Krell KSA 100mkII Clone

[jacco vermeulen]

Originally posted by Mark A. Gulbrandsen
$30.00 plus $48.00 shipping

Wow !
is S.L.C Tek heaven or is that the bonus of being in a mobile business, Mark ?
I thought Tek curve tracers were good for several hundreds of dollars, US alone ?

(for stuff like that i might as well shack up with ZenoModo, or whatever he calls himself this week)

[Zen Mod]

grump grump




























MA24


grump grump

[Mark A. Gulbrandsen]

Don't know what to say.... I just watch E-Bay for stuff I want and need and sometimes even stuff I don't need. I just bought a TEK 7603 100 mhz dual trace scope for 9.95 plus 38.00 shipping. I will just leave this one at work for all to use.

MArk

[Zen Mod]

Originally posted by Mark A. Gulbrandsen
Don't know what to say.... I just watch E-Bay for stuff I want and need and sometimes even stuff I don't need. I just bought a TEK 7603 100 mhz dual trace scope for 9.95 plus 38.00 shipping. I will just leave this one at work for all to use.

MArk

what can I say,except that I'm glad for ya...
and that I'm sorry for me........ufff......e-bay is so far from me.......

usual price of progress (or "progress") -living in country "in transition"

[Bratislav]

Originally posted by Harry3
Also FYI
I tried matching one hundred MPSA42 (NPN) to MPSA92 (PNP) from Onsemi and could not get a close match.

I don't think you ever will. Usually MPSA PNPs have far higher fe (in order of twice that of NPNs).

BUT ! You really only need to match transistors of the same type (in fact the only critical ones are those forming the differential pair) - there is no need to match upper and lower pairs. The only possible problem is that Tr's with higher gain will draw less base current (if everything else is the same) and you might get a slight DC offset at input. Either blocked by a capacitor or trimmed out by adjusting idle current of the input diff pairs.

[jacco vermeulen]

There's the fun part of Jappin devices.

Japanese PNPs also have a higher average hFe than NPNs.
But they come in different hFe classes, and their hFE bell curves overlap.
A lower hFe class GR type batch of PNPs and a batch of BL type NPNs have a higher hFe matching rate than trying to find matching pairs from NPN and PNP devices of the same hFE class.

So, those who go for Japanese and who are not into hFe matching are better off buying same hFe class PNP/NPNs. The hFe matcher buys the highest hFe grade NPNs, and the lower hFE grade PNPs.

[Mark A. Gulbrandsen]

Jacco, You may have just uncovered the reason for Krell switching to the Japan semi's 2SC/2SA devices in the later amps. Easier matching!!

Mark

[PWatts]

I have to agree with the NPN and PNP's not being close enough for matching to one another with the MPS and BC stuff. I didn't experience much better figures when I matched my clone's 2SA/2SC's though, and I bought a huge bag full. NPN-NPN and PNP-PNP was easy. But as jacco said, it's possible I didn't get some of the overlapped hFe classes.

However, for the clone at least matching of the NPN-PNP's isn't really important, at least not compared to matching of each other.

Mark: have you got any feedback on the boards yet?

[Mark A. Gulbrandsen]

I will have the boards later today and will post pics later on or tinight.... So please check back.....

Mark

[Mark A. Gulbrandsen]

At last.......