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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 4th September 2019, 08:07 PM   #891
Stanney2017 is online now Stanney2017  United Kingdom
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I’ll test it again tomorrow and see how it measures.
If good I’ll move on.

Thank you Dennis.

Andrew
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Old 7th October 2019, 04:52 PM   #892
vuongan is offline vuongan  United States
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Default R15 and R16

Papa has noties: with 24VDC:
22V = 2.5V * (R15+4750 ohms)/4750 ohms 22V *4750 ohms / 2.5V = R15 +4750 ohms 41800 ohms = R15 + 4750 ohms
R15 = 37050 ohms.
You would pick the closest 1% resistor, which would be 36K or 36.5K for R15 and R16.
So with 28 vdc we have R15 or R16 is 44650 ohms. But in the schematic resistors 15 and 16 is 41.2 kohm
Which value is right for 28vdc voltage? 44.6 kohm or 41.2 kohm?
Thanks
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Old 7th October 2019, 06:10 PM   #893
Dennis Hui is offline Dennis Hui  Canada
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Sony Vfet Illustrated build guide
41.2K will get you about 20V at T3, whereas 44.6K will get you about 22V.

It's more a question of the rail voltage you want to run the amp at. I suspect
both are fine, though the higher rail will run the vfets a bit hotter, but probably
a little bit more output.

41.2K should give you an amp with performance as documented.

Cheers,
Dennis
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Old 8th October 2019, 01:45 AM   #894
vuongan is offline vuongan  United States
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Quote:
Originally Posted by Dennis Hui View Post
41.2K will get you about 20V at T3, whereas 44.6K will get you about 22V.

It's more a question of the rail voltage you want to run the amp at. I suspect
both are fine, though the higher rail will run the vfets a bit hotter, but probably
a little bit more output.

41.2K should give you an amp with performance as documented.

Cheers,
Dennis
Thanks Dennis!
I didn't read papa's words carefully: 'If your supply is lower than this, you should adjust R15 and R16 down so that
the R19 and R20 have at least 2 volts across them. '. So if we use a bigger power source like 29v or 30v, we can still use this resistor value (41.2Kohm) without changing it, right?
thanks
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Old 8th October 2019, 02:17 AM   #895
Dennis Hui is offline Dennis Hui  Canada
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Sony Vfet Illustrated build guide
Yup. Even with higher initial voltage it will regulate down to roughly the same value.
Of course, your mosfets will run hotter.
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