P-channel mosfets for Aleph

[Peter Daniel]

Can Aleph be built with P-channel devices? I was thinking about IRFP 9130, since I might have some extras from modding A75 into Aleph. Any drawbacks, advantages when using those for Aleph?

 

[rtirion]

Yes, an ALEPH can be build using P Channel mosfets. At least
I do not see to much problems.
To illustrate this I made an example schematic of an ALEPH 3
with P Channel IRFP9140. As you can see you need to change
the input stage a little. (i.e. use n-channel IRF610).
I simulated this circuit, and it behaves very similar to the
original ALEPH 3.

I hope this helps you a little.

 

[HarryHaller]

P Channel

More capacitance less transconductance... Not a good choice.

 

[rtirion]

Just some examples...

Looking at the datasheets

For IRFP240
Ciss 1300 pF
Gfs 6,9 S min. pulse

For IRFP9140
Ciss 1400 pF
Gfs 6,2 S min. pulse

Please check the curves!

So, N-channel are only slightly better, but P-channel will not
make a terrible amplifier.

I remember their use in the original ZEN.
I think they are used in the X series as well.

 

[HarryHaller]

remember their use in the original ZEN.

Yes..... as a fixed current source. The lastest variation of the Zen uses two N channels in the output stage. I wonder why that is?

 

[Peter Daniel]

Yes, I wonder too.
Thanks for schematic rtirion.

 

[Nelson Pass]

I made an Aleph with 9240's just for the hell of it about
8 years ago. I didn't hear or measure much difference,
but the lower price and better availability of the N channels
made it a moot point.

 

[Peter Daniel]

Aleph amps and X series amps are using devices with TO3 cases. What is the major advantage of that package?

 

[Nelson Pass]

They look great. Now that they have been discontinued
and cost a lot more, they look even better!

 

[hitsware]

I made an Aleph with 9240's just for the hell of it about
8 years ago. I didn't hear or measure much difference,
but the lower price and better availability of the N channels
made it a moot point.

I know the Pchannel Hitachis have a failure mechanism (precisely what I don't know) that the Nchannels lack....Seems maybe the IR Pchannels are 1rst to blow also ?????????????????

 

[rtirion]

P-Channel

... I didn't hear or measure much difference,
but the lower price and better availability of the
N channels...

Thanks Mr. Pass. The response I was hoping for.