Article - Sony VFETs part 1

[Nelson Pass]

I am just testing out the front end to my CSX1 and I need to know whether 150mW is too much dissipation for one channel of my 2sk170 and 2sj74 buffer?

To second mighty ZM, no. I run this much all the time myself. Just keep a few spares around...

 

[Zen Mod]

@ ianc13

Papa is pullin' your leg , regarding necessity for spares

his amps aren't known as easily marching back home , for service

that's why is OPLDF starving empty lately

 

[dady]

Good morning good people, for my primitive language I lost the last posts of the thread, could you somebody translate to a comprehensible English, please understand that many outside speakers can't interpretate the slang expressions and abreviatures, I know is problem for you but anybody could be as ignorant as me.
Best regards dudes.

 

[Zen Mod]

translated :

150mW isn't critical

 

[WalterW]

One channel per side. Imagine in the pic there are two units bound for one 3mmX30mmX200mm copper plate, with a kheratec between the Vfet and the copper plate This plates are common here on Europe like standard in construction of electrical distributors. They are really cheap.
RS sales SK88 in 8 € each. They are SK88 in 1000mm long, for industrial sales, is good because you can cut the size you need. Getting one of them you have enough for a 0,4 K/W with 20cm long. I tried in get here on europe but finally I can't.

Thanks dady, I understand. But for a final version I will use these heatsinks: they look even nicer.

 

[WalterW]

I am just testing out the front end to my CSX1 and I need to know whether 150mW is too much dissipation for one channel of my 2sk170 and 2sj74 buffer?

I did have some BL grade in both channels, but after a small accident when wiring up I had to replace one channel and only had a pair of V grade to replace them with...

I know the max dissipation is 400mW on the datasheet for both devices, but am I pushing it with 150mW for each in free air?

Should I try to slip a small heatsink on them or replace with some new BL grade?

Thanks, ianc13

Ah, are you also actually building the amp?

 

[ianc13]

Ah, are you also actually building the amp?

Hi WalterW,

Yes I am - mostly (99%) built at the moment.

I have powered up and checked the input buffers and the 4 bias regulators so far.

Need to double check my wiring and then finally bring up the VFET stages one at a time and try to bias them and set the offsets.

I will post some pictures when I get the chance.

 

[ianc13]

To second mighty ZM, no. I run this much all the time myself. Just keep a few spares around...

Ah - if only I had a JFET spares bin that would allow me to build something truly extreme like a power amplifier with 1176 small signal JFETs per channel

 

[Nelson Pass]

That amplifier will be my emergency spares bin someday - I left the leads long.

 

[juanitox]

for the 1K resistor at the input of the buffer , is it the right value to get no oscillation or can i go lower with a pair of 220R i have ?

 

[jama]

I am hearing this ampli two weeks and now sound better that first days. I love details and complex music sound wonderful. Jacques Loussier Trio playing Bach it is something that it is difficult to forget... My friend dady suggest me try to use other csx1 to biamp my speakers. And I think I will do. I tremble when I think it...
Thanks to all

 

[Zen Mod]

for the 1K resistor at the input of the buffer , is it the right value to get no oscillation or can i go lower with a pair of 220R i have ?

not critical

 

[dady]

Or perhaps the new common drain?

 

[dady]

Here in this thread like others threads of this venerable Forum, there are members with different view points, with different goals and everyone maintain their own thread inside the proper thread. Every point of view in general is as odd as that only the imagination could imitate. Some time I feel that I am completely alone.

 

[Zen Mod]

you're not alone in that ;

I'm alone , too

 

[dady]

добро, хвала
Good, thanks

 

[WalterW]

Today I finished the second channel of the CSX1 and have been listening to it for two hours.
It sounds.... different....very, very detailed in the mids, big soundstage. Very good control and details of frequencies under 80Hz, amazing! It surprised me, a test tone with 34 Hz made my whole room shake....

I think this one is even more detailed than my Aleph J But I have to do 1 on 1 comparison.

Highs are not so pronounced, but they are there.

There is a lot of coloration, especially in the mids and with the BA3 as a preamp in front of it. Is that the third harmonic content I'm listening to?
The amp really has a sound of his own and is easy to listen to.
Gain is higher then I earlier reported. I removed the 220 Ohm output resistors of the DCB1

The bias voltages from the second channel are 6.4 and 9.4Volt, totally different from the other channel. So the VFETs I have, vary a lot.
When more people are building this amp soon, I'm curious what others will report.
I listened to it with the DCB1 in front and sometimes with the 'BA-3 as a pre' in front. Speakers are big 4 Ohm three ways.


Walter

 

[jama]

Congratulations. In two weeks it will sounds better. Try JBOZ too and compare.
Regards

 

[dady]

Congratulations Walter.

 

[Zen Mod]

Fugly!^2