DIY Sony VFET pt 1

[Zen Mod]

But no commercial amps?

When I look at curves for N vs. P-channel VFET they look "identical good".....

what you gonna get with that info?

as in anything else, same case is with Audio Electronic - even in "High End" product area, at least 50% of products are pure junk, taking in account price and especially claims

as far as claims are in case - reading claims and revelations of Audio Periodicals, from time when I started reading them , we should came to level nowadays to be able to fly to Mars (and back, maybe) , sitting on our Power Amps

no go - steps and differences between honestly made and presented projects are much smaller than Reviewers are reviewing

point is -if something is made in factory, it doesn't mean quality guarantee

edit: as already stated (correctly!) few times - be happy that actual P channel VFet follower is not commercial offer

Nelson Pass is , on start and after all, PL

and PL is making commercial products

edit: tech. fact, even if I'm sure that you'll skip it - P Channel Fets (J and V) are much trickier for production than their N channel counterparts
that's the reason that you'll see both just in commercial push pull products, while in cases where just one is used, every factory is following same logic - using part available in greater quantity, while being cheaper
that's called less risky production

though, I can't remember any commercial product made with SITs/VFets, not being push pull

except, of course, FW funny ones

 

[MEPER]

I am happy......having an amp only very few have.....
But only if it will bias up when I put power on it for the first time......before fully assembly.....but that will be tomorrow and not after a couple of glasses Guigal Gigondas red wine. Task is to put feet on and prepare for tomorrow.....

 

[ClaudeG]

Looking at the FE module only... question if you don't mind...

Is there any problem having this FE module running long term / permanently ON (eg connected to the PS) while not having any input signal (open input) and neither being connected on the output (open output).

I can see some loading on the output directly after the transformer on the board so probably open output at board level OK? What about an open input, oscillations, picking up whatever?

Any problem doing so?

Thinking about a way to have the possibility to include and bypass the FE module only (not on the fly, always unit off) while keeping it simple, eg not having to disconnect its power rails...

Thanks for your kind help

Claude

 

[Zen Mod]

no problem

 

[ClaudeG]

Many thanks ZM... it is so usefull to have someone confirming my sometimes very odd thoughts

Looks indeed like a simple 4PDT switch per channel, fitted discretely at the bottom plate, could be all what is needed to switch ON and OFF the FE module. To compare apples with apples, a source with polarity inversion capability and permutating the LS connections at terminal is all what would be needed to retain absolute polarity and negative H2.

Given the Power board can easily be driven directly by any source, and most DAC can inverse polarity by the flick of a switch, might be worthwhile giving it a try one day, to evaluate the impact of the FE board only, especialy if not needing that much gain "most of the time"/ under normal listening conditions...

Thinking out loud...

Claude

 

[Zen Mod]

dunno

I'm not so picky regarding absolute phase and phase of dominant harmonic

with every amp, I'm trying both speaker polarities and I'm leaving one which I prefer more

when I was more eager, younger, whatever - I was obsessed for some time , and got to conclusion that - if I'm taking too much care, I would need to keep one polarity for 50% of my recordings, then opposite polarity for other half

now , I'm just doing what I said in first evaluation, then investing all energy in foot tapping

 

[6L6]

^^ 1000x this.

 

[ClaudeG]

Thanks to both of you

Yes of course, will investigate: that's the fun

So far it seems to be that I am not very sensitive to absolute polarity (have to perform some real tests though, next on list to confirm that), but quite to H2 phase and very to any group delay.

But then I am getting older, who knows how my brain and ears are evolving

Thanks again

Claude

 

[mbrennwa]

I can't remember any commercial product made with SITs/VFets, not being push pull

The Sony TA-N88 used a bunch of 28/82 VFETs, and it was a Class-D amp. I'd say that's not exactly push-pull.

 

[Zen Mod]

 

[Manolo47]

Finished amplifier..... a few questions before power up

I have trimmer pots at their middle position. So, to set the 20v bias, where do I set the measuring probes, from ground to let’s say, the + terminal of C1?
Thanks

 

[music2myear]

step 22 of the guide: Select multimeter to DCV

Red probe to the anode side (the side without the line) of Z1, the zener closest to the Vfet

Black probe to ground

Slowly adjust potentiometer until you read 20V

 

[juanitox]

a gapped trafo, downgrade your px4

you are right , just with the sell of the outptut Transformer i could by another PAss Diy VFet ( if it was allowed ) and anothe one more with the interstage pair
but i like the look of glowing tubes at night and it takes me years to refine it.

in Bass department the Vfet kill it easily , for the medium and highs there is a debate let says tons of Irons vs tons of coupling Caps

 

[nicoch58]

well Pa amp is the dream tube diy's , two stage IT SE no FB !!
that's a big woow

 

[Nelson Pass]

The kits arrive with the pot already adjusted for 20 volts. You are free to play with it, but remember that the dissipation of the vfet is directly proportional to the voltage and is already at 34 watts.

 

[juanitox]

having fun today swapping Capacitor and the Vfet and like all the amps with Cap output adding a 20/30uf Motor run or Russian PIO to the 10000uf output will do no harm and cost not much ( no needs of fancy ones here just find smaller one to fit the case )

but the mother of tones is the 1000uf i don't know why but this one is particulary sensitive . the 1000uf nichicon ES Bipolar sounds very good but not safe as it is just a 16V rated , the SILMIC II sound awfull , the Nichicon FG 1000uf 50V is between the Two all these tested with 1uf film bypass .

next week i will try a WAzooo one here

 

[nicoch58]

put two in series btw find the 25v

 

[WBS]

...but the mother of tones is the 1000uf i don't know why but this one is particulary sensitive . the 1000uf nichicon ES Bipolar sounds very good but not safe as it is just a 16V rated , the SILMIC II sound awfull , the Nichicon FG 1000uf 50V is between the Two all these tested with 1uf film bypass ...

Hmmm. That's the first time I've ever heard of a SILMIC II sounding "awful." I wonder why it would.

 

[fabrice63]

having fun today swapping Capacitor and the Vfet and like all the amps with Cap output adding a 20/30uf Motor run or Russian PIO to the 10000uf output will do no harm and cost not much ( no needs of fancy ones here just find smaller one to fit the case )

but the mother of tones is the 1000uf i don't know why but this one is particulary sensitive . the 1000uf nichicon ES Bipolar sounds very good but not safe as it is just a 16V rated , the SILMIC II sound awfull , the Nichicon FG 1000uf 50V is between the Two all these tested with 1uf film bypass .

next week i will try a WAzooo one here

Juan , are your capacitors all already "burn in " , at least an 100 hours ??

it is well known that the Silmics need long burn in

also , the higher the voltage rating the lower the ESR



.

 

[ClaudeG]

The kits arrive with the pot already adjusted for 20 volts.

Is my reading correct that the 20V don't need to be adjusted and that the boards are supposed to be mounted as delivered, already fine adjusted by Papa?

That would be great news and somewhat different from some early builders which seem to adjust it...

Thanks for your confirmation!

Claude