Are jFets better sounding than mosfets? Tubey, pairing with ferrite or alnico driver etc.
What are the more commonly available, as well as the niché ones? (Just as in mosfet arena, 640, z44 vs 1058, 201)
Any classA scheme with jFet is highly welcomed.
(Information sans rhetoric will be just fine
Thanks
What are the more commonly available, as well as the niché ones? (Just as in mosfet arena, 640, z44 vs 1058, 201)
Any classA scheme with jFet is highly welcomed.
(Information sans rhetoric will be just fine
Thanks
jFETs are mostly small signal devices.
There are a few power jFETs. Availability and pricing is poor.
An alternative to high power Vertical mosFETs, that are in the main designed for switching duty, can be Lateral mosFETs. All these LatFETs are expensive in comparison to the switcher duty VertFETs.
There is at least two pairs of Audio Vertical mosFETs, the Toshiba 2sk1529/j200 & 2sk1530/j201
These too are expensive and availability is limited.
Are you getting the picture.
Vertical mosFETs are cheap
All the alternatives are expensive.
For ClassA you need lots of device dissipation capability. This applies to BJTs and VertFETs and LatFETS and audio VFETs.
The cheapest way to get there is to adopt the cheap switcher duty VertFETs and use many of them biased very high where the crossover distortion becomes extremely low or non existant.
VertFETs are ideal in ClassA. They need a lot of design expertise to get ClassAB to work exceptionally well. But is is done and is good when done right.
There are a few power jFETs. Availability and pricing is poor.
An alternative to high power Vertical mosFETs, that are in the main designed for switching duty, can be Lateral mosFETs. All these LatFETs are expensive in comparison to the switcher duty VertFETs.
There is at least two pairs of Audio Vertical mosFETs, the Toshiba 2sk1529/j200 & 2sk1530/j201
These too are expensive and availability is limited.
Are you getting the picture.
Vertical mosFETs are cheap
All the alternatives are expensive.
For ClassA you need lots of device dissipation capability. This applies to BJTs and VertFETs and LatFETS and audio VFETs.
The cheapest way to get there is to adopt the cheap switcher duty VertFETs and use many of them biased very high where the crossover distortion becomes extremely low or non existant.
VertFETs are ideal in ClassA. They need a lot of design expertise to get ClassAB to work exceptionally well. But is is done and is good when done right.
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With the exception of the Pass SIT1 device, no VFETs (also known as SITs) have been manufactured in the west for at least 35 years. These are similar to power JFETs in that they are depletion mode, but their characteristics most resemble that of a vacuum triode.
It is possible to get the old ones (Sony, NEC, Yamaha) from China, with the usual 'reliability' regarding that what you are getting might not be what you asked for, if you get anything functional, or even, anything at all.
When you can find genuine parts, they are exceptionally expensive (eg. you can get 3-10 Lateral MOSFETs for the price of a single VFET).
These are not to be mixed with ANY kind of MOSFET, lateral or vertical (or other geometries which could be considered somewhere in-between).
What you can do instead, is 'synthesize' a device that behaves very similarly, using local feedback around a combination of MOSFETs.
That being said, some SIT devices have been produced in the ex-USSR as late as 1990s, and they are very usable for audio, IF you know what you are doing. Also, some power JFETs and lateral MOSFETs designed primarily for VHF are available from Russia and other ex-USSR countries, which are extremely linear and could work in class A, for fairly low powers (perhaps up to 10W per device).
It is possible to get the old ones (Sony, NEC, Yamaha) from China, with the usual 'reliability' regarding that what you are getting might not be what you asked for, if you get anything functional, or even, anything at all.
When you can find genuine parts, they are exceptionally expensive (eg. you can get 3-10 Lateral MOSFETs for the price of a single VFET).
These are not to be mixed with ANY kind of MOSFET, lateral or vertical (or other geometries which could be considered somewhere in-between).
What you can do instead, is 'synthesize' a device that behaves very similarly, using local feedback around a combination of MOSFETs.
That being said, some SIT devices have been produced in the ex-USSR as late as 1990s, and they are very usable for audio, IF you know what you are doing. Also, some power JFETs and lateral MOSFETs designed primarily for VHF are available from Russia and other ex-USSR countries, which are extremely linear and could work in class A, for fairly low powers (perhaps up to 10W per device).
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