (pretty much the inverse of output impedance) determines how well the amplifier controls the speaker and avoids interacting with it. Most modern speakers are designed to work best with amplifiers with high damping factors. This means that, with the Atma-Sphere amps, you will end up with a frequency response with a typical speaker that varies WILDLY depending on the impedance of the speaker (and most speakers have impedances that themselves vary pretty wildly). I emphasized that word because we're talking about frequency response variations in the high dB's or even tens of dB's over the audible frequency range. In other words, these amplifiers will interact heavily with speakers, rooms, speaker wires, and anything else. Rather than controlling the sound, the amplifier will sound very different with different speakers (and specific speakers will sound very different with it than with other amplifiers). If that's what's meant by "organic" - where an organic horse goes where it wants to, but an "inorganic" car goes where you tell it to, then maybe we have an understanding. Other than that (to me) serious shortcoming, I would expect them to sound very clean and neutral. (However, remember that, since they will interact with every speaker, and interact differently with every speaker, you won't get to hear that neutrality in other than a limited context.)

In theory there's no reason why you couldn't add lots of gain, and lots of feedback, to an OTL design - which would drastically increase its damping factor. I personally suspect that, if you did that, it would end up sounding exactly like any good solid state design (which I would see as an improvement). However, assuming that there was no difference in sound between them, then there would be nothing to justify the much higher cost of buying (or building) and operating the OTL amp.

--------------

*** I'M GOING TO RECOMMEND AN INTERESTING EXPERIMENT HERE ***

1) Start with a good solid state amp (any of ours will do fine).

2) Buy a pair of good quality, high powered, noninductive (this is important), power resistors of value somewhere around 2.0 ohms. (With 8 ohm speakers, 1 ohm resistors will give you a damping factor of about 8, and 2 ohm resistors will give you a damping factor of about 4; with 4 ohm speakers, 1 ohm resistors will give you a damping factor of about 4, and 2 ohm resistors will give you a damping factor of about 2). You probably want resistors rated for at least ten watts each, or you need to play things very quietly; the resistor will be "burning off" about 1/4 of the power coming out of your amp as heat. Even big ones will get VERY HOT, so sit them on something that doesn't mind heat, or mount them on heat sinks. (A solid state amplifier with a 2 ohm resistor in series will be electrically equivalent to the Atma-Sphere model with the 2 ohm output impedance.)

3) After turning off the power; connect one of those resistors in series with each speaker.

4) Check your wiring carefully, then turn everything back on and listen to some music.

My guess is that you hear will end up being a reasonable facsimile of "that organic sound".

-----------

I have heard several SET amplifiers (I honestly don't remember which tubes they used, or even which amps they were.)
I'm sorry, but what I heard from them was simply a somewhat muffled high end and a lot of distortion, which rose to even worse levels when you turned them up.
The distortion was mostly second harmonic and, rather than sounding grating, it made everything played through them sound "smoothed over" or, as I like to describe it, "like I'm listening with my head in a bucket of Karo syrup".
And, yes, it did "sort of sound nice" with certain music.

Historically, SET amplifiers were the first tube amplifiers.
Tube amplifier designers then spent a lot of time and effort to avoid or eliminate their many shortcomings and audible deficiencies.
(First push-pull, then push-pull Class A/B, then  Williamson ultralinear - all served to improve linearity and reduce distortion.)
These modern design improvements pretty successfully eliminated most of those shortcomings and enabled tubes to produce quite accurate and undistorted audio output.
I personally see little reason to bring back those shortcomings and "re-label" them as virtues

If I'm going to listen to ANY tube amp, it's going to be one which at least makes a "nod" to accuracy and transparency, and not one that deliberately introduces huge changes.

NOTE 1: Obviously, that's just my OPINION, and you are certainly entitled to yours.

NOTE 2: What I said applies to SET POWER AMPS ; when used in a PREAMP, triodes, operated in single ended Class A operating mode (which they usually are), are capable of quite good performance (and excellent sound).

NOTE 3: For reference, I consider myself to be a "purist"; to me, there is precisely ONE correct rendition of a recording, and any variation on that, regardless of how "spectacular" or "pleasing" it may be, is just wrong; and, the more different it is, the more wrong it is. (I'm the kind of guy who color calibrates his monitors and his TV instead of  adjusting the colors "so they look good to me"; and my living room is painted optically neutral grey so as to avoid interfering with the colors on the TV and the monitor.)

But then, beer is just dirty water with rotten plants in it, and wine is just sour grape juice; it IS all a matter of taste.

Also, to get back on subject, by tube amp standards our Carver amps are of the "more modern, cleaner, lower distortion" type. The Carver amps all sound, to me, like what tubes should sound like; you can tell in an instant that they have that tube smoothness and "sweetness" (I hate that word, but you get the idea), but they DON'T sound heavy or "goopy" or "overly mushy" like some tube amps - especially many SET amps - do.

Our Carver amps also actually deliver excellent technical performance - again unlike many tube amps (check out our numbers).

If you actually want an amp with a high end that is completely crushed, and piles of distortion, and totally flubbery bass, then you probably won't like ours.

If you want some tube sound, but in a clean sounding amp - with scads of power, then you WILL like them.

Aug 1, 2013 13:20:02 GMT -5 reed said:

What about OTL [output transformerless] tube amps? With OTLs you actually hear the tubes, not output transformers. I'm owned a couple of Atma-sphere OTL amps ... most organic sound I've ever heard. As previously mentioned, how about SET [single ended triode] amps? The sound of a 2A3 or a 6C33-C triode is spectacular.

[leonski]

2 things I'd like to add.

First:  Macintosh does not use transformers.  They use AUTOFORMERS which are only a single winding, not a double winding device like a transformer.   Such output devices can be used for BOTH tube and SS to great effect.   This may be part of the 'mac sound'.

Secondly, I see a lot of talk about damping factor and NONE about the speaker.  Well, speakers have damping, too.  It is generally called 'Q'.  Or perhaps Qts.     I'm not sure how to encapsulate the relationship, but some speakers simply do NOT work well with Tubes, needing an amp with the ability to drive a wide impedance swing without interaction.  

I've heard a few Very Fine tube systems.  Some used FRSD speakers....Full Range Single Driver...like Lowthar or Fostex in a specialized enclosure like a transmission line.  They are also very flat impedance, generally.  And prettty high sensitivity, so that you can make a LOT of sound with maybe 10 watts or so per side.  

Some speaker with large impedance swings AND high reactance simply work best with transistors....and not all of them are created equal.  Even some highly regarded amps which work well into a resistor, just making heat, fail miserably when you start adding capacitors and inductors to the mix.   Some B&W speakers fall into this category and wll not work well with tubes.  

have fun::

[Chuck Elliot]

Oct 13, 2013 0:18:35 GMT -5 leonski said:

2 things I'd like to add.

First:  Macintosh does not use transformers.  They use AUTOFORMERS which are only a single winding, not a double winding device like a transformer.   Such output devices can be used for BOTH tube and SS to great effect.   This may be part of the 'mac sound'.

Secondly, I see a lot of talk about damping factor and NONE about the speaker.  Well, speakers have damping, too.  It is generally called 'Q'.  Or perhaps Qts.     I'm not sure how to encapsulate the relationship, but some speakers simply do NOT work well with Tubes, needing an amp with the ability to drive a wide impedance swing without interaction.  

I've heard a few Very Fine tube systems.  Some used FRSD speakers....Full Range Single Driver...like Lowthar or Fostex in a specialized enclosure like a transmission line.  They are also very flat impedance, generally.  And prettty high sensitivity, so that you can make a LOT of sound with maybe 10 watts or so per side.  

Some speaker with large impedance swings AND high reactance simply work best with transistors....and not all of them are created equal.  Even some highly regarded amps which work well into a resistor, just making heat, fail miserably when you start adding capacitors and inductors to the mix.   Some B&W speakers fall into this category and wll not work well with tubes.  

have fun::

You may know more than me, but I always thought that Macs used autoformers only on SS equipment. There purpose was to provide a better impedance match between the SS output stage and the speaker.

Tube amps accomplish the same thing with different output taps on the secondary of the transformer.

If you look at the schematic of the classic MC275 you will see a push-pull configuration along with special windings for cathode feedback and a separate winding for the screen grids. But, it is basically a push-pull transformer.

Schematic Link to MC275

[pedrocols]

Soooo what it is the purpose of this thread? Is it to gear someone away from buying a tube amp? If this is not the purpose you guys are doing an excellent job at disguising it...Just sayin'...

[leonski]

Right you are.....the SS stuff gets the autoformers...and apparently not all of it, at that.
This is a real can-o-worms.   Some say autoformers hurt sound....others disagree.....I haven't heard enough of either to 'conclude'.
The 'low output impedance' school of SS stuff I'd call Voltage Source...while adding resistance would tend to simulate Current Source.
Most of todays speakers like the low impedance SS outputs.  
One of Bob Carver's amps had 2 sets of speaker outputs....one of which had some additional resistance in series which gave you the 
choice.  I think that was in the Sunfire line, which still has a following.  Not sure of model#.

The 275?  Doesnt' that design go WAY back?   I just looked at the Stereophile test and they say the first 275 was 1961.   And yes, the
transformer is way more than in/out with additional feedback windings.....way over my pay grade, in detail.   A quick look at the Stereophile
article also discloses that Macintosh 'invented' some very basic circuits, still in common use today.

And since this amp, and many others continue to sell,  I've got to conclude they are doing something right.  The tube systems I've heard at 
shows were good with amps by Manley,  Jolida, ARC and a few others.    Few tube amps except in the very upper reaches of power output are OK for
my panel speakers, but I can HEAR the attraction and smoothness of a good tube system.  

40 years ago, if I'd gone another direction, maybe today I'd be listening to high sensitivity speakers with an old Dynaco Stereo 70......
If I can fit panels into my house, I guess I've got room for a pair of La Scallas.......


www.atma-sphere.com/Resources/Our_Basic_Circuits.php


Link to article on tube technology from a company which really makes high-end amps....

[Chuck Elliot]

Oct 13, 2013 12:18:50 GMT -5 leonski said:

The 275?  Doesnt' that design go WAY back?   I just looked at the Stereophile test and they say the first 275 was 1961.

The design goes way back, but this unit is still in production after 50+ years. One of the finest amps ever designed. I'd have one in a heartbeat if I could afford it!

[leonski]

The 275 has without doubt reached 'classic' status.   Not suitable for my panels, however, so I'm not even looking.

I wonder how 'true' the current model is to the original schematic......besides some obvious stuff like upgrades to caps and thin film resistors?

I hope and wonder if you can even get ceramic tube sockets? 

And good iron is $$$$ (maybe $$$$$) and than you have to pay to SHIP it!  

The good news....is that if Mac BUILT it, they'll FIX it......

[bigus]

In a nutshell, I tend to think of Solid State versus Tubes as cd's versus vinyl.
Solid state gives you that crunchy high end straight forward sound.(cd's)
Tubes give you that overall dynamic sound.(vinyl)
I personally love the tube sound.

As an added plus, I love the fact you can get a different sound with different tubes.....
I'm also putting an end to this myth about panels and tube amps. My amp at 42w drives my Martin Logan Vistas just fine.

[bigus]

Sept 19, 2013 1:44:58 GMT -5 hemster said:

Sept 19, 2013 0:54:32 GMT -5 garbulky said:

I've read this entire thread - which was very informative but nobody (any tube users chime in please) has been able to tell me in detail what tube's sound like. I would like to know. And I understand they sound different, but any descriptions of a particular amp in a system would I think help people that would actually like to know. Maybe even a track referenced.
I heard a VTL tube amp, it was quite a beast - 120 watts and according to our resident B'zilla it sounded closer to solid state than most tubes do. I heard a reduction in bass but it had a smooth sound and there was a "gloss" to it. In treble it was subdued and laid back. A nice amp that was easy to listen to. I didn't have a chance to explore it much but that's what I got from a few minutes. Interestingly no kind of "bloom" was heard that I could attribute to it.

All you'll get is opinions - and they're like ars noses, we all have one!

Some tube amps sound very clean and mellow, others sound warm whereas some others sound very similar to solid state amps. Some preamps sound worse than solid state.  No amount of superlatives will suffice - you really need to listen to some tube gear for yourself.

Even if someone posts how they think their tube gear sounds in their system, it may very well sound different to you. 

I recently had the privilege to audition an old Conrad Johnson PV-15 tube preamp with rolled 6C4 tubes (from the 1960s!) and I thought it sounded very nice.. with vocals and most rock. However when playing some Spirogyra it sounded worse to me than a  Marantz SC-7S1 solid state preamp!

How true, It really is a matter of personal taste. The best way to find out is to demo the gear. Do not trust what others say... Trust your own ears!
Simple as that......

[leonski]

Magnepan HQ in White Bear Lake uses a small amp in the lobby.  I think it is a tube amp, but am not sure.
Sure, Maggies ARE tube friendly....and depending on your listening habits may actually work. The 2 MAIN things to consider are the size of the room in CUBIC feet and the desired loudness.

Electrically, they are a good match with tubes, as they are with any good SS amp.   The trouble is tubes get VERY expensive at the power level needed to make 85db /watt/meter speakers play loudly in a large room.   I don't know how sensitive any of the ML speakers are.

The advantage Maggies have over say.....ML electrostats.....is the reasonably flat impedance 'curve' and they are not a bigtime reactive load.  Electrostats I've seen data on can become very reactive in the high frequencies which puts an additional strain on the amp.   That is an electrical advantage, and somebody can reasonably prefer the SOUND of one to the other and end up needing an amp to match.

Can you make ML panels work with 40 watts per?  Sure, why not?  The ONLY glitch, for me, anyway, it that at higher levels you are almost doubtless clipping the amp.  Even if only for short times.   I don't know the size of your room or listening habits......which matter a LOT.  

And for the guy with 40 watts into his MLs?  I'd love to try the 1L with 35 'A' watts before a graceful transition to AB.  You may notice you listen louder or not, but you may ALSO notice greater clarity and dynamics.  Just a guess.....   Above all?  have fun.

[leonski]

I just looked at the specs for the ML Vista.
THEY call it a 4 ohm speaker.  so far, so good.  Trouble in paradise happens at the (real extreme) high frequency end where the panel drops to 1.2ohms at 20khz.  
The net effect is some kind of interaction with the amp......which may have 1 ohm or MORE output impedance at those frequencies.    I guess that's why 'word is' you need
to be sort of careful with amps for 'stats.  And why 'better' SS may be indicated......

[dmusoke]

Oct 13, 2013 12:13:35 GMT -5 pedrocols said:

Soooo what it is the purpose of this thread? Is it to gear someone away from buying a tube amp? If this is not the purpose you guys are doing an excellent job at disguising it...Just sayin'...

This is the puzzling thing about this thread. It seems Keith has spent lots of ink disparaging tube amplifiers in detail, highlighting all their faults and disadvantages that tube lovers often called positive attributes. Then in a surprising reversal towards the end of last post, he says something nice (I think) about the carver tube amps.

I'm puzzled since I was planning on getting the VTA305M in cherry but with the kind of press Keith has given to tube amps in general, I'm seriously reconsidering my purchase. Its clear he doesn't like them and prefers SS amplifiers and that's obviously fine. I wish he was neutral about them but I understand one has to be true to oneself.


- David