How do soulution amplifiers really work ?

[GMKF]

Hi everyone !

PLEASE CORRECT ME IF I'M WRONG !!!!

So after lots of late nights and reading through Wikipedia and a electronic book called Crecraft Gorham and Sparkes ELECTRONICS I got most of the engineering behind amplifiers and power supplies and SMPS.
So now im trying do understand how Soulution amps work.

The stuff they write:

"From the input the soulution 711 first buffers the music signal. A high performance correction amplifier is then used to capture and correct any deviations in the signal, very quickly and very precisely. Ultra wideband amplification using no feedback loops follows, a less than 10 nanosecond transit time and level accuracy to within 0.1 dB ensuring signal purity. The whole is housed within a sealed module, maintaining a common temperature across all stages to further guarantee precision. The output stage comprises 14 power transistors per channel, all mounted onto a massive copper rail which is temperature controlled for a constant quiescent current. The soulution 711’s impressive low level signal handling is reflected in its raw power delivery. Current levels of 120 A and more are readily attainable."

Thats from their website.
So...

This is from a report on Fairaudio: (In German) (http://www.fairaudio.de/dwt/artikel/2010-firmenberichte/soulution-audio-verstaerker-cd-player-spemot-bericht-2.html)
"Mit seinem einzigartigen Spannungskontrollverstärker mit fest eingestellter Verstärkung und einer Bandbreite bis 80 MHz (linkes Bild; die aufrecht stehenden Platinen haben Silber-Anschlusspins; das Modul ist in Kunststoff vergossen) und einer dreistufigen Strom-Pufferstufe wurde die Feedback-Schleife des Verstärkers um den Faktor 10 verkürzt, um die Arbeitsgeschwindigkeit zu optimieren und Fehler zu minimieren. Seine Stromquellen arbeiten mit einer Bandbreite von 10 bis 100 MHz. Die Ausgangsimpedanzen dieser Netzteile werden sehr niedrig gehalten. „Das Signal passiert meine Spannungsverstärkungsstufe in ungefähr 10 Nanosekunden mit einer maximalen Fehleramplitude von 0,1 dB. Um dieses Niveau an Präzision zu erreichen, brauche ich natürlich konstante thermische Bedingungen.“"

Translated:
With its unique voltage control amplifier design with fixed gain and a bandwidth up to 80 MHz (left picture, the upright circuit boards have silver terminal pins, the module is molded in plastic) and a three-stage current buffer stage, the feedback loop of the amplifier was decreased by the factor 10 to optimize the working speed and minimize errors. Its current sources (power supply) operate with a bandwidth of 10 to 100 MHz. The output impedances of these power supplies are kept very low. "The signal passes through my voltage gain stage in approximately 10 nanoseconds with a maximum error amplitude of 0.1 dB. To achieve this level of precision, of course, I need constant thermal conditions. "

So after some research i found this:

Maybee I finally figured out what they use.... Or a modified version of the design...
https://en.wikipedia.org/wiki/Current-feedback_operational_amplifier


A Servus from
Max

 

[Ken Newton]

An accurate schematic is required. However, the primary design philosophy appears to be the application of loop feedback in conjunction with minimized propagation delay of the feedback signal. The idea being that loop feedback sounds bad due to any delay in feeding the output signal back to the input error amplifier. Delays here are on the order of nanoseconds.

 

[GMKF]

+1 Ken
Thats a theory that sounds promising. Will do more research.
The Current-feedback operational amplifier would match their amps in bandwidth and overall description of design by soulution audio...

 

[Legolas]

+1 Ken
Thats a theory that sounds promising. Will do more research.
The Current-feedback operational amplifier would match their amps in bandwidth and overall description of design by soulution audio...

It is all very odd. My observation is why? Why go to this length and for what gains in Sound quality? Any feedback is seen as a no no in the high end amplifier designs, so I am hoping these amps don't use that. And a correction amplifier? What does that mean exactly. How can any amplifier correct an incoming signal? It needs to have a control to then correct it to that, seems impossible and pointless. I grew up on the idea straight gain stages with no feedback and minimal parts in the signal path sound best.

I would forget the technical blurb, and get some demo's across the price range of other makes, and buy on that merit, not what is in the tech specs IMO.

 

[GMKF]

This thread isn't to discuss how soulution gear sounds. Some people like it, some people don't.
Its more about to decipher their marketing-technical bla-bla into some real usefull information.
Since I heard soulution amps at the Munich Show, and taken home their catalog, I was always wondering what technical solution they use for them to justify such a high amount of parts and pieces in their amps.

Any feedback is seen as a no no in the high end amplifier designs, so I am hoping these amps don't use that. And a correction amplifier? What does that mean exactly. How can any amplifier correct an incoming signal? It needs to have a control to then correct it to that, seems impossible and pointless.

The current feedback operational amplifier corrects "itself" thus increases slew rate and bandwith of the amp.

I grew up on the idea straight gain stages with no feedback

Thats the problem with strong voltage feedback, which is known for creating unwanted effects on the signal. The current feedback amp runs much faster than voltage feedback thus reduces phase shift of the feedback.

 

[Legolas]

I return to my point and 'why'. If the amplifier has enough current the next most important thing besides the PS is signal integrity. Any extra circuits that mess with that IMO are going to negate the positives of it. I haven't heard and Soulution gear. I know a dealer who sells there products in the Uk, and who has a full system at home for his use and demo's. But I know of nobody who owns anything to ask their views. I would suggest there is better gear at this price level that is not relying on techno babble to justify itself. Let the ears do the talk.

 

[Ken Newton]

It is all very odd. My observation is why? Why go to this length and for what gains in Sound quality? Any feedback is seen as a no no in the high end amplifier designs, so I am hoping these amps don't use that.

Beneath humanly perceptible levels of distortion, the gains to be had are largely objective. Feedback properly applied to a linear circuit will measurably reduce the TOTAL harmonic distortion of that circuit, primarily the 2nd and 3rd harmonics, but will also undesirably add higher harmonics, though by a much lesser extent so that the overall total is greatly lowered. Feedback also increases circuit bandwidth and lowers it's output impedance. However, subjective assessments of the sound quality or the musicality of feedback is a matter of personal perception.

By the way, zero feedback circuits featuring overtly audible distortion are usually judged as sounding better once some feedback has been applied.

And a correction amplifier? What does that mean exactly. How can any amplifier correct an incoming signal? It needs to have a control to then correct it to that, seems impossible and pointless. I grew up on the idea straight gain stages with no feedback and minimal parts in the signal path sound best.

Negative feedback doesn't correct errors in the input signal. I corrects errors in the output signal with respect to the input signal. The circuit block responsible for this correction is called an error amplifier. It does this error correcting by electronically subtracting a sample of the output signal from the input signa and utilizing any difference to correct the output signal, thus helping to maintain the output as an more exact copy of the input except in amplitude. I called it an input error amplifier because the circuit block is typically situated at the input to the overall gain stage.

While zero loop feedback may sound subjectively superior to your ears, that is not a universal subjective assessment of negative feedback. Many commercial high-end gain circuits utilize negative feedback. Some use a little, some use a lot, some use none, as you mentioned. In short, I know of no fixed universally applicable formula for obtaining the most musical sound from an audio circuit, and that includes whether or not to employ loop negative feedback.

I would forget the technical blurb, and get some demo's across the price range of other makes, and buy on that merit, not what is in the tech specs IMO.

I agree. To me, and there is much disagreement about this from the objectivists, what most matters is the subjective sound, followed by the price, followed by product reliability.