![]() ![]() Thus part of summer 1963 I put together the transistorized preamp. I had already built a PAS 3, which I noted would not drive this, as the input impedance of the amp was 10 K. ![]() I cannot remember whether it had a two transistor input stage, or just one. that had the system (2AR-4 PAT4-AR turntable) set up. It was the spring of 1963, or Earlier? Seems when I was a frosh in college I did not have it, but by summer 1964 I remember the apt. No 44V transformer could be had, so I had to wind my own. two diodes to be mounted on heatsink, and 200 ohms of trimpot to adj the bias. Had a 2n2904 in a to-5 can, as well as the other driver. It worked rather well, all through my college years. I am happy to say I did build the amp, Though. sometime 1962 I suspect, that it came From RCA. I must have kept it for twenty-five years! Yes, it was the early sixties. Well, I am sad to say I no longer have this peice of paper. Who can post the first commercial advertisement (announcement) from formerly's brand RCA (from any electronic magazine published in the early sixties) concerning the 2N3055 and the first RCA application notes?Īt which time was exactly launched the production? with it being a bass amp i can probably get away with OVERcompensating it. of course it won't have the same "quasi" sound, and won't behave badly when clipped (which isn't so bad since there's no tweeters to fry). i've offered to rebuild my friend's amp (after about 20 years of it being a 65lb preamp) with a fully complementary design, that's a whole lot more stable and MJL4281/4302 output devices, which are a whole lot "beefier" and much more linear. bipolars hog current, and this alone is it's own set of accidents waiting to happen. one of the things that did seem odd to me at the time were the output devices being paralleled with no separate emitter resistors. i had to build my own by following wires and traces. i didn't have a schematic available at the time. ![]() i thought i was making some kind of mistake, until i talked to other amp techs, and found they had all the same experiences. 3 TIMES!!!! and each time, i'd be bringing it up slow on a variac, and when i got to 60 volts WHAM!, the ammeter needle would peg, and bye-bye to another whole set of parts. I rebuilt one of these beasts for a friend. ? - ROCK?īTW - amps in that kind are perfectly suited for evaluation applications, because there is present space enough. Several pics (unfortunately not from my own repair work) you will find in the attachements and about The challenge to achieve stable operation with a super beta push pull quasi complementary follower was too large (because too expensive) for me. The amplifier is running fine since performing this steps. In this case, I had made short work: I reduced the upper half to a normal darlington topology and the lower half to a Sziklai Darlington. Like by several other amps with triplet quasi-complementary super ß buffer in the output also here was unwanted oscillation the main problem - read more from post #20 about Several years ago I had the Acoustic 370 or model 371 (same amp but in combination with 301 bass cabinet) for repair. Click to expand.Thanks for the schematic. ![]()
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