OnSemi FETs?

Khron said:
Ciss for the OnSemi is specced as 3600 (typ) / 5000 (max) pF, as opposed to the 4057 (typ) for the IRFP260N. Comparable, i'd say :smash:

Perhaps, but it's the IRFP240 you should compare with, as it is what Pass specs.
 

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steenoe

Member
2004-03-23 10:43 am
mpmarino said:


Perhaps, but it's the IRFP240 you should compare with, as it is what Pass specs.

Excactly.

The most usefull Onsemi fets (for Pass projects) are the TO220's MTP10N and MTP12P. They are very nice for a BosoZ type PSU. (Drop in replacement) Ofcourse, they carry the J310 also, which gained some popularity lately:)

:)
 

steenoe

Member
2004-03-23 10:43 am
Khron said:
So, in the end, are they worth giving a shot (as long as i've already ordered them), or should i just shove them straight into storage and get some IRFP240's? :xeye:

PS: I must admit, i do like some meat on them bones, so i'm not all into the fashion-model-coatrack look :D :devilr:

Depends on what you want to build. The MTW32's might be worth a shot if used for the cascode devices in a ZenV9. I wouldnt recommend them for the usual Zen's and Aleph.

:)
 
GRollins said:
Don't assume higher capacitance is always a bad thing. I've had at least one circumstance where the higher capacitance part sounded better.

Grey


Nelson Pass said:
If you prefer big bottom...


I kept meaning to get back to this, but got sidetracked. As I've said elsewhere, my comments on a higher capacitance part that sounded better were limited to the above 5kHz region. The devices in question were in a tweeter amp in a quad-amped system. As such, I have no opinion about the balance between the lows vs. highs...only the highs taken on their own merits (or lack thereof).
The question is why a higher capacitance output device might give better highs when--at least on paper--everything would seem to be against it. A partial answer can be found in that the devices were not being asked to handle the entire signal. Released from bass and midrange obligations, the front end no longer has to charge and discharge the Gate to the same degree. With that in mind, there's more current available and the Gate should be much happier.
And yet...a lower capacitance part should have been happier still.
Was I led astray by a painted hussy? Would I have married in haste only to repent at leisure? Would she have turned out to be a high maintenance woman once past the honeymoon?
All good questions. I've thought about this quite a bit since then and have reached any number of potential solutions, but none of them satisfy me. At the moment, I'm leaning towards the idea that the highs would have grown wearing over time. I'm not in a position to say for sure because I pulled out the high capacitance devices and put something else in. At this point I'm within striking distance of putting in an entirely different amp with an entirely different topology and entirely different devices. I hope to scrape together enough money (I've kinda bottomed out for the moment) to buy several different sorts of output devices with the intent to experiment. Full range performance is one thing--but what happens if I restrict my listening to the high end only? I don't know and am trying to keep from speculating until I get a chance to try the whole experiment over. It's an interesting question, to be sure.

Grey
 
steenoe said:


Depends on what you want to build. The MTW32's might be worth a shot if used for the cascode devices in a ZenV9. I wouldnt recommend them for the usual Zen's and Aleph.

:)


In this application, I would bet money that you couldn't tell the difference, even if you used some real big capacitance fets, but as Steen says, for the Zen amps, I'd too say they're a no-go. For the aleph amps, you could just run fewer devices a bit harder, and end up with the same result.

Magura :)
 
Thanks for the input, everyone. :)

But PLEASE, do keep in mind that this is for a headphone amp. So yes, it should be able to cope well with a full-range signal, but otherwise it won't be driven too hard (no more than a few V swing, and not too big a current - my cans are 55ohms, and 90-something dB/mW... yes, MILI-watt :) ).

Thus, given these "working conditions", maybe (just maybe), the greater input capacitance my not take too high a toll on the driving of the output devices.

And again, these are only semi-inexperienced suppositions :D
 

steenoe

Member
2004-03-23 10:43 am
Khron said:
Thanks for the input, everyone. :)

But PLEASE, do keep in mind that this is for a headphone amp. So yes, it should be able to cope well with a full-range signal, but otherwise it won't be driven too hard (no more than a few V swing, and not too big a current - my cans are 55ohms, and 90-something dB/mW... yes, MILI-watt :) ).

Thus, given these "working conditions", maybe (just maybe), the greater input capacitance my not take too high a toll on the driving of the output devices.

And again, these are only semi-inexperienced suppositions :D
The less hard you drive them, the worse:) If you get my meaning?
I am still firmly set on the IRFP510 or IRFP610 for a headphone amp Babbelthingie. The darn Fet's are cheapo enough, why gamble?? Considering the work.... Oh well I can keep on forever.....



:)