Are Switching-intended BJTs likely to be subject for hum, per a chance?
at least that´s what i suspect, i´ve built a 20W range amplifier in class A, and the delivery with my 'real' BJTs for my project hasn't arrived yet, so, for testing purposes i took a pair of swithing BJTs, (2SC4060) and 'voila' the amp works (woks..), but with a awful hum, i tested at slightly lower bias with regular BJTs and...there was no hum...strange!?.. -or maybe not very strange?
..maybe i have to re-engineer my psu, its a standard non-regulated, 500VA toroidal and a capacitor bank@60,000µF, i do think that should be sufficient...
at least that´s what i suspect, i´ve built a 20W range amplifier in class A, and the delivery with my 'real' BJTs for my project hasn't arrived yet, so, for testing purposes i took a pair of swithing BJTs, (2SC4060) and 'voila' the amp works (woks..), but with a awful hum, i tested at slightly lower bias with regular BJTs and...there was no hum...strange!?.. -or maybe not very strange?
..maybe i have to re-engineer my psu, its a standard non-regulated, 500VA toroidal and a capacitor bank@60,000µF, i do think that should be sufficient...
Hey! I've played with 2SC4060's but only for switching, not linear. Switching BJT's have a relatively poor safe operating area compared to one specifically meant for linear, but they would switch *much faster*. That said, is your amplifier oscillating? Stick a scope on and have a look. Maybe the higher speed capability of the '4060 has upset the stability somewhere?
GP.
GP.
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