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In Reply to: Re: Which PP pentode amps sound like solid state ? posted by Kurt Strain on July 26, 2002 at 21:14:18:
Hi Kurt-I find it difficult to believe that you would endorse a gratuitous comment about pentodes sounding like solid state- if the majority of el34/84/KTXX/6550 etc amps commercially made prior to and since SS amps were introduced sounds like SS to you- then I suggest you are in the minority, in fact it's precisely because they do sound different that they still enjoy enormous and growing poularity. (If you really think Oscillatus' point was "very" reasonable"- perhaps you can answer which current production PP pentode sounds like a SS amp ?)
If you want to undertake a statistical analysis from which to derive an opinion- perhaps you could ask for a poll as to whether pp pentodes sound like SS amps- if you could stand the howls of laughter.
If you insist that generalizations are helpful- then a generalization that a component should be considered on its own merit is more helpful than a completely unsupported blanket statement about amplifier design.
You yourself have taken many innovative steps in amplifer design- and successfully integrated many different circuit elements in a search for better performance. If you believed in generalizations then why not leave well enough alone ?- Would the statement "SS components have no place in tube amplifier designs and can only detract from the performance of the amplifier" be a reasonable generalization ? Of course you don't really believe in generalizations- you try things out for yourself and make your own mind up- your many posts on CCS's etc and your 45 pp amp are a testament to your disregard for commonly held beliefs.
And you know yourself that a pp amp if properly implemented can yield a musical result on par with any other design.
This hobby is about the details, wouldn't you agree ?
Follow Ups:
> > PP will give you more power, and better bass.I agree, for tubes at least with zero NFB, without even trying hard. As a result, you get better bass control since the power supply modulations are 100 times less on average than a similarly built SE.
> > SET will give you (IMO) a _much_ more musical sound, but lower power, hence requiring more efficient speakers. < <
That's your opinion, and I agree. For it to show its musical qualities, the prerequisite is a suitable speaker to match. A very natural sound to me. For more detail and bass tightness, trying to hope for PP bass, more PS circuitry and design is required, something that can also be applied to the PP amp and then the PP amp wins again in bass.
> > PP sounds somewhere in between solid state and SET to me.
I agree since I know you mean PP tube here. SS amps are almost all PP designs, except for a few, like Pass designs. Tube PP will diminish the even order distortion and not cover the odd ones well. PP is a topology that does this, no matter the device, so expect some degree of residual PP sonic signature in all PP amps. My PP45 amp is great for bass performance and tone, but is bettered by all my SET amps for tone. Therefore, I find PP tube amps similar to SS amps and SET amps in that they share much of each of those characteristics, and hence lies somewhere in between in terms of sound. Now this PP45 will easily be liked by many as the ultimate compromise, just plain best amp. But if you gotta have all the SET tone you can get, get a SET. If you gotta have all the bass control you can get, get a SS PP amp. The PP triode amp is in between.
> PP triodes are better than PP pentodes however.That's your opinion, by using the term "better", and I generally agree. The best PP pentodes are still awesome, IMO, and do better than triodes sometimes. I love the KT88 PP AirTight ATM-2, for example, as one of the best high power amps I could get. For low power, I'm inclined to look for small triodes and small high quality transformers to get more of everything.
> > A big PP pentode amp with negative feedback starts to sound so much like SS amps that I wouldn't bother. :-) < <
Some common commercially successful amps are that way, such as Audio Research. They start overlapping into some good MOSFET and bipolar designs. I've heard that the bigger the pentode amp, the more SS sterility they get unless much is worked on, and I have nothing that tells me it would do otherwise. Then the amps get so expensive that a lot of voicing tricks are justified and explored, but big paralleling makes them sound more SS to me. Same is true of massively paralleled triode amps in many cases, like OTLs, IMO. Less is true about the Music Reference RM-9 I had, since it was pretty silky with good EL-34's, but not the tone nor detail of smaller DHT triode PP, and nothing like a SET, even a EL-34 SET using the same tubes, as I once had. More SS sounding for sure, but not extremely so in that case. PP pentodes are a step toward SS sound compared to triode PP, almost always as my experiments tell me. More massively paralleled pentodes get worse, and even in SS, more massively paralleling transistors makes it get generally more bleached out, "SS-like". The better transistor amps for your money will go to the low powered amps, in all likelihood, using no paralleling.
Physics are physics, but evaluation of the physics demands an opinion about that. There are many processes for making IC's for example, because there's usually a best one for the application in mind.
maybe I'm not insane after all :-)I just wanted to say, I am not talking out of ignorance. I have owned, repaired, designed and built hifi tube amps. I have worked with tubes since I was a teenager 25 years ago. My generalisations were reporting the way I have experienced things.
thanks for your response Kurt,I took issue with the statement about bass for many reasons, but probably the least of which is hum modulating the signal via the plate or grid supply (if that is what you are referring to)- in a well designed supply, this should not be an issue with a SE amplifier (esp parafeed). Similarly, there are many PP amplifiers built with less than ideal transformers/ matched tubes.
There are many SE amps which give up nothing to SS or tube PP amps with regard to bass response/detail/impact/clarity/weight- with the right transformers and speakers of course. And that's one reason not to generalize about amplifiers in isolation to the task you give them- and generalizing without mentioning the transformers used is to ignore a vital element in an amplifier's performance.
Which leads me to my final point for the interests of not dragging this into a SS vs Tubes debate (ie that there is something dislikeable with "the SS sound"- you describe it as sterile, but I have never read a satifactory definition of "tube" sound, and the archives are full of such discussions without any consensus beyond personal preference)- that these generalizations are only valid IF you accept the "all else being equal" premise.
"All else being equal" is a false premise for amplifier topology and triode/ pentode /( and esp. SS comparisons). Clearly, all else cannot be equal- from the design to the tube to the transformer to the driver to the splitter etc.- far too many variables to categorically state that all or most X type amplifers must have a particular sound (perhaps even worse are comparisons based on price,such as a $1K SET compared to $1K pp, but this is probably a substantial consideration when people shop for a new amplifier).
If the premise for "All else being equal" was to be summarized as " no compromise" (ie one designer/mfgr's no compromise PP compared to another's no compromise SE), then you are talking about the exceptional amplifers- tube or SS- which provide the highest levels of listening performance.
Which means you get back to talking about real amplifiers- not how a theory sounds, but as I said previously, about discussing a component based on its merit.
Sure- there are some generalizations which are helpful- such as listening for oneself is the only way to discover one's preferences, or to always consider an amplifier's performance with regard to the speaker it is driving, and the quality of an amplifier's components and construction play a large part in the performance of that amplifier.
Perhaps we can agree on that much ?regards,
You're looking at the system approach, and look toward what is showing up in state-of-the-art examples. That's what I also do, sometimes. But then that's not an "in general" statement anymore about what on average you can expect to get for your money. That's a "where has this approach ultimately taken us, no-holds-barred" statement. Even still, I think the ultimates in any of those approaches lead to very similar conclusions about how they sound, but not what is preferred. SETs still need the right speaker which ultimately provides a list of advantages and disadvantages when properly paired. OTLs still need their right speaker and have a different set of advantages/disadvantages. PP pentodes and solid state comes in again with their best solutions for some speakers which again has other sets of advantages/disadvatages. And the combinations are nearly infinite, but there is a pattern many have noticed. What is the best sound now possible is the preference that most disagree on, but how they sound is more agreed on even though it's subjective. It's like taste preference for Coke or Pepsi on the ultimate cola, but if polled you can see there's a pattern that people perceive Pepsi as sweeter, or is it the other way around? :-)No approach has removed their amp from the chain as being unheard. Some are very close, and even if there is a perfect "blameless" amp, the rest of the system is not, and why not help fix their problems with an amp that touches it up the way we think makes it better? It's even possible to reduce system distortion by adding inverse distortion effects from the amp.
I'm still working on why do PP amps in general flatten the soundstage and widen it compared to SET amps. Happens all the time. But then direct radiators image deeper than horns, and so the high power PP amps with DR speakers can ultimately have a bigger performance envelope there. If done carefully, DR speakers with SETs image the furthest in depth, but not width. Then you re-direct the speakers for more width, but then is the soundstage envelope any bigger? But I think I shall relieve myself of this burden on my brain for now. This is where you come in and say "these methods are different, but similar enough that it just doesn't matter which way you go." True, but I have seen generalizations work out and.....
because I have a PP 6L6 amp, and damn, I am really pissed to hear from an expert that it actually sounds like SS !! I've been wrong all these years!! Many thanks to Oscillatus for setting me right. All these years I didn't realize that the wonderful, mellow detailed sound I've been hearing could actually be obtained from SS! And here I've been, collecting tubes at great cost, tweaking the amps, listening happily - and I was wrong! Well, you learn something every day.Now, I have a SET amp also - 45 tubes - and I love it, but I still prefer the PP amp! Should I go SS there also?
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