original la sound amps.. crappy? decent?

[shagone]

Interresting. can anyone explain the self oscillating design further? i have heard of it but don't know much about it.

[EnvisionAudio]

Originally posted by shagone
Interresting. can anyone explain the self oscillating design further? i have heard of it but don't know much about it.

A self oscillating power supply is simply a resonant tank circuit with feedback. Adding a tertiary winding to the transformer and passing it through an auxillary core coupled to a feedback circuit sets the oscillation frequency of the power supply. This functions as a current-mode control, but variable frequency rather than pulse width. Pulse width actually is a function of frequency in these designs as higher frequencies move the BL curve further away from optimal and the operation becomes discontinuous. Current limiting in these designs is handled in such a manner.

Design of self-oscillating power supplies can be difficult to get right. I've never tried since there are dozens of adequate control IC's on the market for all manner of designs. I only maintain vague knowledge for situations where I need to repair one.

[damage]

Originally posted by EnvisionAudio


LA Sound - AKA Metrosound vintage 1992. Not ALL oldskool amplifiers are worth owning.

Actually, I have a Hermosa amp I just got off eBay to practice repairs upon to find out it works fine. It too runs TIP35s and TIP36s. It uses ST parts for the outputs and 2 pairs of Int. Rect. IRFZ44s for the PS. It also has provisions for 2 more pairs.

The surprising part is that it uses 1% metal film resistors and propylene caps.

Not sure how it sounds yet other than quick testing.

[ppia600]

I sold mine to a guy at work and it sounded great. It sounded like a lot more than 75 by two but thats probably because we were running it 2ohm stereo into two sets of eclipse speakers.