Why not?
I can assure you that I did not buy one of these SKA kits. I have zero intention of ever doing so. You could not give me one. I'm not interested, since I can get the same ill-concieved design at Circuit City from any one of a number of Big Box manufacturers, and believe me, if I never hear another one of these MOSFET monstrousities as long as I live it will be too soon. Sonically, they are mediocre at best, and this is one area where I and Doug Self agree 110%: the topology is irredeemably bad. I have no intentions whatsoever to rip off that design. I have my own designs for SS amps that are way better.
Where do you think I got the schemos anyway? Greg published, not one, but two iterations of this design on his own durn website, and they were freely available to anyone who could click a mouse for at least three months. That was well before this thread ever saw its first post. That, alone, renders whatever claims to "IP" he thinks he has null and void.
Furthermore, his claim to "IP" is absolutely, completely, totally bogus.
That comes straight from here: http://www.diyhifi.org/amplifierguru/guru_002.htm I'm not making this nonsense up. There is nothing, nada, zero, zip, zilch that is in any way, shape, or form "unique" about a topology that eliminates the VAS. I have a schemo which is identical to this, and the date on it is 1980. Greg's idea is nearly thirty years old. That makes it Prior Art, and that renders any IP claims null and void.
I can assure you that I did not buy one of these SKA kits. I have zero intention of ever doing so. You could not give me one. I'm not interested, since I can get the same ill-concieved design at Circuit City from any one of a number of Big Box manufacturers, and believe me, if I never hear another one of these MOSFET monstrousities as long as I live it will be too soon. Sonically, they are mediocre at best, and this is one area where I and Doug Self agree 110%: the topology is irredeemably bad. I have no intentions whatsoever to rip off that design. I have my own designs for SS amps that are way better.
Where do you think I got the schemos anyway? Greg published, not one, but two iterations of this design on his own durn website, and they were freely available to anyone who could click a mouse for at least three months. That was well before this thread ever saw its first post. That, alone, renders whatever claims to "IP" he thinks he has null and void.
Furthermore, his claim to "IP" is absolutely, completely, totally bogus.
That comes straight from here: http://www.diyhifi.org/amplifierguru/guru_002.htm I'm not making this nonsense up. There is nothing, nada, zero, zip, zilch that is in any way, shape, or form "unique" about a topology that eliminates the VAS. I have a schemo which is identical to this, and the date on it is 1980. Greg's idea is nearly thirty years old. That makes it Prior Art, and that renders any IP claims null and void.
hmm...
...methinks he doth protest too much...
If the topology is so uninteresting and unoriginal, there's clearly no point in furthering it's dissemination, especially in the light of the authors explicit request to keep it in the hands of paying customers.
Nobody really cares if you want to buy one or not, but Greg believes he has invented something, and as such he is attempting to patent it. I think he has a right to make money from something that he developed. If you don't think it's worthy of your consideration, so be it, voice that opinion, then shop for or build something different, but this has nothing to do with giving away something that isn't yours to give.
Even if the schematic itself is technically unoriginal, Gregs specific interpretation of it may still be protected as a form of original art.
I've never heard a SKA, and in no way am I claiming it is good bad or indifferent, just that Greg has the rights to the fruits of his labours.
Stuart
...methinks he doth protest too much...
If the topology is so uninteresting and unoriginal, there's clearly no point in furthering it's dissemination, especially in the light of the authors explicit request to keep it in the hands of paying customers.
Nobody really cares if you want to buy one or not, but Greg believes he has invented something, and as such he is attempting to patent it. I think he has a right to make money from something that he developed. If you don't think it's worthy of your consideration, so be it, voice that opinion, then shop for or build something different, but this has nothing to do with giving away something that isn't yours to give.
Even if the schematic itself is technically unoriginal, Gregs specific interpretation of it may still be protected as a form of original art.
I've never heard a SKA, and in no way am I claiming it is good bad or indifferent, just that Greg has the rights to the fruits of his labours.
Stuart
OK, fine, it's not worth argueing about. I promise that I won't reveal any schemos even if asked via e-mail.
Keeping good relations with the rest of the forumers is more important anyway, and if that's the consensus, so be it.
"If the topology is so uninteresting and unoriginal, there's clearly no point in furthering it's dissemination..."
You sure got that right.
Keeping good relations with the rest of the forumers is more important anyway, and if that's the consensus, so be it.
"If the topology is so uninteresting and unoriginal, there's clearly no point in furthering it's dissemination..."
You sure got that right.
"I have my own designs for SS amps that are way better."
Miles, the proof of the pudding is in the eating, and I think it´s unfair to bash a product ( in a somewhat selfrighteous way), that you have never heard...A little bit more humility, and we will presumably take more interest in your writing, I guess.
Regards
Håkan
Miles, the proof of the pudding is in the eating, and I think it´s unfair to bash a product ( in a somewhat selfrighteous way), that you have never heard...A little bit more humility, and we will presumably take more interest in your writing, I guess.
Regards
Håkan
Hi Miles,
A thread about the prior art diagram might be useful as a study. It will not be about Greg's amp, but rather the forerunner.
-Chris
A thread about the prior art diagram might be useful as a study. It will not be about Greg's amp, but rather the forerunner.
-Chris
ok, thanks all for clarifying!
I was curious if my own design from some 14 years ago had any similarities at all. Trying to relate the designs to something I know (or knew). I'll probably look into the GEM instead.
Regards
I was curious if my own design from some 14 years ago had any similarities at all. Trying to relate the designs to something I know (or knew). I'll probably look into the GEM instead.
Regards
Miles,
I think you were a bit harsh; the SKA is a pretty good amp from all reports, very clean and punchy, and there is no doubt Greg is very keen to protect what he regards as his exclusive IP. That's his perception; let him live with it, and if he wants to take out a patent, let's wait and see if he is granted it. Suffice to say a patent is expensive, almost impossible to police, and lines the pockets of the legal fraternity - that is his choice.
There are undoubtedly other good amps around, of course we both know that!! Would you care to discuss your ideas?
Cheers,
Hugh
I think you were a bit harsh; the SKA is a pretty good amp from all reports, very clean and punchy, and there is no doubt Greg is very keen to protect what he regards as his exclusive IP. That's his perception; let him live with it, and if he wants to take out a patent, let's wait and see if he is granted it. Suffice to say a patent is expensive, almost impossible to police, and lines the pockets of the legal fraternity - that is his choice.
There are undoubtedly other good amps around, of course we both know that!! Would you care to discuss your ideas?
Cheers,
Hugh
AKSA said:
I'm always willing to discuss, and I don't need to rely on anything that's not already available from Greg's website. The A Number One problem with this design is that it, like many a Big Box design, or any number of schemos I've already seen floating around the Solid State forum, is that it uses MOSFET finals with a topology that was originated for Class AB2, BJTs. Of course, the Big Box manufacturers like this topology since no OPT is cheaper than even the cheapest OPT. Unforch, it doesn't work at all well with MOSFETs.
The MOSFET has the worst cross-over behaviour of all the active devices. (See: Distortion in Power Amplifiers). Take a good look at the residuals from a Class AB2 MOSFET amp that Self shows. No way can that mess sound good. The problem is made even worse due to the fact that "complimentary" MOSFETs are a good deal less "complimentary" than complimentary NPN/PNP pairs. If you're designing a high efficiency, Class D RF amp, then that imbalance doesn't matter since you have one or more LC tuned circuits and/or BPFs between the finals and antenna to clean up the mess. It's no good for audio. For audio, MOSFETs need to stay out of Class AB2.
Here are two more big problems:
it's nothing to get excited about. Take a good look at the characteristic for any power MOSFET, and see where Vds= 2.0V is. That will be on a grossly non-linear part of the characteristic. Furthermore, the internal device capacitance does funkey things at such low Vds's. Now, I'll use power MOSFETs as drivers for RF triodes, especially the notoriously hard to drive 845. However, I want at least a 20V margin, and 40V is even better. The SKA needs rails of at least +/- 75Vdc, and 100Vdc would be even better. Operating MOSFETs right up against the rail is OK if you're making an electronic break for an induction coil, but that's way too thin for audio.
He says he's using the common source topology. That means massive input capacitance, and that, in turn, means a likely slew rate problem. This input capacitance is also notoriously nonlinear. Again, no good for audio, where it's best to bury it by using the common drain (a.k.a. source follower) topology instead.
"I think you were a bit harsh; the SKA is a pretty good amp from all reports, very clean and punchy..."
Clean, punchy, yada, yada, yada. Given enough time, you can get used to anything. I had a MOSFET based amp that speced even better than the SKA, and got similar wonderful reviews. Up until a year ago, I might have agreed. That was before I built both a BJT based solid state amp, and an 807 based hollow state amp, both of which absolutely blew it away. The sound coming from the MOSFET amp sounded like throwing a heavy blanket over the speeks. There was no sense of spaciality, details were so badly missing that hearing familiar CDs through the new amps was like hearing a whole new CD. With one piece, Otters Dance, I could not even hear a passage that I knew was there. The bass was overly loud and sounded like monotonic thumping, lyrics were noticeably hard to understand, and vocalists faded into the same bland background. That's solid state sound at its absolute worst. Needless to say, I stripped that Big Box MOSFET amp down for parts to build a big induction coil, and the rest of it is providing a home for a family of field mice in the shed out back.
Furthermore, the harmonics coming from that thing ruined the tweeters of the Technics speeks I was using with it. There is no way that I'll allow any MOSFET amp that uses the BJT OTL topology anywhere near the Bose speeks that the 807 amp is driving.
Miles Prower said:
Hi Miles,
Is that your only listening experience with mosfet amp?
Was it vertical or lateral mosfet?
Are tou sure that this specific mosfet amp unit had no problem?
Is it possible that the design of the latest 2 other amps you have tried was simply better and the relation that you make with the mosfet output transistor just a coincidence?
Just some thoughts....
Yes I tend to agree - I do not regard the ska as the best ever possible design but it is never-the-less pretty good - nice and clear and quite smooth n natural. I think it would be wise to hear one before you dismiss it.
The desription of it's apparent ills you mention do not match my experience of listening to it.
The desription of it's apparent ills you mention do not match my experience of listening to it.
Hi Miles,
Any chance you could post the schematics of any amps that are similar to the SKA? (if it doesn't infringe anyones copyright) To date, I haven't seen similar designs.
regards
Any chance you could post the schematics of any amps that are similar to the SKA? (if it doesn't infringe anyones copyright) To date, I haven't seen similar designs.
regards
I find it somewhat "out of place" discussing an unseen design.
- As the complete amp is somewhat different to the simplified schematic Greg posted on his homepages.
And I find it stupid just dismissing all MosFet amplifiers...
Like me; I hate belt drive turntables...but would not dare saying that they never can sound good. I still do not like tubes...but the same goes here.
Arne K
- As the complete amp is somewhat different to the simplified schematic Greg posted on his homepages.
And I find it stupid just dismissing all MosFet amplifiers...
Like me; I hate belt drive turntables...but would not dare saying that they never can sound good. I still do not like tubes...but the same goes here.
Arne K
Miles Prower said:
Agreed.
On the other hand, anyone is free to use a better complementary for the IRFP240 and scale it to full class A use.
Doesn't sound half bad on electrostats, and a witty response to Greg's mother earth routine.
Some day, Mr Ball will refrain from blaiming the monkey for having a bad owner.
I gathered that Mr Ball offers a lot of guidance to the ones who buy his SKA kits.
The boards, schematic, and the time Mr Ball put into his design alone more than justify what he charges for a kit.
Let a patent attorney decide on his claim of IP.
In case that it's granted, you'll undoubtedly have seen stranger things happen.
And in case you're still waiting for someone to state that the SKA sucks, i mentioned on Hawaii5.o-rg to Mr Ball that it's not the best i've experienced. Frankly, i favor ozon layer killer Dino's.
This place is filled with people who claim superior sound quality of topologies and metal plate loudspeakers that already gave me a headache a quarter of a century ago.
Why continue to play Don Q. to take away the pleasure it apparently must give them ?
Greg Erskine said:
Miles, I'd be interested to learn what 1980 design you were referring to in your earlier post.
Regards,
Milan
Hi,
just had a look at schematic in post129.
There is very little that is similar to the topology in the SKA.
ccs on LTP , but all else is different.
Maybe I'm looking at the detail rather than overall.
just had a look at schematic in post129.
There is very little that is similar to the topology in the SKA.
ccs on LTP , but all else is different.
Maybe I'm looking at the detail rather than overall.
Miles Prower said:
Hi Miles,
As an SKA user I've got to disagree with the downer on mosfet amps in general, and the SKA in particular. Personally, I'm quite a fan of commercial mosfet offerings such as Gamut, Belles and Halcro, and the SKA can hold its head up in that company.
I'd like to hear Gregs rebuttal, as I don't have the technical nous to explain why it works better than it should.
As far as Self goes, he seems to know his stuff, but from what I've heard from other quarters his amp designs sound like average PA quality at best. I may be off the mark though.
There have been a number of people now suggesting they can do a better job than Greg, but until they put up with pcbs or kits its all irrelevant to me. The SKAs ain't vapourware, and they kick the **** of commercial kit at 10 or even 20 times their price.
I'm as impressed with mine today as I was when I first built it.
SKA vs post 129 schematics comparison?
I agree with AndrewT, there is almost nothing similar to what Grag has already disclosed ( I do not have the real schematics though), here are the main differences:
1) SKA should have symetrical diff input stage with passive loading and bootstrap circuit and post 129 does not have that at all
2) SKA should not have a traditional VAS but post 129 has a differentral in lieu of the VAS
3) SKA should be complementary output mosfet while post 129 is QUASI complementary (N channel)! To that effect, the pots 129 has a boosted +25V supply
4) SKA should be common source output stage but post 129 is QUASI.
I use "should" since I do not have the real schema.
So really, the schematics of post 129 does not compare at all.
AndrewT said:
I agree with AndrewT, there is almost nothing similar to what Grag has already disclosed ( I do not have the real schematics though), here are the main differences:
1) SKA should have symetrical diff input stage with passive loading and bootstrap circuit and post 129 does not have that at all
2) SKA should not have a traditional VAS but post 129 has a differentral in lieu of the VAS
3) SKA should be complementary output mosfet while post 129 is QUASI complementary (N channel)! To that effect, the pots 129 has a boosted +25V supply
4) SKA should be common source output stage but post 129 is QUASI.
I use "should" since I do not have the real schema.
So really, the schematics of post 129 does not compare at all.
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