Author Topic: A brief explanation of the GS Ultra Linear circuit (and why it's brilliant)  (Read 443 times)

Offline capetownwatches

Graham Slee has seemingly figured out how to get a solid state device to sound just like a tube amp.



"It's been my intention to recreate the original valve sound for years as they always "told the story" better! Our Ultra-Linear technology is the result of two years almost solid research, exhaustive development and testing. We researched how to mimic all the valve’s sonic characteristics to improve our products. We found a number of op-amps (integrated circuits) which could be made to perform just like valves!" – Graham Slee

So what is the secret to the Solo Ultra-Linear's incredible sound? Well, there are many, but for one its distortion characteristics are quite unlike any other solid state headphone amp. Generally speaking, solid state distortion increases in proportion to frequency, so when there's lots of high frequency information distortion increases and this is highly noticeable when playing complex music.

"Graham Slee products with Ultra-Linear technology feature significantly wider bandwidth just like the best valve amps. We call this innovation Ultra-Linear because that was the tag used to describe the great performance of the best sounding valve amps from the mid 1940s." – Graham Slee

The distortion from the Solo Ultra-Linear remains consistently low throughout the audio spectrum, because it has exceptionally wide bandwidth. Most solid state headphone amps have limited bandwidth and use negative feedback to not only fix distortion and noise but also to widen the bandwidth of the device. All this really does is add distortion in the form of glare to the high frequencies and affects bass and mid frequencies by smearing the leading edge of the note. If highs are distorted much of the fine detailing in the bass and  mid frequencies is also lost. By linearly improving distortion throughout the entire audio band the sound stage comes alive as you've never heard before.

Like most headphone amps except for the ridiculously expensive, the Solo Ultra Linear is basically a pair of transistor assisted op-amps, but these are no ordinary op-amps! Graham Slee chose one of the very few op-amps which feature one of the best output stages ever designed. Featured in Wireless World in 1969 and authored by J L Linsley Hood this circuit remains the most musical of all output stages and runs class-A.
To these Graham Slee adds their proprietary open-loop bandwidth widening technique and the difference is  truly staggering.

https://www.musicdirect.com/headphone-amp/graham-slee-solo-ultra-linear-diamond-edition-headphone-amp
« Last Edit: July 06, 2019, 09:08:35 PM by capetownwatches »


Solo Ultra Linear=NFB11.32=Little Dot Mkll=SRM252S=BM DAC1 USB=RL Concero
LCD2F=HD600=SR207=DT990 600=K612Pro=K240S=K171Mkll=M4U2=Y50=Ayra 5=Cables Various

Offline Scubadude

  • Trade Count: (+42)
  • AVForums Super Veteran
  • ****
  • Posts: 1,494
  • Total likes: 53
  • Depressed? Cans on, volume up, ignore the world!
Interesting read Arie!  I heard that amp and I did not find it valve-like ... as you know my perception was that it was thin and bass-shy.  I know the Slee is very highly rated ... the late Rodney Gold is on record saying its the best he had heard. So maybe I didn't give it a proper chance. 

Interestingly, the last two headphone amps I acquired (why does that sound excessive?) do a fine job of simulating valve amp performance.  The PS Audio GCHA and Krell KSA-5 (clone ... the original would be truly excessive) are both Class A, solid-state designs with deep power supplies and careful component selection.  They also share the clarity, swinging dynamics and sweet mids I associate with the best valve amps. And they have a similar downward tilt.  And they both sound phenomenal with LCD2 and HD800 but like crap with Elear ... although I think that reflects the Elear's dislike of high output impedance amps rather than the amps per se.
"We should no more let numbers define audio quality than we should let chemical analysis be the arbiter of fine wines."  Nelson Pass

Offline capetownwatches

Interesting read Arie!  I heard that amp and I did not find it valve-like ... as you know my perception was that it was thin and bass-shy.  I know the Slee is very highly rated ... the late Rodney Gold is on record saying its the best he had heard. So maybe I didn't give it a proper chance. 

Interestingly, the last two headphone amps I acquired (why does that sound excessive?) do a fine job of simulating valve amp performance.  The PS Audio GCHA and Krell KSA-5 (clone ... the original would be truly excessive) are both Class A, solid-state designs with deep power supplies and careful component selection.  They also share the clarity, swinging dynamics and sweet mids I associate with the best valve amps. And they have a similar downward tilt.  And they both sound phenomenal with LCD2 and HD800 but like crap with Elear ... although I think that reflects the Elear's dislike of high output impedance amps rather than the amps per se.

How long was the amp powered up while you had it, and how many hours did you manage to listen? My experience was similar to yours in that initially it did sound underwhelming, much like you describe it. However, the amp had not been used in many months and after about 72 hours it was a different beast entirely. Slee says that (amongst other things) the caps used require a long warm up time and continuous power. Whatever it is, the amp literally transformed: deep, accurate bass where previously it was absent, mids filled out dramatically, treble extended and oh so smooth and grain-less. Soundstage width and depth improved and one of the highlights is the detail this amp can extract. I heard further improvement after about 5 days and now it's very good indeed, to the point where I might say it's the best I've heard, period. Definitely pairs better with higher impedance headphones (HD600/DT990 600Ω) but is absolutely excellent with 70Ω LCD2 as well.

Does it sound valve-like? (Tube-esque?) I think it does, to the extent that it has a very musical presentation, smooth and organic but very detailed and dynamic, with seemingly endless headroom and bass extension, the result of very wide bandwidth and very low distortion. This amp is the culmination of great design and careful tuning by real human beings who know what they are doing. It's a pleasure to listen to for long periods.

You need to pop in and give it a proper listen sometime...find an excuse to visit the Cape!



Solo Ultra Linear=NFB11.32=Little Dot Mkll=SRM252S=BM DAC1 USB=RL Concero
LCD2F=HD600=SR207=DT990 600=K612Pro=K240S=K171Mkll=M4U2=Y50=Ayra 5=Cables Various

Offline canman1971

Graham Slee has seemingly figured out how to get a solid state device to sound just like a tube amp.



"It's been my intention to recreate the original valve sound for years as they always "told the story" better! Our Ultra-Linear technology is the result of two years almost solid research, exhaustive development and testing. We researched how to mimic all the valve’s sonic characteristics to improve our products. We found a number of op-amps (integrated circuits) which could be made to perform just like valves!" – Graham Slee

So what is the secret to the Solo Ultra-Linear's incredible sound? Well, there are many, but for one its distortion characteristics are quite unlike any other solid state headphone amp. Generally speaking, solid state distortion increases in proportion to frequency, so when there's lots of high frequency information distortion increases and this is highly noticeable when playing complex music.

"Graham Slee products with Ultra-Linear technology feature significantly wider bandwidth just like the best valve amps. We call this innovation Ultra-Linear because that was the tag used to describe the great performance of the best sounding valve amps from the mid 1940s." – Graham Slee

The distortion from the Solo Ultra-Linear remains consistently low throughout the audio spectrum, because it has exceptionally wide bandwidth. Most solid state headphone amps have limited bandwidth and use negative feedback to not only fix distortion and noise but also to widen the bandwidth of the device. All this really does is add distortion in the form of glare to the high frequencies and affects bass and mid frequencies by smearing the leading edge of the note. If highs are distorted much of the fine detailing in the bass and  mid frequencies is also lost. By linearly improving distortion throughout the entire audio band the sound stage comes alive as you've never heard before.

Like most headphone amps except for the ridiculously expensive, the Solo Ultra Linear is basically a pair of transistor assisted op-amps, but these are no ordinary op-amps! Graham Slee chose one of the very few op-amps which feature one of the best output stages ever designed. Featured in Wireless World in 1969 and authored by J L Linsley Hood this circuit remains the most musical of all output stages and runs class-A.
To these Graham Slee adds their proprietary open-loop bandwidth widening technique and the difference is  truly staggering.

https://www.musicdirect.com/headphone-amp/graham-slee-solo-ultra-linear-diamond-edition-headphone-amp

One name i have not heard of for many years - Linsley Hood, in the 90s you could purchase the LH Class A 1969 Clone in Kit or ready built with chassis from RS Electronics - late Dan Jacobs.

Offline psychoacoustics

How long was the amp powered up while you had it, and how many hours did you manage to listen? My experience was similar to yours in that initially it did sound underwhelming, much like you describe it. However, the amp had not been used in many months and after about 72 hours it was a different beast entirely. Slee says that (amongst other things) the caps used require a long warm up time and continuous power. Whatever it is, the amp literally transformed: deep, accurate bass where previously it was absent, mids filled out dramatically, treble extended and oh so smooth and grain-less. Soundstage width and depth improved and one of the highlights is the detail this amp can extract. I heard further improvement after about 5 days and now it's very good indeed, to the point where I might say it's the best I've heard, period. Definitely pairs better with higher impedance headphones (HD600/DT990 600Ω) but is absolutely excellent with 70Ω LCD2 as well.

Does it sound valve-like? (Tube-esque?) I think it does, to the extent that it has a very musical presentation, smooth and organic but very detailed and dynamic, with seemingly endless headroom and bass extension, the result of very wide bandwidth and very low distortion. This amp is the culmination of great design and careful tuning by real human beings who know what they are doing. It's a pleasure to listen to for long periods.

You need to pop in and give it a proper listen sometime...find an excuse to visit the Cape!

sounds like I should also have kept it switched on longer..  :facepalm: :ROFLMAO:

Offline capetownwatches

sounds like I should also have kept it switched on longer..  :facepalm: :ROFLMAO:

Ja Antonie... :dop:

Slee recommends keeping it powered up 24/7, advice with which I see no reason not to comply.
The amp actually went through a number of distinct phases: underwhelming, much better, treble nasties, nirvana!  :thinking:
This transition is well documented on the Slee forums.
« Last Edit: July 13, 2019, 08:23:34 AM by capetownwatches »


Solo Ultra Linear=NFB11.32=Little Dot Mkll=SRM252S=BM DAC1 USB=RL Concero
LCD2F=HD600=SR207=DT990 600=K612Pro=K240S=K171Mkll=M4U2=Y50=Ayra 5=Cables Various

Offline AlleyCat

^^^ Arie, so there goes another myth : Cables, passive components, etc, needs to be run in ?

And run in to sound their their best.

As always, use the manufacturers manual, advice, suggestions, etc..
"Not everything meaningful is measurable, and not everything measurable is meaningful" - Floyd Toole

Offline capetownwatches

^^^ Arie, so there goes another myth : Cables, passive components, etc, needs to be run in ?

And run in to sound their their best.

As always, use the manufacturers manual, advice, suggestions, etc..


No question that amps have a burn in period Allan, some more than others though, and in some the changes are more noticeable.


Solo Ultra Linear=NFB11.32=Little Dot Mkll=SRM252S=BM DAC1 USB=RL Concero
LCD2F=HD600=SR207=DT990 600=K612Pro=K240S=K171Mkll=M4U2=Y50=Ayra 5=Cables Various