Sony VFET Amplifier Part 2

[nicoch58]

In Part 2 Nelson wrote:
"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.
I guess we need some clarification on the concequences of using the standard 18Vac supply.

good question ...

 

[Variac]

Probably not at least until we send the files out for manufacture. As I've mentioned, you'll hear about it here!

Is there a signup sheet for the PCBs?

 

[Soundhappy]

Thanks Variac
Best regards

 

[pinnocchio]

Variac,

You should remove the link of the burning amp festival 2015. I clicked this link and it brought me to some weird site with tons of popups. Luckily it was on the iPhone so I didn't get infected with a virus or trojan.

Do

 

[Variac]

Thanks do,

In the past some people have mentioned this but it isn't consistent. I tried just now and got a porn site! Then I tried again, and got the BAF site....weird! Well, you're right, there's something wrong there and I'll remove it

 

[WBS]

Heatsink requirements for 2SJ28

I'm wondering if one of these would be sufficient for a pair of 2SJ28.

They would look pretty cool in a point to point build.

 

[Eric]

A 54c rise at 80w dissipation for a 5" length makes me thing these are too small. Even the 37c rise at 50w is too much heat. Perhaps one per transistor is better.

 

[WalterW]

Depends on what amp design you are going to build with them. In the original VFET part 2, Nelson uses two outputs paralleled, biased at 19V and 0.5 A each. So around 20 Watt total. That will work on this heatsink. but you will need two of these, because the 2Sk82s need a heatsink too
Also the regulators need a heatsink.

 

[Eric]

Thanks Walter, I think my mind went back to the Part 1 article with the quote of 100w of heat per channel...

 

[WBS]

Depends on what amp design you are going to build with them. In the original VFET part 2, Nelson uses two outputs paralleled, biased at 19V and 0.5 A each. So around 20 Watt total. That will work on this heatsink. but you will need two of these, because the 2Sk82s need a heatsink too
Also the regulators need a heatsink.

Thanks for your advice.

I'm looking forward to an SE design using only 2 P channel vfets, perhaps a ccs mentioned earlier by Papa, or maybe the recently unveiled V-Fetron. I'm thinking that I'll only need enough dissipation for a pair of 2sj28.

 

[WalterW]

Thanks Walter, I think my mind went back to the Part 1 article with the quote of 100w of heat per channel...

Correct the CSX1 is 1.5 A x 31 V x 2 = 95 Watt dissipation ( with the regulator) so whole other beast

 

[Nelson Pass]

So here's the good news.

I have the new boards working with single pairs and I will write them up
shortly.

Of course as usual there were a couple errors on the artwork, but I'll fix that
up and then off it goes for fab.

I'll post more information shortly.

 

[wdecho]

So here's the good news.

I have the new boards working with single pairs and I will write them up
shortly.

Of course as usual there were a couple errors on the artwork, but I'll fix that
up and then off it goes for fab.

I'll post more information shortly.

Great News

 

[nicoch58]

Thanks Nelson !!

 

[Variac]

You're so

 

[hifibluedevil]

So here's the good news.

I have the new boards working with single pairs and I will write them up
shortly.

Of course as usual there were a couple errors on the artwork, but I'll fix that
up and then off it goes for fab.

I'll post more information shortly.

Awesome

 

[Dennis Hui]

Thank you for the wonderful news!

Cheers,
Dennis

 

[WBS]

Drum roll.....

 

[Bones13]

Great to hear the ongoing progress. NP's estimate awhile back put the kit being done in late April. Here's to hoping that progress continues.

Thanks!

 

[dantwomey]

Slightly off topic, the Moon W-5 layout intrigues me,

The chassis' stiffness and solidity are impressive. Under the lid and behind the *"-thick front panel are two hefty 1000VA toroidal transformers; each amp channel has four 22,000µF smoothing capacitors, a roomy and clean printed circuit board, and eight TO-3-cased power transistors arranged as four sets of matched pairs. The power transistors are bolted to an extrusion mounted to the inside of the curved heatsinks, which form the side walls of the chassis. Generous heatsinks are mounted to many of the smaller transistors on the pcb. Overall, this is an impressively executed design.
Read more at Simaudio Moon P-5 preamplifier & W-5 power amplifier Page 2 | Stereophile.com

I wonder what TO-3 devices they use? I'm wondering where I'm going to find room for my 600VA toroid let alone two 1000VA transformers!

Regards,
Dan