845 SET can drive some speakers not often associated with SET, power supplies with these quite substantial, around 900V plate voltage with these. With the right speakers a nice 300B amp running top tier 300B tube like the new Western Electric is sublime, never heard any pp that can replicate harmonic structure of these.
@sns A typical 845 SET makes about 20 Watts at full power, which will be about 10% distortion. By contrast a Dynaco ST35 can make 17 Watts with about 1% distortion. At any power level, the Dynaco will outperform the 845 not just in terms of distortion by also bandwidth- it will go lower and go higher.
I get that the raw THD does not tell the whole story.
So then it comes down to that seductive bit. I've found that distortion obscures detail, and having run an LP mastering operation as well as a recording studio, I have a number of LPs that I know exactly how they are to sound. That's the sticky bit; since I know how they are supposed to sound I've yet to find any SET at any price (including 845 based amps) that can do as well as a PP amp of only 15-20 Watts (usually EL84 based, FWIW). That is, if being faithful to the actual recording/signal is important while being able to present it in a relaxed way with authority that allows one to listen all day (or night).
I'm still left with the million dollar question, being,
" what makes a great amp and what makes a good amp? "
Is there such a choice available?
@pindac Yes, there is.
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I've heard for extended periods PP Amp's and Set Amp's as well as OTL Amp's.
Some from Brands that have managed to aquire exposure around the Globe, some not so well recognised as a name.
Some as a build using a Kit Design as the fundamental.
Some being quite heavily modified in relation to their basic design.
Some from a recent production period and others extending back to being undeniably a die for Vintage Model
I'm still left with the million dollar question, being,
" what makes a great amp and what makes a good amp? "
Is there such a choice available?
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On one hand I'm surprised by lack of support for SET here, on the other, not. The speaker is a critical part of the equation, flea power SET's, 300B and down really only fit for horns, single drivers, perhaps dual driver with minimalist crossovers, 845 and some other relatively high power transmitter tubes can run some speakers in 95db efficiency realm but I doubt many have owned these amps. PP have the ability to run large number of speakers SET really not fit for, so easy to understand the preference.
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This is a loaded question to me. I wonder what the responses would be if it was flipped to "Would you rather own a Great SET amp or Good Push Pull amp".
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Per bass issues with SET. Over decades of using both pp and SET I've found bass performance to be highly variable. I've probably had more issues with overly resonant, one note bass with pp vs set. What I've discovered over the long term is speaker and amp has to be a sympathetic match, the right tool for the job. One needs both high efficient and impedance friendly speakers for SET, also need amp with quality power supply, meaning some reserve capacity, finally quality transformers. 845 SET can drive some speakers not often associated with SET, power supplies with these quite substantial, around 900V plate voltage with these. With the right speakers a nice 300B amp running top tier 300B tube like the new Western Electric is sublime, never heard any pp that can replicate harmonic structure of these.
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As I said above, I don't have a clear sense of which is inherently better. I own very low-powered versions of SET and pushpull amps, but they are not comparable in design so I cannot draw any conclusion. But, over the years I have made some general observations. First, the very best sounding triode tubes are all quite low in output power (e.g., 45 and 2a3), and using them in SET topology means one must have highly efficient speakers or use them only to deliver modest listening levels. By efficient, I mean something approaching or above 100 db/w with 8 ohm or higher nominal impedance). Second, as Atmasphere noted above, they need an air-gapped output transformer to deal with saturation and one can only partially offset the loss of inductance by making the core massive. This means the output transformer is usually very expensive; cheap SET amps with puny transformers sound whimpy to me.
But, with proper speakers and a quality build, SET amps deliver a very "pure" sound that can be quite seductive. While bass tends to be not as tight and punchy as that of a good pushpull amp, the bass has its own positive attributes--it has natural and subtle differences of tone while pushpull bass is much tighter and punchy at the cost of sounding a touch "mechanical" (sameness). I have no disagreement with someone finding the balance of attributes favoring SET amps. But, I do disagree with the "magic" qualities ascribed to SET amps; you can hear the same qualities in pushpull amps, perhaps not in the same balance, but there is nothing exclusive to SET sound.
We have not even considered OTL amps in this discussion. A well implemented OTL amp can have explosive dynamics and sound very vivid without being harsh or unpleasant as one might expect with that kind of dynamics.
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I think that it might depend on what you most find glorious in your listening. I have owned several good to great PP amps; for many years I used the renaissance VAC 70/70, 2 parallel 300Bs per phase per side. This amp did everything superbly well. Eventually it needed TLC and yet more tubes (and a matched quad of good 300Bs is a bit painful) and I switched to the (SS) Pass XA 25.
The lure of tubes got me again and I have built a couple of Elekit SET amps.
The performance of the TU-8900 (with upgraded caps and OPTs) is utterly glorious, most of the time. Its rendering of subtle details, at low volumes especially, makes one stop breathing so as not to interfere! It does this in a way unmatched by the VAC amp.
The one technical advantage of a single ended design (or an SS amp) is that there are no OPT zero crossings. Even in full class A, where the tubes are biased out of cut off during a complete cycle, the OPT is still at zero (given perfect channel matching) at signal zero.
I listen to a lot of chamber and choral liturgical music where the ability to reproduce ppp passages, and the decay of notes, superbly is a vital factor in my enjoyment. The performance of full ffff orchestral tuttis is not on a par with a great pp amp, but note that my Rockport Atria speakers are rated at 87dB at 2.83v rms.
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I built SE amps for years--2A3, 300B, 845--because I could. ;-) No feedback, no 'scope needed, just crasm in as many expensive parts as you could and eventually you could get pretty good sound. But having developed the skills to build a really good PP amp, I'll never go back. I'm with Ralph--a good 20-35 wpc PP amp can be a real joy. I've settled into the Williamson design because if its tonal veracity. For my money a moderately-powered Williamson gives you everything an SE amp offers plus a lot more in terms of bandwidth, speaker control and low distortion.
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Ralph,
I also wanted to thank your for your always insightful and educational expertise. Your input on this topic is invaluable, and has me much closer to the direction to go in. Much appreciated, as always.
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Wonderful contribution from Ralph as normal; thank you. Will just offer that PP ultralinear can be awesome. With TV tubes (that were not available when vintage amps were built and that no current tube amp builders specify...wrongly IMO) that swing high voltage as drivers, big inducors to smooth current and eliminate the need for signal capacitance, KT77s which are specified for high voltage (can handle up to 800 volt plate voltage) and are optimized for 43% OT tap and custom specified high voltage OTs configured for 43% tap, 4xKT77 140 watt monoblocks result. These 75 lb. beasts absolutely manhandle the Northcreek crossovered B&W Matrix 801 S2 12 inch woofers while also delivering delicacy, nuance and accuracy.
For the xenolith family, this is the right answer for our audio amplification.
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@OP Unless its a 100 dB/w/M speaker, then PP.
Every SE amp I've heard just collapses when trying to drive "normal" speakers at anything above "polite" volume levels.
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we have sold many different tube amplifiers
over the years most single ended amplifiers are too low in power and are too load dependent to be the amplifier of choice.
we had the unison s6 a parallel set which was good sounding but didn’t have the punch of the push pull designs.
over 20 years there have been a few stand outs
Master sound compact 845
Line Magnetic 845
Synthesis a100
Zesto bia200
Dave and Troy
Audio intellect NJ
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I have a 60w Frenzel PP that can take kt88’s, 676, and k120s… I am also one of the audiophools on the Decware waiting list for a Sarah 300b SET…. Depending on if I liked the Sarah more, I was considering selling the Frenzel to help pay for it. Now, I am wondering if I should bi-amp the Frenzel to the bass and let the Sarah handle the mids and highs… hmmmmm….
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I have abias against non-linear amps and due to their topology single ended amps(tube and solid state) are non linear. They amplify the top half of their signal differently than the bottom half. If you like the sound that's fine but that's poor fidelity. As A friend once said it's - Color me perfect.
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I have loved SETS for a long time, but I simply cannot afford a "great SET". And, being retired, never will.
@nightfall I’ve yet to hear an SET at any price that could beat a good quality PP tube amplifier. I’ve been investigating SETs since the first started to show up in the early 1990s so I’ve heard quite a lot of them.
If your speakers can make bass and if you don’t want to bi-amplfy then you will want to pay attention to this next fact:
Most SETs have troubles with bass, since the output transformer has to have a saw cut in its core to reduce DC saturation which otherwise causes a lot of distortion. Sorry if this sounds a bit technical.
The output transformer works due to something called inductance.
Inductance is what allows a long bit of wire that might have only 200 Ohms resistance to have an impedance of 3000 to 9000 Ohms when wound inside an output transformer. Power tubes used in SETs need that kind of load to work properly. That saw cut I mentioned vastly reduces inductance at low frequencies, which in turn means the load on the tube is much lower too. This is bad for the power tube and causes it to make a lot more distortion while also running hotter.
As a result there’s no SET made that can make full power at 20Hz. But there are a good number of PP tube amps that can; there’s no need for that pesky saw cut in a PP output transformer.
So let’s imagine that you were considering a powerful 20 Watt SET (that’s a lot of power for an SET BTW). Most SETs, because they don’t use feedback have only about 20-25% usable power before distortion causes them to sound ’dynamic’; IOW above that power level distortion masquerades as dynamics. That is why you read about how ’dynamic’ SETs are but its really just distortion.
PP tube amps OTOH have about 90-95% usable power. So in the case of the 20 Watt SET, it would have about 5 Watts of clean power where a 20 Watt PP tube amp would have 18 Watts or so.
A PP tube amp of that power is usually a lot less expensive than an SET of that power, probably several times. If the PP tube amp is properly designed and built, by most audiophile metrics it will ’sound’ better than any SET of the same power and likely a lot of SETs with considerably less power.
But for PP tube amps 20 Watts is about the golden point where you can get both really wide bandwidth and decently low distortion. A good example of such an amplifier is the Dynaco ST35; if you find one in good condition (there are vintage ones and new ones) you’ll find them causing SETs pain and shame on speakers like the ones you mentioned with no worries.
They are rare but there are PP tube amps of even less power- like 5 Watts. Any SET of that power level will fall flat on its face in comparison, if musicality and neutrality (so it can play any kind of music easily) is your goal.
Now if you’re stuck on an SET there is hope. If you limit the bass it sees (like 200Hz and above) that will get rid of most of the problems with the bass. You’ll have to bi-amplify of course. FWIW the most successful systems I’ve heard that use SETs take this approach.
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Push Pull in Ultralinear mode…
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The one that sounds the best in my system
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Wolf:
I have a SS Musical Fidelity X-A1 that sounds like a really good tube amp, but I need to take it apart and re-apply the heat sink grease before putting it back into action (forgot to do so when repairing a manufacturer's assembly error).
Been setting for years as I still need to replace the metric tools stolen from the boot of my car, but now reminded I'm on it right now on Amazon.
DeKay
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If I could one only have one amp, then yes, a great PP, class A, preferably with just one pair of power tubes to keep things pure and simple. Flexibility would rule the decision. But a great SET with the right speakers is a special experience that I would not wish to give up. Fortunately, I don’t have to choose.
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I switch between a push-pull class A Pass XA-25 and a Dennis Had SEP (pentode) tube amp. Both sound beautiful and I really don't know why I swap them out except for feeling bad for the one that's not being used. Nobody wants a sad, unused amp.
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Thx for the link -- very helpful .. Much more reading to do, and music listening, of course..
From the Gospel according to Aiken: (this was my very question - how can a push-pull be Class A ?
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For audio amplification, a class A amplifier can be either single-ended or push-pull. Now, you might be thinking, how can a push-pull amplifier be class A? Doesn’t one side amplify half the waveform and the other side amplify the other half? Isn’t this why we use a phase splitter? These are common misconceptions. You can, indeed have a true class A amplifier that operates in push-pull mode. Amplifier class has absolutely nothing to do with output stage topology. If the output tubes on either side of a push-pull pair are biased in class A (halfway between cutoff and saturation), then the current in each side will still flow for the full 360 degrees of the input cycle, just in opposing directions. As one tube’s current increases from the midpoint, or idle, bias current, the other tube’s current is decreasing by an equal amount. The output transformer sums these oppositely-phased currents to produce the output waveform in the secondary winding. As one side reaches saturation, the other side reaches cutoff, just as they would in a single-ended class A amplifier. Neither side cuts off at the full, unclipped output power of the amplifier. The output power of a push-pull class A amplifier is exactly twice the output power of a single-ended class A amplifier operating under the same conditions of plate voltage, bias, and effective load impedance.
DeKay (from AudioKarma)
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Do you mean Class AB when you say PP or do you mean Class-A Push-Pull? There is a BIG difference between Class-AB PP and Class-A PP. If you meant Class-A PP, then a great Class-A PP would be a no-brainer, I think.
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Good DH/SET...
Been using OK/inexpensive DH/SET 2A3 mono blocks for 20+ years (tubes used sell for way more than the amps) and used an Audion DH/SET 300B prior to the 2A3 amps.
I use vintage wide band drivers/speakers without added tweeters/subs and that's enough for me.
DeKay
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I owned both PP & SET tube amps over the last almost 40 years w/ several different speakers in different rooms. There’s no hard & fast rules about any of them but the midrange detail & realism of a good SET amp is tough to beat at lower to maybe moderate volumes even w/ high sensitivity speakers. They do run out of gas quickly though when pushed at all & the distortion increases rapidly beyond their power rating or even sometimes that their rated power. They have no real “headroom “ . I have landed on PO amps for that reason as I enjoy loud volumes at times & have a big room.
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I’ve had both, including a 75 watt Allnic amp that supports switching from SET to PP. I’ve a large sound treated listening space. With my Tannoy speakers and Studer open RTR, I prefer PP. Stronger bass, deeper soundstage, more dynamism, and greater low volume detail were observed with PP.
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I have a great SE 46 amp and several great PP amps. I prefer each of the PP over the SE.
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@ghdprentice + 1 - For me, I care a lot more about how I enjoy the sound than how it got to sound that way.
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I don't know how anyone can answer this conclusively, or for you, every situation entirely unique, variables go on and on. To start with how do you define great vs good, why a great push pull vs only a good SET, why not great to great? If your criteria for great is price, this may not hold for SET. There are many boutique/small operation builders of SET amps, they can custom build you an extremely high quality amp for relatively low price.
Personally, I've had a number of push pull and SET amps (2a3, 300B, 845) over the decades, thus far SET for me. These days only mono blocks with quality transformers and power supplies, both critical for SET. EL34 my fav push pull tube, very nice mids, still don't compare with immediacy, illusion of performers in room SET is capable of. On the other hand just received Bendix 6094 mono blocks (EL84 iteration), these 12wpc push pulls, reportedly EL84 most closely resemble SET with more impact, we shall see. Bottom line, so many variations of tube amps, only you can determine what's best for your situation.
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@nightfall--would you please tell us the two amps in question? I am particularly interested in learning the name of the PP amp.
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I cannot say that any topology is obviously superior to another even under narrow parameters, such as a particular output range, much less without any such restriction. My favorite amps have all been relatively low powered tube amps. The two very best amps I've heard are wildly different in design. One is a Western Electric 59 amplifier which is a pushpull 252 amp (crazy rare and expensive). The other favorite is a custom made OTL amp that is one of a kind; the owner has jokingly said that he might be willing to sell it to me for $250,000 for the pair.
Of the amps I own, I happen to prefer my pushpull 349 amp over a much more expensive parallel 2a3 SET amp, but, they are different in so many ways there is no way to attribute differences to topology. Only on a very general basis of hearing many different amps over the years that I can sort of generalize that I tend to prefer low-powered pushpull amps over SET amps because they deliver a bit more punch.
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I have two friends with smaller listening spaces, with low power SETs, both sound terrific, meanwhile we all love the sound of my 45 wpc P/P Cayin Tube Amp here (and the 30 wpc P/P Fisher 80AZ Mono Blocks before this). We all have tube preamps,
I've never heard a SET here, my 16 ohm horn speakers from 1958 are extremely efficient, my Cayin has the ability to play in Triode at 22 wc, I prefer the Ultralinear 45wpc option.
I occasionally hear a speck of hum in their systems at idle. Mine is always dead quiet. Both my friends have had problems and needed to ship their SETs out for repairs a few times.
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Again, per the speaker manufacturer, either will work well with the speakers I have.
I have loved SETS for a long time, but I simply cannot afford a "great SET". And, being retired, never will.
I have no opportunity to listen to the specific push pull amp I am considering, but did hear its predecessor at an audio show, quite some time ago, and was left amazed. I am absolutely certain, based on a great deal of research, further show reports, and many specific reasons, that it is unquestionably world class.
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It depends on the amp in question and matches with the speakers. Currently using 2a3 SET monos but I've used and loved PP amps as well.
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Have to go with great over good.
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Whichever sounds better / more to your taste. Sorry, that may sound unhelpful. But I never make decisions on technology. Any component is the product of the design vision and components. If you can't hear them then do a number of AI searches comparing the sound quality of the two. Read reviews.
I have an amp that operates in linear and triode mode (no secret Audio Research REF 160s). The difference is small but important... I always run it in triode mode. I would have still ended up with this amp even if it only had one mode.
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Best of both worlds and the New Pathos Inpol amp uses the vacuum tube as part of the gain stage and also in pure class A in a true dual mono design ,
verypopulsr in Europe in the U.S a boutique 35+ year own company
all made in. Italy and a work of art !
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I am evaluating Amp's at the current time.
I have high efficiency Speakers for the SET Amp' which are also experienced being driven by what I will class as an exceptional PP Amp'.
A SS Neurochrome Monoblock Design Amp' is currently available to be tried.
In comparisons between the PP and SET, on the Speakers selected, the SET has blown me away, where making a good impression is part of the assessment both Amp's are parity.
More evaluations using a Analogue and Digital Source are to continue.
I believe the SET has a place in my system.
I'm keen to learn what the N'chrome is able to create in my own system, as all other demo's of different N'chrome Models used in different systems, when being compared to other Amp's has ended with the N'chrome being the star with the X Factor.
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Definitely a great PP over a good SET. 1) great is better than good, 2) compatability with a SET is a loaded term--no manufacturer wants to turn away a customer if it sort of works, and 3) more people than you would think clip their SETs (and other low power amps) and don't recognize it.
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I have both: three Single End tube amps and several PP amps. The latter have the best sound and versatility for use with a variety of speakers. The SE amps require proper speaker matching and are limited in power/watts. SE amps are not inherently better sounding.
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