DIY progress report

[Nelson Pass]

Originally posted by gl
The F3 is clearly a magic sounding piece judging from the reviews. But how much of it is the JFETs and how much is NP's skill at creating a first class context.

The cascoded Mosfet is a nice piece, but the JFET has a lot
less distortion - to the extent I can contrive an apples-to-apples
comparison, I estimate about 1/5 the distortion at ordinary
frequencies and even less at the top end.

[gl]

Originally posted by Nelson Pass
I estimate about 1/5 the distortion at ordinary
frequencies and even less at the top end.

Outstanding! Thank you.

As I look at the 6moons photos it looks as though the F3 voltage regulator is modulated like the one in the Zen V3?

I also assume that the apples-to-apples mosfet would have been something smallish like a 610?

Thanks again.

GL

[Nelson Pass]

Originally posted by gl
As I look at the 6moons photos it looks as though the F3 voltage regulator is modulated like the one in the Zen V3?

No, it is constant.

[hifimaker]

Originally posted by GRollins
Guys, bear in mind that these parts weren't designed with us in mind. As so often happens, we're taking the scraps from the table; accidental beneficiaries of other technologies.
Noise? Whuzzat? These things are supposed to be used in computer power supplies. They could care less about noise. According to my contacts at Lovoltech, they had never considered linear use in any context, much less audio. They were designed as switches. It's quite accidental that they have any application in audio at all...
Grey

I remember reading an interview last year with Dan D'Agostino that Krell had custom manufactured Mosfets for better audio performance.

If I remember correctly, he stated that there were no Mosfets made for audio applications and Krell contracted with TI to custom manufacture Mosfest for audio rather than leveraging what is currently available in the marketplace. The minimum order for custom TI devices was 1 million parts.

Grey, after the Jfets - any chance for a custom GB?

I wonder if Nelson has ever considered taking this path and custom building a semiconductor?


-David

[GRollins]

$1,000,000 is slightly beyond my reach, I'm afraid. Perhaps after I win the lottery or write (and sell) the Great American Novel. Given that all I have time for are short stories, the odds of the second option occuring are about on a par with the first.
You have to take these "custom-made" claims with a grain of salt. If you have someone--let's say On-Semi--stamp a stock part with your company logo, it becomes a "custom" part. Sounds good in the literature, it may even sound good in the equipment, but it's not any different from the regular transistor that you could buy...if only you knew which one to order.
You want one that says diyAudio? That would be a trip. Strike fear and envy into the hearts of all your audio buddies.

Grey

[hifimaker]

D'Agostino actually went into a rather lengthly explaination regarding the performance of stock mosfet parts intended for switching rather than audio. It sounded like Krell's research was rather extensive and more than rebranding. Could be all hype though.

-David

[Circlomanen]

but the JFET has a lot
less distortion - to the extent I can contrive an apples-to-apples
comparison, I estimate about 1/5 the distortion at ordinary
frequencies and even less at the top end.

Does this acount for the local current feedback that the source resistor on the JFet gives?

[analogair]

1 Mill custom mosfet's
One would sure have to build a lot of amp's

[Nelson Pass]

Originally posted by Circlomanen

Does this acount for the local current feedback that the source resistor on the JFet gives?

Yes, that is to say that it would if you chose that particular
test bed.

[Circlomanen]

Thanks Mr Pass!