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In Reply to: RE: With only 93dB in most rooms you're going to need some power. posted by morricab on September 09, 2021 at 13:06:38
I know that to prevent phase shift as a designer you have two options. The first is to have wide bandwidth, the 2nd to have high feedback (+35dB). The latter isn't practical for tube amps and most solid state (insufficient gain bandwidth product, insufficient phase margins), so they have to go with the former.
To prevent phase shift at 20Hz you have to be flat to 2Hz. To go to 10KHz without phase shift you need to be flat to 100KHz.
Phase shift at a single frequency is inaudible. But over a spectrum of frequencies its perceived as a tonal coloration and can affect the soundstage presentation.
So are you telling me there are high power (+30 Watts) SETs out there that have full power bandwidth from 2Hz to 100KHz?? That would be really impressive; I know of very few P-P amps that can do that!
Follow Ups:
http://aries-cerat.eu/products/amplifiers/concero-65
Power: 65W
Power consumption per channel: 400W
Noise floor: -90db(Ref) un-weighted
Gain: x2.7 (8.5db)
Inputs: RCA, AC link proprietary input
Energy storage: 2000j
1,800VA power transformer
Signal bandwidth: 10Hz-110KHz @80% max power
Output impedance: User selectable(impedance matching system)
1.6ohm(8ohm setting),0.8ohm(4ohm),0.4ohm(2ohm setting)
Distortion: -70db H2 @ 1W -50db H2 @10W
Adjustable bias on the fly
Output and driver on line monitors
No capacitor in signal path
SuperCapacitors used for output and driver power supply(1mohm ESR
capacitors)
Dimensions: 490mmW X 590mmD x 350mm (Reference line)
Weight: 95kg each
http://aries-cerat.eu/products/amplifiers/concero-25
Specifications:
Power : 20W ~ 25W depending on bias setting
Gain: X1 (x7 medium gain)
Noise floor: <-100db A-weighted
Power Bandwidth: 15Hz ~ 80Khz -3db @ 20W
Tube list: 1x Elrog 845, 1x RCA 814 (per channel)
Power Consumption @ idle: 200W
Dimensions: 550 mm W x 430 mm D x 280 mm H
Weight : 65Kg each, unpacked.
Not quite 100Khz but I doubt the phase shift is too significant
http://aries-cerat.eu/products/amplifiers/diana-forte-mezzo
Specifications
Max Power: 60W SE Class A (70W peak)
Max Power bandwidth: 15Hz- 110Khz
Noise floor: 100db
Combined gain: X 20 (26db)
Dimensions: 570mmW X 590mmD X 350mmH
Weight: 110Kg unpacked
Tubes: 2X814, 4 X 813
https://www.nataudio.com/products/vacuum-tube-power-amplifiers/item/27-transmitter-hps.html
echnical Specification
Name Value
Type Single Ended Class "A" Triode
Power Output max. 80 Watts @ 1 kHz
Frequency Response 8 Hz to 110 kHz -3dB
Input impedance 100 k ohms parallel with 100pF
Input Sensitivity 1.5 V RMS for 80 Watts
Gain 24.50 dB (x18.8)
Noise 110 dB below rated output "A" weighted
Tube Complement 2 x 6N6P, 1 x QB5/1750
Power Requirement 110 to 240 VAC @ 50 to 60 Hz, 370 VA max. (set in factory)
Dimensions 11.8" (300 mm) wide ´ 20.9" (530 mm) deep ´ 10.2" (260 mm) high
NET Weight approx. 89 lbs (40 kg) unpacked / per block
TOTAL Weight approx. 220 lbs (100 kg) packed in polypropylene crate / per pair
https://www.nataudio.com/products/vacuum-tube-power-amplifiers/item/24-se1-gm70.html
Technical Specification
Name Value
Type Single Ended Class "A"
Power Output up to 25 W @ 1 kHz, 8 ohms taps
THD 0.95% @ 20 W @ 1 kHz
Frequency Response 10 Hz to 70 kHz
Input Impedance 100 kohms parallel with 100pF
Input Sensitivity 1 V RMS for 25 Watts Output @ zero feedback
Gain 23 dB (x14)
Noise 108 dB below rated output "A" weighted
Tube Complement 1 x EC1010, 1 x 3E29 & 1 x GM70 (3 tubes/block, 2 tubes inside a chassis)
Power Requirement 220 to 240 (110 to 120) VAC @ 50 to 60 Hz, 180 VA max.
Dimensions 11.8" (300 mm) wide x 20.4" (520 mm) deep x 10.2" (260 mm) high
NET Weight approx. 60 lbs. (25 kg) unpacked / monoblock
TOTAL Weight approx. 133 lbs. (60 kg) packed in two polypropylene crate
Not quite 100Khz but 70Khz isn't bad...
https://www.ayonaudio.com/product/ayon-crossfire-evo-mono/
Bandwidth to 60Khz...
http://www.mastersoundsas.it/1/power_amplifiers_4432639.html
MasterSound amps have bandwidths of 80Khz + ...
https://www.wavac-audio.jp/ec300b_e.shtml
One of the better 300B amps out there...rated to 100Khz...
https://www.wavac-audio.jp/ec838_e.shtml
also to 100khz
None go to 2 Hz but several are single digits Hz while getting to 100Khz or close.
http://aries-cerat.eu/products/amplifiers/ianus-series/essentia
https://www.nataudio.com/products/hybrid-power-amplifiers/item/155-magneto.html
Something different for you. Single ended, single element hybrids that are OTL...
We still see in all these examples that bass impact will be an issue. Its the full power (not the 'signal bandwidth', whatever that means) bandwidth that really tells what is going on, keeping in mind that in this particular application, the OP will be pushing the amps for all that power.
I agree that if you can do 80KHz its probably just fine. But in terms of 'bass grunt and control' you'll be able to do better on account of the phase shift in the bass region will be robbing the amp of the impact that's really there in the recording.
As I said, its usually the bass region that gets compromised, although I'm sure they sound musical.
Hi Ralph!Brad is 100% correct. As an owner of an amp by one of the manufacturers he mentioned i.e., a 135LB, 40W/ch, Mastersound Reference 845, SET amp/integrated amp -{ depending on which I select, but I use it as an amp with a Don Sachs "Custom" SP14 preamp }- for the past 20+ years it has produced the most musical presentation you could imagine! I use it with 92 dB sensitive, Phase Coherent, Reference 3A Taksim speakers in a 15.7" W x 12.7" D room with an 8ft to 10ft sloped ceiling. The speakers are placed on the 15.7" W wall and where the ceiling is 8ft H.
When I listen to music I listen to about 75% smooth jazz, i.e., Spyro Gyra, Fourplay, Flim & the BB's, Acoustic Alchemy, etc., and 25% Prog-rock, i.e., Genesis, Kansas, YES, Marillion, Boston, etc. Now when I listen I usually like to listen to music a bit on the louder side, but not blasting the music by any means. The music is always musical with clean, crystal-clear highs due to the Taksim's pure Beryllium dome tweeter which uses a single, non-inductive, capacitor as the sole high pass filter! And below that wonderful sounding tweeter is a single, wideband, 8" driver with absolutely no Whizzer!
The rated freq. response is 31Hz to 40KHz and I can tell you the bass is deep enough I've never thought of getting a subwoofer. Why should I when a couple of times I've even been asked where the sub is? Truth be told I've never enjoyed listening to music as much as I do with the Mastersound/Reference 3A combo. Ralph if you ever visit Orlando, FL. send me a private message and I'll give you a way to get in touch so you can come over and hear what it sounds like for yourself. I think you'd be very surprised by what you hear. I just got the Taksims a few short months ago and I know I still am...
Thetubeguy1954 (Tom)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
Edits: 10/08/21
Have you used a sound pressure level meter to see how loud you're actually playing the system?
Ralph,
Believe it or not, I actually have an SPL app but never thought to measure the loudness. This coming Saturday when my wife goes shopping I'll be sure to set the preamp at a normal listening volume --- for me --- and measure what the loudness actually is! Now you have me curious...
Thetubeguy1954 (Tom)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
Nice speakers the Ref 3as. I owned 3 different pairs; Master Control MMC upgraded to the same Be tweeters as in yours, Le Integrale which I upgraded the soft dome tweeter to a better one and La Veritas... a smaller floorstander than the Le Integrales. All had the 8 inch hyper exponential driver with no xover. I upgraded to Odeon horns where I have stayed to this day. I am sure you're make a good combo with the Mastersound.
Hi Brad!
I may be mistaken, but I believe you may have mentioned owning some Reference 3A speakers before upgrading to your Odeon horns in the past! Perhaps you'd be willing to tell me what sonic improvements, other than an increase in sensitivity, you heard when upgrading to the Odeon horns? Your impressions about the sonic improvements you heard when switching from 3A to Odeon would be very much appreciated. Thanks for your time...
Thetubeguy1954 (Tom)
Central Florida Audio Society -- SETriodes Group -- Space Coast Audio Society
Full-range/Wide-range Drivers --- Front & Back-Loaded Horns --- High Sensitivity Speakers
Primarily dynamics...the Odeons sound significantly more realistic with acoustic instruments, particularly horns, strings and especially piano. There is more "action" in the presentation with a stronger sensation of a real person putting pressure on keys and hitting strings (for a piano) or the draw of the bow on strings. The blatt of horns is far more real (my daughter plays trumpet so i have a contemporaneous comparison) and gets a lot closer to my believing i am hearing the real thing.
Coherence and tonality are similar and the basic sensation of transparency is also similar...until you take into account the "action" and dynamic scaling. Then you realize there is additional information coming through with the Odeons that was not coming through with the Ref 3As.
Another friend of mine had Ref 3As (He also had the Master Control MMC like me...both of us upgrading to Be tweeters), that he got to replace Verity Audio Rienzi speakers. Then he heard my Odeons and was bowled over and went out and bought first a pair of Rigolettos (not the current version, which is hugely dynamic as well) and then a pair of No. 32s (a great, great speaker). His system now is very realistic sounding (with Aries Cerat Diana integrated amp that he bought from me) and doesn't think of upgrades anymore.
Just quietly off topic: those Odeon Rigoletto 2020 speakers do something for me. When I downsize, they are on the list! Back to normal programming.
Cheers.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
I just ordered myself a pair! Are they better than my 20 year old Odeon La Bohemes? But they are so good for so little money I had to have a pair. They are also dramatically better than the previous, already very good Rigolleto.
I say, go for it!
I was going to say the money is not so little...- the point is though that they appear to represent good value at their price point.
Let us know what you think when you've lived with them for a while. I'm curious!
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
In today's high end world, 6.5K is pretty low money for the level of performance I heard.
Bass is a problem of using too small of a core leading to saturation and a huge amount that increase in distortion that is surely audible as the harmonics run right through the midrange. The amps I linked mostly have huge output iron (particularly Aries Cerat...that weight is about iron.) so saturation is almost non-existent and bass has slam and control as well as texture.
Frequency response of the Hirata Tango 805 transformer. Maybe does not qutie meet your requirements, but from a listening perspective is more than acceptable at 50 watts. If you haven't heard one, perhaps talking it down is inappropriate.
The issue here is the OP is using speakers that are bit low in efficiency for use with SETs. I find that if you push an SET hard enough that it sounds 'dynamic' you're pushing it too hard, since that dynamic quality is caused by distortion. This is why you see so many comments about how 'dynamic' an SET is for its power output in reviews. They're simply asking too much power of them.
I suggested that he get an amp of at least 60 watts but to be successful with that kind of power he's going to need an amp that he can push to at least 90% of full power. You can't do that with SETs, not if you want to hear what they are all about.
This particular transformer is a bit curious as its equipped with a feedback winding. Have you heard it with the feedback applied?
No Ralph that is called clipping and it sounds unpleasant not dynamic.
Peter Van Willenswaard demonstrated that a SET will generate several times higher voltage on dynamic peaks than its static rating. Waveforms looked not real good but he declared it still sounded audibly clean.
I tend to agree, providing the power
supply can quickly supply the peak's
requirements without causing the amp
to go into clipping or time-delay
distortions.The "extra dynamics" that people note
when pushing a SET with an ordinary
power supply is current sag and LAG.
This causes the speaker woofer cone to misbehave,
causing the effect by pushing and pulling the woofer cone
as an AFTER EFFECT (time-lagged) effect of
the power supply sagging and restoring..This effect is initially started by a musical
low-frequency pulse, but it has departed
from following the music-- it departs from the music--
it's not following the music ON TIME.
The time sequence is LATE and distorted. The dynamic effect
is fake......The effect is eliminated by giving the SE amp low-DCR,
fast attack and quick restore power, with minimal timing
issues and minimal voltage & current sag when pulsed by
a low frequency "hit". The more repetitive these pulses
are, the more the conventional power supply lags behind the
music (in SE operation).. in many aspects, pushing and pulling
the woofer cone, when it shouldn't.Power supplies for SE amps must be low DCR, super fast, and
must be much larger than the amp is calculated to need....,
for instance, a power supply for a one-watt amp should be
the same electrical size as one for a 75 watt push/pull amp.At one audio show, a visitor asked me to take the front grille
off of my speakers so he could watch the woofer cones.He said, "if I see that cone move more than 1/32nd
inch, I'm outta here! And I expect great bass."He later said, "now that amp has a great power
supply".Next year, he asked if that pair of amps was still
around-- he wanted them.The man would go all over the Hotel, listening to music and
looking at woofer cones!-Dennis-
Edits: 10/02/21 10/02/21 10/02/21
-unless we're using different definitions. Since I have an technical/engineering background, I'm used to seeing amps clip on an oscilloscope and so define clipping as that point when a sine wave can no longer be increased in amplitude and so the amp clips off the top bit- that is where the term comes from.
But Stereophile defines clipping as 'anything above 1% THD' which is a different thing altogether!
So I'm not talking about clipping since we're talking about an amp that might only be making 50% of full power (although at that power level its in danger of being overloaded due to the logarithmic nature of the ear).
Yes, only with the feedback applied, per the schematic. I gather Hirata Tango made custom order transformer sets specifically for certain Shishido designs. Apparently the Shishido designs were initially produced commercially in Japan by Fine Arts, and later by Wavac (using ISO Tango or later xformers).
Not questioning your intent. OP asked specifically for SET options that he could try. I agree with you that limited power SET would likely not work acceptably with his speakers. Given the 6db down point at 30 Hz, bottom end of the speakers might be limited anyway. Don't know.
There is potentially a large difference between pure performance specs and musicality. Specs certainly do not assure musicality, and some pretty poor spec equipment can sound great. Listener impressions, like many on this thread, can be very useful (taken with caution).
There is potentially a large difference between pure performance specs and musicality. Specs certainly do not assure musicality, and some pretty poor spec equipment can sound great. Listener impressions, like many on this thread, can be very useful (taken with caution).
IME this is everything to do about the distortion signature. If there isn't a nice 2nd or 3rd harmonic to mask the higher orders, the latter will be audible as harshness and brightness since the ear converts distortion into tonality. The 2nd and 3rd are relatively innocuous so the ear can tolerate a lot of it.
I'm of the opinion that the distortion signature is more important than the amount of distortion. The signature will say how smooth the amp is. If you can get the same signature but at a lower overall level, you can get more detail.
So SETs do fairly well in this regard because of the 2nd harmonic. But you can get a better distortion signature by going fully differential and balanced from input to output. This will cause the predominate harmonic to be the 3rd (which is treated by the ear same as the 2nd) but at about 1/10th the level. Further, because distortion is compounded less from stage to stage throughout the circuit, the overall distortion will be lower and as the order of the harmonic is increased, its amplitude will fall off faster.
The SET has what is called a Quadratic Non-Linearity and the fully differential amp has a Cubic Non-linearity.
IMO/IME the cubic non-linearity is better because its smoother and more detailed. Its also quite a bit lower distortion. For example, our amps make about 0.5%THD with no feedback while an SET does about 10% before clipping. But the SET might make 7 watts, while one of our amps might make 60, 140 or even 200 watts. If you run them at the same power levels the SET can run, the distortion is a lot lower since both amps have the property of distortion dropping to unmeasurable as you decrease the output power.
So that's one thing. Another thing to look for is that the distortion should be the same at 100Hz, 1kHz and 10kHz. A lot of solid state amps (which otherwise have great specs) actually have distortion rising as frequency is increased; their feedback is falling off with frequency due to insufficient gain bandwidth product. This is part of the reason they are bright and harsh (the other being that feedback has suppressed the lower ordered harmonics).
So yeah, the specs don't tell the whole story but we do know how the amp is going to sound based on what we can measure. Its just that the measurements you need to see never show up on the spec sheets, and for that matter what's often considered important quite often isn't; its marketing rather than engineering.
If there isn't a nice 2nd or 3rd harmonic to mask the higher orders
Hey Ralph,
do you have a good reference on this? I have seen it mentioned in passing but have never seen a good paper on the concept.
dave
the article below isn't it but its certainly worth a read, from Nelson Pass.
I'd like pointers to the articles.
It is interesting that Nelson wrote the linked info back in 2013 and since then I hear he has been playing with the phase of the harmonics in successive stages so any 2nd generated remained in phase rather than nulled. Take a simple driver and output with a typical H2 dominant distortion spectra and the nature of the phase inversion puts the even order harmonics from each stage out of phase from the other creating a new overall spectra where the evens partially null leaving the odds to possibly dominate. The story goes Nelson would inset a 1:1 inverting transformer between the stages to keep the evens summing in phase so 2nd dominates and each following order declines.
The above is a rough paraphrase from my fuzzy memory... if anyone knows nelson's current thoughts please chime in.
dave
If you google "preamp variable 2nd harmonic added" you see that people are getting 'tube sound' with plug-ins and the like that add a variable 2nd harmonic.
Nelson made a harmonic generator that did that- he sold kits at the Burning Amp festival. Link below.
I am specifically looking for a citing in support of the following statement:The 2nd and 3rd are relatively innocuous so the ear can tolerate a lot of it.
this seems to suggest they are on equal footing and 1% 2nd is equivalent to 1% third. My experience has been that even order distortions are "friendlier" than odd and as the order increases the level of distortion needs to go down substantially to avoid objectionable sonics.
In respect to Nelson's 2d generator, I am having a hard time understanding what he actually means by the phase of the H2. As near as I can tell he is operating under the belief that there will already be some H2 in the signal and by adding additional H2 from an external source the phase relationships of the two are important.
I dove into spice and built a simple 300B stage that has 1.3% distortion with this spectra.
I then attenuated the signal to make it a unity gain stage and fed it to the grid of a second 300B operating in the same manner. I could then reverse the phase of the two "H2 generators" to illustrate what I believe to be the two conditions (H2+ and H2-) that nelson is referring to and came up with these two spectra.
if we then compare these harmonic profiles to nelsons genral tonal description things become much more (or less??) clear
from listening tests we learn that there is a tendency to
interpret negative phase 2nd as giving a deeper soundstage and improved localization than
otherwise. Positive phase seems to put the instruments and vocals closer and a little more
in-your-face with enhanced detail.It does seem to me that this is not a 100% direct correlation to exactly what nelson is discussing but I cannot envision how the phase of any given distortion spectra is relevant until it is combined with another spectra so you can get sum and difference effects. The biggest 2nd order generator in a system is typically the air speaker driver interface so none of this exists in a vacuum.
dave
Edits: 09/21/21
Take a look- see what you think.
the two things that strike me in the article (and the linked article by Lynn Olson) that jump out at me are this thought referenced to Norman Crowhurst:
Research by Norman Crowhurst points out that feedback mostly reduces the level of the 2nd and 3rd harmonics, leaving the upper harmonics more or less alone, or sometimes at higher level than before feedback. It doesn't take very much level of a 5th, 7th, or 9th harmonic to make the sound "bitter", "dry", "clinical", "cold" "small" "dynamically limited" or "harsh". This is all part of the psychoacoustics of distortion and masking.
This is all in reference to feedback reducing distortion and has nothing to do with masking even though both 2nd and 3rd are mentioned.
Later on in the article he does get into masking but at that point the "masking" generator is a tubed circuit that generates only 2nd order distortion and the "tube noise" raises the noise floor to bury all of the existing harmonics higher than 2nd in the increased noise floor.
both of the points that I extracted from a precursory glance do not seem to support the idea that the third harmonic is benign and helps mask higher orders. He does call 2nd order "sonic gold" but in all of the examples the third is way down and not seemingly a factor in the "sonic flavor" I do like that they give both the measured objective and the sonic subjective results for a number of different music selections which allows the reader to get a better feel for the relationships at hand.
dave
The pattern definitely matters, which is implied here by Crowhurst as the higher orders are largely left alone and the 2nd and 3rd are reduced having a negative impact on the sound.
Cheever also finds that SPL affects the sensitivity to high orders and the ear is more tolerant at higher SPL. This is why having no high order harmonics at lower SPL is critical because our hearing sensitivity to them is the highest.
-
I agree that anything odd other than the 3rd is not perceived well. They become more audible the further they are from the fundamental tone. That is why the 3rd is considered innocuous as the 2nd (and to a lessor degree, the 4th). I read this somewhere in the last 2 weeks but pounding google hasn't resulted in the page I viewed.
If you want to look at an example of where the 3rd shows up, look at any sort of analog tape recording. A properly working tape machine will have a primary distortion amount of the 3rd generated at 0VU which might be 3% at +3VU. Its also a product of output transformers although I've not spent a lot of time on the latter.
A lot of people say that a good reel to reel can't be touched by any other format; it would appear that the 3rd harmonic is relatively innocuous on that basis alone.
It seems that the 2nd and 3rd are somehow helpful to assist the ear/brain system in making out soundstage depth; I was interested to see that Nelson commented on that too. I've noticed using direct mic feeds in the studio if you use an amp that makes significant lower ordered harmonic distortion as opposed to one that does not, you seem to get a more accurate sense of depth out of the monitor system. I don't know why this is but Nelson's comment about this is not the only one I've seen. I'd love to see more research on that but I'm not holding my breath...
There are manufacturers that design to specs and those that design to produce sound. Pretty sure that both can not be the #1 consideration (since there is only one first).
The Tango winders probably came from generations of winders, since skills/jobs were generally passed down. Unlikely that these were trained engineers, but their connection with the product allowed them to create exceptional transformers. Which came first - the transformer or the spec? Meet the spec rather than fully optimize the xformer? There is a reason for exceptional products, and it goes beyond technology.
I consider/buy equipment based on sound rather than spec. Then I can be happy listening to music, rather than being proud that I have an expensive, high spec system that just sounds the way it sounds.
Everyone I knew that was playing around with building OPTs had a garage full of prototypes. And certainly with any transformer-coupled amp the OPT is the heart of its nature and quality.
The OTLs allowed me to get crazy bandwidth. Before I started bandwidth limiting in the voltage amplifier some of my prototypes (this was in the 1970s) could be used as a Radio Frequency booster amplifier- I used one to make 50 watts as a booster for a walkie talkie at 27MHz. But that sort of bandwidth can cause tweeters to get damaged if any RF gets into your system so we never made any production amps with that sort of bandwidth.
But we do make them that have no phase shift at 20Hz or 20KHz. Since I've also produced LPs from some recordings that I've done I have a pretty good idea of what that actually sounds like. I recommend any audiophile do something similar if they can; having a real reference recording on hand really allows you to know what you're hearing.
I used to think that there were things that could not be measured that we are hearing. I don't think that anymore; instead I've come to realize that usually what's happening is that most of what's important that we can measure never gets reported on the spec sheets. To that end, I feel that the distortion signature (the spectrum of harmonics generated) is more important that what the THD is; if you can get the signature right then its OK to get low THD but not the other way 'round!
Phase shift is important in my book. You don't need bandwidth to get it right if you run enough feedback, but if you're not running enough or if you run none then you need bandwidth. You can't hear phase shift at any one frequency but the ear will perceive it as a coloration if it occurs over a spectrum. So an amp that is rolled off at 50KHz can sound dark as a result.
I like what the head engineer at Scott said about this decades ago:
"If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing."​
I would simply add that it helps to also understand how the ear perceives sound and how that relates to engineering. Most spec sheets ignore human hearing perceptual rules.
Make a single ended OTL!
http://aries-cerat.eu/products/amplifiers/collatio-series
I spotted a few false comments on that page.
There are class A OTLs. There are OTLs that are zero feedback. This statement from that page is entirely false:
Feedback is mandatory in this designs to cancel out the artifacts generated by the problems of not true complimentary driving of the signal, and of course cross-over distortion.
Cross-over distortion isn't a thing if the circuit is designed correctly... I could go on but its clear that there is misinformation on that page.
Good perspective. Hopefully one day I will get to hear one of your OTL amps.
OTL has interested me for several years, so I had the objective of renovating a Futterman H3 just to hear it. The right occasion / opportunity never occurred. An Atma-Sphere would likely be a bit more practical. It certainly would provide an interesting and relevant listening experience of a unique approach to music amplification.
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