Hi Gk,
how does that fit the conventional description of ClassA?
Surely a different description would be more appropriate.
how does that fit the conventional description of ClassA?
Surely a different description would be more appropriate.
AndrewT said:
Well, when discussing the individual stages of which the amplifier is composed, there are class A stages and class AB stages.
When Technics made amplifiers using this concept a couple of decades ago, their marketing guys called it "A+".
Hi,
Typical of what salespersons will resort to when attempting to increase profit rather than improve the product and many of these far eastern products could do with some serious improving.
implying better than ClassA, when in fact (as reported by many commentators) it was at best worse than ClassA and some said the equivalent to "rubbish".
Typical of what salespersons will resort to when attempting to increase profit rather than improve the product and many of these far eastern products could do with some serious improving.
The patent is #4,115,739 Sano, Hirosha, Hirota 4/18/77.
It seems to me, however that there were two versions of
the Technics Class A product - one of them was simply a
nonswitching output stage, which (interestingly) was about the
same as an amplifier I did once (see the thread "My first amplifier")
I did not take that design to market - and it was notably inferior
to the design discussed above.
😎
It seems to me, however that there were two versions of
the Technics Class A product - one of them was simply a
nonswitching output stage, which (interestingly) was about the
same as an amplifier I did once (see the thread "My first amplifier")
I did not take that design to market - and it was notably inferior
to the design discussed above.
😎
AndrewT said:
🙄
Well gee, you have class A performance with less than half the dissipation. I'd say that's better than ordinary class A, wouldn't you? Oh wait, once upon a time someone called a Technics amp rubbish. Oh darn, I must be building a rubbish amplifier then too.
Hi Gk,
you have jumped to a conclusion I did not even imply and had no intention of implying.
I was referring very specifically to the Far Eastern practice of inventing classy sounding names for circuit implementations that do not necessarily improve performance. They often come up with "improvements" to try and persuade the gullible to part with their money, at far too frequent intervals, as they continue to chase profit margin to the detriment of quality. They are very good at making equipment cheaper to manufacture, but not so good at making it better in the sound quality stakes.
I never implied that your circuit or your improvements or your attitude came anywhere close to matching the big Internationals. I suspect "profit" isn't even in your DIY vocabulary.
Remember this started with Technics A+ which is NOT ClassA on which I have read a few reports.
I have not seen any reports on your amplifier.
you have jumped to a conclusion I did not even imply and had no intention of implying.
I was referring very specifically to the Far Eastern practice of inventing classy sounding names for circuit implementations that do not necessarily improve performance. They often come up with "improvements" to try and persuade the gullible to part with their money, at far too frequent intervals, as they continue to chase profit margin to the detriment of quality. They are very good at making equipment cheaper to manufacture, but not so good at making it better in the sound quality stakes.
I never implied that your circuit or your improvements or your attitude came anywhere close to matching the big Internationals. I suspect "profit" isn't even in your DIY vocabulary.
Remember this started with Technics A+ which is NOT ClassA on which I have read a few reports.
I have not seen any reports on your amplifier.
AndrewT said:
Andrew, it is unlike you to generalise like that. Accuphase, Luxman, Denon, Yamaha, Sony, Nakamichi, Technics, Pioneer, Leben, Kondo are a few that springs to mind that are not bad by anyones standard.
Kindest regards
Nico
7 times the 10 mS power, 7 times the capacitance. Sounds
like about 7 parallel IRFP240's.
Whoops, only 3 times the DC dissipation - must be the package...
😎
like about 7 parallel IRFP240's.
Whoops, only 3 times the DC dissipation - must be the package...
😎
Yes, that's about what it looks like to me. These may also be the kind of power MOSFETs that have the different gate structure (I forget what they are called - they were mentioned earlier in this thread) that results in performance characteristics that are not necessarily best for audio output applications.
Bob
Bob
Can someone post a copy? I don't even know if the MOSFET or the BJT is on the bottom.Upupa Epops said:
But did you try pretending to switch the amp but didn't, to see if they would still 'hear' a difference? If not, your results are meaningless.Nico Ras said:
Nixie said:
I think it is nearly impossible to make generalizations about MOSFET or BJTs in regard to which one sounds better.
Many out there have done a fine job of building poor performing amplifiers in each of these technologies. By the same token, there are many sterling examples in each technology. What matters most is how well the designer applied the particular technology that he chose to work with. Each technology has its own different dragons to slay.
Cheers,
Bob
I'm not sure if you replied to the first or second half of my post. In case it was the first, in such a hybrid cascode I would expect there would be some difference depending on which of the devices is in which position, just like in the case of other hybrids (IGBTs).
Nixie said:
IRF511/IRF9521 and MJ15024/MJ15025, MOSFET at the rail side.
BI-MOS still sounds funny.
I can post a pic of the A-100 output stage when my digcam batteries are rejuiced.
I should do a "dislectyc" class, i meant MOSFET at the output side. 
I wonder how many also built this thing, pretty neat with 3 separate rail voltages; +/- 20Vdc, 55Vdc and 50Vdc.
=>
I wonder how many also built this thing, pretty neat with 3 separate rail voltages; +/- 20Vdc, 55Vdc and 50Vdc.
=>
Just picking up from post 591 or thereabouts in this thread (Glen, Bob, jcx et al on output stage error correction), attached below is some of the stuff I've been looking at wrt to bipolar error correction. I am getting some pretty intersting full power THD-20 results in simulation using an op-amp and bootstrapping the supplies to the output stage. If I understood the circuit and discussion around Glen's proposal, the whole output stage is enclosed in the error correcting amplifier loop but the trick used to overcome op-amp supply limitations was to bootstrap the supplies to the output. In the attached circuit, the output is driven from the VAS and the error correction signal summed at the base of the output stage pre-drivers, so the approach is a little different. Output open loop distortion into 8 ohms is around .005%, and importantly, into 2 ohms around 0.01%. In simulation, this kind of performance can normally only be had by running well into class A. I figure that if this got enclosed in a global -ve feedback loop, THD-20 could go down by another 20db or so.
I was very intersted to read about the possible op-amp power supply interactions and jcx's analysis.
I have a 'test bed' amplifer (Ovation amp - its in another thread so you can take a look there if you want to) up and running so will try this scheme out on it in a few weeks.
Bob/jcx maybe you care to comment
rgds
NB - attachment is for LT Spice
I was very intersted to read about the possible op-amp power supply interactions and jcx's analysis.
I have a 'test bed' amplifer (Ovation amp - its in another thread so you can take a look there if you want to) up and running so will try this scheme out on it in a few weeks.
Bob/jcx maybe you care to comment
rgds
NB - attachment is for LT Spice
CFP for output stage is prone to oscilation, local oscilation.
But why so many amps uses CFP for the pre-driver, like this one (Q19-Q3)?
http://www.diyaudio.com/forums/attachment.php?s=&postid=1135809&stamp=1171534308
Is the CFP stable in the predriver position?
Why it needs CFP in the predriver? Why not just use darlington?
But why so many amps uses CFP for the pre-driver, like this one (Q19-Q3)?
http://www.diyaudio.com/forums/attachment.php?s=&postid=1135809&stamp=1171534308
Is the CFP stable in the predriver position?
Why it needs CFP in the predriver? Why not just use darlington?