BOSOZ Question

[nick5]

Hi,

Is 2SK951 or IRFIBE20G a good replacement for the IRF 610 MOSFETs provided in NP article ?

Thanks.
Nick

 

[eLarson]

Compare the Cgd values, for starts.

 

[nick5]

This is what I was able to get from the net and corresponding datasheets:

2SK951
======
Input Cap.= 350 pF (typical), 500 pF (Max)
Output Cap.= 60 pF (typical), 90 pF (Max)

IRFIBE20G
========
Input Cap.= 530 pF (typical)
Output Cap.= 150 pF (typical)

IRF 610
======
Input Cap.= 140 pF (typical)
Output Cap.= 53 pF (typical)

IRF 510
======
Input Cap.= 180 pF (typical)
Output Cap.= 81 pF (typical)

From the above comparisons. it appears that IRFIBE20G is not a good candidate but 2SK951 (from Fuji Electronics) seems to have a relatively comparable capacitance. My original question was to find out the impact of 2SK951 or IRFIBE20G on the sound quality of this preamp. I haven't started the project yet but trying to investigate all options before kicking it off.

Any ideas you can share is appreciated. Thanks again.

Nick

 

[eLarson]

If there were a difference it would be in the treble, I suppose. That could, in turn, lead to an impression of it being a little more 'bass-y'.

Is the power dissipation going to be okay? The IRF510, 610 could dissipate about a watt without a heatsink, and more with one. What is it for the 2SK951?

There is another thing, which might be harder to figure, given the current that it is usually spec'd at vs. what is used in a BoSoZ, and that is the gfs.

 

[nick5]

Thanks eLarson.

I'm not worried about heat dissipation my plan is to use large H/S after reading other posts which talked about how hot the MOSFETs get. The 2SK951 max power dissipation is 40W vs 36W for the IRF610.

I've decided to buy few IRF's and match them for this project using NP article on matching. I will do the same for the 2SK951's but will first build the preamp with IRF's and then swap them with 2SK951 and compare. I also heard that IRF510 is a better sounding in this topology (a little tuby....). Will try them as well. Who siad DIY isn't fun....

Nick

 

[eLarson]

Good luck. Let us know how it comes out.