I can agree with Mike! I've got a Soderberg-modified Forte Model4, which I'll compare to any solid state amp made today. Its combination of detail and sweetness, along with a wide, deep soundstage make it a contender -especially at the used prices you can find them for nowadays.
Just my 2 cents...
-chas
John Linsley Hood published a comparison of IGBT, MOSFET and BJT's when used in an identical amplifier. It was commissioned by Toshiba in order to show of their complementary IGBT's (App. note X3504)
The result was that MOSFETS had by far the lowest distortion followed by BJT's and then IGBT's. The only area that the IGBT's won was in maximum output power at clipping.
The result was that MOSFETS had by far the lowest distortion followed by BJT's and then IGBT's. The only area that the IGBT's won was in maximum output power at clipping.
IGBT amp: Forte 4a
I have a Forte 4a with the Soderburg mods (black gate caps, and I think different (faster) rectifiers, and better output lugs.)
It sounds GREAT on my Quad ESL-57's, best solid-state amp I've heard on them.
The Forte 4a is easily as musical as any modern SS amp I've heard, and I've gotten to audition quite a few of the "famous names" and the "obscure niche amps" in this system, which is equipped with a level-matching A/B power amp comparison switch. I'm sure Nelson Pass is right and part-matching must be a pain, but there's something about the sound that is just "right." Maybe the harmonic spectra? I dunno.
Best $800 I ever spent, that forte 4a. It made a friend who just dumped $15,000 into some Uber-amp cry when he heard the Forte 4a sounding clearly better.
I have a Forte 4a with the Soderburg mods (black gate caps, and I think different (faster) rectifiers, and better output lugs.)
It sounds GREAT on my Quad ESL-57's, best solid-state amp I've heard on them.
The Forte 4a is easily as musical as any modern SS amp I've heard, and I've gotten to audition quite a few of the "famous names" and the "obscure niche amps" in this system, which is equipped with a level-matching A/B power amp comparison switch. I'm sure Nelson Pass is right and part-matching must be a pain, but there's something about the sound that is just "right." Maybe the harmonic spectra? I dunno.
Best $800 I ever spent, that forte 4a. It made a friend who just dumped $15,000 into some Uber-amp cry when he heard the Forte 4a sounding clearly better.
Not only here some guy's claim, IGBT's are first choice for audio output power stages.
Check out in this case also this thread:
http://www.diyaudio.com/forums/soli...0d201-gt20d101-used-e-g-elektors-cfb-amp.html
Who can post an overview of currently available types suited for this application?
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Matching..
I do not care much for trying to match combined multi-devices like this or the MT-200 transistor.. On top of that, I have yet to hear a good sounding amp that uses MT-200. I'm just not a fan of combined packages at all.
It seems this just adds extra difficulty to an already complicated process.
More likely to drift off spec too..
Now for budged constraints and compromises, that is up to the user what is a good deal.
I shoot for dead accuracy and reliability.
I do not care much for trying to match combined multi-devices like this or the MT-200 transistor.. On top of that, I have yet to hear a good sounding amp that uses MT-200. I'm just not a fan of combined packages at all.
It seems this just adds extra difficulty to an already complicated process.
More likely to drift off spec too..
Now for budged constraints and compromises, that is up to the user what is a good deal.
I shoot for dead accuracy and reliability.
MT-200
You are wrong. MT-200 transistors can test good but still be bad. I went through this with a HK-3490 receiver. They are like two transistors hooked together inside, and they can pass a diode check and still be bad.
These receivers sound grainy just like a Sony receiver I had that used these same type of outputs.
I understand that there may be variations to this type of package that are single die, but I know that some common ones I have fixed were darlington style like a 2SD2401 . A quick google search will show many part numbers for these that are darlingtons inside. Just search MT-200 Darlington.
.. Didn't mean to get off topic here.. The IGBT isn't exactly the same thing inside.
You are wrong. MT-200 transistors can test good but still be bad. I went through this with a HK-3490 receiver. They are like two transistors hooked together inside, and they can pass a diode check and still be bad.
These receivers sound grainy just like a Sony receiver I had that used these same type of outputs.
I understand that there may be variations to this type of package that are single die, but I know that some common ones I have fixed were darlington style like a 2SD2401 . A quick google search will show many part numbers for these that are darlingtons inside. Just search MT-200 Darlington.
.. Didn't mean to get off topic here.. The IGBT isn't exactly the same thing inside.
I want to say that, with combined packages, I do believe they can be curve trace
matched, or pulse matched? - so, I would categorize them somewhere
between op amps and individual components. - probably alot closer to components.
Some of the new semi's I've been getting have been pretty close tolerance..
matched, or pulse matched? - so, I would categorize them somewhere
between op amps and individual components. - probably alot closer to components.
Some of the new semi's I've been getting have been pretty close tolerance..
You are right, Sanken do make a Darlington MT200 package.
They show 4 pairs of single BJTs and 3pairs of Darlington in their website.
Audio ?Sanken Electric
Anyone that uses a Darlington in their discrete power amplifier output stage do so for reduced assembly cost, not for improved performance.
You would have done better changing the darlington to the better performing separate driver and output device and rejigging the commercial amplifier for best performance.
They show 4 pairs of single BJTs and 3pairs of Darlington in their website.
Audio ?Sanken Electric
Anyone that uses a Darlington in their discrete power amplifier output stage do so for reduced assembly cost, not for improved performance.
You would have done better changing the darlington to the better performing separate driver and output device and rejigging the commercial amplifier for best performance.
Hi all, gosh this is an old post but I've to add my five cents here.
Built the IGBT amp form Elektor and yeah their schematics needed some improvements to get the setup stable. Now, I started this project back in time when it was published, today still using it at home every day. I know folks in the high-end audio industry and they looked at me as I was the devile when I said: I am about to build an IGBT amp, what???
Know what, friend of mine came over the other day and listened to my amp, he owned the Forte Model 4 and T-200 as well and he was just fascinated by how this sounded. He also had bigger stuff like Krell. Really, no matter what kind of transistor you use, MOS, BJT or IGBT, it's the schematic that counts.
You own an IGTB amp, if possible with current feedback as mine (Alexander amp): just keep it, don't sell it, you won't find better in that price segment, really. Say that since also owning some other standard amps (NAD350C) and rare ones (JVC A-X9), mine is the best (not because I did it but because it really sounds better). My speakers: BW-604S3.
Cheers C
Built the IGBT amp form Elektor and yeah their schematics needed some improvements to get the setup stable. Now, I started this project back in time when it was published, today still using it at home every day. I know folks in the high-end audio industry and they looked at me as I was the devile when I said: I am about to build an IGBT amp, what???
Know what, friend of mine came over the other day and listened to my amp, he owned the Forte Model 4 and T-200 as well and he was just fascinated by how this sounded. He also had bigger stuff like Krell. Really, no matter what kind of transistor you use, MOS, BJT or IGBT, it's the schematic that counts.
You own an IGTB amp, if possible with current feedback as mine (Alexander amp): just keep it, don't sell it, you won't find better in that price segment, really. Say that since also owning some other standard amps (NAD350C) and rare ones (JVC A-X9), mine is the best (not because I did it but because it really sounds better). My speakers: BW-604S3.
Cheers C
Going on memories from over a quarter century ago, I believe there were several versions of Mark Alexander's amp published in various Ap Notes and articles. Did his AES paper feature IGBTs?
Can you still get P-channel IGBTs?
I haven't read Alexander's (now expired) patent but I believe the novelty in his amplifier is how he used an opamp's power pins as signal outputs. Have you tried to determine how much of what you like about your IGBT amp is due to the IGBTs, and how much is due to Alexander's circuit topology?
Dale
P channel IGBT
HGTD8P50G1
HGTD8P50G1 datasheet - 8a, 500v P-channel Igbts
HGTD8P50G1, HGTD8P50G1S, HGTD8P50G1S9A suppliers list
Probably others too
HGTD8P50G1
HGTD8P50G1 datasheet - 8a, 500v P-channel Igbts
HGTD8P50G1, HGTD8P50G1S, HGTD8P50G1S9A suppliers list
Probably others too
This was old when Jung published in 1975:
Attachments
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