Quote audiopip
" in fact he may have well gone to Ferguson TV first"
You're right he did, and that's what he told me. Thanks for reminding me. Come to think of it, i'm sure that's why he moved up north, as Thorn had a TV etc factory in Bradford i believe ?
He also told me that's how he formulated some of his ideas and transposed them into his later audio designs/work. Working on video signals HF/RF etc, requires high Slew rates, amongst other things.
He realised this was one of the areas audio amplifiers were lacking. In order to provide better performance in this respect, he made it one of his goals to try and achieve this. Which is what he did in the SuperMos range, and the one we worked on together, that didn't get released. I mentioned my building a test amp of this earlier in the thread.
Regards
" in fact he may have well gone to Ferguson TV first"
You're right he did, and that's what he told me. Thanks for reminding me. Come to think of it, i'm sure that's why he moved up north, as Thorn had a TV etc factory in Bradford i believe ?
He also told me that's how he formulated some of his ideas and transposed them into his later audio designs/work. Working on video signals HF/RF etc, requires high Slew rates, amongst other things.
He realised this was one of the areas audio amplifiers were lacking. In order to provide better performance in this respect, he made it one of his goals to try and achieve this. Which is what he did in the SuperMos range, and the one we worked on together, that didn't get released. I mentioned my building a test amp of this earlier in the thread.
Regards
Last edited:
Hi Zero D,
Sorry in the process of moving house, so haven't looked at this for a while.
In the late 80's I did some work on a switched mode power supply for a MOSFET amp for a nameless company (didn't get paid...bet that strikes a chord with a few people) and the output stage was very similar to Les's design. We listened to a large number of amps, bipolar and MOS, and the configuration used by Les in the SuperMOS 1 won out in terms of sound quality, although from an engineering perspective it is moderately hideous!
One interesting effect is the fact that the FETS are turned on fast, but kind of 'flop' off. This behaviour would bring meltdown to a transistor amp of course, but the FETs have no secondary breakdown so put up with it, as long as the heatsink is large enough.This tends to produce a kind of HF signal induced class A operation (we would call it shoot thru in the power supply industry!) and although the HF distortion performance was very poor, the amp sounded very good. 20KHz sinewave testing kills it of course, but it's fine on a music signal....unless you have high HF content, or instability, possibly the reason these early modules die young.
If the output pair are 'on' for HF signals I guess it means there is no spray of high order odd harmonics to get fed around the feedback loop!
So I guess Les's promotional material was a 'little misleading', but I believe the sound quality claims, which have been confirmed by a number of purchasers of these modules on this forum. Having experimented with bipolar output circuits for a number of years and been less than convinced I may well revisit the MOSFET amp. I'll keep you posted!
Sorry in the process of moving house, so haven't looked at this for a while.
In the late 80's I did some work on a switched mode power supply for a MOSFET amp for a nameless company (didn't get paid...bet that strikes a chord with a few people) and the output stage was very similar to Les's design. We listened to a large number of amps, bipolar and MOS, and the configuration used by Les in the SuperMOS 1 won out in terms of sound quality, although from an engineering perspective it is moderately hideous!
One interesting effect is the fact that the FETS are turned on fast, but kind of 'flop' off. This behaviour would bring meltdown to a transistor amp of course, but the FETs have no secondary breakdown so put up with it, as long as the heatsink is large enough.This tends to produce a kind of HF signal induced class A operation (we would call it shoot thru in the power supply industry!) and although the HF distortion performance was very poor, the amp sounded very good. 20KHz sinewave testing kills it of course, but it's fine on a music signal....unless you have high HF content, or instability, possibly the reason these early modules die young.
If the output pair are 'on' for HF signals I guess it means there is no spray of high order odd harmonics to get fed around the feedback loop!
So I guess Les's promotional material was a 'little misleading', but I believe the sound quality claims, which have been confirmed by a number of purchasers of these modules on this forum. Having experimented with bipolar output circuits for a number of years and been less than convinced I may well revisit the MOSFET amp. I'll keep you posted!
Last edited:
@ audiopip
Hi, yes i wondered what had happened to you ! Hope your move is going well, and nice to see you posting again with more info
Me too, got the T shirt.
I was very interested to hear about the output configuration you were working on, you say as used by Les in the SuperMOS amps. How did you, or they, get hold of a "genine" SuperMOS circuit diagram ? Or was it one supposedly back engineered by others ?
The reason i'm asking is because, i feel that from what i've read, and know, i'm not sure if anyone has 100% correctly achieved that, as yet. If at least one person had done so, and publicised it, and someone had built it exactly as Les designed, and then tested it for distortion/slew rate/ etc etc, i'm convinced it would measure up as advertised by Les.
I mentioned in an earlier post that, a VERY key important piece of the jigsaw, is a tiny spiral HF inductor etched into the PCB as a copper track. To my knowledge, nobody had ever mentioned this before in any of the data/info/ etc the've written about SuperMOS, or is shown in any diagrams i've seen. Les told me this was crucial to the amps operation. I saw this spiral with my own eyes, as i actually partially built up a number of PCB's with components on several occassions for him.
Your description of (HF signal induced class A operation) sounds intriguing i must say. I can't confirm or deny if this technique was in any way part of Les's SuperMOS circuits, as i don't know. It really would be something if the SuperMOS circuits could actually be built 100% as intended by Les. Also if they tested/performed as claimed even with mainly standard parts, what a revelation that would be ! I do know for a fact, that several transistors were batch tested for gain, as i did numbers of these round at Les's for him. Also at least some of the output MosFets were carefully sourced and matched. I say at least, because on occassion he "may" have used other types, if the preferred ones were not available, to be able to complete an order.
If you could (revisit the MOSFET amp) that would be welcomed by many people i'm sure.
Please do keep us posted, i for one can't wait !
Regards,
Zero D
PS - I tried to reply to your PM, but you it set not to receive them !
Hi, yes i wondered what had happened to you ! Hope your move is going well, and nice to see you posting again with more info
Me too, got the T shirt.
I was very interested to hear about the output configuration you were working on, you say as used by Les in the SuperMOS amps. How did you, or they, get hold of a "genine" SuperMOS circuit diagram ? Or was it one supposedly back engineered by others ?
The reason i'm asking is because, i feel that from what i've read, and know, i'm not sure if anyone has 100% correctly achieved that, as yet. If at least one person had done so, and publicised it, and someone had built it exactly as Les designed, and then tested it for distortion/slew rate/ etc etc, i'm convinced it would measure up as advertised by Les.
I mentioned in an earlier post that, a VERY key important piece of the jigsaw, is a tiny spiral HF inductor etched into the PCB as a copper track. To my knowledge, nobody had ever mentioned this before in any of the data/info/ etc the've written about SuperMOS, or is shown in any diagrams i've seen. Les told me this was crucial to the amps operation. I saw this spiral with my own eyes, as i actually partially built up a number of PCB's with components on several occassions for him.
Your description of (HF signal induced class A operation) sounds intriguing i must say. I can't confirm or deny if this technique was in any way part of Les's SuperMOS circuits, as i don't know. It really would be something if the SuperMOS circuits could actually be built 100% as intended by Les. Also if they tested/performed as claimed even with mainly standard parts, what a revelation that would be ! I do know for a fact, that several transistors were batch tested for gain, as i did numbers of these round at Les's for him. Also at least some of the output MosFets were carefully sourced and matched. I say at least, because on occassion he "may" have used other types, if the preferred ones were not available, to be able to complete an order.
If you could (revisit the MOSFET amp) that would be welcomed by many people i'm sure.
Please do keep us posted, i for one can't wait !
Regards,
Zero D
PS - I tried to reply to your PM, but you it set not to receive them !
Re post # 36
I wonder if this is the same person ?
John Nicholls of the Sinclair instrument range "fame" ? Sinclair Radionics Cambridge - Planet Sinclair: Other Products: Multimeters
I wonder if this is the same person ?
John Nicholls of the Sinclair instrument range "fame" ? Sinclair Radionics Cambridge - Planet Sinclair: Other Products: Multimeters
Hi Zero D,
I thought I had PM turned on now...DOH, I'll check it out again.
I don't know John Nicoll of Sinclair although I have had some contact with Richard Torrens who is also a Sinclair veteran.
The circuits i have seen are all available from this forum, they include a pencil drawn circuit and two CAD drawn circuits. I would like to think that the pencil sketch came from Les, but it may well be reverse engineered.
I have actually produced a bit of an analysis of these circuits, which are all generally similar. There are some inconsistancies which I will talk to you about 'off line'.
The 'dynamic' class A operation is really a defect. But in this case it seems to work audibly much better than it should technically. This seems to be a common facet of audio!
I thought I had PM turned on now...DOH, I'll check it out again.
I don't know John Nicoll of Sinclair although I have had some contact with Richard Torrens who is also a Sinclair veteran.
The circuits i have seen are all available from this forum, they include a pencil drawn circuit and two CAD drawn circuits. I would like to think that the pencil sketch came from Les, but it may well be reverse engineered.
I have actually produced a bit of an analysis of these circuits, which are all generally similar. There are some inconsistancies which I will talk to you about 'off line'.
The 'dynamic' class A operation is really a defect. But in this case it seems to work audibly much better than it should technically. This seems to be a common facet of audio!
@ audiopip
Yes PM's sorted now You needa cooling baby
How about that !
If anyone has further info on the "possible" John Nicholl/s connection, please share
I have those.
I believe they are, as i very much doubt Les would have released them. I have some comments to make about them, offline for now anyway.
Great, understood.
Genius
You should have my PM by now,
Regards
Yes PM's sorted now
You needa cooling baby How about that !
If anyone has further info on the "possible" John Nicholl/s connection, please share
I have those.
I believe they are, as i very much doubt Les would have released them. I have some comments to make about them, offline for now anyway.
Great, understood.
"Could" be he discovered that, but for whatever reason/s it worked, if indeed that's what it actually is ?
.
Genius
You should have my PM by now,
Regards
Hi There
replying to an old thread again ... no, not the same 'Jon Nicoll' (though I do confusingly also have a 'John Nicoll' incarnation.
I did build a few Uncle Clive circuits from his Bernard Babani books in the seventies, so there is a connection of sorts...
Cheers
Jon N
PS:
I forgot to mention that I, too, did a patent search on Les Sage years ago. I seem to remember I actually found something ... IIRC it was for some sort of tuning device or indicator for FM radio. I'm also pretty sure there was a connection with Thorne.
It may only have been a patent applied for rather than granted, otherwise i'd probably have tried to get a copy. As it was, from the listing it wasn't obviously related to the amp work, and I was by no means certain it was the same chap (I had visions of Les being much older at the time than he seems to have been). But give the various mentions of him working at Thorne, maybe it was.
If I find any more details I'll post them here.
Regards
Jon N
I forgot to mention that I, too, did a patent search on Les Sage years ago. I seem to remember I actually found something ... IIRC it was for some sort of tuning device or indicator for FM radio. I'm also pretty sure there was a connection with Thorne.
It may only have been a patent applied for rather than granted, otherwise i'd probably have tried to get a copy. As it was, from the listing it wasn't obviously related to the amp work, and I was by no means certain it was the same chap (I had visions of Les being much older at the time than he seems to have been). But give the various mentions of him working at Thorne, maybe it was.
If I find any more details I'll post them here.
Regards
Jon N
Here's a patent with Les' name on it:
Stereo indicating circuit - Google Patent Search
US patent 004455673 - Stereo indicating circuit
In a circuit for indicating reception of stereo signals (for use in e.g. a radio tuner or television) audio signals prevailing in the left (L) and right (R) output channels are applied to respective limiting circuit and the output signals derived are fed to OR gate. When a monoaural signal is...
Inventors: Douglas R. P. Topping, David W. Walton, Leslie R. Sage
Assignee: Thorn Emi Ferguson Limited
Stereo indicating circuit - Google Patent Search
US patent 004455673 - Stereo indicating circuit
In a circuit for indicating reception of stereo signals (for use in e.g. a radio tuner or television) audio signals prevailing in the left (L) and right (R) output channels are applied to respective limiting circuit and the output signals derived are fed to OR gate. When a monoaural signal is...
Inventors: Douglas R. P. Topping, David W. Walton, Leslie R. Sage
Assignee: Thorn Emi Ferguson Limited
I never saw any of the updates to this thread until now - funny how little bits have been added over the years and people are still interested!
I'd still love to build one if I get the time, but seeing as my original posts were 6 years ago it'll probably never happen.
Just in case they're any use to anyone with more spare time than me(!), I've put a ZIP archive of all the photos I took during my manual de-potting process. In particular it's clear to see that there's definitely no special "PCB inductors" or anything on the PCB - at least on this SuperMOS variant.
File is here: (click to download - hopefully).
Pic of the PCB underside is here (it's single-sided only):
I've still got one working module (an original SuperMOS) and another failed SuperMOS1 if anyone's got any good ideas for them...
I'd still love to build one if I get the time, but seeing as my original posts were 6 years ago it'll probably never happen.
Just in case they're any use to anyone with more spare time than me(!), I've put a ZIP archive of all the photos I took during my manual de-potting process. In particular it's clear to see that there's definitely no special "PCB inductors" or anything on the PCB - at least on this SuperMOS variant.
File is here: (click to download - hopefully).
Pic of the PCB underside is here (it's single-sided only):
An externally hosted image should be here but it was not working when we last tested it.
I've still got one working module (an original SuperMOS) and another failed SuperMOS1 if anyone's got any good ideas for them...
@ jonn
Hi thanks for info & the Patent # I would say it MUST be the same Les Sage @ Thorn Emi Ferguson Limited based on that. Plus he had a Ferguson Tuner/Pre/Amp combo at home which i saw/heard that he said he helped design.
@ brianmarchant
Yes he & his Infamous modules etc live on
Thanks very much for the Zipped pics
Your
Yes indeed It would be great if someone could test it with Top notch gear, to prove the specs claimed for it. Naturally with the module set up & wired etc as per Les's detailed instructions etc.
Hi thanks for info & the Patent # I would say it MUST be the same Les Sage @ Thorn Emi Ferguson Limited based on that. Plus he had a Ferguson Tuner/Pre/Amp combo at home which i saw/heard that he said he helped design.
@ brianmarchant
Yes he & his Infamous modules etc live on
Thanks very much for the Zipped pics
Your
link isn't working ?
Yes indeed
It would be great if someone could test it with Top notch gear, to prove the specs claimed for it. Naturally with the module set up & wired etc as per Les's detailed instructions etc.Ooops - fixed!
I'd like this too, but I'm not entirely sure what gear I'd need and what tests to do. I've got access to a good GHz storage 'scope, so maybe I'll investagate further. I built my amp exactly to Les's wiring spec., so it's good to go for testing if I ever get around to it...
By the way, does anyone know what was in Les's equally mysterious "DC Protection Modules"?
Hi to all,
Its very interesting to see all the interesting threads on Les Sage's SuperMos.
I was also attracted by all those advertisments back in the 80s but was too poor to buy them then. Anyone remember 'Audio Conversions' ? In issue 12 and 13, he published 'Active loudspeakers' and designed a superlow distortion buffer. When I can affort to buy the kits, I learnt that he was dead and the kit was no longer available. I spent hundreds of pounds to source the specific transistors and built the Active crossover but was unable to get it to work. Did anybody tried to built that circuit?
I recently trying to learn to use the LT spice program and fed the circuit into it. It does seem to work. I haven't learnt the way to compute its distortion yet. I would like to know how other thinks. It is another Les's 'joke'?
Its very interesting to see all the interesting threads on Les Sage's SuperMos.
I was also attracted by all those advertisments back in the 80s but was too poor to buy them then. Anyone remember 'Audio Conversions' ? In issue 12 and 13, he published 'Active loudspeakers' and designed a superlow distortion buffer. When I can affort to buy the kits, I learnt that he was dead and the kit was no longer available. I spent hundreds of pounds to source the specific transistors and built the Active crossover but was unable to get it to work. Did anybody tried to built that circuit?
I recently trying to learn to use the LT spice program and fed the circuit into it. It does seem to work. I haven't learnt the way to compute its distortion yet. I would like to know how other thinks. It is another Les's 'joke'?
Hello all,
Just to give this old thread another kick…I'm looking at my SMOS2 board right now and there are 19 small signal transistors present. Both schematics previously posted show 12. Power and FET counts are the same.
I don’t think the schematics are accurate for a SMOS2 or there were some serious design changes over the production period!
I drew out the schematic over 15 years ago but it didn’t look right. Whether that’s because I made mistakes or there is crazy stuff going on I don’t know.
As I mentioned in the other Les Sage thread, these amps caused minor AM interference so maybe Les’s current modulators did indeed modulate!
Just to give this old thread another kick…I'm looking at my SMOS2 board right now and there are 19 small signal transistors present. Both schematics previously posted show 12. Power and FET counts are the same.
I don’t think the schematics are accurate for a SMOS2 or there were some serious design changes over the production period!
I drew out the schematic over 15 years ago but it didn’t look right. Whether that’s because I made mistakes or there is crazy stuff going on I don’t know.
As I mentioned in the other Les Sage thread, these amps caused minor AM interference so maybe Les’s current modulators did indeed modulate!
Good that this is still going!!
I never got around to testing my SuperMOS (I can't remember if my remaining working channel is SuperMOS or SuperMOS1...), but I did find the amp in the loft. I'll try and take it to work to make some basic measurements if I get time, and maybe de-pot it if it's the earlier SuperMOS. I've never seen a SuperMOS2, but I think the claims at the time were that they were very different.
I never got around to testing my SuperMOS (I can't remember if my remaining working channel is SuperMOS or SuperMOS1...), but I did find the amp in the loft. I'll try and take it to work to make some basic measurements if I get time, and maybe de-pot it if it's the earlier SuperMOS. I've never seen a SuperMOS2, but I think the claims at the time were that they were very different.
Can you post the schematic that you drew, maybe one of us can complete or correct the rest.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.