Hi!
In the attached link you can see that the Thorens Tem 3200 use only one giga power mosfet, 800W/300A.
Could somebody tell me what is that Mosfet? What type?
Maybe it would be suitable for some Pass amp.
http://www.6moons.com/audioreviews/thorens/thorens.html
Greets:
Tyimo
In the attached link you can see that the Thorens Tem 3200 use only one giga power mosfet, 800W/300A.
Could somebody tell me what is that Mosfet? What type?
Maybe it would be suitable for some Pass amp.
http://www.6moons.com/audioreviews/thorens/thorens.html
Greets:
Tyimo
Yes those big ones seem interesting but come with some problems. They tend to be expensive an 800w device is probably
going to cost $30 or more. And the darn input capacitence
is also huge something like 12,000pf for a 800w device!
They do have the added feature of not requiring a heatsink
insulator. By the way Nelson said in his original ZEN article
that he did play with some 600w mosfets.
going to cost $30 or more. And the darn input capacitence
is also huge something like 12,000pf for a 800w device!
They do have the added feature of not requiring a heatsink
insulator. By the way Nelson said in his original ZEN article
that he did play with some 600w mosfets.
Apart from all those disadvantages mentioned, these industrial MOSFETs do not really have high transconductance at low bias current, which is what you want really for audio.
If you want high gain (transconductance) MOSFETs, you are better off using UHC MOSFETs, e.g. 2SK2955. There are even P-devices, so you are not forced to do quasi or circlotron. AND you can still parallel them if you really want them to dissipate 800W.
Patrick
If you want high gain (transconductance) MOSFETs, you are better off using UHC MOSFETs, e.g. 2SK2955. There are even P-devices, so you are not forced to do quasi or circlotron. AND you can still parallel them if you really want them to dissipate 800W.
Patrick
It does say: One single 800W N-ch MOSFET per phase leg..
Which makes it a traditional push-pull amplifier anyway.
Could be this device: http://ixdev.ixys.com/DataSheet/45a81247-0066-484b-ab00-c06a6a893e15.pdf
Which makes it a traditional push-pull amplifier anyway.
Could be this device: http://ixdev.ixys.com/DataSheet/45a81247-0066-484b-ab00-c06a6a893e15.pdf
This whole topic was discussed at length over a year ago - not on the Pass Labs section though.
A good search should find it.
Andy
edit - found it
http://www.diyaudio.com/forums/showthread.php?s=&threadid=117555&highlight=
A good search should find it.
Andy
edit - found it
http://www.diyaudio.com/forums/showthread.php?s=&threadid=117555&highlight=
You can find higher current devices on IXYS.com but then with lower Voltage. It appears this way of selecting MOSFET's is based more on testosteron than common sense.
The oversized MOSFET will have too much Gate capacitance, making the closed loop slow. And the only place you dont want slowness is in the closed loop. That, combined with the unlinear low current region of any MOSFET, is what makes your amplifier sound hard and metallic.
Always select the smallest MOSFET that will do the job, for this kind of amplifier.
The oversized MOSFET will have too much Gate capacitance, making the closed loop slow. And the only place you dont want slowness is in the closed loop. That, combined with the unlinear low current region of any MOSFET, is what makes your amplifier sound hard and metallic.
Always select the smallest MOSFET that will do the job, for this kind of amplifier.
what about the case?
Forget about those transistors, the real issuse is that Thorens copied my industrial design for the chassis!
Thorens-
Me-
Forget about those transistors, the real issuse is that Thorens copied my industrial design for the chassis!
Thorens-
Me-
An externally hosted image should be here but it was not working when we last tested it.
Tyimo said:
These are not insoluble problems...
The main question is:
What is that industrial 800W/30A mosfet???? Code number??
Tyimo
They are being phased out in place of IGBT's. Power Mosfets for motor use died 10-15 years ago. I can give you part numbers if you really want?
Most are three phase but I could find single phase types.
PS. Do you have a curve tracer, can you measure capacitances, Ton/ Toff etc. Without these details (no need to specify alot of this for motor use) What about phase margins when using the devices?
PS. they are never one mosfet die per se, usually paralleled and some with drivers
Kevin
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