Join Date: Nov 2003
Location: flyover country
6 channel hybrid amp project
I'm shooting for 200wrms/8 ohms a channel in a 3U rack mount chassis, so space is a consideration. Right now it looks like a 1500VA 120vct toroid transformer with choke input filtering. Due to space limitations, I'm planning to wind my own chokes and have just ordered three '300VA' rated toroid cores from Alpha Core gapped to 1mm that I plan to wind myself. Their prices for cores are very good and they gap them for only a nominal fee. I am considering paralleling each of the two chokes with a film capacitor tuned to 120hz with the choke to boost the impedance and lower the minimum loading required to keep the output voltage from rising to well under the quiescent bias of the six channels outputs (each will use 3 pair of 2SK1530's and 2SJ201's with the input and driver planned to be a 6K11 compactron).
It appears that I'll be running these cores pretty hard at peak power, and having seen another poster in diyaudio claim that he can get 200wrms from an amp using a 60VA toroid transformer in a capacitor input supply, I wouldn't be too surprised if the gapped cores could saturate under very heavy loading. Even though they're not intentionally 'swinging chokes', I was wondering if I might get some of that type of regulation with this filter arrangement. We're probably talking real worst case scenarios here - clipping into 4 ohms on each of the 6 outputs - maybe about 2000 watts rms total, according to my estimates.