IRF 230 or IRFP 140, what's better for AlephX ?

[Peter Daniel]

I have still IRF230 mosfets in TO3 cases (which I was using for A75) and IRFP140 mosfets (TO 247 cases) which I bought recently. What would be a better choice for Aleph X with 20V rails?

[AudioFreak]

IRFP140

[Peter Daniel]

That's what I thought, thanks.

[Petter]

First of all, these are different form factor devices. The P model will be normally be better at transferring heat to sink except that you have the TO3 version which will be better still at about a square inch of contact area.

Secondly, it will depend on many factors -- one of my methods for sorting devices is to first look for devices which have relatively high on-resistance as this often goes hand in hand with low gate charge, not to mention gate charge which does not vary all that much with gate voltage.

'40 devices are usually more heavily optimized for swithing than '30 devices. Switching transistors are not optimized for linearity.

100 series devices are optimized for higher currents than 200 series devices. This is not necessarily an advantage.

What I have learned (from others) is that IRF units are typically not considered to be the best audio devices around -- where only a few manufacturers seem to make them sound good (with Pass being perhaps the most well known proponent). Japanese devices receive more positive "street credibility".

The question is thus one of taste, and I suspect both devices can be cajoled into sounding very good. There have been similar device discussions in the past where even NP has participated. The short answer is that it probably does not matter that much what you choose (an answer which I personally don't like).

Next time I purchase devices, I will try Japanese.

In your case, I would expect the 230's to sound smoother and based on other posts, the 140's to possibly have more robust bass.

Petter

[Peter Daniel]

So we are back to square one. I have enough of both devices and mounting is not a problem either. The amps would be used for mids and highs, so optimal sound would be preffered in that region. So you say that 230 would be smoother?....Maybe this is a better choice then.

As to Japanese devices, the price is still an issue, especially if you buying more for matching.

[Petter]

Price:

If you like me have already purchased and standardized/matched you are kind of locked in

Be sure to let us know what your findings are if you decided to try both.

Petter

[Coulomb]

Please excuse my iognorance yet again. What is an AelphX, I see constant references to this Mystery Amp. Where can I find specs, Designs, Schematics, anyone making PCB's. I had always assumed the X stood for the version number, instead of the full name.

Anthony

[skaara]

There are no original schematics/pcbs for that amp.. Ppl are trying to make an amp like the original amp with some speculation and their own knowlege, ill make my alephx when there will be original schematic, if it will ever be?

[Coulomb]

Peter why do you prefer the IRFP140 over the 240 and 244 again? Do you find there are sonic differences or is it due to the differences in the specs? If so over than voltage ratings, what do you find objectionable?

Anthony

[Coulomb]

.. Ppl are trying to make an amp like the original amp with some speculation and their own knowlege

Well I really like the Pass X200, I was thinking of trying to squeeze more than 100 Watts out of an Aelph II.

Anthony