Join Date: Jul 2008
Location: Pretoria, South Africa
Hi All. I have a Bedini 25.25 Class-A power amp. I bought it 2nd hand in 1984, and never switched it off. After almost 14 years I noticed the one channel was louder than the other - a cap in the feedforward circuit (J Bedini's words) had gone soft. Replaced it on both channels and never looked back. Eventually had to replace the reservoir caps (7200uF x2) with Philips 10 000uF (with 0.1 & 1uF bypass caps). 3 years ago a lightning strike put paid to the amp. A good friend (Isis Amp designer) repaired it for me - I already had the new transistors (MJ802 to replace the 2N3055H, & BC560 to replace MPSA transistors on the input voltage multiplier etc). No resistors were replaced. Alan's comment was when he switched it on the sound was very "grainy". He left it for an hour and then started listening and the graininess was gone; massive sound stage, definition etc. When I put it back in my system I switched it on and walked away - past experience. 1 hour later bliss. AAMOI the Bedini runs at roughly 55°C. The MJ802s made a massive improvement to the the bass definition, the top end and overall speed (attack) of the system. The mid-range was considerably better than previously. No doubt the 24/7 on for so many years had helped the components degrade and the sound to change, but we don't always notice the change as it happens gradually.
I have not been using my system as much as I used to, and the electricity supplier has hiked their tariffs somewhat, so I only switch on when I'm going to relax and listen - I still leave it for at least a half-hour before I try listening, else it sounds grainy; and this includes the AudioLab 8200CDQ source. Like a car engine, electronics operate optimally at a specific temperature, and need a little time time to settle in when new. Maybe some top notch engineers can explain it to us, but for now I'll just enjoy the music.
Ferret. - There are only 10 types of people. Those who understand binary and those who don't.
Last edited by ferret; 16th December 2012 at 11:24 AM.
Reason: readability; added some commas