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-   -   Aleph 3/30 MOS-FET Choice? (http://www.diyaudio.com/forums/pass-labs/68925-aleph-3-30-mos-fet-choice.html)

Skorpio 1st December 2005 12:09 PM

Aleph 3/30 MOS-FET Choice?
 
I am considering 5 different types:

IRFP044N:
175deg junc, 1.3deg/W, 16S trans, 1500pF, 2.30EUR

IRFP048N:
175deg junc, 1.1deg/W, 22S trans, 1900pF, 3.30EUR

IRFP054:
175deg junc, 0.65deg/W, 25S trans, 4500pF, 4.35EUR

IRFP150:
175deg junc, 0.65deg/W, 13S trans, 2800pF, 2.60EUR

IRFP240:
150deg junc, 0.83deg/W, 7S trans, 1300pF, 2.60EUR

In the original ZEN paper, it was stated that 044 types gave 100% less distortion than 244 types.....is that due to transconductance? And will this performance be Aleph relevant?

In another article NP states IRPF240 af on of his favorites....to me it looks inferiour?

To me IRFP048N looks like the best compromise between Gm, heat and Cin.....any comments?

And is the large difference in Rth between the types (all TO-247AC) real or just datasheet figures (from 0.65 to 1.3), in my application it raises junction temperature from 73 to 88 degrees...

Nelson Pass 1st December 2005 07:20 PM

Look at the transconductance of these chips as compare to
the capacitance, and you'll see that there is some proportionality.

High transconductance is desirable for low distortion at all
frequencies, but capacitance will compromise the high frequency
performance, partly because it limits the bandwidth but mostly
because the capacitance is non-linear, generating distortion
at high frequencies.

If you are building a low frequency amplifier, you go with the
fatter chips and the higher transconductance (S). If you are
making a tweeter amplifier, you go with low capacitance. If
the amplifier is full range, you make your compromise as you
choose.

:cool:

Skorpio 1st December 2005 08:19 PM

Thank you!;)

If not for the thermal resistance I am in for the 048 or 044 devices, but migth consider 244 also....

:confused:

Dr. ODD 10th December 2005 08:03 AM

Hello

I know this was discusst before but maybe there are some new experiences by someone.
Does the 5th Generation Mosfet`s from IRF ( the ones whith the n like 044n) have advatages or disadvantages over the 3. Generation ( like 044 or 240 ). I dont mean Power Ratings or capacitance. Are there some listening experiances?

:confused: :confused: :confused:

Mark A. Gulbrandsen 13th December 2005 04:56 AM

My Aleph 2's have the 240's in them and they sound glorious!!!!!

Mark

uli 16th December 2005 04:22 PM

Quote:

Originally posted by Dr. ODD
Hello

I know this was discusst before but maybe there are some new experiences by someone.
Does the 5th Generation Mosfet`s from IRF ( the ones whith the n like 044n) have advatages or disadvantages over the 3. Generation ( like 044 or 240 ). I dont mean Power Ratings or capacitance. Are there some listening experiances?

:confused: :confused: :confused:


IMHO the 5th generation is just optimized for switching purposes,
not audio amplification. I would use approved devices like 240 etc.

Uli

:nod: :nod: :nod:


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