D1 IV Mosfet
Currently having a PCM63 dac with D1 iv stage, after many years i would like to build another one and see if i can improve. (better power supplies, caps, wiring, pcb layouts etc)
Well i'm at it i was wondering if there would be a improvement possible with a different mosfet. (lower impedance for the dac)
ZVN2210g? Instead of irf610? Let me know your thoughts or suggestions.
you can go only up - IRFP240
I built a D1 I/V stage using ZVN3310's. I dropped the supply rails to +/- 22V on mine. It sounds pretty good to my ears, but I've never heard an actual D1 to compare.
I actually posted yesterday asking for suggestions for high transconductance surface mount MOSFETs to use in an ES9038PRO-capable D1 I/V stage and just came across this thread this morning.
I've put together a list of devices to test for transconductance under the operating conditions of the circuit and would love any recommendations for additional MOSFETs to add!
The supply rails are +/-6V, operating current is 1.09A, and max gate threshold is ~4V, so I've mostly focused on MOSFETs at or around logic level.
Here's the list so far:
Transconductance seems to be a vary important criterion for you.
Since this is a Common Gate Mode circuit, transconductance is the
reciprocal (mathematically and literally) of the input impedance, we
ask the question - what input impedance are you trying to achieve
Thanks Nelson, appreciate you taking a look.
In order for the ESS DACs to stay in current-output mode they need to be loaded into as close to a virtual ground as possible. Ideally in the mOhm range, given the low output impedance of the DAC (~200R). Higher input impedance pushes the chips into voltage-output mode and prevents you from reaching the data sheet DNR and THD specs.
I suppose a better way to frame my question and search might be, given that I need a high transconductance MOSFET with a low-ish gate threshold voltage, are there any other audio-beneficial characteristics I should be considering? Or specific lines of MOSFETs known to be audio-friendly when in the signal path under these conditions?
Maybe 2sc4793 instead of mosfet
I would be interested in seeing any data that shows the performance
degradation into loads greater than 0 ohms.
Probably want to bias around half an amp.
Maybe also worth checking out SiC Jfets in to247 package. United SiC
SSM3J355R has typical gm in excess of 10S @ 1A however it would need cascoding as its limited to 1W dissipation being a thermally enhanced SOT-23. Oh and its also a P-channel device. Threshold voltage <-1V.
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