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D1 IV Mosfet
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Old 19th July 2017, 03:26 AM   #1
maartentje is offline maartentje  United States
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Default D1 IV Mosfet

Hi,

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.

Thanks Martin
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Old 19th July 2017, 09:41 AM   #2
Zen Mod is offline Zen Mod  Serbia
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D1 IV Mosfet
you can go only up - IRFP240
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Old 23rd July 2017, 08:40 PM   #3
metalman is offline metalman  Canada
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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.
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Old 1st August 2017, 03:48 PM   #4
Sabrosa is offline Sabrosa  United States
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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:

IRL40S212
IRL40SC228
IRL60S216
IRFS7430PbF
IRFS7534PbF
IRF2204S
PSMN1R5-30BLE
PSMN3R4-30BLE
PSMNR90-30BL
CSD19535KTT
CSD19536KTT
CSD18510KTT
CSD18542KCS
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Old 1st August 2017, 08:44 PM   #5
Nelson Pass is offline Nelson Pass  United States
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D1 IV Mosfet
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
and why?
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Old 8th August 2017, 10:55 PM   #6
Sabrosa is offline Sabrosa  United States
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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?
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Old 8th August 2017, 11:36 PM   #7
2 picoDumbs is offline 2 picoDumbs  Australia
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Maybe 2sc4793 instead of mosfet
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Old 9th August 2017, 12:22 AM   #8
Nelson Pass is offline Nelson Pass  United States
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I would be interested in seeing any data that shows the performance
degradation into loads greater than 0 ohms.
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Old 9th August 2017, 12:30 AM   #9
2 picoDumbs is offline 2 picoDumbs  Australia
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Quote:
Originally Posted by Sabrosa View Post
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?
TO264 Lateral Mosfet.
Probably want to bias around half an amp.

Maybe also worth checking out SiC Jfets in to247 package. United SiC
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Last edited by 2 picoDumbs; 9th August 2017 at 12:40 AM.
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Old 9th August 2017, 12:58 AM   #10
abraxalito is offline abraxalito  United Kingdom
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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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