SET amp owners thread

[microstrip]

(...) The best sounding amp I have ever had that contained transistors was a single ended one. It was actually a hybrid where it was a tube input, tube driver and a single large MOSFET on the output stage. It was huge, it was hot and it sounded amazing after playing music for about 2 hours straight. Not sure why it took so long to come on song but that is why I sold it ultimately. That said...it still did not sound like an all tube SET...it was something different again...not surprising given the output device was a MOSFET with a totally different distortion character from a triode.

Why keeping such great products anonymous? Can you tell us what was the brand and model?

BTW, I remember that several old class A Krell amplifiers suffered from similar problems. Some even needed about six hours before reaching optimum sound quality.

 

[morricab]

Why keeping such great products anonymous? Can you tell us what was the brand and model?

BTW, I remember that several old class A Krell amplifiers suffered from similar problems. Some even needed about six hours before reaching optimum sound quality.

I have many times... NAT Symbiosis SE.

 

[Salectric]

It beats me why threads like these create such acrimony. Why can't we just accept that SET amps sound different from PP tube amps and from all ss amps, and just leave it at that? Trying to explain WHY they sound different never leads to anything constructive since nobody knows exactly why amps sound different. Not to mention why resistors, capacitors and wire all sound different.

What is constructive is to explain our preferences for one type over another and to describe particular combinations of components that sound especially good together.

 

[morricab]

It beats me why threads like these create such acrimony. Why can't we just accept that SET amps sound different from PP tube amps and from all ss amps, and just leave it at that? Trying to explain WHY they sound different never leads to anything constructive since nobody knows exactly why amps sound different. Not to mention why resistors, capacitors and wire all sound different.

What is constructive is to explain our preferences for one type over another and to describe particular combinations of components that sound especially good together.

Nothing wrong with a robust debate. No one is calling anyone names yet...

Also, it has always been more interesting to me WHY something behaves the way it does rather than just the thing itself. WHY do people find some sound more real and others don't? What does data collected on psychoacoustics say about it? This can lead down a rabbit hole of disagreement but so what? People think science is smooth and flowing and people agree...but they don't. I have seen people stand up at conferences and yell at the speaker that they are full of it or liars or both. The process of understanding is messy.

 

[Atmasphere]

This was clearly not what I meant.

Push–pull output - Wikipedia

en.wikipedia.org

"Symmetrical construction of the two sides of the amplifier means that even-order harmonics are cancelled, which can reduce distortion.[1]"

"Symmetrical push–pull
Each half of the output pair "mirror" the other, in that an NPN (or N-Channel FET) device in one half will be matched by a PNP (or P-Channel FET) in the other. This type of arrangement tends to give lower distortion than quasi-symmetric stages because even harmonics are cancelled more effectively with greater symmetry."

What is clear from these descriptions (and others in the Wiki page) is that even order distortion is created in each half of the push pull stage due to the inherent behavior of the devices (Mosfets and bipolars will both make all harmonics as single ended devices...at least when not biased Class A...see paper by Boyk and Sussmann). This even order distortion due to the devices is cancelled by the symmetry of the circuit design ...therefore what I said about the distortion being removed by the circuit is essentially correct. It is being generated by the inherent qualities of the devices and cancelled (i.e removed) by the symmetry of the circuit and having those out of phase. The better the symmetry, the greater the cancellation.

Yes the feedback tends to accentuate the higher orders but it won't accentuate orders that have been cancelled by the push/pull design. So, odd high order harmonics (the worst kind) will be added and enhanced.

With regard to the Krell: https://www.stereophile.com/content/krell-full-power-balanced-350mc-monoblock-amplifier-measurements

As you can see it is only 1 db down at 100Khz and the distortion vs. frequency is quite flat...so this doesn't fit with your argument that the Krell lacks the Gain Bandwidth Product to support its feedback. There are many feedback amps that have a rising distortion with increasing frequency (some alarmingly so) and those I would agree with you meet your argument and that probably leads to problems in the highs and overall tonality. The Krell though, measurably doesn't have this issue. I have actually heard this amp many years ago with a pair of Wilson CUB speakers and although I don't like the overall tonality and "feel" I got from the amp I have to admit it's highs were very clean and the soundstage was very deep and wide with a superbly low noise floor. You can see this also with the high frequency IMD measurement which shows virtually nothing.

My point about feedback and interaction is different than what you are talking about. I am aware of the reduced output impedance, which means less variability for a voltage source and a speaker that likes that. I am talking about what comes back from the speaker, the so-called back EMF, and it's interaction with the amplifier circuit if global feedback is used. Have you read the papers form Otala? It is not about frequency response of the speaker it is about distortion products from the amplifier.

We're on the same page here until the last paragraph. I did read Otala. I disagree with his conclusion. Here is how output impedance interacts with back EMF: the lower the output impedance the less the output section is affected by the back EMF. What Otala didn't have available to him was an amplifier that had sufficient feedback and at all frequencies. Again, this is a matter of control theory and I just have to assume he did not understand that he was working with amps with poorly designed feedback loops. You can safely ignore his conclusions as a result. When you have a higher back EMF it messes with the output section more; it acts to load the output section more at whatever frequencies of which the EMF is composed since its an opposing voltage.

However, in the case of the Krell, the 3rd is suppressed enough that its unable to mask the higher orders.

Perhaps I need to be more clear: in a tube amplifier with no feedback, operating class A, if it is fully balanced and differential, then its primary distortion product will the 3rd harmonic, and that harmonic will be a large enough amplitude that it will mask higher ordered harmonics. At this point you can append the other comments I've made describing how the distortion works out.

I was not talking about traditional solid state designs like the Krell; mostly because I've never seen one have the same distortion spectra as a tube amplifier. But- if you did find one that had the same distortion spectra as an SET it would sound exactly the same (once FR errors were removed as a variable).

My comment immediately above applies to class D as well. Here's something you might want to know: class D amps vary in sound character at least as much as tube amps do! Some are terrible in the bass, others in the mids and highs while some are downright musical in every regard. Put another way you might have heard 10 different class d amps and still would not really have any idea of what they sound like, what they do and what they do not do. They are that variable. This is partially because for the last 60 years its been an evolving technology (first proposed in the tube era and one of the first production amps for hifi was made in the last 1960s; it was rated at 10 watts and really only made 3 and AFAIK was a flop) and its simply taken a while to sort a lot of its issues out; like any other emerging tech was on a sigmoid curve.

I used to be abused of the notion that there are things that you can hear that can't be measured. The problem is most of the important measurements are either never made and/or not published. Those differences you hear between various amps? Other than frequency response issues (often having to do with how the amp interfaces with the load due to output impedance), its the distortion signature that's being described (again, this is because the ear converts all forms of distortion to tonality). That is very measurable! But there is IMO a lack of awareness of what the significance of what these measurements tell us. For example the Krell amp you cited; it appears that you were construing it to be an example of what I was talking about when it was obvious to me that it was not, on account of the amplitude of the 3rd harmonic being insufficient (and the otherwise rather high amplitude of succeeding harmonics). Its not an example because the masking principle of the ear is not invoked.

 

[cal3713]

Nothing wrong with a robust debate. No one is calling anyone names yet...

I also appreciate the lean towards understanding (or at least discussing) why here on WBF and think that the debates, even when they wander, do help make progress towards that goal.

At the least it makes the back-and-forth more interesting. I can't stand reading the "your ears are terrible, you're so stupid, only my experience is correct (p.s. yeah, I've never actually heard that gear)" cock-contests on Audiogon.

 

[gleeds]

Bonzo75, thanks for starting this thread. We do not have any SE amplifiers in the house currently but we are bringing in Destination Audio amplifiers once I can make room for their beautiful, ultra-high-efficiency horns. In the meantime, while attending the Florida Audio Expo we happened upon the pairing of Blumenhofer horn speakers powered by the Takatsuki 300B integrated amplifier from Japan. In a word, the sound of the pairing on classical music was sublime. I suspect the amplifier would create similar magic with other high-efficiency loudspeakers.

 

[charles1dad]

"Nothing wrong with a robust debate. No one is calling anyone names yet...

Also, it has always been more interesting to me WHY something behaves the way it does rather than just the thing itself. WHY do people find some sound more real and others don't? What does data collected on psychoacoustics say about it? This can lead down a rabbit hole of disagreement but so what? People think science is smooth and flowing and people agree...but they don't. I have seen people stand up at conferences and yell at the speaker that they are full of it or liars or both. The process of understanding is messy"

Well said @morricab and I agree wholeheartedly. I find the discussions on this forum interesting and insightful far more often than not and why I've drifted here away from Audiogon lately. Keep it up! No one is being insulted or disrespectful in my opinion.
Charles

 

[bonzo75]

Bonzo75, thanks for starting this thread. We do not have any SE amplifiers in the house currently but we are bringing in Destination Audio amplifiers once I can make room for their beautiful, ultra-high-efficiency horns. In the meantime, while attending the Florida Audio Expo we happened upon the pairing of Blumenhofer horn speakers powered by the Takatsuki 300B integrated amplifier from Japan. In a word, the sound of the pairing on classical music was sublime. I suspect the amplifier would create similar magic with other high-efficiency loudspeakers.

Destination Audio 45s are excellent amps.

 

[Fred Crane]

Destination Audio 45s are excellent amps.

I'm a big fan and the importer, (So i better like them.) To that end, here's something with the soul of the Destination 45 monos with 1300 or so volts...also from Destination.

 

[cal3713]

"Nothing wrong with a robust debate. No one is calling anyone names yet...

Also, it has always been more interesting to me WHY something behaves the way it does rather than just the thing itself. WHY do people find some sound more real and others don't? What does data collected on psychoacoustics say about it? This can lead down a rabbit hole of disagreement but so what? People think science is smooth and flowing and people agree...but they don't. I have seen people stand up at conferences and yell at the speaker that they are full of it or liars or both. The process of understanding is messy"

Well said @morricab and I agree wholeheartedly. I find the discussions on this forum interesting and insightful far more often than not and why I've drifted here away from Audiogon lately. Keep it up! No one is being insulted or disrespectful in my opinion.
Charles

Good to see you over here Charles. And exactly true regarding the non-mass-consumer side of science.

 

[morricab]

I'm a big fan and the importer, (So i better like them.) To that end, here's something with the soul of the Destination 45 monos with 1300 or so volts...also from Destination.

An integrated... good one!

 

[Fred Crane]

An integrated... good one!

I know you enjoy a good sized integrated : ) (don't you love those Athos speakers too!)

 

[Fishfood]

Any opinions/experience with Audio Note Kit SET amps? Would love to know if they are worth the money. I can get a built Mentor 300b with C Cores and NOS tubes (but just Chinese no name 300bs) for less than $3k. Maybe there are other better options at that price point?

 

[bazelio]

Any opinions/experience with Audio Note Kit SET amps? Would love to know if they are worth the money. I can get a built Mentor 300b with C Cores and NOS tubes (but just Chinese no name 300bs) for less than $3k. Maybe there are other better options at that price point?

I looked in to those AN Kits. I'd say look beyond them.

 

[olivier]

Any opinions/experience with Audio Note Kit SET amps? Would love to know if they are worth the money. I can get a built Mentor 300b with C Cores and NOS tubes (but just Chinese no name 300bs) for less than $3k. Maybe there are other better options at that price point?

I only have experince with the 5.1 DAC. it is well built, has nice parts and sounds really good

 

[Legolas]

So I some long term experience with the ANK kits, both amp kits and DAC kits. It all depends on your expectations. If you expect the kits to anyway get close to Audio Note UK products, you will be disappointed. If however, you want the fun of building an amp kit then maybe go for that.

IMO I would say buy a finished product tube amp by another more reputable brand on the used market. You will get a better sound and longer term reliability IMO, as long as you take care what you buy used of course.

What gets me annoyed by ANK is they have clung onto the shirt tails of Audio Note UK products and sound, image, and it is totally not true. They have almost zero connection to Audio Note UK products. For example the OPTs are made in Canada, and Andy Grove at Audio Note has zero involvement in the design of current ANK products.

Finally, have a look at the resale value of any ANK kits, and what does that tell you....

 

[olivier]

So I some long term experience with the ANK kits, both amp kits and DAC kits. It all depends on your expectations. If you expect the kits to anyway get close to Audio Note UK products, you will be disappointed. If however, you want the fun of building an amp kit then maybe go for that.

IMO I would say buy a finished product tube amp by another more reputable brand on the used market. You will get a better sound and longer term reliability IMO, as long as you take care what you buy used of course.

What gets me annoyed by ANK is they have clung onto the shirt tails of Audio Note UK products and sound, image, and it is totally not true. They have almost zero connection to Audio Note UK products. For example the OPTs are made in Canada, and Andy Grove at Audio Note has zero involvement in the design of current ANK products.

Finally, have a look at the resale value of any ANK kits, and what does that tell you....

Well there is a "small" difference in price whith Audio Note, isn´t it?
And they offer finished products, too

 

[Legolas]

My point is, ignore the Audio Note connection, there is no none. And proceed on the basis.

If the kits were actually competitive v finished products by decent brands, tube maps, DACs, then they should come clean and change the name of the company and the names of the products. My point.

 

[olivier]

Well they say that they have common roots with Audio Note UK. But you are correct, nowadays there isn´t