But , for as i understand , you cannot exceed transistors Vce rating , even if choke is used.In this case , only efficiency is incresed... By the way , could somebody explain why using a choke as a collector load does not cause full power bandwidth problems ?
I was thinking about quasi complementary AB output stage , but the PNP transistors , 2SA1968 , seems to be hardly avalable.
Regards,
Lukas
I was thinking about quasi complementary AB output stage , but the PNP transistors , 2SA1968 , seems to be hardly avalable.
Regards,
Lukas
1200V IGBTs are rugged and quite cheap in comparison with MOSFET. Bridge output stages should be also considered, because 600V IGBTs are much more common (check IRG4BCxxx series from International rectifier and SKPxxNxx series from Infineon). For high voltage low-cost (switching) bipolar transistors check MJE1300x and MJE1800x series from On Semiconductor.
Series connecion of two or three lower voltage transistors with active dividers is another alternative, and of course, high efficiency class H is just an improvement over series connection. For example, consider an amplifier having +-1200V supplies tappered at 200V intervals (that may even come from a single pair of 200V rails with capacitor-diode multipliers), each interval having its own diode and output device (the problem here is to design a suitable VAS).
Series connecion of two or three lower voltage transistors with active dividers is another alternative, and of course, high efficiency class H is just an improvement over series connection. For example, consider an amplifier having +-1200V supplies tappered at 200V intervals (that may even come from a single pair of 200V rails with capacitor-diode multipliers), each interval having its own diode and output device (the problem here is to design a suitable VAS).
Hi,
Not necessarilry HV transistors have low hFE.Some have 30 or so.But their SOA is greatly decresasing with collector-emitter voltage.Because of this i am watching for fets now...
IRFBG20/30 1000V MOSFETS are cheap and easy to get.I am not sure if they are really suitable for audio , but , using a strong n/f, should work...
Regards,
Lukas.
Not necessarilry HV transistors have low hFE.Some have 30 or so.But their SOA is greatly decresasing with collector-emitter voltage.Because of this i am watching for fets now...
IRFBG20/30 1000V MOSFETS are cheap and easy to get.I am not sure if they are really suitable for audio , but , using a strong n/f, should work...
Regards,
Lukas.
How about these?
Hi,
ther are a few High-Voltage-Trannies/-Modules with Uce in the kV-range.
Sensitron SCP-4979 is a module with 4 IGBTs, each 2.500V/1A
The Powerex CM200HG-130H is a single IGBT-Power Module with 6.500V/200A, the CM400HB-90H is a 4.500V/400A module.
Even though these are quite slow devices with high input-/output-capacitances, they should be fast enough for audio frequencies.
I don´t know anything about availibility and cost of these devices, but on the first glance they seem quite interesting fo me to replace the Pentodes in a ´classical´ High-voltage ESL-amp.
With such high Uces there should be no need for cascaded designs with their problems of generating the drive signals for the Bases/Gates.
Any comments?
jauuu
Calvin
Hi,
ther are a few High-Voltage-Trannies/-Modules with Uce in the kV-range.
Sensitron SCP-4979 is a module with 4 IGBTs, each 2.500V/1A
The Powerex CM200HG-130H is a single IGBT-Power Module with 6.500V/200A, the CM400HB-90H is a 4.500V/400A module.
Even though these are quite slow devices with high input-/output-capacitances, they should be fast enough for audio frequencies.
I don´t know anything about availibility and cost of these devices, but on the first glance they seem quite interesting fo me to replace the Pentodes in a ´classical´ High-voltage ESL-amp.
With such high Uces there should be no need for cascaded designs with their problems of generating the drive signals for the Bases/Gates.
Any comments?
jauuu
Calvin
Hi,
Transistors as well as Tubes have to be driven within their parameter´s limits. So why should a tranny be less reliable than a tube in a specific application??
A high- quality high-voltage amp for ESLs will be a inefficient design with quite strong heat development.
So it should be advantegous to use devices that don´t need heating at all.
A topology like a CCS loaded emitter-basis comes to my mind, eventually as a cascaded design (reducing the stress on the active devices), working in class A. Should allow for a very linear amp with sufficient current capabilities, without getting too inefficient.
jauu
Calvin
Transistors as well as Tubes have to be driven within their parameter´s limits. So why should a tranny be less reliable than a tube in a specific application??
A high- quality high-voltage amp for ESLs will be a inefficient design with quite strong heat development.
So it should be advantegous to use devices that don´t need heating at all.
A topology like a CCS loaded emitter-basis comes to my mind, eventually as a cascaded design (reducing the stress on the active devices), working in class A. Should allow for a very linear amp with sufficient current capabilities, without getting too inefficient.
jauu
Calvin
Hi,
I have had no much experience with tube amps.But some blind tests reveal that testers were unable to identify good Tube amplifiers vs discrete ones(with one exception when amp is soft-overloaded).
So , my opinion , discrete approach is much more practical.Transistors don't need regular replacement , too.
Regards,
Lukas.
I have had no much experience with tube amps.But some blind tests reveal that testers were unable to identify good Tube amplifiers vs discrete ones(with one exception when amp is soft-overloaded).
So , my opinion , discrete approach is much more practical.Transistors don't need regular replacement , too.
Regards,
Lukas.
Bazukaz said:
Well then, the only best way to know for sure which is better for you is to build a set of each.
I am anoither tubophile like Brian. OOPs, sorry Brian, not implying you are tubby. I meant tube-o-phile.
Not only because I hear better sound from tubes but because I know tubes and high voltage are a better reliability mix Tubes won't go pop in a picosecond like most sand devices will if something ever goes slightly wrong.I also live in a cold country so extra heat in my house is a bonus.
Tu be or Tubbi
Hi,
well, there are tubes and there are tubes. Having worked with KR-Audio I can honestly say..These babies are The Tubes. Nothing will top a KR-300Bxls or an T-1610...but guess what!! The driver stages in these exceptionally good sounding amps are FETs! Simply because they offer a superior signal handling in togetherness with an simpler and more straightforward design. Too, all these tubes are pure triodes. A lot of poweramp designs, especially the high voltage designs rely on pentodes. Signal handling of pentodes and MOS-FETs is very similar. So there is imo no reason at all not to opt for an simpler transistor design.
jauu
Calvin
Hi,
well, there are tubes and there are tubes. Having worked with KR-Audio I can honestly say..These babies are The Tubes. Nothing will top a KR-300Bxls or an T-1610...but guess what!! The driver stages in these exceptionally good sounding amps are FETs! Simply because they offer a superior signal handling in togetherness with an simpler and more straightforward design. Too, all these tubes are pure triodes. A lot of poweramp designs, especially the high voltage designs rely on pentodes. Signal handling of pentodes and MOS-FETs is very similar. So there is imo no reason at all not to opt for an simpler transistor design.
jauu
Calvin
Re: Tu be or Tubbi
Fets are the best the sand industry has been able to come up with to approach the superior audio performance of a good vacuum tube.
Perhaps KR skimped and used Fets as drivers because it they had put another custom tube in there nobody mortgaging just one house would be able to afford their amplifier.
KR is like a different planet when it comes to tubes. There was a very successful tube industry happening half a century ago without any influence from KR, and without the boutique prices. Fortunately one can have truly excellent tube audio without the KR expense.
This is only MY opionion.
Calvin said:
Fets are the best the sand industry has been able to come up with to approach the superior audio performance of a good vacuum tube.
Perhaps KR skimped and used Fets as drivers because it they had put another custom tube in there nobody mortgaging just one house would be able to afford their amplifier.
KR is like a different planet when it comes to tubes. There was a very successful tube industry happening half a century ago without any influence from KR, and without the boutique prices. Fortunately one can have truly excellent tube audio without the KR expense.
This is only MY opionion.
Hi Victim,
don´t guess..read! "Simply because they offer a superior signal handling in togetherness with an simpler and more straightforward design." At KR they´ve tried out several tubed driver topolgies, but always came back to the MOSed driver stage because of its simplicity and superior performance!
jauu
Calvin
don´t guess..read! "Simply because they offer a superior signal handling in togetherness with an simpler and more straightforward design." At KR they´ve tried out several tubed driver topolgies, but always came back to the MOSed driver stage because of its simplicity and superior performance!
jauu
Calvin
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