what about 2SC5171 with 200Mhz, i think faster than c3503? but cob is higher? and easier to mount in main heatsink without mica (plastic to220)
5171/1930 is a fantastic drivers pair from Toshiba, but they are practically unavailable except some old stocks - they are not produced anymore as far as I know.
Lateral FETs are excellent drivers but they are also almost unavailable in decent quantities these days.
Sanken's 4883/1859 are very good as well and still available.
Lateral FETs are excellent drivers but they are also almost unavailable in decent quantities these days.
Sanken's 4883/1859 are very good as well and still available.
Tohiba TTC004/TTA004 can be good driver, for 80-100W amplifier. They are available from Mouser.
Sajti
Sajti
Cool 🙂 Just please bear in mind the feedback network is rather low-impedance (around 600 ohm), so when you test standalone, VAS is heavily loaded, so standalone measurements will not be correct. You need some OPS to have the thing running well.
VAS transistors require the heatsinks. But it looks like the idle currents are somewhat higher than expected - let's see the voltage drop across the VAS emitter resistors.
VAS idle current is expected to be around 7mA, meaning you need to have 700mV across R20 or R23 (schematic from the post #20).
In case it's higher than that, you need to slightly increase the value of R17, R18.
Be careful with NS OPS - 7mA VAS current is a bit higher than it normally expects (5.5mA or so). So, probably it will make sense to set the VAS current down to 5.5mA, increasing R17, R18.
In case it's higher than that, you need to slightly increase the value of R17, R18.
Be careful with NS OPS - 7mA VAS current is a bit higher than it normally expects (5.5mA or so). So, probably it will make sense to set the VAS current down to 5.5mA, increasing R17, R18.
Referenz INP+NS OUT
+/-50V
idle current=60mA
Offset=0mV
Vinp=916mV
Vout+25v RMS/6R just beffor clipping.
R17,R18=33R
VAS current=7.2mA
Dead silent!
+/-50V
idle current=60mA
Offset=0mV
Vinp=916mV
Vout+25v RMS/6R just beffor clipping.
R17,R18=33R
VAS current=7.2mA
Dead silent!
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Sorry Jeff no speaker connected yet!
Test patterns first.
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