What are the advantages/disadvantages of different amp topologies?
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Republicoftexas69
Well-Known Member
You were the one to make the generalized comment about class D. I am not the one demeaning the topology. I am very content with both my tube and GaN amplification.
That's precisely what I mean by an exciting listen. If you visit a concert hall or good jazz venue, you expect (or at least hope) to be thrilled by the experience. That's what I want from my audio system and, like you, this includes horn speakers. I've never heard speakers that sound more life-like, exciting and goosebump-inducing than good horns. These need to be fed by an equally suitable amp that can keep the life-like experience in the recording as accurately as possible.
When I switched from SETs I was expecting a Class A amp to win me over and indeed the Accuphase was a lovely amp, though perhaps a little too "polite" - the Sugden wasn't a contender). The AB GamuT offered superb and dynamic sound but was let down by its attempts to destroy my 100+ dB horns by its powerup and down scary thumps! The Mark Levinson was a costly disappointment as were some others in my home tests. The NAD M33 was a match to all and won over because of its life-like presentation of sound, supported in no small way by its incredible price and feature package. It meant that I could afford to further upgrade my speakers. And no regrets for abandoning my lovely SETs though
Republicoftexas69
Well-Known Member
Your signature and industry affiliations show your proclivities so no point in pursuing your opinions as they are understandably biased. It is a very nice line of equipment you distribute. Cheers.
I think maybe you are right, I think the subject is more complex because every amplifier should be match to the speaker.
Good amplifier/speaker Matching change the tone (harmonics) structure so it is not easy to judge .
I am not against SET , I am not fan of PP , I just think this subject is complex.
Of my favorite efficient speaker set ups, two single drivers - Yamamura and Pnoe - one had a current state SS amp made for a single driver (by Yamamura), the other had a tetrode (46) by Mayer, I guess wired in triode mode. Iirc the early 1.25 watts were single ended and the next ones, around 3w were push pulls. He is welcome to correct.
Of the 5 Dual FLHs, one had SETs (300b, Leif's), one had single ended pentode (Misho's), one had the SS Kaneda replica which Hiraga followers follow, one had Silvercore 833c and 304 TL (so transmitter SETs), and one had the Silvercore 833c biamped with Ear 100w amp.
the Universums use higher powered SETs - tried many on those
of the more compromise speakers, Devores to me sound best with parallel SETs like NAF 2a3 and Airtight 300b over higher power SETs, push pulls, or hybrids.
The Kondo entire chain sounds great on Diesis, Klangfilm Bionor, and on Sigma MAAT
I have tried BerningQuadrature Z, Einstein OTL, and the Atmasphere M60 mk2 on some efficient speakers. Was not same quality as above including a direct compare of the M60 mk2 with Tektron GM70 on the horns fp10. The M60 had great bass and speed but less decay and tonal magic compared to the Tektron. This was using a Hattor passive preamp.
Of the 5 Dual FLHs, one had SETs (300b, Leif's), one had single ended pentode (Misho's), one had the SS Kaneda replica which Hiraga followers follow, one had Silvercore 833c and 304 TL (so transmitter SETs), and one had the Silvercore 833c biamped with Ear 100w amp.
the Universums use higher powered SETs - tried many on those
of the more compromise speakers, Devores to me sound best with parallel SETs like NAF 2a3 and Airtight 300b over higher power SETs, push pulls, or hybrids.
The Kondo entire chain sounds great on Diesis, Klangfilm Bionor, and on Sigma MAAT
I have tried BerningQuadrature Z, Einstein OTL, and the Atmasphere M60 mk2 on some efficient speakers. Was not same quality as above including a direct compare of the M60 mk2 with Tektron GM70 on the horns fp10. The M60 had great bass and speed but less decay and tonal magic compared to the Tektron. This was using a Hattor passive preamp.
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NAF 2A3 is PP class A triode…as is their 300b amp. Only the 845 and 211 models are SET from NAF.
I compared a SET (using two WE275A drivers built by Don Garber) with a FET (First Watt F3 built by Nelson Pass) and there was no comparison. Despite both the hollow state and solid state amplifiers running as class A "triodes" with very simple configuration, the F3 lacked life compared to the WE275A. Why?
I am no engineer (maybe Atmosphere can chip in here) but I had read that triode valves have more distortion than FETs but it is predominately in the 2nd harmonic (like the harmonics coming from real instruments) and that solid state has less distortion but spread out in the odd-order harmonics, which grates a little. Any truth at all in this presumption?
One last thing Morricab; did you compare the measurements from all those amplifier reviews and come up with any revelations?
Republicoftexas69
Well-Known Member
Republicoftexas69
Well-Known Member
So let’s hear about it. you are the expert I want to learn from your trials and errors. You are the one condemning all Class D and GaN. I simply enjoy both my GaN and tube topologies. Or do we need to simply flip the switch, think I will either way.
No idea why the F3, which seems to be a single stage SE(Transistor) cascode (JFET and MOSFET), doesn't sound better than it does. I guess there is a reason why recent designers are making a triode/FET hybrid as a single element (Silbatone/Silvercore, NAT and Aries Cerate at least)...you need whatever the tube is doing in a single ended fashion (high voltage...high dynamics) to getting really good sound.
Mostly it is about distortion pattern and distortion vs. frequency...assuming you are using the amp well within it's power envelope.
The SETs, on average, have a smoothly descending harmonic pattern from 2nd on down to the noise floor. Unfortunately, Stereophile is not consistent in showing 1Khz results. IMO, 50Hz is problematic for most SETs because of the transformer core saturation (also seen in the distortion vs. frequency plots with a sharp rise with power into low frequencies) and so the FFT is a lot messier than it is at 1Khz. I would steer clear of SETs that suffer bad core saturation as that distortion will bleed well up into the midrange and I think is largely responsible for an overly warm "tubey" sound.
The OTLs and most other PP amps, will have reduced or even missing even harmonics and while the low/no feedback OTLs tend to have a decreasing order as well...it is without the even order harmonics, which tends not to sound as natural because, outside of electronics, that is not how physical objects make harmonics and overtones.
When I had my NAT Symbiosis SE, it was a very frustrating amplifier. The first reason was that until it had been playing continuously for about 2 hours, it sounded rather flat and somewhat boring. Not bad mind you but just kind of "meh". At some point, the clouds would part and the rays of sunlight would come through and in some ways it would sound glorious. Incredible transparency and natural tone and huge dynamics (it was 100 watts...so quite powerful for a single ended design); however, it still was slightly flat spatially and a bit "dark" in the highs...something I hear in a lot of PP Class A SS amps using MOSFETs. So, I never completely fell in love with it.
That said, I am not inherently opposed to single ended transistors because KR Audio, which uses SS for the input AND driver stages, and only tube for the output stage, sound very good overall. Perhaps not the last word in resolution but definitely good and great space and dynamics. Tonally, they tended to have a bit of a midbass bump but that actually appealed with a lot of speakers that are lean there.
My history is well documented throughout WBF...I will not waste time recapping it here for your benefit.
Knock yourself out. If they sound equivalent to you...lucky you...
Republicoftexas69
Well-Known Member
Did not say that they sounded equivalent. Said that I enjoy them both based on the positive attributes of each and what they bring to my enjoyment of music. Enjoy your evening and I will stop wasting your time. Yes your demineier is quite well documented.
So, are you saying PP and OTL put out odd order harmonics so don’t sound natural, and SETs put out even order from 2nd down to noise floor (no 3rd order?) and thus sound more natural? Adding, that core saturation in SETs ( even the best? ) down around 50 Hz is the reason SETs sound lush?
yes the First Watt F3 used JFETs, don’t think Mosfet’s however?
Don't have a dog in this hunt, and not getting into any of the technical stuff. But it is interesting to compare how the sonic attributes of SET amps tend to be described in language compared to everything else. FYI - two reviews of the same SET amp, from two different reviewers, 18 years apart:
Review: Viva Solista Integrated Amplifier - Twittering Machines
Michael Lavorgna's Twittering Machines: HiFi with a twist
twitteringmachines.com
Not at all! That really isn't a benefit of SETs:
FWIW PP really doesn't have that problem unless the amp isn't biased properly or its malfunctioning. It literally isn't a thing and hasn't been for my entire adult life.
I remember when I was working in the Allied Radio Shack service department I'd see some cheaper solid state amps come in where it was obvious the bias had not been set up properly from the factory. There would be a little notch distortion and it was really easy to hear. So I would set the bias (most solid state amps of the 70s and 80s have both a bias and DC Offset control in the circuit) to get rid on the notch. At first I did it on the oscilloscope but it was so audible I found I could do just as well setting it by ear.
Class D amps are immune to that problem if they have an output filter for the switching frequency and all of them I've ever seen do. Its possible to do a Class D without the filter using some fancy servo techniques but those techniques open the design to a crossover issue so no-one uses it.
So its not something that SETs bring to the table that other amps don't.
If he is (I have him on ignore since his comments on this topic have mostly been incorrect) then he's incorrect. Again.
You can't group all OTLs together- just as you can't group all class A amps together (since they can be SET, PP, solid state and single-ended solid state...) since their topologies can be radically different. For example, there are single-ended OTLs. The Futterman circuit combined single-ended and PP, with a unique driver with regenerative gain and in some cases as much as 60dB of feedback. Our OTLs have only a single stage of gain- less complexity then even SETs (which usually have 3 stages of gain) with usually 2 orders of magnitude less distortion than an SET running at the same power level despite no feedback.
Tape machines make odd ordered harmonics too (even the tube studio machines) and no-one seems to be complaining about them! So you can regard his comments as unreliable.
My take away in general from listening to countless amps / topologies and what not lately .......
Tube amps smear the sound in regards to top solid state like CH precison , FM acoustics , Robert Koda The Gryphon Apex and a couple of others .
What they may be lack a bit is the glorious voice reproduction that top tubes can produce like ARC VAC JADIS CAT and a couple of others.
Tube amps smear the sound in regards to top solid state like CH precison , FM acoustics , Robert Koda The Gryphon Apex and a couple of others .
What they may be lack a bit is the glorious voice reproduction that top tubes can produce like ARC VAC JADIS CAT and a couple of others.
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