Sony VFET Amps

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#42
Binkman said:
Mate: You and I understand quality of sound
reproduction doesn't rely on high wattage. And the best class A amps
though not efficient run out of steam at 45 watts maybe? At 4ohms that's
enough to do some serious damage.

My point still is it would have been a remarkable marketing scheme for sony..
Click to expand...

I certainly appreciate the charm of the little Class A amplifiers. In this case,
when consulted, Sony asked if they could be made to drive the AR-1's
specifically (and provided a pair). This came out to approximately 200 watts
into 4 ohms with a good level of "control".

I don't think the few copies that will be made are much of a threat to anyone,
but with a little luck someone will figure out how to get Class D to do the
job with the same signature.

😎
 
#44
They draw about 400 watts each.

Always alert to a little tutorial opportunity:

I biased them at 3 amps (per side) which conventionally results in a 6 amp
peak in Class A, and when you do the math you would expect a 288W Class A
peak into 8 ohms, 144W peak into 4 ohms.

This would mean 144W rms Class A into 8 ohms (which it will not deliver due
to voltage limitations). It would also mean 72 watts rms Class A into 4 ohms.

However, there are no Source resistors on the VFETs, not needed as they
share nicely and have a near-zero temperature coefficient. So the curve
of the conduction is basically square law, and when you observe the
cutoff characteristic of the output stage you see that the Class A envelope
is increased by about 75%, so instead you get about 125 W rms Class A into
4 ohms, and that means a 250 W peak, which is probably where that spec
came from in the announcement.

😎
 
#46
I have a few Sony amplifiers with Vfets, just waiting for a beautifully simple schematic from Mr Pass for a 10watt or so amplifier into 16Ohm Ocellia widebanders. I`m keeping a bunch of matched Vfets aside for just such a project. I may one day move from 300b amps when that happens. 🙂
 
#52
Nelson Pass said:
However, there are no Source resistors on the VFETs, not needed as they share nicely and have a near-zero temperature coefficient. So the curve of the conduction is basically square law, and when you observe the cutoff characteristic of the output stage you see that the Class A envelope is increased by about 75%, so instead you get about 125 W rms Class A into 4 ohms, and that means a 250 W peak, which is probably where that spec came from in the announcement.

😎
Click to expand...

Very nice Nelson! You may be interested to know that Ian Hegglun is busy with cube law class A for a future Linear Audio issue. This will have an even better efficiciency ratio. I think these concepts of square and cube law characteristics are a hidden secret for high-efficiency class A.

Jan
 
#58
vdi_nenna said:
So the last of the vfets gave been bought out?
That sucks.
Click to expand...
This is fragment of e-mail i have received from Acronmanelectronics
about 2SK82/2SJ28 in stock:

"Some other customers may have interest to get a few more hundreds pieces for their project.

regards
chee leong

- acronmanelectronics "

:$:ad news for modest diyers...after commands of amplifiers for interested rich audiophiles who read this Stereophile article
we be without very quickly:scared:😱:gnasher::scared::scared:
Fragment from Stereophile:
" Eventually, he uncovered a stash in Singapore and bought all of them, enough to make the single pair of “Sony VFET Amplifier 40 Year Commemorative Edition” amplifiers at CES. This uses 24 pairs of VFETs as complementary followers and front-end/driver circuitry based on a Pass Labs’ XP topology."

Nelson Pass said:
Monoblock. 32/ch

😎
Click to expand...
Greedy Papa with SonyVfet's :lickface:but economic with his exclusive Pass-sit1's 🙁😕😀:rofl:

Best regards
 
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