I am curious if anything needs to change in this amp to happily drive a 32ohm load. I emailed Nelson about this a few weeks ago and didn't get a response. I wasn't aware of the impending birthday!
My partner wants to drive his Meze Empyrean 2 with a current source, so we picked the F1. We figure that since they are a near perfect resistive load, they should be happy being driven by a current source. We are completely aware that it's a speaker amp and extremely powerful for headphones. If there are replacement output devices that perform much better than the originals, I'd be interested.
I'm most of the way done producing a board for it, completely different from Nelson's design and more like the diyaudiostore boards. I plan to use one of the Universal Mounting Spec revisions. I will share these when I'm done if it's ok with Nelson. I may also make a teeny weeny desktop version that uses Noctua fans.
Happy Birthday Nelson! Thank you for sharing your knowledge and designs with the community.
TL;DR
1. F1 or F1J for use driving 32 ohm planar headphones. Anything need to change for good performance?
2. Making boards for IRF240/9240PBF new parts and DIYAS UMS, will share when finished if ok with Nelson.
3. Substitute devices for better performance?
My partner wants to drive his Meze Empyrean 2 with a current source, so we picked the F1. We figure that since they are a near perfect resistive load, they should be happy being driven by a current source. We are completely aware that it's a speaker amp and extremely powerful for headphones. If there are replacement output devices that perform much better than the originals, I'd be interested.
I'm most of the way done producing a board for it, completely different from Nelson's design and more like the diyaudiostore boards. I plan to use one of the Universal Mounting Spec revisions. I will share these when I'm done if it's ok with Nelson. I may also make a teeny weeny desktop version that uses Noctua fans.
Happy Birthday Nelson! Thank you for sharing your knowledge and designs with the community.
TL;DR
1. F1 or F1J for use driving 32 ohm planar headphones. Anything need to change for good performance?
2. Making boards for IRF240/9240PBF new parts and DIYAS UMS, will share when finished if ok with Nelson.
3. Substitute devices for better performance?
For a headamp use I would try and change the output devices (Q1 & Q2) to something like IRF510, 610, 520.
Less Ciss, still high enough Gm, and importantly low Qg (gate charge).
IRFP240 needs to be run at high enough current (0.7 - 1A) to reach 100kHz and above.
With 510, 610, 520 you'll need 150 - 350mA to drive your cans.
For that you'll need to recalculate the values of a few resistors, which is not difficult.
My 2c.
Less Ciss, still high enough Gm, and importantly low Qg (gate charge).
IRFP240 needs to be run at high enough current (0.7 - 1A) to reach 100kHz and above.
With 510, 610, 520 you'll need 150 - 350mA to drive your cans.
For that you'll need to recalculate the values of a few resistors, which is not difficult.
My 2c.