Nigel, I would say you have got correct listening impressions, but your interpretation of the differences goes completely against of my vision.
The holographic effect (perfect soundstage and microdetails, in other words) is not a kind of distortion or drawback, it just reflects superiority in some aspects of tubes and tube schematics. As I mentioned above, with proper choice of transistors, passive parts and by employing special schematics, one can overtake a top quality tube sound in ALL ASPECTS, including holography, soundstage, no listening fatique, everything. However, such SS amp design is not practical for high output powers, therfore people pay almost no attention to it. But, for me, possibility to replace 10-20W tube amp by a similar power SS, and even with rise in audiophile sound quality, seems like a breakthrough.
Holographic sound
Vladimir you are correct and I was trying to open a discussion . The holographic quality is not easily related to measurements . My modified Hitachi has it . I sent three new designs of current mirror to my fellow designers just before going sick with Parkinson's disease ( no real problems except soldering and writing longhand if asking ) . I think they believe it affects my ability to have a conversation so only said my new current mirrors are good ( which one ? ) ! Apparently measured with Audio Precision test facility it is as near zero distortion as this planet has ever seen ( I doubt that as the maths don't support it ) . I have no interest in that as apart from crossover distrotion I never thought it important . However my fascination with symmetry probably has done something ? The weirdest part of this is that amplifier does have holographic qualities . I suspect your amplifier is better than mine . Out of respect I will try very hard not to copy what you have said . However I will try the devises one day . We have to get our money back so I suspect it will be a few years before we try harder and use new devices .
One test I use is a locomotive entering a station . On a tube amplifier I have used ( 211 tube in SE with pentode voltage regulator ) one can almost see everything ( Quad 57 's ) . On my amplifier it is 98% as good and very similar tonally . Then a whistle from the locomotive is sounded . On my amplifier you can hear the roof of the station which is not possible with the tube amp , the beauty of that sound has to be experienced to believe it . Virtually 5 Hz to 40 kHz must be there . The average power when doing this was 4.5 W by oscilloscope ( both and no detectable excursion above it ) . My amplifier does 1000 VA 1 ohm if I ask it to ( PA vesrion , never has been sold as real PA requires a different animal . It is a theoretical amp , a friend did build it and liked it . He introduced me to the Hitachi via it when borrowing his book of GEC tube designs many years ago . Another Nigel called Copin ) .
Vladimir .I listen to these recently and liked them . Any good ? Even with NAD 3020 and a little bass boost they had a bit of magic about them . Like Spendor BC1 only better . The man/team that made them I am certain enjoyed Vodka as they were not BBC in the woodworking .
http://www.ebay.co.uk/itm/RUSSIAN-MADE-RADIOTEHNIKA-HI-FI-SPEAKERS-1970S-/180693375779#ht_793wt_1090
Vladimir you are correct and I was trying to open a discussion . The holographic quality is not easily related to measurements . My modified Hitachi has it . I sent three new designs of current mirror to my fellow designers just before going sick with Parkinson's disease ( no real problems except soldering and writing longhand if asking ) . I think they believe it affects my ability to have a conversation so only said my new current mirrors are good ( which one ? ) ! Apparently measured with Audio Precision test facility it is as near zero distortion as this planet has ever seen ( I doubt that as the maths don't support it ) . I have no interest in that as apart from crossover distrotion I never thought it important . However my fascination with symmetry probably has done something ? The weirdest part of this is that amplifier does have holographic qualities . I suspect your amplifier is better than mine . Out of respect I will try very hard not to copy what you have said . However I will try the devises one day . We have to get our money back so I suspect it will be a few years before we try harder and use new devices .
One test I use is a locomotive entering a station . On a tube amplifier I have used ( 211 tube in SE with pentode voltage regulator ) one can almost see everything ( Quad 57 's ) . On my amplifier it is 98% as good and very similar tonally . Then a whistle from the locomotive is sounded . On my amplifier you can hear the roof of the station which is not possible with the tube amp , the beauty of that sound has to be experienced to believe it . Virtually 5 Hz to 40 kHz must be there . The average power when doing this was 4.5 W by oscilloscope ( both and no detectable excursion above it ) . My amplifier does 1000 VA 1 ohm if I ask it to ( PA vesrion , never has been sold as real PA requires a different animal . It is a theoretical amp , a friend did build it and liked it . He introduced me to the Hitachi via it when borrowing his book of GEC tube designs many years ago . Another Nigel called Copin ) .
Vladimir .I listen to these recently and liked them . Any good ? Even with NAD 3020 and a little bass boost they had a bit of magic about them . Like Spendor BC1 only better . The man/team that made them I am certain enjoyed Vodka as they were not BBC in the woodworking .
http://www.ebay.co.uk/itm/RUSSIAN-MADE-RADIOTEHNIKA-HI-FI-SPEAKERS-1970S-/180693375779#ht_793wt_1090
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This depends on what kind of power are you aiming for. The more power you want, the more output devices you have to use. However, as long as you are happy staying at or below say 50 WRMS into 8 Ohms, you can make it happen with just one pair of output devices, which simplifies things greatly.
The alternative could be a balanced design, perhaps. Then again, an amp well done is an amp well done in any technology.
Audiophile quality russian made speakers do not exist in the nature, except for maybe some very recent efforts.
Владимир, I beg to differ. For decades, over here in Serbia, we have had a steady supply of Russian loudspeakers, and they were surprisingly good and relatively very cheap. They still fetch good prices even today, on the second hand market.
You didn't know about this, of course, they were made for exports only, a nice, old socialist trick they all did, including the locals.
For hard currency only.
Earlier units had drivers with Alnico magnets...
This comment is plain STUPID!
RUSSIAN MADE RADIOTEHNIKA HI-FI SPEAKERS FROM 1970'S | eBay
Take it easy, Vladimir, Nigel's comment was a bit of British humor, that's all. I'm sure he meant no harm.
If anyone, it's the BBC who should feel hurt.
Look back for full quote .
It wasn't meant as an insult . More as an indication that a less than willing worker might produce a thing of quality . It opens a discussion . My Cuban electricity meters just the same . It is a lack of leadership in small things . Sometimes other small things like correct design matter more than small things like aesthetics .
My limited experience of working in the east has been about drinking lots of Vodka and getting on with the job . My English boss got very angry with me one day and said I was supposed to be setting a specification . To which I said I had . That product is the best we ever have made . The reason it was so good is I didn't waste time in the discussion . I just set an impossible specification and said it's that or don't bother . We all laughed and got very drunk . No hangover after was my great surprise . I think also it went very well because I risked annoying my boss and got stuck in with the engineers . I think he was so excluded , he didn't like it very much . They have remarkable training and one day will wake up and realize how potentially important that training can be .
Sorry if I offended anyone . I still maintain the cabinets looks to me to be assemble by that route . It was so bad as to be almost sabotage
I asked my translator what he remembered of Soviet days . He said the day he no longer had to call his teacher Soldier . We plan a trip on Trans Siberian Railways to celebrate . Again my boss is not very happy about that ( thinks it's a daft waste of 8 days , in deep winter also ) .
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Take it easy, Vladimir, Nigel's comment was a bit of British humor, that's all. I'm sure he meant no harm.
If anyone, it's the BBC who should feel hurt.
That's the point exactly . Remember Robin Marshall and Spencer Hugues were friends of mine ( LS3/5A .... BC 1' s ) . One of my student customers went on to be one of the last paid entrants to the BBC ( research scholarship). He lived at " Christmas Cottage " in a small village . If you live at " Christmas Cottage " one has to work at the BBC . He built an advanced 78 turntable if I remember correctly . That's the problem of knowing me . Look what happens .
I ran the shop at no profit until 1997 to get it to 50 years . It had a glorious history and created the company SSL . We had a small mantfactuiring side also and sold components . FAL in Japan identical .
https://www.google.co.uk/search?q=s...CtHf8QPDsdDRCg&ved=0CLoBELAE&biw=1237&bih=849
Starting from almost zero, other than my old technician days, Self, Cordell and Jones provided the background so I could understand what the folks here were talking about. I have now circled back to building speakers as the trip down amp lane led me to where the real problem seems to lie, in the tweeter breakup. A problem I am finding very difficult to deal with. I did wind up with a couple of greatly improved sounding DH-120's and RB 951's. Following James B's concept, I have a DH 220 to clean up. A side note, I now know why the same quality as was built in the 80's costs so much more now. Adding all the protection circuits is not easy. Same amp with the extras demanded now, including bling packaging, really raises the price.
I really hope to solve the tweeter problem and confirm that better amps, like John's 1200 I picked up, were objectionable to my wife's sensitive hearing because they were not masking problems like the Rotel's were. I understand what the differences in the amps are and why they make such a large difference in the sound. (as if anyone in this thread needs to be convinced amps sound different
)
I was given this when going to borrow a book one day from a certain Nigel Copin ( PA engineer ) . I never looked back . I have replaced the outputs with Szikai pairs and was pleasantly surprised . I beleive John who writes here has a FET input Szikai . I never thought of that and it makes a lot of sense as the square law helps ( thanks also Vladimir ) .
Biasing is covered well by Self
Try single VAS . CCS . Try better current mirror to VAS . Try CCS to LTP
USE Exicon FET's .
Spend big money on PSU . Now you know everything I ever learnt .
I have the world supply of 2SD756 of gain > 480 .
The amp seems bomb proof and will scale to 1000 W 1 ohm .
5.6 mA is the ideal driver current .
Nigel
BTW my version of this pushes an Audio Precision test station to it's limits I am told . They guys have run off with my design in so much they never send those graphs ( it seems impossible what they say from the maths , in a kind way one said what planet is Nigel from as he never equaled my results ) . However changing bias changes the sound ! That is in the noise floor stuff . This amplifier is a bit like showing you a F1 engine of 20 years ago . All the same ,finding out how it works is easy . You will have to forget a lot of what Self on Audio says . He is not wrong . He is going on a slightly wrong route .
I was gifted this so I gift it back to the world .
The HF sound of this amp is very good .
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I don't geddit.
He's walking tall and strong, but on a "slightly" wrong route, yet he's still right?
Exactly how do you put all this together? It's like saying somebody will be ligthing a fire at the bottom of the ocean, even if that's impossible, but it's not.
you really need to look at the latest edition - Self gets better, includes more material, better references
you really are wasting a lot of time, risk missing both the obvious and unobvious that he does point at if you don't at least know what Self has to say on any particular audio circuit
doesn't mean his work is comprehensive, is "the final word" - but its a lot better than almost anyone will derive/discover themself, "pick on the street"
same for Cordell's book - knowing what is known saves lots of time - real engineers are lazy - look it up, "steal the best"...
you really are wasting a lot of time, risk missing both the obvious and unobvious that he does point at if you don't at least know what Self has to say on any particular audio circuit
doesn't mean his work is comprehensive, is "the final word" - but its a lot better than almost anyone will derive/discover themself, "pick on the street"
same for Cordell's book - knowing what is known saves lots of time - real engineers are lazy - look it up, "steal the best"...
Agree. Coupled with thoughtfulness and a good foundation in basic principles, we are fortunate to have such references, those two in particular. One still must be wary of taking everything that appears as indisputable or the last word in comprehensive: there is only so much room in a book, and they are a lot of work to write, especially the references, and especially when you wish to reproduce a graph or a table and need permission from the sources.
Several here still need to sort things out a bit more.
Nigel, your design should be fairly low in slew rate, because you did NOT degenerate the input differential pair, or use a jfet pair, like Bob Cordell or I might use.
TVR, I would not think of the HCA-1200 as an ideal amp, it is really a pretty good 'home theatre' amp, but I would not use it for serious listening. It just does not have enough Class A bias, etc. If you can find an old Electrocompaniet Otala design, I would be very interested in what your wife hears.
Nigel, your design should be fairly low in slew rate, because you did NOT degenerate the input differential pair, or use a jfet pair, like Bob Cordell or I might use.
TVR, I would not think of the HCA-1200 as an ideal amp, it is really a pretty good 'home theatre' amp, but I would not use it for serious listening. It just does not have enough Class A bias, etc. If you can find an old Electrocompaniet Otala design, I would be very interested in what your wife hears.
John . Much has changed with that amp . To protect some easy yet important details I wont say too much more . In the last PCB I included input pair degeneration . We don't use the original input transistor , we have a very low noise group .
Slew rate is acceptable for real music and is symmetrical . I have tried upping the slew rate and thought the sound suffered . Could not support that with measurements I should add .
The slightly wrong route I refer to is saying the double LTP has poor repeatability and symmetry as hinted at by D Self . Nothing could be further from the truth if just basic selection of components and care is taken . The input pair are locked with constant voltage clamps of the LTP 2 .
If the design has a flaw it is the need for state of the art transistors . High voltage and high gain coupled with good Ft . Ironically discreet non SMD transistors of this quality are becoming rare . Some say we need to advance our designs . Difficult in view of that .
In my experience this is the only minimalist design which has any right to be amongst the best amps . It is to me like the Dynaco A 70 . The ability to scale it up or bridge it is incredible .
I have even built versions of it using bootstrapped CCS which was highly successful .
Input tail resistor can be made very long and on a separate supply if CCS not used . I prefer a quiet PSU's rather than fancy common mode rejection ability . Good quality low current PSU's cost peanuts .
One excellent thing with this amp is building a D Self version is easy . Just leave bits out . BCV 61 makes an ideal current mirror if required , it's low voltage is not a problem as the LTP2 clamps it at about 2 V .
No one seems to know who originated the design . Rumour has it , it was a Californian engineer working for Hitachi .
It's special quality is with the human voice . It drives Pro-audio type speakers very well and has the Naim quality they call PRaT .
Slew rate is acceptable for real music and is symmetrical . I have tried upping the slew rate and thought the sound suffered . Could not support that with measurements I should add .
The slightly wrong route I refer to is saying the double LTP has poor repeatability and symmetry as hinted at by D Self . Nothing could be further from the truth if just basic selection of components and care is taken . The input pair are locked with constant voltage clamps of the LTP 2 .
If the design has a flaw it is the need for state of the art transistors . High voltage and high gain coupled with good Ft . Ironically discreet non SMD transistors of this quality are becoming rare . Some say we need to advance our designs . Difficult in view of that .
In my experience this is the only minimalist design which has any right to be amongst the best amps . It is to me like the Dynaco A 70 . The ability to scale it up or bridge it is incredible .
I have even built versions of it using bootstrapped CCS which was highly successful .
Input tail resistor can be made very long and on a separate supply if CCS not used . I prefer a quiet PSU's rather than fancy common mode rejection ability . Good quality low current PSU's cost peanuts .
One excellent thing with this amp is building a D Self version is easy . Just leave bits out . BCV 61 makes an ideal current mirror if required , it's low voltage is not a problem as the LTP2 clamps it at about 2 V .
No one seems to know who originated the design . Rumour has it , it was a Californian engineer working for Hitachi .
It's special quality is with the human voice . It drives Pro-audio type speakers very well and has the Naim quality they call PRaT .
I was just thinking to warn nigel that in this thread there are many people with very high expectation on amps. The circuit he posted was just too far behind.
The topology is common (no secret). If the amp is not really like what is posted, then what was the meaning of "presenting the world with a gift".
Too much compensation/sacrifices (to get some benefits) in that amp. In 2012 we want everything. And LF means more to the crowd than HF.
I would say the same and if you look carefully I say exactly that . I am not prepared to show how it evolved , I have friends who invested big money in it . They would not be very pleased if I was to show what we did . It is an excellent starting point to learn from and should not get you off to a bad start . Minimalism is a school in it's own right . We Brits have a deep aversion to complex amplifier designs . When I say deep I understate it .
What many forget is there is strong evidence to suggest that an amp like this is many hundreds of % better than the human ability to discern . That is a conversion for others . However commonly held beliefs would be that what I have just said is true .
There is something odd about perfecting a machine beyond what we can hear .
However I have found that things which have no easy explanation can be heard . If instead of the usual evolution attention is focused on power supply design there are big advantages to be had .
Personally I would say this amplifier is good enough to say it gets close to perfection . I have heard enough of others to know .
As said it's a gift I am giving back to the world .
What many forget is there is strong evidence to suggest that an amp like this is many hundreds of % better than the human ability to discern . That is a conversion for others . However commonly held beliefs would be that what I have just said is true .
There is something odd about perfecting a machine beyond what we can hear .
However I have found that things which have no easy explanation can be heard . If instead of the usual evolution attention is focused on power supply design there are big advantages to be had .
Personally I would say this amplifier is good enough to say it gets close to perfection . I have heard enough of others to know .
As said it's a gift I am giving back to the world .
Yes, I believe so. I can see the "beauty" in the circuit. I definitely prefer to listen to this than a crescendo (same old design).
This is a simple circuit, but to get the most out of LF we have to complicate it. And when perfect amp is the objective (are we talking about an amp close to perfection??) may be there is nothing to hope for in this topology.
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