Fet Matching Question for Aleph-X

[PrimeCase]

Hi All
I'm just in the process of getting the parts together for an Aleph-X (nice work everyone, thank you)and I'm wondering about the matching process and also the number of each type to order to ensure I have enough matched to make replacement/servicing easier, bear in mind this is the most ambitious project I have undertaken. And after reading some users mishaps and difficulties I was starting to wonder if this is beyond me!

I have seen on the Pass DIY web site the procedure for matching the differential and output devices, is this the correct way to match these devices?.....or possibly here
Fuzzy on FET matching?

some additional information.........

I have a highly stabilized PSU which I can vary between 11-15v but no true lab PSU (current source)and also a regular DMM with resolution to 10's of millivolts. The amplifier will be using rails of approx 15v and may be as low as 13v after messing with CRC or CLC configurations, I'm looking at approx 6-9A bias once the supply voltage is known (FYI transformers from large UPS's are almost perfect for this).

How close should I match the 9610's and at what current?
Likewise with the 044's?

finally I'm going to be attempting to use 8 outputs rather than 4 for better low impedance load driving ability so assuming my Fet's will need matched in 4's how many should I order to cover my bases and Mr Murphy's most likely appearance early in the amplifiers life

I'm fairly confident in my abilities but I want to be 100% before I potentially give myself a headache during the building of the amplifier.

many thanks

Kevin

[Coulomb]

There are several threads spanning this topic already, you should do a search before starting a new Thread.
Here is the link to one of them.

Aleph-X builder's thread.

Anthony

[PrimeCase]

Anthony
I came up with one hit on a search and it wasn't specifically about matching these particular devices (I'm aware they all behave similarly), I am also aware of the builders thread and I may have missed something but the question was posted for reassurance more than anything else and for possibly other insight.

Now I have that cleared up how many should I buy?
would the method in the link in my first post be adequate for matching?

thanks

Kevin

[Nelson Pass]

Originally posted by PrimeCase
Hi All I'm just in the process of getting the parts together for an Aleph-X (nice work everyone, thank you)and I'm wondering about the matching process and also the number of each type to order......

You aren't Mr. Wu in disguise are you?

[till]

hehe

[finneybear]

Probably you should ask this guy for help?

http://myweb.hinet.net/home1/prbstech/Order/IRFP240.htm


His price may be cheaper, too! Hehe

[PrimeCase]

Hey Nelson.......I'm not that amitious LOL., instead just a little paranoid.

anyway it looks like I'm just going to have to fudge this one



Kevin

seriously a ballpark figure?....anyone.....???

also is $0.90 per device a good deal for IRFP044's?

[sianturi]

Originally posted by PrimeCase

also is $0.90 per device a good deal for IRFP044's?

It's a good deal. I think you should take it. I bought mine for $2.59 a piece at digikey.

[Coulomb]

Originally posted by PrimeCase
Hey Nelson.......I'm not that amitious LOL., instead just a little paranoid.

anyway it looks like I'm just going to have to fudge this one



Kevin

seriously a ballpark figure?....anyone.....???

also is $0.90 per device a good deal for IRFP044's?

It is a good price just make sure they are no remarked knock offs. The best price I have seen is from Future Active

http://www.future-active.com/Comerge...CTIFIER%20CORP

$1.80 US Cheaper if you buy 50 or more.

Anthony

[PrimeCase]

The prices are from Richardson electronics.....I'll be ordering 50 on Monday....I'll bear in mind the other prices if they are not going to be available for a while as the web site states out of stock!....typical

Kevin