Fab ,
From listening experiences in exchanging transistors , IMO there is a world of difference between a transistor designed for general purpose switching applications , and one designed for audio use . Trying to figure out why , looking at the data sheets ,
quite often a transistor designed for audio applications has the noise figure specified and the family of curves is shown .
For darlingtons , I'm wondering if a KSD560 and its partner KSB601 might be a better suggestion .
https://www.mouser.ca/datasheet/2/308/1/KSD560_D-2314707.pdf
Or a BDX53B and its partner BDX54B
https://www.mouser.com/datasheet/2/308/bdx53b-d-293935.pdf
.
Actually , all this being said , from listening , my own preference is MOSFET's on the output .
For us mere mortals , lateral MOSFET's 2sj313 and 2sk2013 are unobtainable .
Switching MOSFET's FQP3n30 and FQP3p20 are discontinued , but may be obtainable .
Then as an act of desperation , there are switching MOSFET's IRFP610 and IRFP9610 .
https://www.vishay.com/docs/91023/irf610.pdf
Surely , someone must make an n and p lateral MOSFET in a TO-220 case .
.
For us mere mortals , lateral MOSFET's 2sj313 and 2sk2013 are unobtainable .
Switching MOSFET's FQP3n30 and FQP3p20 are discontinued , but may be obtainable .
Then as an act of desperation , there are switching MOSFET's IRFP610 and IRFP9610 .
https://www.vishay.com/docs/91023/irf610.pdf
Surely , someone must make an n and p lateral MOSFET in a TO-220 case .
.
Hi Underhill
I have the BDX53B and its partner BDX54B in my stock but could not find time to try them yet…maybe because like you I prefer the mosfet version…..
From the datasheet I do not find the IRFP610 and IRFP9610 complementary…… I am not keen to try them.
IRFP510/9510 may be a better choice….
Lateral mosfet medium power to-220 are long gone and no other manufacturers have come with a product like that (that I am aware).
Only higher power lateral mosfet are available nowadays ..
Fab
I have the BDX53B and its partner BDX54B in my stock but could not find time to try them yet…maybe because like you I prefer the mosfet version…..
From the datasheet I do not find the IRFP610 and IRFP9610 complementary…… I am not keen to try them.
IRFP510/9510 may be a better choice….
Lateral mosfet medium power to-220 are long gone and no other manufacturers have come with a product like that (that I am aware).
Only higher power lateral mosfet are available nowadays ..
Fab
Fab ,
Thanks for the recommendations on this , IRFP510 / 9510 look to be one of the few TO-220 choices available .
https://www.vishay.com/docs/91015/irf510.pdf .
I build , measured , and listened to a similar circuit with 2sk246 BL and 2sj103 BL biased at 4.5mA ,
and they seemed to have enough current to be able to drive a single die ECX10n20 and ECX10p20 .
For these Exicon MOSFET's the data sheet says Ciss = 500pF , so I lowered the gate resistors to 68 R and set the bias to 100mA .
Looking on the data sheet , 100 mA is barely on the family of curves .
https://www.exicon.info/PDFs/ecx10n20.pdf
But with this circuit , on my old scope , a triangle wave of 20KHz measured well .
As a preamp , it sounded great on my B&W 110 test speakers .
.
Thanks for the recommendations on this , IRFP510 / 9510 look to be one of the few TO-220 choices available .
https://www.vishay.com/docs/91015/irf510.pdf .
I build , measured , and listened to a similar circuit with 2sk246 BL and 2sj103 BL biased at 4.5mA ,
and they seemed to have enough current to be able to drive a single die ECX10n20 and ECX10p20 .
For these Exicon MOSFET's the data sheet says Ciss = 500pF , so I lowered the gate resistors to 68 R and set the bias to 100mA .
Looking on the data sheet , 100 mA is barely on the family of curves .
https://www.exicon.info/PDFs/ecx10n20.pdf
But with this circuit , on my old scope , a triangle wave of 20KHz measured well .
As a preamp , it sounded great on my B&W 110 test speakers .
.
One recommendation I can make without reserve is the transformer .
Split bobbin transformers have low capacitive coupling between the primaries and secondaries .
Yet E cores can hum , and r cores can be difficult to source .
But Hammond makes the 229 series which are rated up to 48VA
https://www.hammfg.com/electronics/transformers/power/229
Running these up to 1/2 their rating , should be able to supply enough power for a preamp .
The one issue is that they are board mounted .
.
Split bobbin transformers have low capacitive coupling between the primaries and secondaries .
Yet E cores can hum , and r cores can be difficult to source .
But Hammond makes the 229 series which are rated up to 48VA
https://www.hammfg.com/electronics/transformers/power/229
Running these up to 1/2 their rating , should be able to supply enough power for a preamp .
The one issue is that they are board mounted .
.
Hi Vunce
yeah I may have juste a pair or two of the 2SK216/2SJ79….
But since they are so hard to get genuine parts I was not tempted to test that for the community…..I can anticipate that the overall open loop gain of the preamp would be considerably reduced thus even lower feedback factor… so a sightly different sound for the better or worse, a question of taste……
but I encourage people to try these lateral mosfet with some minor resistors values change Of course….for example no degeneration resistors needed would also help to reduce too much open loop gain….
Fab
yeah I may have juste a pair or two of the 2SK216/2SJ79….
But since they are so hard to get genuine parts I was not tempted to test that for the community…..I can anticipate that the overall open loop gain of the preamp would be considerably reduced thus even lower feedback factor… so a sightly different sound for the better or worse, a question of taste……
but I encourage people to try these lateral mosfet with some minor resistors values change Of course….for example no degeneration resistors needed would also help to reduce too much open loop gain….
Fab