Hi all-
I'm new to this forum and I really like what I see. I am recently retired after 40 years in the electronic industry. I've worked on everything from DC to daylight. My passion has always been audio.
Back in the late '70s - early '80s, Popular Electronics published plans for a 500w power amp with HEXFET outputs. It's a beautiful design and I always wanted to build it. I have spent days on the web trying to find the schematic. Is there anyone that knows about the amp I'm referring to and know where I could find the schematic?
Any help would really be appreciate!
I'm new to this forum and I really like what I see. I am recently retired after 40 years in the electronic industry. I've worked on everything from DC to daylight. My passion has always been audio.
Back in the late '70s - early '80s, Popular Electronics published plans for a 500w power amp with HEXFET outputs. It's a beautiful design and I always wanted to build it. I have spent days on the web trying to find the schematic. Is there anyone that knows about the amp I'm referring to and know where I could find the schematic?
Any help would really be appreciate!
I can't recall the design but you may get lucky here:
POPULAR ELECTRONICS: Consumer Electronics and Experimenter magazine
Many copies of that era are listed.
POPULAR ELECTRONICS: Consumer Electronics and Experimenter magazine
Many copies of that era are listed.
I have come across a number of successful power amp designs using HEXFET's. The HEXFET is kind of a VMOS-LMOS hybrid. Bob Cordell has designed a few. I haven't heard of anyone using power fet's in a Sziklai pair. Too many capacitance problems that end up as oscillations and the Sziklai topology is a beta multiplier and doesn't work with Gm. FET's work quite well in parallel. IMHO
Yeah, that Hitachi LatFET Monster! Strange that current balancing source resistors are missing. In the article they claimed they aren't necessary due to the inherent positive tempco of mosfets. I've always thought that this would only apply if they operate as switches?
Btw, that double transistor is obsolete since decades now.
Best regards!
Btw, that double transistor is obsolete since decades now.
Best regards!
The double transistor is as obsolete as the Hitachi Power MOSFETs.
Indeed source resistors are redundant here. Current balancing was excellent within one charge. At that time I built 5kW Mono blocks with 36 Hitachi pairs in parallel without source resistors that served the German Navy over years.
Elektor made the Crescendo and some variants like the Hexfet 60 (IRF540&9540) as well as a IGBT version. There might be others.
The pic is of the Hexfet 60 amp
My audio hobby, now profession started with this amp. Never had trouble with the oscillations (used Bradley resistors mostly, maybe that's why?).
They really started to sound "right" with 2 fet's in parallel.
The IGBT version had awesome bass quality. Sadly that was all there was to it.
The original Crescendo use, iirc, Hitachi fet's. Apart from the higher current draw when cold, you really didn't need any source resistors at all. The modern Exicon also don't, none of the lateral fets do.
Edit
They have run out of available pcb's on Elektor.nl
The pic is of the Hexfet 60 amp
My audio hobby, now profession started with this amp. Never had trouble with the oscillations (used Bradley resistors mostly, maybe that's why?).
They really started to sound "right" with 2 fet's in parallel.
The IGBT version had awesome bass quality. Sadly that was all there was to it.
The original Crescendo use, iirc, Hitachi fet's. Apart from the higher current draw when cold, you really didn't need any source resistors at all. The modern Exicon also don't, none of the lateral fets do.
Edit
They have run out of available pcb's on Elektor.nl
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I also never had issues with the original Crescendo amplifier, most probably 'cause I've built it along the supplements Elektor has published in the months after December 1982. It was the first serious amplifer of mentionable output power that I've built and it still works flawlessly until now.
Best regards!
Best regards!
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