Robin said:
I have always liked the sound of the Sankens however in high volt applications, they seem to blow easier than TOS or MJ's, i.e. 90v and above. Whenever I would Substitute a Sanken in one of my power amps with 90v rails, they would blow, 1302's and MJ's would live longer... just my personal experience. (PS: The Sankens I tried were the A1294/ C3263 pairs, 130w and 230vce devices.)
MOSFET input impedances aren't 'high', they are capacitive! and they turn also into low-value resistive at LF when a reasonably low-value gate bleeder resistor is added to provide quick enough turn-off
This capacitive impedance due to Cgs, Cdg and Cds and the resistive component due to bleeder resistors may be actually lower than the input impedance of a conventional darlignton. Impedance advantages should be carefully analyzed for each circuit
This capacitive impedance due to Cgs, Cdg and Cds and the resistive component due to bleeder resistors may be actually lower than the input impedance of a conventional darlignton. Impedance advantages should be carefully analyzed for each circuit
Upupa Epops said:To sajti : By my mosfet amps is full power bandwidh over 300 kHz - if you know this, nothing is problem. I add, that they aren't some 10 W *******s, but 100 W and more. SR 100 V/ microsec
With proper designed amplifier it's possible. I also made mosfet amplifier with IRFP240/9240 output devices. I not used predriver for the mosfets, but the VAS runs with 80mA bias, and drive them easily. I checked with scope, and with 150W/4ohm, the 200kHz sine wave was perfect.
But with VAS stage designed for darlington connected BJTs, are not suitable to drive mosfets directly. Driving mosfet by BJT follower, can results oscillation, beacuse emitter follower hates capacitive load.
sajti
Question....NAD 218 THX++
If I want to make the most out of this....I am going to use a active filter and the NAD as a SUB-bass amplifier, and let the vocals and highers be handled by the in this respect superior Electrocompaniet (AW-60DMB).
The output devices in the NAD are the somewhat unknown 2SB1317/2SD1975.
Would it be a good idea to replace theese Panasonic BJT's with some (used, but 100% OK) 2SC3281/2SA1302 devices I am certain is original Toshibas ?
If I don't remember wrong the 3281/1302 devices is mentioned somewhere on the net as very capable (if not the best) of delivering bass-slam, and that is indeed my goal with this NAD-amp.
Lyra
If I want to make the most out of this....I am going to use a active filter and the NAD as a SUB-bass amplifier, and let the vocals and highers be handled by the in this respect superior Electrocompaniet (AW-60DMB).
The output devices in the NAD are the somewhat unknown 2SB1317/2SD1975.
Would it be a good idea to replace theese Panasonic BJT's with some (used, but 100% OK) 2SC3281/2SA1302 devices I am certain is original Toshibas ?
If I don't remember wrong the 3281/1302 devices is mentioned somewhere on the net as very capable (if not the best) of delivering bass-slam, and that is indeed my goal with this NAD-amp.
Lyra
2SB1317
Specs for this are 180V, 15A, 150W with gain 60-200. ft is 20Mhz. The Toshiba pair have a higher voltage rating, mostly very close for specs otherwise. Lower average current gain.
Could you swap them out, sure. Would you hear a difference, only if you can hear power cords too. I think you'd be wasting your money.
-Chris
Specs for this are 180V, 15A, 150W with gain 60-200. ft is 20Mhz. The Toshiba pair have a higher voltage rating, mostly very close for specs otherwise. Lower average current gain.
Could you swap them out, sure. Would you hear a difference, only if you can hear power cords too. I think you'd be wasting your money.
-Chris
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