ZVP3310 - Good choice as input fet for Aleph 30

[hifinerd]

Edit: My thread title was supposed to be a question not a statement, but I can't edit it accordingly.

Hi All,

Firstly, let me apologise if what I am about to say is completely incorrect. I am very new to this and know nothing Always keen to be set straight.

I have been informed that modern IRF9610s are not as linear as the older versions due to differing manufacturing techniques. Whether this is significant or not, I have also been thinking that perhaps the 9610 is over rated as an input fet for the Aleph amplifiers, and that a smaller signal fet may be more linear in this application.

It seems to me that using any fet that is significantly overrated for a task means also dealing with more gate capacitance which is a bad thing. NP pushes the running of fets at high currents ideology, and it seems that the 9610s are also not being pushed in this application. That said, I know NP has his reasons for everything, and I am sure there is a good reason why he chose the 9610 that I am not aware of.

Anyway, I have been looking for a direct drop in improvement that will not require any resistor/bias changes. This rules out any JFETs.

I have stumbled across the ZVP3310, which is cheap, readily available and has less than half the input capacitance of the 9610 (50 pf vs 170pf). It can easily be dropped into existing boards by simply twisting the pins around and should require no resistor changes. NP also used it in ZV4, so I guess it can't be too bad. Edit 2: I also see in the ZV4 article that NP actually tried several fets and found the 3310 to be superior to the 9610 in that application, which is promising

Any thoughts on the suitability of the ZVP3310 to this task, and how it would perform both objectively and subjectively?

Your advice is appreciated!

Greg.

[BobEllis]

I vaguely remember an Aleph shootout posted a couple years back where an amp built with ZVP3310s was preferred over the irf9610 version. So, yes, it is a suitable alternative in this application.

here's the thread Pass Shootout In Salt Lake City Part-2

[hifinerd]

Perfect, thanks! That is exactly what I wanted to hear, and reading the shootout I get the impression it has exactly the effect I would have expected.

Greg.

[BobEllis]

Happy to help

[dhole]

sounds interesting... Ive got some aleph 5s that might like a bit of a tweak. Dont suppose anyone has a source of the zetex parts in to-220 ?
dave

[hifinerd]

TO92 version easy to get in any quantity from digikey.

The TO92 package will work fine with your TO220 boards, but you will need to reverse a few of the pins by twisting them around. No biggie though.

[BobEllis]

For an Aleph input pair you don't need the TO-220 dissipation, as the dissipation is only ~10mA x Rail voltage. You should keep an eye on the CCS dissipation, though. ~20 mA x (rail - 9)

Mouser carries them, too if you want to avoid the minimum order charge.

Use insulation stripped from hookup wire to prevent accidents with lead routing. Sort of forces you to keep them long - and allows you to glue the pair together to help with thermal drift.

[AndrewT]

I bought mine in the UK. I wish I could be helpful and remember who from.

Farnell has stock search ZVP2* ZVP3* ZVN2* ZVN3* at prices around 25p to 100p depending on type and quantity.

The ZVN2110g in sot223 looks attractive.
Where would this version be suitable?

[hifinerd]

Originally Posted by BobEllis

~20 mA x (rail - 9)

Mouser carries them, too if you want to avoid the minimum order charge.

Oh dear, I didn't notice the digikey minimum order was for a bulk quantity, only that the number was one!

So I assume that with my aleph 30 and +/-25v rails it will be fine for the ccs?

Great idea with the insulation.

[dhole]

Andrew

Would love to know your source in the uk, farnell only carries surface mount type. I guess i would want to match em so Im after 20 i guess.
Dave