I am designing a supply for a tube preamp (A few old skool passive EQ stages😀). It will be fairly high gain (To make up for the EQ losses) so I'll need low ripple above all else. I'll be putting it in a 1u 19" rack, so space is an issue.
The heater supply has to run off a 6.3v winding, hence the shottkey diode and half wave setup. As you can see ripple is taken care of by a pair of capacitance multipliers. (Which also supply a slow turn effect)
The plan is to put the rectifiers in a shielded compartment, and the 'regulators' in the main compartment to minimise hum.
Just wanted to get some opinions before I build anything....
Also, anyone got any suggestions for a better HV mosfet than the IRF820?
The heater supply has to run off a 6.3v winding, hence the shottkey diode and half wave setup. As you can see ripple is taken care of by a pair of capacitance multipliers. (Which also supply a slow turn effect)
The plan is to put the rectifiers in a shielded compartment, and the 'regulators' in the main compartment to minimise hum.
Just wanted to get some opinions before I build anything....
Also, anyone got any suggestions for a better HV mosfet than the IRF820?
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Hi ,
The 0.47uF bypass cap should really go at the gyrator input . I used to use darlington pairs of TIP50 rather than mosfets in gyrators , used to get the odd f.u.c.t (failed under constant test) mosfet every now and again . Is that a half-wave rectified PSU on the heaters ? If so I'd get rid of that and use a bridge
cheers
316a
The 0.47uF bypass cap should really go at the gyrator input . I used to use darlington pairs of TIP50 rather than mosfets in gyrators , used to get the odd f.u.c.t (failed under constant test) mosfet every now and again . Is that a half-wave rectified PSU on the heaters ? If so I'd get rid of that and use a bridge
cheers
316a
Hi 316,
Yep the darlington is a much better idea. I was going to use the mosfet because I thought they were more rugged in this setup.🙄 But if BJT's are ok here I'd definately prefer to use them.
I only have 6.3v ac at the heater winding of the transformer so I need a very low drop across the rectifier. I'm using indirectly heated tubes, so I figured a small amount of lower order ripple won't hurt. The gyrator is supposed to take care of all the higher order stuff. Am I being unrealistic?
Thanks,
WS
Yep the darlington is a much better idea. I was going to use the mosfet because I thought they were more rugged in this setup.🙄 But if BJT's are ok here I'd definately prefer to use them.
I only have 6.3v ac at the heater winding of the transformer so I need a very low drop across the rectifier. I'm using indirectly heated tubes, so I figured a small amount of lower order ripple won't hurt. The gyrator is supposed to take care of all the higher order stuff. Am I being unrealistic?
Thanks,
WS
Hi ,
You should really use another transformer 😉 Either that or connect a pair of diodes as a voltage doubler . I don't like the idea of half wave rectified anything , unless it's only got an LED on the end of it
cheers
You should really use another transformer 😉 Either that or connect a pair of diodes as a voltage doubler . I don't like the idea of half wave rectified anything , unless it's only got an LED on the end of it
cheers
I know. But I like this Tx 😀 (It's a cute little toroid that fits in my case!) With a voltage doubler I'll waste more power. Oh btw the heater winding is only rated at 2.5A, and I'll probably use 2A of heater current eventually if I can. (I wanna see how many 6sn7s I can fit in 😀 ) Surely the doubler will also give me lots of ripple anyway?
A tube heater is a bit like a vintage LED 😉
Is it worth a try?
A tube heater is a bit like a vintage LED 😉
Is it worth a try?
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