SET amp owners thread

[morricab]

Again, of course they do! As I pointed out earlier, even though Klispsch is in the business of higher efficiency speakers, they really don't expect that anyone will be using tubes with their speakers, although they are tolerant if you call them on the phone and admit to such

But Klipsch did use the 1 watt/1 meter spec back about 50-60 years ago when such a thing was far more useful. My aunt owned a Bogen integrated tube amp with Klispch corner horns back in the 1960s and was one of my more formative exposures to what a more upscale system could do. I was interested in the system so she dug out the brochures which she still had on hand so I know this from that experience.

JBL spec'ced their L100 Century (the original, not the reissue) as

Klipsch makes it clear that they are defining sensitivity as dB for 1 watt at 1 meter...So, I guess they are still using the same spec as they did 50-60 years ago and probably still call it sensitivity...like most of the rest of the world...

Some examples from JBL:

file:///C:/Download/4430-and-4435_manual.pdf
given as Sensitivity in 1w @ 1m

file:///C:/Download/4401_manual.pdf
Also given as Sensitivity in 1w @ 1m

Also classic compression drivers were given as Sensitivity in 1w @ 1 m
file:///C:/Download/2440_manual.pdf

Here's an old Altec speaker

https://manualzz.com/doc/3001999/altec-lansing-1218a-user-s-manual

Note that they give it as "Pressure Sensitivity" and it is in dB per 1 watt @ 1 meter.

Here is the famous model 19 with 99db sensitivity at 1 w@ 4 feet

http://www.lansingheritage.org/images/altec/specs/home-systems/model-19/page2.jpg

The Barcelona:

http://www.lansingheritage.org/images/altec/specs/home-systems/873a-barcelona/page2.jpg

Seems Altec liked to use the term "pressure sensitivity" but not efficiency.

I don't see evidence of these two classic American, high sensitivity speaker makers using the word efficiency with a db/w/m specification. There was one mention on an old 604 duplex ad that said highest efficiency...but gave no actual numbers. I have seen later speakers like the Altec Model 18, which used a late version of the 604 (or 605) that gave the spec in dB/w/m but called it "Pressure Sensitivity" just like the others.

 

[Atmasphere]

Klipsch makes it clear that they are defining sensitivity as dB for 1 watt at 1 meter...So, I guess they are still using the same spec as they did 50-60 years ago and probably still call it sensitivity...like most of the rest of the world...

Some examples from JBL:

file:///C:/Download/4430-and-4435_manual.pdf
given as Sensitivity in 1w @ 1m

file:///C:/Download/4401_manual.pdf
Also given as Sensitivity in 1w @ 1m

Also classic compression drivers were given as Sensitivity in 1w @ 1 m
file:///C:/Download/2440_manual.pdf

Here's an old Altec speaker

https://manualzz.com/doc/3001999/altec-lansing-1218a-user-s-manual

Note that they give it as "Pressure Sensitivity" and it is in dB per 1 watt @ 1 meter.

Here is the famous model 19 with 99db sensitivity at 1 w@ 4 feet

http://www.lansingheritage.org/images/altec/specs/home-systems/model-19/page2.jpg

The Barcelona:

http://www.lansingheritage.org/images/altec/specs/home-systems/873a-barcelona/page2.jpg

Seems Altec liked to use the term "pressure sensitivity" but not efficiency.

I don't see evidence of these two classic American, high sensitivity speaker makers using the word efficiency with a db/w/m specification. There was one mention on an old 604 duplex ad that said highest efficiency...but gave no actual numbers. I have seen later speakers like the Altec Model 18, which used a late version of the 604 (or 605) that gave the spec in dB/w/m but called it "Pressure Sensitivity" just like the others.

I think you can easily see what is going on- in the old days they simply used the word 'efficiency' as in the JBL example I gave and later simply changed the word to sensitivity, which really isn't how it works and for the most part no-one cares.

In order to know when you are applying 1 watt, you have to measure the impedance of the speaker at the frequency at which the power is being applied and then to the math to determine what voltage to apply to know when you are at 1 watt. The sensitivity spec is much easier since you merely apply 2.83 volts- and this is part of the reason sensitivity has taken over (this is also why digital took over since its so much easier to use in the recording studio). FWIW, '2.83volts' might seem quite arbitrary to many reading this, but it makes more sense when you know the legacy (which is what we've been talking about) is 1 watt at 1 meter assuming an 8 ohm load.

In any event, when you are using a zero feedback tube amplifier the efficiency spec is more useful since the amp can't double power as the load impedance is halved.

One area where this can get particularly pesky is when the speaker employs dual woofers in parallel. In such a case, the midrange and tweeter have an 8 ohm impedance and efficiency that is 3dB higher than that of the woofers, but the dual woofers cause the voltage source amplifier (IOW, solid state amp) to put out twice as much power into that woofer array and so the woofers keep up with the rest of the drivers. But when you put a power source amplifier on that speaker, such as an SET, you'll find that the amp is not making enough power for the woofers and so the system will have less bass and will be tonally tilted towards the highs. Although its not likely to be used with an SET, the B&W 802 is a good example of a speaker like this and there are many more as high end audio is plagued with designs like it. They are no good for zero feedback tube amps and not great for tube amps employing feedback (which can allow them to act like a voltage source but instead of doubling power as impedance is halved they halve power as impedance is doubled; part of why tube amplifier power is so expensive) either. I don't think they do solid state amps any favors either- the last thing you want any amplifier to do is work hard for a living- it will make more distortion and that distortion will be audible as less detail, brighter and harsher.

If there was ever a reason to be suspicious of the sensitivity spec when it relates to SETs this is it!

So when you see a loudspeaker that has a 96dB sensitivity spec, do your due diligence; do the math and convert the sensitivity to efficiency by looking at the impedance of the speaker. If its 4 ohms subtract 3dB from the figure...(while 96dB might be barely usable with an SET, 93dB simply isn't unless you are nearfield in a smaller listening environment). If it has a dual woofer array and is '8 ohms compatible' be very suspicious- there is a very real chance it won't work as expected with an SET. In this way you'll get a better idea of whether the speaker is a candidate for your amp.

Now there is a lot of 'common wisdom' (which might be a type of oxymoron) that you get the speaker you love first and then the amp that drives it. But any SET user knows that isn't how it works. SET users feel that SETs are the kind of amp that really brings home the music, so for them they have chosen the amplifier first- now they have to sort out what speaker works. This is why knowing the difference between the sensitivity spec and the older efficiency spec is so important to them.

(And FWIW since our OTLs also do not use feedback, this is a topic that I've been dealing with literally for decades; back in the 1970s I realized that if the speaker demanded that the amp have feedback, there was a good chance it would never sound like real music. This was and is because most amps that can behave as voltage sources lack the required amount of feedback to sound right; when you don't have enough feedback there will be distortion added by the feedback itself through the process of bifurcation of the input signal when combined with the feedback at the feedback node in the amp. No solid state amp made in the 1980s and most of the 1990s or before ever had enough feedback which is why there is a tubes/solid state debate. insufficient feedback will cause the amp to sound bright and harsh; typical solid state complaints. IMO/IME this is why there are still tubes around for audiophiles.)

 

[morricab]

I think you can easily see what is going on- in the old days they simply used the word 'efficiency' as in the JBL example I gave and later simply changed the word to sensitivity, which really isn't how it works and for the most part no-one cares.

In order to know when you are applying 1 watt, you have to measure the impedance of the speaker at the frequency at which the power is being applied and then to the math to determine what voltage to apply to know when you are at 1 watt. The sensitivity spec is much easier since you merely apply 2.83 volts- and this is part of the reason sensitivity has taken over (this is also why digital took over since its so much easier to use in the recording studio). FWIW, '2.83volts' might seem quite arbitrary to many reading this, but it makes more sense when you know the legacy (which is what we've been talking about) is 1 watt at 1 meter assuming an 8 ohm load.

In any event, when you are using a zero feedback tube amplifier the efficiency spec is more useful since the amp can't double power as the load impedance is halved.

One area where this can get particularly pesky is when the speaker employs dual woofers in parallel. In such a case, the midrange and tweeter have an 8 ohm impedance and efficiency that is 3dB higher than that of the woofers, but the dual woofers cause the voltage source amplifier (IOW, solid state amp) to put out twice as much power into that woofer array and so the woofers keep up with the rest of the drivers. But when you put a power source amplifier on that speaker, such as an SET, you'll find that the amp is not making enough power for the woofers and so the system will have less bass and will be tonally tilted towards the highs. Although its not likely to be used with an SET, the B&W 802 is a good example of a speaker like this and there are many more as high end audio is plagued with designs like it. They are no good for zero feedback tube amps and not great for tube amps employing feedback (which can allow them to act like a voltage source but instead of doubling power as impedance is halved they halve power as impedance is doubled; part of why tube amplifier power is so expensive) either. I don't think they do solid state amps any favors either- the last thing you want any amplifier to do is work hard for a living- it will make more distortion and that distortion will be audible as less detail, brighter and harsher.

If there was ever a reason to be suspicious of the sensitivity spec when it relates to SETs this is it!

So when you see a loudspeaker that has a 96dB sensitivity spec, do your due diligence; do the math and convert the sensitivity to efficiency by looking at the impedance of the speaker. If its 4 ohms subtract 3dB from the figure...(while 96dB might be barely usable with an SET, 93dB simply isn't unless you are nearfield in a smaller listening environment). If it has a dual woofer array and is '8 ohms compatible' be very suspicious- there is a very real chance it won't work as expected with an SET. In this way you'll get a better idea of whether the speaker is a candidate for your amp.

Now there is a lot of 'common wisdom' (which might be a type of oxymoron) that you get the speaker you love first and then the amp that drives it. But any SET user knows that isn't how it works. SET users feel that SETs are the kind of amp that really brings home the music, so for them they have chosen the amplifier first- now they have to sort out what speaker works. This is why knowing the difference between the sensitivity spec and the older efficiency spec is so important to them.

(And FWIW since our OTLs also do not use feedback, this is a topic that I've been dealing with literally for decades; back in the 1970s I realized that if the speaker demanded that the amp have feedback, there was a good chance it would never sound like real music. This was and is because most amps that can behave as voltage sources lack the required amount of feedback to sound right; when you don't have enough feedback there will be distortion added by the feedback itself through the process of bifurcation of the input signal when combined with the feedback at the feedback node in the amp. No solid state amp made in the 1980s and most of the 1990s or before ever had enough feedback which is why there is a tubes/solid state debate. insufficient feedback will cause the amp to sound bright and harsh; typical solid state complaints. IMO/IME this is why there are still tubes around for audiophiles.)

How far back in time do you want to go Ralph? Clearly JBL and Altec were using Sensitivity in dB as far back as the late 1950s...when tubes and the current source power amps were the norm. I think companies knew what they were doing with regard how to refer to a watt and that the impedance of the speaker plays a role in how a watt is determined. I know exactly what the 2.83V is...I even stated it clearly in a post or two above...no need to lecture...

I thought your small OTLs do use some feedback.

In the old days a lot of drivers had higher impedance, like 12 or 16 ohms. Putting those in parallel would not give cause for concern of a low impedance speaker. BTW, it is obvious that if the speaker is average of 4 ohms that with 1 watt the sensitivity will drop by 3db...

BTW. 96db is quite usable with a SET...it is not borderline. 93db is also no problem in rooms as big as 30 sqm. It really depends on how loud you listen and the distance you sit. Most people I know sit well within 4 meters of the speakers (I typically am around 3 meters in my setups or even a bit less). Rooms up to about 30 sqm. and that listening distance work just fine with SET (I am not necessarily talking about 2 watt SET here but more like 15-30 watt SET). I have heard so many successful setups with 20-30 watt SET and 91-100db speakers that I know it is possible to get great sound in that range. Of course once you get around 100dB then the low powered SETs become a lot more viable.

I don't really agree with this ultra high feedback concept based on amps I have heard that implemented it (all Class D of course because you can't go that high with the feedback for tubes or even normal SS). Bruno Putseys was the guy pushing this concept with his Ncore designs (and Mola Mola commercial offerings). I personally haven't heard a single Ncore based design that sounded correct to me. You claim you have one that sounds amazing...what is it? Something you designed? I am more than open to trying it out. I am not a vintage romantic...I simply gravitated towards what sounded the most realistic to my ears (went through a couple of OTLs along the way...).

 

[Atmasphere]

How far back in time do you want to go Ralf? Clearly JBL and Altec were using Sensitivity in dB as far back as the late 1950s...when tubes and the current source power amps were the norm. I think companies knew what they were doing with regard how to refer to a watt and that the impedance of the speaker plays a role in how a watt is determined. I know exactly what the 2.83V is...I even stated it clearly in a post or two above...no need to lecture...

I thought your small OTLs do use some feedback.

I don't think its clear that JBL was using 'sensitivity' as they rated the L100 Century in efficiency. That would have been about 1970.

Our two smallest OTLs use about 2dB of feedback which is far too little to deal with the kind of impedance changes I mentioned in my last post. You are not quite correct in saying:

In the old days a lot of drivers had higher impedance, like 12 or 16 ohms. Putting those in parallel would not give cause for concern of a low impedance speaker.

-if the rest of the speaker had an impedance much higher or for that matter much lower. But keep in mind that the vintage stuff had level controls for the mids and highs as the voltage response was an unknown.

BTW. 96db is quite usable with a SET...it is not borderline. 93db is also no problem in rooms as big as 30 sqm. It really depends on how loud you listen and the distance you sit. Most people I know sit well within 4 meters of the speakers (I typically am around 3 meters in my setups or even a bit less). Rooms up to about 30 sqm. and that listening distance work just fine with SET (I am not necessarily talking about 2 watt SET here but more like 15-30 watt SET). I have heard so many successful setups with 20-30 watt SET and 91-100db speakers that I know it is possible to get great sound in that range. Of course once you get around 100dB then the low powered SETs become a lot more viable.

To do this you would violate the rule of only expecting 20-25% of full power out of the amp, and so I think you'll find that if you interview people using SETs in this manner that they will report how 'dynamic the amp is for so little power'; this is because higher ordered harmonics are appearing on the leading edges of transients. The ear uses the higher ordered harmonics to sense sound pressure; hence 'dynamic'. But its really distortion masquerading as 'dynamics'. If you really want to hear what the amp is really all about, you simply need more efficiency out of the loudspeakers!

I don't really agree with this ultra high feedback concept based on amps I have heard that implemented it (all Class D of course because you can't go that high with the feedback for tubes or even normal SS). Bruno Putseys was the guy pushing this concept with his Ncore designs (and Mola Mola commercial offerings). I personally haven't heard a single Ncore based design that sounded correct to me. You claim you have one that sounds amazing...what is it? Something you designed? I am more than open to trying it out. I am not a vintage romantic...I simply gravitated towards what sounded the most realistic to my ears (went through a couple of OTLs along the way...).

We were granted a class D patent two years ago this November. We have a class D concept we are working on and its entirely our own design. Its a self-oscillating amplifier and runs about 38dB of feedback. We've built a few and it demonstrated for me that the distortion signature is far more important than the amount of distortion. In our case it worked out that the issues that cause distortion in the amp result in lower ordered harmonics, and they are similar to a tube amp in the regard that they have enough amplitude that they mask the presence of the higher orders, although overall the amp has over an order of magnitude lower distortion than our OTLs. I've not made a direct claim about how these amps sound as that would violate the terms and conditions that allow me to post on most websites.

Bruno is brilliant, but IMO he is making a mistake in offering his modules as a thing you can build up. This includes the input circuit; and depending on how well you do with that and the power supply you're going to get really variable results! IME you really don't want to use a Switch Mode Power Supply since SMPS units tend to have lots of current limiting protections which can make them tricky to use in an audio amplifier; you can get around that by going custom but no SMPS supplier will pay attention to you if you can't order 1000 units at a time. So if the amps you heard didn't have their ducks in a row you really won't know what a class D amp can really do.

 

[morricab]

I don't think its clear that JBL was using 'sensitivity' as they rated the L100 Century in efficiency. That would have been about 1970.

Our two smallest OTLs use about 2dB of feedback which is far too little to deal with the kind of impedance changes I mentioned in my last post. You are not quite correct in saying:

-if the rest of the speaker had an impedance much higher or for that matter much lower. But keep in mind that the vintage stuff had level controls for the mids and highs as the voltage response was an unknown.



To do this you would violate the rule of only expecting 20-25% of full power out of the amp, and so I think you'll find that if you interview people using SETs in this manner that they will report how 'dynamic the amp is for so little power'; this is because higher ordered harmonics are appearing on the leading edges of transients. The ear uses the higher ordered harmonics to sense sound pressure; hence 'dynamic'. But its really distortion masquerading as 'dynamics'. If you really want to hear what the amp is really all about, you simply need more efficiency out of the loudspeakers!



We were granted a class D patent two years ago this November. We have a class D concept we are working on and its entirely our own design. Its a self-oscillating amplifier and runs about 38dB of feedback. We've built a few and it demonstrated for me that the distortion signature is far more important than the amount of distortion. In our case it worked out that the issues that cause distortion in the amp result in lower ordered harmonics, and they are similar to a tube amp in the regard that they have enough amplitude that they mask the presence of the higher orders, although overall the amp has over an order of magnitude lower distortion than our OTLs. I've not made a direct claim about how these amps sound as that would violate the terms and conditions that allow me to post on most websites. View attachment 81344

Bruno is brilliant, but IMO he is making a mistake in offering his modules as a thing you can build up. This includes the input circuit; and depending on how well you do with that and the power supply you're going to get really variable results! IME you really don't want to use a Switch Mode Power Supply since SMPS units tend to have lots of current limiting protections which can make them tricky to use in an audio amplifier; you can get around that by going custom but no SMPS supplier will pay attention to you if you can't order 1000 units at a time. So if the amps you heard didn't have their ducks in a row you really won't know what a class D amp can really do.

JBL L100 Century - Vintage Speakers Review at Audio Nostalgia

Review of JBL L100 Century – vintage bookshelf speakers from 1970s. History of the speakers, look and feel of the drivers and enclosures, technical specifications as well as author’s subjective opinion about their sound. All of this supported with many photos and a video.

audionostalgia.co.uk

Not sure where you are getting JBL rated it in efficiency...reference please.

So, in fact not all your OTLs are feedback free...its ok to say so rather than be misleading by saying that none of your amps use feedback (especially now that you have a mega feedback amp).

I need to go back to this so-called "rule" that one shouldn't use a SET beyond 20-25% of it's rated power. Are you the one who has come up with this "rule"? I would like to see some evidence that this true because what I have seen from good SETs is that the distortion is rising steadily and smoothly with increase in power but as the SPL is also increasing the effect of increasing distortion is offset as perception of distortion is SPL dependent. I don't think this can be a hard and fast rule but might be applicable for using a SET with lower sensitivity speakers where the distortion relative to SPL would not allow as good masking. I might point out that your amps would also have this same issue...at least the ones without negative feedback as they too will have rising distortion with increasing power in the same manner as a SET.

In addition, I don't think your characterization as to what is happening for distortion products is correct. High order harmonics will be indicative of loudness but not necessarily a perception of dynamics. As these products rise there is the sensation of oppression on the ears as unpleasant artifacts are being introduced creating a desire to turn down the volume. Tube amp dynamics are probably more due to the compression that occurs as they reach their limits but also what Peter Van Willenswaard observed that they can deliver much more instantaneous voltage than a transistor amp...so they perform way beyond their static rating.

The new Class D amp you have is not a commercially available product from you despite having a patent for 2 years...why not?

 

[jeff1225]

I don't think its clear that JBL was using 'sensitivity' as they rated the L100 Century in efficiency. That would have been about 1970.

Our two smallest OTLs use about 2dB of feedback which is far too little to deal with the kind of impedance changes I mentioned in my last post. You are not quite correct in saying:

-if the rest of the speaker had an impedance much higher or for that matter much lower. But keep in mind that the vintage stuff had level controls for the mids and highs as the voltage response was an unknown.



To do this you would violate the rule of only expecting 20-25% of full power out of the amp, and so I think you'll find that if you interview people using SETs in this manner that they will report how 'dynamic the amp is for so little power'; this is because higher ordered harmonics are appearing on the leading edges of transients. The ear uses the higher ordered harmonics to sense sound pressure; hence 'dynamic'. But its really distortion masquerading as 'dynamics'. If you really want to hear what the amp is really all about, you simply need more efficiency out of the loudspeakers!



We were granted a class D patent two years ago this November. We have a class D concept we are working on and its entirely our own design. Its a self-oscillating amplifier and runs about 38dB of feedback. We've built a few and it demonstrated for me that the distortion signature is far more important than the amount of distortion. In our case it worked out that the issues that cause distortion in the amp result in lower ordered harmonics, and they are similar to a tube amp in the regard that they have enough amplitude that they mask the presence of the higher orders, although overall the amp has over an order of magnitude lower distortion than our OTLs. I've not made a direct claim about how these amps sound as that would violate the terms and conditions that allow me to post on most websites. View attachment 81344

Bruno is brilliant, but IMO he is making a mistake in offering his modules as a thing you can build up. This includes the input circuit; and depending on how well you do with that and the power supply you're going to get really variable results! IME you really don't want to use a Switch Mode Power Supply since SMPS units tend to have lots of current limiting protections which can make them tricky to use in an audio amplifier; you can get around that by going custom but no SMPS supplier will pay attention to you if you can't order 1000 units at a time. So if the amps you heard didn't have their ducks in a row you really won't know what a class D amp can really do.

When will you start shipping the new class D amps Ralph?

 

[Atmasphere]

JBL L100 Century - Vintage Speakers Review at Audio Nostalgia

Review of JBL L100 Century – vintage bookshelf speakers from 1970s. History of the speakers, look and feel of the drivers and enclosures, technical specifications as well as author’s subjective opinion about their sound. All of this supported with many photos and a video.

audionostalgia.co.uk

Not sure where you are getting JBL rated it in efficiency...reference please.

So, in fact not all your OTLs are feedback free...its ok to say so rather than be misleading by saying that none of your amps use feedback (especially now that you have a mega feedback amp).

I did provide the JBL reference earlier- I don't see the point in linking it again.

I need to go back to this so-called "rule" that one shouldn't use a SET beyond 20-25% of it's rated power. Are you the one who has come up with this "rule"? I would like to see some evidence that this true because what I have seen from good SETs is that the distortion is rising steadily and smoothly with increase in power but as the SPL is also increasing the effect of increasing distortion is offset as perception of distortion is SPL dependent. I don't think this can be a hard and fast rule but might be applicable for using a SET with lower sensitivity speakers where the distortion relative to SPL would not allow as good masking. I might point out that your amps would also have this same issue...at least the ones without negative feedback as they too will have rising distortion with increasing power in the same manner as a SET.

Because our amps are fully differential they have distortion cancellation at every stage throughout the amp, so it does not compound distortion as much from stage to stage as you see in an SET. This means that the THD at full power is about 1/20th (0.5% THD at full power) that of an SET; this is the result of a cubic non-linearity as opposed to the quadratic non-linearity of an SET. Additionally higher orders fall off at a faster rate.

It seems to me that what you are not understanding is that even though the lower ordered harmonics that the SET makes will mask the higher orders, that does not mean that the ear does not respond to their presence. Again, the ear/brain system uses the higher ordered harmonics to sense sound pressure. Whether you can hear them outright (as in a solid state amp) is irrelevant- the ear still interprets them as sound pressure. Below 20-25% of full power these harmonics are at a very low level (one of the advantages of an SET is that as you decrease the power, the distortion drops to unmeasurable, which is why they have a very good first watt); above that level (which is very close to clipping since clipping is only 6dB more than 25% of full power; musical transients can be a lot more than 25% of amplifier power so this number is very conservative) they can't be ignored by the ear.

In addition, I don't think your characterization as to what is happening for distortion products is correct. High order harmonics will be indicative of loudness but not necessarily a perception of dynamics. As these products rise there is the sensation of oppression on the ears as unpleasant artifacts are being introduced creating a desire to turn down the volume. Tube amp dynamics are probably more due to the compression that occurs as they reach their limits but also what Peter Van Willenswaard observed that they can deliver much more instantaneous voltage than a transistor amp...so they perform way beyond their static rating.

If you think about where the power is, most of the time its the leading edges of transients. When the higher orders show up in quantity only on the leading edges, it imparts a sense of 'dynamics'. I did explain earlier that this is the case. Peter is correct but what's being ignored here is that SETs are Power Paradigm devices and most solid state amps are Voltage Paradigm devices. This literally means that an SET will have highly variable voltage output depending on the load while a solid state amp will not- its voltage output will be constant. More information is at this link:

Resources: Paradigms in Amplifier Design

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

www.atma-sphere.com

The new Class D amp you have is not a commercially available product from you despite having a patent for 2 years...why not?

Yeah- we had a prototype only 6 months into the project that demonstrated to us that this was worth pursuit. It had a few artifacts that you had to listen past- a little high frequency buzz and some hiss. Additional work slowly reduced those artifacts before and after the patent was issued. We now have the noise floor down to the point that on my horns I have to have my head in the mouth of the horn to hear it. So the short answer is 'it took a while'

When will you start shipping the new class D amps Ralph?

We've already shipped a few from our first run of semi production to people from whom we are looking for comments. Confirmation bias can be a terrible thing; we think we like what we hear, we think it has low distortion, we think it measures well otherwise, but when it comes down to it, we really want to know that others hear the same thing we do. We've run into supply side shortages that have really slowed things down in the last 3 months but we are working on the next run of amplifiers right now. I expect with all the delays they will be shipping in October...

 

[Duke LeJeune]

We've already shipped a few from our first run of semi production to people from whom we are looking for comments. Confirmation bias can be a terrible thing; we think we like what we hear, we think it has low distortion, we think it measures well otherwise, but when it comes down to it, we really want to know that others hear the same thing we do. We've run into supply side shortages that have really slowed things down in the last 3 months but we are working on the next run of amplifiers right now. I expect with all the delays they will be shipping in October...

I'm a recipient of one of those semi-production pairs, which has since been forwarded to the next person (who told me that he is buying the pair). In my opinion this new Class D amp sounds like Ralph's OTL amps. The difference is, the way it interacts with a loudspeaker's impedance curve is characteristic of a solid state amp, not an OTL amp (or other high-output-impedance amp like an SET). This of course opens up a much wider range of speaker options.

Let me try to put into perspective how much I like Ralph's amps:

Every single one of my loudspeaker designs (going back to my first commercial product in 2005) has compatibility with his smaller OTL amps, the S-30 and/or M-60, as a primary requirement. At audio shows, I have shown with Ralph's amps more than all others combined. I never imagined there would be an amplifier which combined easy speaker compatibility with OTL-class sound quality, much less in such an otherwise user-friendly format. The only downside is that my speakers will no longer be "especially compatible with Atma-Sphere amps", so my marketing department will have to come up with a new pitch.

I will be purchasing a pair of the full-production version when they become available, because I want to be able to ship a fully representative demo pair to the skeptical-but-curious.

 

[matakana]

This is of particular interest, SET using the 6c33c tubes, all totally custom built to customers spec, and remote too , nice!

 

[MrC.]

IME you really don't want to use a Switch Mode Power Supply since SMPS units tend to have lots of current limiting protections which can make them tricky to use in an audio amplifier;

This suggests you are using a linear power supply with magnetics instead of chips to convert power. Does this amp double voltage into a half impedance load? What are it’s outputs into 8, 4, 2 ohms?

 

[Atmasphere]

This suggests you are using a linear power supply with magnetics instead of chips to convert power. Does this amp double voltage into a half impedance load? What are it’s outputs into 8, 4, 2 ohms?

It will, but not into 2 ohms (its current limited, so as long as the amp isn't at full power it will double power into 2 ohms from 4 ohms). But if there is a 2 ohm dip in the impedance curve of the speaker it will handle that just fine. Right now they are 100 watts into 8 ohms and 200 into 4.

 

[the sound of Tao]

Very happy with this move. The WE300Bs really have brought in a big chunk of magic. I was toying for going with another amp for the main system but I doubt that it would have bought the kind of step up that went with these WE300Bs.

$1500 usd a pair is a good chunk of cash but nothing in the scheme of the high end and what this upgrade has brought with it. I’ve heard plenty of top end amps and what I’m now getting out of this current setup may not necessarily be universally better than all but very definitely is competitive and more on point for what I really love. This WE300B balance fits beautifully with all upocc silver signal cables and brings with them a lovely fleshy balance, full lively dynamics and a real sense of effortless musical ease and flow.

The Linlai moly 805s will likely be the next change up for this amp. Each step is just moving closer again to where I would like to get it. Based on what I am hearing I’ll likely get in a few pair of the WE300Bs this year. One pair as back-up for this system and the other to run in the LM Set for the Harbeth 40.2s. The new WE is way good

 

[morricab]

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Very happy with this move. The WE300Bs really have brought in a big chunk of magic. I was toying for going with another amp for the main system but I doubt that it would have bought the kind of step up that went with these WE300Bs.

$1500 usd a pair is a good chunk of cash but nothing in the scheme of the high end and what this upgrade has brought with it. I’ve heard plenty of top end amps and what I’m now getting out of this current setup may not necessarily be universally better than all but very definitely is competitive and more on point for what I really love. This WE300B balance fits beautifully with all upocc silver signal cables and brings with them a lovely fleshy balance, full lively dynamics and a real sense of effortless musical ease and flow.

The Linlai moly 805s will likely be the next change up for this amp. Each step is just moving closer again to where I would like to get it. Based on what I am hearing I’ll likely get in a few pair of the WE300Bs this year. One pair as back-up for this system and the other to run in the LM Set for the Harbeth 40.2s. The new WE is way good

I have heard that the WE 300bs are pretty "midrangey" tubes compared to modern (read East European) alternatives. Any observations on this? I have a small pair of 300b monos on my DIY system and I use the TJ Mesh plates, which sounded very open and "delicate"...perfect for the high frequency compression drivers they power.

 

[the sound of Tao]

I have heard that the WE 300bs are pretty "midrangey" tubes compared to modern (read East European) alternatives. Any observations on this? I have a small pair of 300b monos on my DIY system and I use the TJ Mesh plates, which sounded very open and "delicate"...perfect for the high frequency compression drivers they power.

I had originally thought about the Linlai moly 300Bs also Brad but the decision came down for me in that the pre is OTL, the system is OB and mid bass is very open and it is all wired up throughout with upocc silver cables. I bought just one pair of the WE300Bs figuring if the balance wasn’t where I wanted to go I’d also get in the 300B Linlai tubes then as well to try.

The Linlai moly 805s will be the next port of call. From the moment I heard the WE300B they had a rightness to them but it’s within a system context and immediacy and resolution aren’t shortfalls on this setup at all. I’ll be honest I’m absolutely loving the outcome and not thinking at all about wanting anything different from these tubes. If I had different cables though I may well have travelled down a different path or not quite so assured in this one… but this (very fortunately) has exactly unfolded just as envisioned as an ideal direction for this system. Just super happy with these.

 

[morricab]

A couple of new SETs to play with

 

[morricab]

The first is the Amare Musica Entropy Diamond, which is only 2 tubes per channel. Both are DHT both from EML. The input driver tube has about 20db if gain but can also serve as a 5 watt output tube. The actual output tube is an EML 1605, good for 23 watts.
The second Is an Ayon Helios, which is a 40 watt PSE using the 6c33c triode driven by a pair of EL84s and a 12AU7 input stage.

 

[Cableman]

Audiopax Model 88 Mk2 amps with GEC 1960s KT88s and Siemens 1960s ECC81 pre drivers. All cryogenically treated. The amps have the utterly unique but near impossible to set (because of the ‘infinite’ settings quandary - when is it set correctly ?- thankfully I was able after many MANY failed attempts to do it) amp/speakers Timbre Lock device.

Loudspeakers: Audiopax Ref 100s

 

[DeadWax]

View attachment 81809
View attachment 81810
Very happy with this move. The WE300Bs really have brought in a big chunk of magic. I was toying for going with another amp for the main system but I doubt that it would have bought the kind of step up that went with these WE300Bs.

$1500 usd a pair is a good chunk of cash but nothing in the scheme of the high end and what this upgrade has brought with it. I’ve heard plenty of top end amps and what I’m now getting out of this current setup may not necessarily be universally better than all but very definitely is competitive and more on point for what I really love. This WE300B balance fits beautifully with all upocc silver signal cables and brings with them a lovely fleshy balance, full lively dynamics and a real sense of effortless musical ease and flow.

The Linlai moly 805s will likely be the next change up for this amp. Each step is just moving closer again to where I would like to get it. Based on what I am hearing I’ll likely get in a few pair of the WE300Bs this year. One pair as back-up for this system and the other to run in the LM Set for the Harbeth 40.2s. The new WE is way good

Which 300B tubes were you using before the WE's?...stock? I'm using the EML 300B-XLS's in my LM805 and am quite happy but I have to say these WE's are intriguing. Just wondering if I'd recognize much of an incremental difference in sound over the EML's.

 

[marslo]

The first is the Amare Musica Entropy Diamond, which is only 2 tubes per channel. Both are DHT both from EML. The input driver tube has about 20db if gain but can also serve as a 5 watt output tube. The actual output tube is an EML 1605, good for 23 watts.
The second Is an Ayon Helios, which is a 40 watt PSE using the 6c33c triode driven by a pair of EL84s and a 12AU7 input stage.

Those Amare amps ( De Forest Pre and Diamond monoblocks) were the best I auditioned at home with my former AG Duo Omega.

 

[christoph]

Those Amare amps ( De Forest Pre and Diamond monoblocks) were the best I audioned at home with my AG Duo Omega.

Even better than the Ayon C3?