High efficiency horn speaker amp question

[christensenleif@msn.com]

if members of this forum were as conscious of global warming and eco footprint, they wouldn´t be here in the first place imo

 

[microstrip]

Yes, the Nagras are quite small for what they are. I also noticed that the measurements in Stereophile show a large rise in distortion in the bass that indicates an undersized output transformer.

The measurements of the Nagra VPA in Stereophile show a distortion rising in a straight line from 1kHz down to 10 Hz at low power - IMHO not enough to conclude that there is an undersized output transformer, that usually shows as a bent line around ~80 Hz. At the time I owned it I found that it used a toroidal output transformer and that it was hard to keep the push pull bias well balanced . This is extremely critical in an output toroidal as they saturate very easily with a little amount of DC current, creating high distortion. I have no experience with toroidal output transformers, but it looked large!

AFAIK Nagra latter released a fix to the bias unbalance problem.

 

[christensenleif@msn.com]

I have Tommy Hørning SATI toroid OPTs on my 300Bs
Plitron and Vanderveen in NL produces/d them as well

 

[morricab]

It's always rather sad when someone has shut his mind so thoroughly against (for examplw) solid state or (particularly) Class D that he's not even prepared to test others' results.

My avantgarde Duo XDs sound good with my SET monos, but certainly now sound even better with Purifi-based Class D amplification. Furthermore, because the amp is so efficient and costly componants are not wearing out (as they are with valve amps), I now listen to far more hours of music that when I used valves. And my electricity bill is unaffected - and the Environment is happy too!

Give it an unbiased try. Get a NAD M33 on loan and give it a 7-14 day trial before reverting back to your valves - you may be surprised at how much you enjoy (and most likely prefer) the Purifi sound.

PS - Just noticed that you have a vested interest in plugging valves. You import and distribute valve amps, but that shouldn't stop you from trying a good SS amp is the security of your own home. You needn't tell your customers! Or you could look for alternative / additional brands to distribute - ones that don't contribute quite so much to customers' power bills and global warming.

Well, I have owned three different Class D amps over the years and heard dozens of others...I am not lacking in experience wrt. this technology suffice to say. I have it on good account that the Purifi Class D modules are quite lean and dry sounding... I admit not to hearing this exact Class D module. I never worried limiting my hours listening to my tube gear...when I need new tubes, I get new tubes. Electricity is cheap in Switzerland...about the only thing that is.

Doubt I can get a trial as this is probably only a local offer.

Yes, I have a vested interest but that followed the preference not the other way around (it is not my day job but side business...my day job is developing pharmaceuticals for inhalation (Asthma and COPD)).

I am not concerned with the puny amount of electricity even a big SET or OTL generates. As I have said, I have heard almost all of the latest Class D tech...enough to know that it lacks the realism I seek...this was also true when I had big panel speakers. I moved to horns because I heard the purity of SET (I am not a big fan of PP tubes for the most part either) and wanted speakers that could exploit this.

 

[morricab]

The measurements of the Nagra VPA in Stereophile show a distortion rising in a straight line from 1kHz down to 10 Hz at low power - IMHO not enough to conclude that there is an undersized output transformer, that usually shows as a bent line around ~80 Hz. At the time I owned it I found that it used a toroidal output transformer and that it was hard to keep the push pull bias well balanced . This is extremely critical in an output toroidal as they saturate very easily with a little amount of DC current, creating high distortion. I have no experience with toroidal output transformers, but it looked large!

AFAIK Nagra latter released a fix to the bias unbalance problem.

Ok, so it is not undersized per se but saturating probably anyway (different cause, same problem)? Could be but regardless this means that the bass control will suffer.

 

[morricab]

I have Tommy Hørning SATI toroid OPTs on my 300Bs
Plitron and Vanderveen in NL produces/d them as well

WHat is the potential advantage of a toroid other than they probably weigh less without all the iron?

 

[Addicted to hifi]

And do you really think all things are equal??

Got that from a 1970s phase linear add.

 

[christensenleif@msn.com]

a friend had Phase Linear 700 on B&W DM70 and the sparks came out of the electrostatics when he pushed on

 

[christensenleif@msn.com]

I read some

WHat is the potential advantage of a toroid other than they probably weigh less without all the iron?

wider frequency range is a claimed advantage

 

[microstrip]

Ok, so it is not undersized per se but saturating probably anyway (different cause, same problem)? Could be but regardless this means that the bass control will suffer.

Curiously the VPA's sounded much better than we could expect from its measurements - but depending a lot on the speakers - the Sonus Faber Amator was a nice match. I used them with the PLP preamplifier and could easily return to this system, probably with an high impedance, higher efficiency speaker ...

 

[christensenleif@msn.com]

I felt the VPA had more money invested in exterior than interior

 

[ddk]

It's always rather sad when someone has shut his mind so thoroughly against (for examplw) solid state or (particularly) Class D that he's not even prepared to test others' results.

My avantgarde Duo XDs sound good with my SET monos, but certainly now sound even better with Purifi-based Class D amplification. Furthermore, because the amp is so efficient and costly componants are not wearing out (as they are with valve amps), I now listen to far more hours of music that when I used valves. And my electricity bill is unaffected - and the Environment is happy too!

Give it an unbiased try. Get a NAD M33 on loan and give it a 7-14 day trial before reverting back to your valves - you may be surprised at how much you enjoy (and most likely prefer) the Purifi sound.

PS - Just noticed that you have a vested interest in plugging valves. You import and distribute valve amps, but that shouldn't stop you from trying a good SS amp is the security of your own home. You needn't tell your customers! Or you could look for alternative / additional brands to distribute - ones that don't contribute quite so much to customers' power bills and global warming.

It's not sad, happy or shutting one's mind down for not liking a topology. Of course there's good and bad in all topologies but there are qualities and character each type has, specially in the bass, that one might not like which is apart from power requirements of a speaker. As for myself I can’t drive with a Lamm SET, I don’t want it.

david

 

[ddk]

if members of this forum were as conscious of global warming and eco footprint, they wouldn´t be here in the first place imo

Not unconscious some of us have brains and think for ourselves !

david

 

[matakana]

I have Tommy Hørning SATI toroid OPTs on my 300Bs
Plitron and Vanderveen in NL produces/d them as well

Rock on Tommy!

 

[matakana]

I felt the VPA had more money invested in exterior than interior

The aluminum sides were pretty thin though.

 

[Atmasphere]

WHich Class D Ralph? I haven't heard one yet that I think correctly reproduces the treble range and mids have always sounded very dry to me.

Ya had to ask- we've been working on a class D project for the last 4 years. We're testing Beta production right now, so one of our own design.

No because you have typically corrupted that first watt to get the other 199.

With many high power amplifiers this is quite common! You can see it in the specs- as you decrease power, there is a point at about 4-7% of full power where the distortion is lowest and then climbs back up below that point. If your amplifier never gets out of that region you'll never hear what that amp can actually do. SETs have a property of decreasing distortion as power goes to zero which is why they are popular on horns, but they are by no means the only amps that can do that- our OTLs also do that (which is why we have a lot of horn customers) and so do a number of class D amps.

It's always rather sad when someone has shut his mind so thoroughly against (for examplw) solid state or (particularly) Class D that he's not even prepared to test others' results.

One problem you can run into which is very real- which is that many horns are not designed to work with amplifiers with a low output impedance! This can shift the crossover frequency and cause the horn to operate outside of its intended bandpass. For more on this see:

Resources: Paradigms in Amplifier Design

Voltage Paradigm vs. Power Paradigm. Competing Paradigms in Amplifier and Loudspeaker Design, Test, and Measurement.

www.atma-sphere.com

So this might not be the issue of a closed mind so much as its an issue of incompatibility.

WHat is the potential advantage of a toroid other than they probably weigh less without all the iron?

Bandwidth (as an OPT), lower cost, less weight and less radiated magnetic field (IOW more efficient). But core saturation is a very real issue, requiring that the power tubes be dynamically matched on a curve tracer on order to prevent saturation distortion. IMO toroids are too unforgiving to be suitable as an OPT simply because curve-tracer-matched power tubes are not available from tube suppliers- you're almost entirely on your own to come up with a curve tracer (Tektronix made a very nice one as a plug-in for their old oscilloscopes...) and someone that knows how to use it...

 

[morricab]

Curiously the VPA's sounded much better than we could expect from its measurements - but depending a lot on the speakers - the Sonus Faber Amator was a nice match. I used them with the PLP preamplifier and could easily return to this system, probably with an high impedance, higher efficiency speaker ...

I will know soon as a friend of mine is getting a pair to put with his Sonus Fabre Olympica III speakers. He already had Jazz preamp and classic DAC from Nagra.

 

[acg]

I have listened to a few very efficient horn speakers in the past driven buy very low output amps and it was excellent at low to medium volume, but once you try to go past these levels the sound deterioration was noticeable.

I does not have to happen. Sounds like less than ideal amplifier/speaker match. Were these commercial horn systems?

Horn speakers can sound as good powered by a SS amp as by an SET. If the SS amp is carefully chosen of course.

Agreement from me, although theoretical because I have never actually heard a good SS on horn, but I am sure they do exist.

Bottom line: horns help SETs out a lot, but its not the other way around.

For sure horns do help SET amps to be able to operate as they need to, largely due to the shortcomings of the particular amplifier topology, but not always. But you also mentioned a number of reasons why SET amps help horns, so the relationship is somewhat symbiotic. It is still easy to "mess up" a SET amp on horns that are not suited to the particular amplifier. (I also concur with your comments on distortion characteristics in your post #98).


But it seems as though most people here are talking about a single amplifier driving 20Hz-20kHz which is not really feasible for 99% of (horn) loudspeakers and your typical SET amp for a number of technical reasons that I will not go into right now (did it in another thread already). Where the SET thing really comes into its own is multi-amping. And to some extent diy. Listener problems of volume, bass, complex music et cetera which occur in systems where the SET amp is not well matched to the loudspeaker can all be made to go away with multi-amping and perhaps some diy effort if so inclined.

I love and listen to SETs and horns every day (six way active system). But I do acknowledge that for optimum performance the particular technical shortfalls of the SET amplifier topology needs to be accommodated by the loudspeaker. A single Class D amp is a much simpler, less expensive and easier fix...if you can live with it...than multiple SET amps.

 

[Addicted to hifi]

I does not have to happen. Sounds like less than ideal amplifier/speaker match. Were these commercial horn systems?



Agreement from me, although theoretical because I have never actually heard a good SS on horn, but I am sure they do exist.



For sure horns do help SET amps to be able to operate as they need to, largely due to the shortcomings of the particular amplifier topology, but not always. But you also mentioned a number of reasons why SET amps help horns, so the relationship is somewhat symbiotic. It is still easy to "mess up" a SET amp on horns that are not suited to the particular amplifier. (I also concur with your comments on distortion characteristics in your post #98).


But it seems as though most people here are talking about a single amplifier driving 20Hz-20kHz which is not really feasible for 99% of (horn) loudspeakers and your typical SET amp for a number of technical reasons that I will not go into right now (did it in another thread already). Where the SET thing really comes into its own is multi-amping. And to some extent diy. Listener problems of volume, bass, complex music et cetera which occur in systems where the SET amp is not well matched to the loudspeaker can all be made to go away with multi-amping and perhaps some diy effort if so inclined.

I love and listen to SETs and horns every day (six way active system). But I do acknowledge that for optimum performance the particular technical shortfalls of the SET amplifier topology needs to be accommodated by the loudspeaker. A single Class D amp is a much simpler, less expensive and easier fix...if you can live with it...than multiple SET amps.

tannoy westminister horns. 5 watt set.it distorted on the vocals on medium volume.

 

[acg]

tannoy westminister horns. 5 watt set.it distorted on the vocals on medium volume.

Well, I would expect that to happen. Optimistic 99dB/w/m sensitivity so your 5w SET will tap out at 105dB max before clipping, less at the listening chair. As mentioned elsewhere, if optimal sound is your goal, a SET amp needs to run low at most 20% of max power for the peaks, so that amp should not really use more than 1w to sound "good"...which is not loud enough. It would probably work ok on 110dB sensitivity speakers though.

Something like a 15w SET may have worked ok on your Westminsters, but probably not.