50watt class-b amp mx50v6

[ljm_ljm]

Originally Posted by jleaman

what's the price of these little guys

there little guys very cheap.is only equivalent to a steak,

[ljm_ljm]

Originally Posted by wahab

hi, superb this amplifier...
the bc546/556 are to92 part, not TO126...it can stand 0.21W
but only with a little heatspreader..otherwise, it will be too hot..
vce is 65v, and your amp is 70V supply..
can i suggest bc639/640 instead? they are 80V/1W..
or for low Cob, bf469/471 with cob 1.8 pf...
coumpound pair have not less crossover than emitter follower..
with feed back, they have more distorsion at low level...
and yes, the sanken are hard to find here in france too,
as diyers, whe have difficulty accessing good devices..
for the final stage, darlingtons would work, no doubt,
providing you re adjust the bis circuit, but apart from the sankens,
i don t know other darlingtons with such good caracteristics..
there s still the 2SB1587/2SD2438 also from sanken, but they are
only 8A/75W rating, for the rest they are 150V/50-60 Mhz..
surely hard to find and expensive as well...
the best is perhaps to stick with 2 drivers + power trans, as in the
schematic..

thanks
bc546 bc556 can stand 0.65w at 25C temperature.
BC546 Q12 Q4 VCE=65V,amp is + -35v
Q12 V(CE) + Q4 V(CE)=70V
Q4 CE voltage is 35V，is not 70V.
we can calculation through the simulation software.
i use sanken 2SA1186 2SC2837 70M 100W in amp output stage.
it performance nice.
i will pay attention to you mention components.

[wahab]

Originally Posted by ljm_ljm

thanks
bc546 bc556 can stand 0.65w at 25C temperature.
BC546 Q12 Q4 VCE=65V,amp is + -35v
Q12 V(CE) + Q4 V(CE)=70V
Q4 CE voltage is 35V，is not 70V.
we can calculation through the simulation software.
i use sanken 2SA1186 2SC2837 70M 100W in amp output stage.
it performance nice.
i will pay attention to you mention components.

0.65W at a 25C CASE TEMPERATURE...i.e, on an infinite heatspreader...

when Q12 conduct at 100%, Q4 is off and see a VCE of 70V
less the gap and emitter resistor voltage drop of Q12, this make 68V AT LEAST..
power transistors are good, but for safe operation ,
replace as follow :
Q4, Q9 : BD140
Q5. Q12 : BD139



all the best..

[ljm_ljm]

Originally Posted by wahab

0.65W at a 25C CASE TEMPERATURE...i.e, on an infinite heatspreader...

when Q12 conduct at 100%, Q4 is off and see a VCE of 70V
less the gap and emitter resistor voltage drop of Q12, this make 68V AT LEAST..
power transistors are good, but for safe operation ,
replace as follow :
Q4, Q9 : BD140
Q5. Q12 : BD139



all the best..

thanks .
i have some the 2SB649 2SD669.
do you know what the whole plastic parts for TO220 transistor
darlington,preferably.

[wahab]

here the main simulation of the amp..

all simulated with output at +29 dbU,8 ohm load,
wich is 50 w RMS ,close to clipping..

1KHZ THD is 0.03 %
10 KHZ THD is 0.05 %
400HZ /7 KHZ 4/1 ratio IMD is at 0.03 %
2 to 200 KHZ bandwith, almost flat..
1.5 uS rise and decay time, slew rate is 25V/uS

also a 10KHZ sine wave on 8 OHM + 1 uF LOAD....

this seems encouraging, and i m going to build
one again for verifications purposes, using the
new transistors councelled by hugh dean..
next post when the thing is assembled..

regards,

wahab

[jleaman]

Looks like your using some nice wire, same silver wire as my self

J'

[ljm_ljm]

In the new version, I used the VAS = 2 N5551. It can work more VCE

[MosfetBoy]

Hi there, firstly, thanks for a wonderful amp project, it sounds excellent.
It appears that the boards power supply max is 45V

My transformer is 35Vac and 300VA.

DC output after my 20000uF of cap should be around +-50VDC . Will this be too much for the board?

i currently have it running on a 30VA 15-0-15 transformer and the amp sounds wonderful.

Thanks and Regards
John