And here I am @1.9A -- and, being greedy for an even hotter design from ZM & Pa. 😈SissySIT @1.7A certainly feels close to that 🤣
Turning my apartment into a balmy sauna...
Member
Joined 2006
https://www-dempa-co-jp.translate.g...=ja&_x_tr_tl=en&_x_tr_hl=zh-TW&_x_tr_pto=wapp
"Prof. Kaneda, a leading figure in DC amplifier designs, has adopted ROHM's SiC-MOSFETs in his recent diy DC amplifier design. Compared to silicon power MOSFETs, and to large-current MOSFETs, SiC-MOSFETs are superior in terms of vividness of sound and versatile expressiveness of musical tone changes." [He has been keen on using SiC MOSFETs ever since 2012 as seen in his publications on MJ magazine]
(Prof. Kaneda certainly knows the capabilities of VFETs/ SITs very well. Attached are the 1973 photo of him with other amp designers in a roundtable discussion on "Rethinking of VFET amps". The other photos display the listening contest event of Triode vs VFET amps in 1973)
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At Digikey there are about 100 SiC candidates of interest in terms of power, package, price, availability.
In my experience it is not easy to pinpoint the ones most suitable for audio. Some are completely unworkable,
some seem "ok" and some not so much.
A couple years ago I gathered up 15 candidates and put them in a simple common source circuit and gave
them a short evaluation. Basically it's a crap shoot, and I did not find any that stood out as better than the
SemiSouth parts like the R100 or R085.
Still, most of them are not so expensive that you can't give them a try, and this makes for a fun exercise
by itself. For those not entertained by such a thing, you might want to go with Kaneda's choice.
I still have a batch of the depletion mode R085's, waiting for a future project...
In my experience it is not easy to pinpoint the ones most suitable for audio. Some are completely unworkable,
some seem "ok" and some not so much.
A couple years ago I gathered up 15 candidates and put them in a simple common source circuit and gave
them a short evaluation. Basically it's a crap shoot, and I did not find any that stood out as better than the
SemiSouth parts like the R100 or R085.
Still, most of them are not so expensive that you can't give them a try, and this makes for a fun exercise
by itself. For those not entertained by such a thing, you might want to go with Kaneda's choice.
I still have a batch of the depletion mode R085's, waiting for a future project...
Member
Joined 2006
Both sides had their fans...as usual.😁
It's from the parallel universe. 😀
Noticed that Prof. Kaneda started out with Rohm SCT2080KE in 2012, and subsequently Rohm came out with SCTMU001F (a Si MOSFET for audio use with internal surge absorbing schottky diode removed, and some reported that SCT2120AFC as a replacement with similar sonic performance). His latest choice is SCT3080AR.
Dcamp.biz released a lower power SCT2H12NZ based Kaneda amp board which is more economical; its half the power of SCT2450KE that is also used often. 😁
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SCTMU001F (SCT2120AF quite similar)
Ciss 1218pF
Coss 102pF
Crss 14pF
Yfs 1S at 1.3A
SJEP120R100
Ciss 670PF
Coss 103pF
Crss 97pF
Yfs ~5S at 1.3A
IRFP240
Ciss 1300pF
Coss 400pF
Crss 130pF
Yfs 2.3S at 1.3A
To quote Nelson :
I did not find any that stood out as better than the SemiSouth parts like the R100 or R085.
Cheers,
Patrick
Ciss 1218pF
Coss 102pF
Crss 14pF
Yfs 1S at 1.3A
SJEP120R100
Ciss 670PF
Coss 103pF
Crss 97pF
Yfs ~5S at 1.3A
IRFP240
Ciss 1300pF
Coss 400pF
Crss 130pF
Yfs 2.3S at 1.3A
To quote Nelson :
I did not find any that stood out as better than the SemiSouth parts like the R100 or R085.
Cheers,
Patrick
Member
Joined 2006
The latest he is using is SCT3080AR: 😀
SCT3080AR
Ciss 571pF
Coss 39pF
Crss 19pF
Yfs 1.2S at 1.3A
SCTMU001F (SCT2120AF quite similar)
Ciss 1218pF
Coss 102pF
Crss 14pF
Yfs 1S at 1.3A
SJEP120R100
Ciss 670PF
Coss 103pF
Crss 97pF
Yfs ~5S at 1.3A
IRFP240
Ciss 1300pF
Coss 400pF
Crss 130pF
Yfs 2.3S at 1.3A
SCT3080AR
Ciss 571pF
Coss 39pF
Crss 19pF
Yfs 1.2S at 1.3A
SCTMU001F (SCT2120AF quite similar)
Ciss 1218pF
Coss 102pF
Crss 14pF
Yfs 1S at 1.3A
SJEP120R100
Ciss 670PF
Coss 103pF
Crss 97pF
Yfs ~5S at 1.3A
IRFP240
Ciss 1300pF
Coss 400pF
Crss 130pF
Yfs 2.3S at 1.3A
I’m going to be a nitpicker again, but what’s the point of quoting / comparing the capacitances at arbitrary voltages? 500V, 200V, 100V and 25V, respectively. Only the last one is appropriate for a typical Pass design. Looking at the charts, around 25V the capacitances are not that disimilar…
You measured that in the J2, or how do you measure THD in what circuit ?
Have you compared bandwidth well ?
But it is not SiC, so according to Prof Kaneda, it cannot be good enough. 🤓
Happy New YEar,
Patrick
Have you compared bandwidth well ?
But it is not SiC, so according to Prof Kaneda, it cannot be good enough. 🤓
Happy New YEar,
Patrick
Thanks for EUVL for clarifying potential downsides of only testing for THD, which could be coming at the expense of other performance considerations.
I used this as the motivation needed to address some gremlins in my measurement setup and moved to using a laptop as well. In the end, the payoff was worth it and it looks like the FDA24N50F is a worthy candidate to move to sound quality testing despite being a 'mere' mosfet 😉
THD - 0.0065% (just shy of 1W into 8R)
Frequency Sweep
10K Square wave using the built-in signal generator (digital)
Happy New Year FABs!!!
Stephen
I used this as the motivation needed to address some gremlins in my measurement setup and moved to using a laptop as well. In the end, the payoff was worth it and it looks like the FDA24N50F is a worthy candidate to move to sound quality testing despite being a 'mere' mosfet 😉
THD - 0.0065% (just shy of 1W into 8R)
Frequency Sweep
10K Square wave using the built-in signal generator (digital)
Happy New Year FABs!!!
Stephen
Looking good, Stephen - what circuit are you using for these tests? Sorry if I missed it. Also, did you adjust any other parameters as you tested the different parts?
this is probably a greenhorn question, but how did you decide/calculate the minimum inductance needed for TDV? I’m still wrapping my head around inductors 🙂
🤔"Ringing" in the New Year with those square waves?
Happy New Year!!!
🤣
I learned something new today! Thanks WBS for identifying this for me as ringing. I thought it was due to a cheap signal generator but I just ran a loopback and will expect something much closer to this in the future. Time to put the FDA24N50F on the naughty list for 2023.
Happy New Year!!!
You need to measure frequency response to 1MHz to catch those peaks further up that cause your ringing.
The square wave is a good test, so you have some stability issues to solve.
And you need to test also with some reactive load.
https://www.diyaudio.com/community/...se-for-a-simple-cheap-load.91479/post-1072498
https://www.diyaudio.com/community/...se-for-a-simple-cheap-load.91479/post-1073195
Patrick
The square wave is a good test, so you have some stability issues to solve.
And you need to test also with some reactive load.
https://www.diyaudio.com/community/...se-for-a-simple-cheap-load.91479/post-1072498
https://www.diyaudio.com/community/...se-for-a-simple-cheap-load.91479/post-1073195
Patrick