Speaker Oasis...Bionor

[thedudeabides]

Thanks for the info morricab.

Maybe I don't quite "get it" because I've had a Pass Labs amp in my system for some eight years now and it still sounds pretty sweet to me.

Best.

 

[morricab]

Thanks for the info morricab.

Maybe I don't quite "get it" because I've had a Pass Labs amp in my system for some eight years now and it still sounds pretty sweet to me.

Best.

Have you owned a SET?

 

[PeterA]

With regard to SOTA SS amps, it used to be that their goal was to push the level of distortion down to a level where it was "inaudible"...except that it really wasn't because the main cure for distortion, negative feedback, apparently doesn't work psychoacousticaly as expected. That has to do with how it creates and shifts the harmonic order from low to high and creates a pattern never seen in nature. The pinnacle of this was Halcro and is now probably Soulution or a few others out there. However, there are several others, like Pass and darTZeel that have gone with much less negative feedback and you can see this clearly in STereophile measurements. This has sonic consequences as well but interestingly seems to be at least as well received. NONE of them have anything close (except perhaps the Pass Class A amps) to what Cheever (and much earlier Jean Hiraga) would have considered a "natural" harmonic progression.

Keith Howard also did an interesting test where he wrote some computer code to add distortion to a digital music file. He could put all kinds of patterns at many different levels to simulate amplifier distortion. You can read this article online at Stereophile. He found that the undistorted file sounded the best but the least destructive was a monotonic pattern with alternating even and odd harmonics in an exponential decay of level, which is the pattern of a good SET. The worst was the all odd order distortion, which is typical of a Class AB push pull amplifier with negative feedback. DarTZeel has a picket fence of low and high order harmonics at about the level regardless of order (see Soundstage measurements for this amplifier by googling NHB108 and soundstage review).

So, while the SS designers can disagree (Nelson Pass actually seems to more or less agree though) the results of tests indicate that they should pay more attention to psychoacoustic properties.

Great post, morricab. I was going to ask about Nelson Pass' single ended Class A designs. The Pass team is know to do a lot of listening tests in addition to measurements as they fine tune each design. They do seem to combine certain strengths of both SS and tube sound, to my ear.

I have not owned SET amps as I'm not sure any could drive my speakers properly.

 

[morricab]

Great post, morricab. I was going to ask about Nelson Pass' single ended Class A designs. The Pass team is know to do a lot of listening tests in addition to measurements as they fine tune each design. They do seem to combine certain strengths of both SS and tube sound, to my ear.

I have not owned SET amps as I'm not sure any could drive my speakers properly.

THere are several that could do the job with Magico Mini IIs. KR Audio, Ayon, NAT, NAF and some good chinese ones like Line Magnetic can all drive them just fine. You might like getting the amp right and then optimize the speaker...just a thought...

 

[LL21]

Great post, morricab. I was going to ask about Nelson Pass' single ended Class A designs. The Pass team is know to do a lot of listening tests in addition to measurements as they fine tune each design. They do seem to combine certain strengths of both SS and tube sound, to my ear.

I have not owned SET amps as I'm not sure any could drive my speakers properly.

THere are several that could do the job with Magico Mini IIs. KR Audio, Ayon, NAT, NAF and some good chinese ones like Line Magnetic can all drive them just fine. You might like getting the amp right and then optimize the speaker...just a thought...

Hi, Morricab, i have actually copied and pasted posts from you from 8 years ago regarding Wilson X1s, Apogee Grands, etc and kept them in my 'Audio Articles' file...thanks for the many, many years of interesting and enlightening posts!

As for your comment on SETs, that is most interesting...i remember asking about FM Acoustics from one of their US dealers, and he admitted that using the FM 411 amp to drive the Magico Minis actually caused them to shut down/go into protection mode. We were discussing whether the FM 411s could drive anything...he said 'yes'...and when i specifically asked about the magico minis, he said 'okay, that is an exception...he had tried them himself, and the amp went into protection due to the wicked impedance/whatever that is hard on amps.

If an SET amp could drive them, that teaches me something about [some] SETs which i did not know before. perhaps that also explains how Audiocrack has so successfully driven his incredibly huge Genesis 1.1s with Kondo SETs and manages take-your-breath away dynamics and scale.

 

[bonzo75]

Hi, Morricab, i have actually copied and pasted posts from you from 8 years ago regarding Wilson X1s, Apogee Grands, etc and kept them in my 'Audio Articles' file...thanks for the many, many years of interesting and enlightening posts!

As for your comment on SETs, that is most interesting...i remember asking about FM Acoustics from one of their US dealers, and he admitted that using the FM 411 amp to drive the Magico Minis actually caused them to shut down/go into protection mode. We were discussing whether the FM 411s could drive anything...he said 'yes'...and when i specifically asked about the magico minis, he said 'okay, that is an exception...he had tried them himself, and the amp went into protection due to the wicked impedance/whatever that is hard on amps.

If an SET amp could drive them, that teaches me something about [some] SETs which i did not know before. perhaps that also explains how Audiocrack has so successfully driven his incredibly huge Genesis 1.1s with Kondo SETs and manages take-your-breath away dynamics and scale.

Rhapsody too drives his Magicos with Kondos (and with Vitus).

 

[PeterA]

Rhapsody too drives his Magicos with Kondos (and with Vitus).

Does Rhapsody have Mini IIs? I think they are harder than the current Magico lineup.

 

[bonzo75]

Does Rhapsody have Mini IIs? I think they are harder than the current Magico lineup.

No but you should check with him if he has tried it since he is a Magico dealer so will have experience. That's rsvinta on this forum

 

[PeterA]

THere are several that could do the job with Magico Mini IIs. KR Audio, Ayon, NAT, NAF and some good chinese ones like Line Magnetic can all drive them just fine. You might like getting the amp right and then optimize the speaker...just a thought...

Thanks for the advice, morricab. I used to own the Pass XA100.5 but found that they did not quite have enough power for the Mini II. The 160.5 is better, though I was not aware that it is not right. At the moment, I'm quite happy with my combination, and am not interested in changing amps or speakers.

Sorry to be so off topic. Back to horns.

 

[microstrip]

THere are several that could do the job with Magico Mini IIs. KR Audio, Ayon, NAT, NAF and some good chinese ones like Line Magnetic can all drive them just fine. You might like getting the amp right and then optimize the speaker...just a thought...

The Mini IIs sounded great with the Audio Research REF750s - they did not sound "mini" anymore. Unfortunately it was also a lot of heat and 40 power tubes!

An old net acquaintance told me he drives his Mini II's with a pair of David Berning's Quadrature 200 driven by an Atmasphere MP-1.

 

[FrantzM]

Not even the degrees, the fundamental type of distortion is different. The SS amps are much further away in what is psychoacousticly acceptable.

http://dancheever.com/main/cheever_thesis_final.pdf

http://www.gedlee.com/downloads/Distortion_AES_I.pdf

http://www.gedlee.com/downloads/Distortion_AES_II.pdf

http://www.stereophile.com/reference/406howard/#oYgmJM1yF3xlQvjy.97

I am familiar with Geddes position and just to make sure, I re-read the papers you linked us to ... It could be that I did not understand your previous statement thus asking you to clarify it... Are you saying SS impose less of their character on the reproduction or that they are less psychoacoustically acceptable than SET? If your contention is the latter, the Geddes papers you referred us to doesn't support that point of view .. All the contrary.
I haven't read the Cheever apers yet

 

[ddk]

Hi, Morricab, i have actually copied and pasted posts from you from 8 years ago regarding Wilson X1s, Apogee Grands, etc and kept them in my 'Audio Articles' file...thanks for the many, many years of interesting and enlightening posts!

As for your comment on SETs, that is most interesting...i remember asking about FM Acoustics from one of their US dealers, and he admitted that using the FM 411 amp to drive the Magico Minis actually caused them to shut down/go into protection mode. We were discussing whether the FM 411s could drive anything...he said 'yes'...and when i specifically asked about the magico minis, he said 'okay, that is an exception...he had tried them himself, and the amp went into protection due to the wicked impedance/whatever that is hard on amps.

If an SET amp could drive them, that teaches me something about [some] SETs which i did not know before. perhaps that also explains how Audiocrack has so successfully driven his incredibly huge Genesis 1.1s with Kondo SETs and manages take-your-breath away dynamics and scale.

Gen 1 is an easy load nothing like the small Magicos!

david

 

[morricab]

I am familiar with Geddes position and just to make sure, I re-read the papers you linked us to ... It could be that I did not understand your previous statement thus asking you to clarify it... Are you saying SS impose less of their character on the reproduction or that they are less psychoacoustically acceptable than SET? If your contention is the latter, the Geddes papers you referred us to doesn't support that point of view .. All the contrary.
I haven't read the Cheever apers yet

No, you are not correct. The distortion mechanisms that Geddes introduces are typical for push/pull Class AB amplifiers and it is also clear from the papers that the THD and IMD are very poor predictors of sound quality (even arguably slightly ANTI-predictors!). The GedLee metric takes into account weighting for higher order harmonics that are more damaging to sound quality and level. Masking of disotrtion is better the closer the harmonic is to the fundamental and at higher signal levels. SETs work the best where it is most critical, i.e. low levels and with low order harmonics and SS amps work best where it is least important, i.e. high signal levels (look at distortion vs. power curves between the two and it becomes obvious).

Negative feedback helps to push down low orders of harmonic distortion (2nd and 3rd order) but at the expense of creating a myriad of low level high order harmonics as demonstrated by Crowhurst. Geddes models make it clear that this is less preferrable sonically. CHeever reemphasizes this and makes it more explicit. Push Pull amplifiers generate predominately odd order harmonics, which are generally more dissonant and they suffer from zero crossing distortion that makes a whole picket fence of distortion products.

Not sure how you were interpreting Geddes conclusions. The drive to push THD to super low levels with lots of negative feedback doesn't jive with research being done on correlation with hearing preference.

 

[FrantzM]

Not even the degrees, the fundamental type of distortion is different. The SS amps are much further away in what is psychoacousticly acceptable.

No, you are not correct. The distortion mechanisms that Geddes introduces are typical for push/pull Class AB amplifiers and it is also clear from the papers that the THD and IMD are very poor predictors of sound quality (even arguably slightly ANTI-predictors!). The GedLee metric takes into account weighting for higher order harmonics that are more damaging to sound quality and level. Masking of disotrtion is better the closer the harmonic is to the fundamental and at higher signal levels. SETs work the best where it is most critical, i.e. low levels and with low order harmonics and SS amps work best where it is least important, i.e. high signal levels (look at distortion vs. power curves between the two and it becomes obvious).

Negative feedback helps to push down low orders of harmonic distortion (2nd and 3rd order) but at the expense of creating a myriad of low level high order harmonics as demonstrated by Crowhurst. Geddes models make it clear that this is less preferrable sonically. CHeever reemphasizes this and makes it more explicit. Push Pull amplifiers generate predominately odd order harmonics, which are generally more dissonant and they suffer from zero crossing distortion that makes a whole picket fence of distortion products.

Not sure how you were interpreting Geddes conclusions. The drive to push THD to super low levels with lots of negative feedback doesn't jive with research being done on correlation with hearing preference.

Yet ... Geddes use a Pioneer receiver as his amplification of choice...

Perhaps we should bring this to a different thread care to open it ? It is an interesting discussion as we came to different conclusion reading the same papers .. Would likes other to chime in...

 

[morricab]

Yet ... Geddes use a Pioneer receiver as his amplification of choice...

Perhaps we should bring this to a different thread care to open it ? It is an interesting discussion as we came to different conclusion reading the same papers .. Would likes other to chime in...

He has a speaker designer's bias. What one believes inherently is also something that can bias one's judgement.

 

[microstrip]

Yet ... Geddes use a Pioneer receiver as his amplification of choice...

Perhaps we should bring this to a different thread care to open it ? It is an interesting discussion as we came to different conclusion reading the same papers .. Would likes other to chime in...

Frantz,

Others have chimed in WBF several times about this subject. We had contributions of Ralph Karsten and I referred to studies of Jean Hiraga. We have references about models of some designers, such as Vladimir Lamm. Most information is proprietary of designers and they do not want to share it openly. Also most people will consider them as "opinions" as they are not per reviewed contributions in scientific papers.

Lots of information concerning this interesting subject is spread and accessible in the net but as far as I know no one wrote a PhD thesis or a review paper on it. IMHO if you are really interested you must carry your own search and please your healthy curiosity. I did it long ago as curious amateur, but I am not knowledgeable enough about the subject to educate people. I recently learned a lot just surfing in the diyAudio.com forum http://www.diyaudio.com/ - some experts participate there and they have very open debates.

Unfortunately some of the most interesting articles on the subject were from the 60's and 70's and I do not have easy access to them any more, neither the time or interest of the past. One of the most delicious I read was even from the 50's in a Bell Labs publication that referred against bias expectation of DIY audio builders ... Letters to the editor and the respective well though answers, one or two months later, were also a great source of information. But no, I have not kept any records of this search.

 

[morricab]

Frantz,

Others have chimed in WBF several times about this subject. We had contributions of Ralph Karsten and I referred to studies of Jean Hiraga. We have references about models of some designers, such as Vladimir Lamm. Most information is proprietary of designers and they do not want to share it openly. Also most people will consider them as "opinions" as they are not per reviewed contributions in scientific papers.

Lots of information concerning this interesting subject is spread and accessible in the net but as far as I know no one wrote a PhD thesis or a review paper on it. IMHO if you are really interested you must carry your own search and please your healthy curiosity. I did it long ago as curious amateur, but I am not knowledgeable enough about the subject to educate people. I recently learned a lot just surfing in the diyAudio.com forum http://www.diyaudio.com/ - some experts participate there and they have very open debates.

Unfortunately some of the most interesting articles on the subject were from the 60's and 70's and I do not have easy access to them any more, neither the time or interest of the past. One of the most delicious I read was even from the 50's in a Bell Labs publication that referred against bias expectation of DIY audio builders ... Letters to the editor and the respective well though answers, one or two months later, were also a great source of information. But no, I have not kept any records of this search.

Indeed, the work of Crowhurst is also very interesting in this field. He found that not only does negative feedback generate a myriad of high order components, this actually serves to create an artificial "noise" floor that instead of being true noise that is uncorrelated with the signal, it is a signal modulated noise floor that masks low level information.

Going back even further there was work by the BBC engineer D.E.L. Shorter. He came up with a relatively simplistic weighting function as to the relative audibility of increasing harmonic order. I actually did an interesting paper experiment where I took the distortion data that one can obtain from Soundstage online, which has a nice consistent set of data for 1Khz sine wave FFT spectra. They also have distortion with power and wiht frequency. I took the sum of harmonics and then weighted it as per Shorter and found that the weighting had a dramatic impact in the distortion amounts from each amp. Once weighting was applied the SETs did very well indeed and were ranked higher than their SS counterparts, some of which had low low distortion. That is because when it is the square of the harmonic order it gets to be a quite steep increase in significance. Also, I readjusted for the power used in the measurements.

I did this for like 20 amps or so of all different types. Unfortunately I had a hard drive crash and lost the file. I haven't had the drive to start again from scratch but if my memory serves, the best amp from a distortion POV once weighted with Shorter's equation was the Wyetech Labs Topaz 211 based SET. I might try to build it again someday but it is time consuming and I have a lot less of that these days.

Based on Cheever's work, he indicates that Shorter's equation was not extreme enough to truly capture the impact from the high order harmonics. His equation captures SPL level as it affects the masking ability of the hearing mechanism.

 

[LL21]

All i can say is this last several posts have been (for me) some of the most fascinating to read...as Micro says, i have also enjoyed reading Ralph Karsten's posts about this as well. Thanks, gents (Morricab, Micro, FrantzM). Feel free to keep going!

Morricab - on the SS side, i am just curious to know whether you found certain SS designs met your preferred criteria better? I inquire (naturally) of Class A SS with no global negative feedback.

 

[PeterA]

Morricab - on the SS side, i am just curious to know whether you found certain SS designs met your preferred criteria better? I inquire (naturally) of Class A SS with no global negative feedback.

Good question, Lloyd. How does this sound compare to SETs, in a general sense.

 

[morricab]

All i can say is this last several posts have been (for me) some of the most fascinating to read...as Micro says, i have also enjoyed reading Ralph Karsten's posts about this as well. Thanks, gents (Morricab, Micro, FrantzM). Feel free to keep going!

Morricab - on the SS side, i am just curious to know whether you found certain SS designs met your preferred criteria better? I inquire (naturally) of Class A SS with no global negative feedback.

From my POV, only single ended transistor or hybrid single ended has potential. I tried this route not too long ago with the 70Kg (154lb!) NAT Symbiosis SE, which was basically an all-out assault on the Single ended hybrid. It sounded...really good once it got past the 2 hour mark of actually playing music. It had the tonality of a SET but there was still a bit of transistoriness until about 2 hours of playing. Then it got sort of psychadelic sounding... I finally sold it because waiting 2 hours to sound like it could was annoying and didn't fit my listening habits.

If you have sensitive speakers the Pass SIT amps or the Pathos TT might be interesting...one is pure SS and the other is a hybrid with transistor output. At the extreme end of the scale there is the Ypsilon monos that are hybrid SET. There are also some old Blue Circle BC2s out there that sound pretty good supposedly.

Note, I didn't mention a push/pull amp...