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Sony Vfet Illustrated build guide
Sony Vfet Illustrated build guide
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Old 14th February 2017, 05:13 AM   #51
henryve is offline henryve  South Africa
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Jim

Received my kit, and I see that my 2SK82s are marked 97 each, while my 2SJ28s are marked 115 and 116. So I don't have as close a match as I believe was true for your batch.

Would I have to adjust some of my resistors to compensate for it?
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Old 14th February 2017, 06:05 AM   #52
Fabian85 is offline Fabian85  Germany
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Quote:
Jim

Received my kit, and I see that my 2SK82s are marked 97 each, while my 2SJ28s are marked 115 and 116. So I don't have as close a match as I believe was true for your batch.

Would I have to adjust some of my resistors to compensate for it
Read the manual on this project carefully and this question is easily answered :-)
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Old 14th February 2017, 06:50 AM   #53
henryve is offline henryve  South Africa
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Quote:
Originally Posted by Fabian85 View Post
Read the manual on this project carefully and this question is easily answered :-)
Thanks. I didn't see this doc. I read through the Part 1 and 2 docs though. Pretty clear.
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Old 14th February 2017, 07:05 AM   #54
Soundhappy is offline Soundhappy  France
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Originally Posted by henryve View Post
Thanks. I didn't see this doc. I read through the Part 1 and 2 docs though. Pretty clear.

@ Henryve

No worry this numbers are ok.
Read Mr Pass article again.
Best regards
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Old 14th February 2017, 07:25 AM   #55
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by henryve View Post
Jim

Received my kit, and I see that my 2SK82s are marked 97 each, while my 2SJ28s are marked 115 and 116. So I don't have as close a match as I believe was true for your batch.

Would I have to adjust some of my resistors to compensate for it?
Read Papa Diy words :
http://www.diyaudio.com/forums/pass-...ml#post4979955
Your match of 2SJ28 have 0.1 V difference that perfect !
Not easy to find that close transistors.

This DiyVfet amplifier work great without matched transistors
because is only one pair version and use trimmers to adjust anyway.
Hooorayyy
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Old 14th February 2017, 07:35 AM   #56
alvinlim is offline alvinlim  Malaysia
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Originally Posted by Analogico View Post
Brumjam,

In Papa's words:

"I used an ordinary First Watt type supply design, documented elsewhere, with 22 VAC transformer secondaries to provide +/-28 volts DC. 24 or 25 VAC will work fine, running a little hotter. The minimum recommended for this amplifier is +/-27 volts, but it will run OK with a little lower supply if you adjust the values of R13 through R16 for lower voltage."
This is where I got confused with the documentation. The Firstwatt DIY Sony Vfet addendum mentioned that "This amplifier is designed to operate with voltages between about +/-26V DC and +/-30V DC." and "Other parts of the circuit are not very sensitive to supply values. Practically speaking, you should not try to make this amplifier with rail voltages below 20 volts, and above 32 volts.". 22VAC secondaries are rare in this region, and I can easily get 24VAC secondaries. 24VAC secondaries will give me a bit more than 32V DC (32.5v). Can I use 24VAC secondaries and change R15 and R16 to 56k ohm? Or should I try to have one custom-made with 22V secondaries?

Thanks!

Last edited by alvinlim; 14th February 2017 at 07:52 AM.
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Old 14th February 2017, 09:33 AM   #57
Brumjam is offline Brumjam  United Kingdom
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Quote:
Originally Posted by alvinlim View Post
This is where I got confused with the documentation. The Firstwatt DIY Sony Vfet addendum mentioned that "This amplifier is designed to operate with voltages between about +/-26V DC and +/-30V DC." and "Other parts of the circuit are not very sensitive to supply values. Practically speaking, you should not try to make this amplifier with rail voltages below 20 volts, and above 32 volts.". 22VAC secondaries are rare in this region, and I can easily get 24VAC secondaries. 24VAC secondaries will give me a bit more than 32V DC (32.5v). Can I use 24VAC secondaries and change R15 and R16 to 56k ohm? Or should I try to have one custom-made with 22V secondaries?

Thanks!
Exactly Alvin. That's the section of text I was referring to in my post. If it's designed to operate from 26v I should be ok, however the other quote suggests 27v as a minimum. My other transformers will give me about 32v. It sounds like either way it is necessary to change R15 and R16 which is fine.
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Old 14th February 2017, 09:35 AM   #58
henryve is offline henryve  South Africa
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24V puts it too close to 32V for me to be content, given that I already have a hot environment in summer. I would not want it to run unnecessarily hot.
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Old 14th February 2017, 06:20 PM   #59
Gyuri is offline Gyuri  Hungary
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Let's see a practical (and working ) example:
My toroid about 650VA, it has four pair secondaries with 24VAC, without load.
Each pair of secondaries has a dedicated diode bridge, and capacitor bank of 4x22000Uf/35VDC.
It gives me +/-29.7VDC at the amp +/- input point, there is some loss on paralleled 4xR0.47Ohm of CCRCC power supply.
I have 102-103mV through R32, so there is almost exactly 1A current flow.
Chosen resistor value is 42.2Kohm for R15/R16.
It gives me almost exactly 20VDC on testpoints T3/T5.
I'm wondering, may I go a little higher, say 22-23VDC?
Click the image to open in full size.
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Old 14th February 2017, 08:51 PM   #60
noelectrix is offline noelectrix  Europe
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this post ist even–steven-rule concerning spamming the tread but also context of building the vfet-amp : ) so hope itīs ok to ask here.

I decided to etch my own PSU–PCB fot the Pass V-Fet since the shipping cost just for the universal PSU is a bit high (and i forgot to add it with the kit). Last not least also a little diy-sweat in recognition to the great convenient kit.

I decided to do it F7-like with the last caps seperate for one railvoltage/channel like in this sketch (postet by nelson, so i hope itīs ok to show it again)
Click the image to open in full size.Click the image to open in full size.
Question: can anybody recommend a value for the Rīs and how many to use per rail/capacitor?

The "stock" Universal PSU recommends for each rail 4pcs of 0.45R , so 8 for the whole PSU. Should i use 2pcs of the 0.45R per rail (so 4 times 2 pcs) or still 4 times 4pcs per rail?

Maybe easy thing made complicated your insight is welcome

Last edited by noelectrix; 14th February 2017 at 08:54 PM.
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