Probably not - if you note the connection from the junction of the bottom of R12 and the collector of Q6 back to the junction of the top of VR1 and the bottom of C4, the gain is "strapped", linearizing out all the foibles of crossover distortion and what-not.
This quasi complementary Darlington arrangement seems to operate without the need for a center-tapped secondary transformer. What are the audio ramifications of not using a center-tapped secondary?
Well, other than having a beta of five, they're just fine. In fact, I once had a job in a Rat Shack repair department, and when we'd get an amp or receiver with blown output TO3s, we'd just routinely slap a couple of 3055s in there.
And you don't need that quasi-circuit since they invented the MG2955. ;-)
And you get great big thumps in the speaker when the thing charges the cap to ~1/2 VCC unless you put a relay or switch in.
I had an old heathkit that used that output stage (more or less). It had an annoying hiss that would eventually die out. Some time later I added a switch and relay so it would default to no speakers when turned on (to prevent my girlfriend from waking me when she powered it up) that got rid of the hissing too. Changing the output cap finally cured it - the hiss would be gone before I could troubleshoot it.
I think mine was the AR15 and I think the AR1500 was the first split supply receiver with DC coupled output stage.
I had a part time job repairing consumer electronics and kept a big bipolar cap on my test speaker to avoid blowing it whilst troubleshooting. That and a variac to raise the voltage slowly, saved a lot of grief.
I had two sets of three 24 Ohm 300W non-inductive resistors in parallel for an eight ohm loads, with small speakers and dropping resistors so I could test amps at or near full power without breaking the windows. It was very handy for testing guitar amps for rock bands.
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Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
Me too. I had three 2 ohm 75 watt resistors bolted to a chunk of aluminum, and switches so I could short the series cap and/or switch in the dummy load resistors.
Them were the good old days...
Now days they use a lot of modules. I fixed an old (late 80's) X brand receiver for a friend recently with four high power Darlington output modules. If I didn't find the silly (discontinued) things on a surplus web site ($15 ea), it probably would be too expensive to fix. I doubt one could make a living fixing what they turn out today (if it ever breaks)
I keep my homebrew discrete mosfet alive and it is damn near indestructible. I had several hot strikes from the Tesla coil hit the speakers and the only damage was a 100K 1/4W resistor opened that was supposed to provide a ground reference to the input of the output stages. I think the TC did it...
I've seen a 4' Tesla Coil make a football player scream like a little girl, so what chance did that tiny resistor have? ;-)
Another handy item was a good 4" speaker mounted in an old Alliance U100 rotor control case with a line transformer, a couple switches and a pair of banana jacks. The front of the case had a piece of perforated metal between the speaker and the case. It let the sound out, but protected the cone. The bottom metal plate was installed with contact cement so it didn't rattle.
One switch selected either 25V / 4 Ohm or 70V / 8 Ohm and the other selected high or low impedance. It was quite handy looking for the right pair of wires on school intercoms, paging systems and other speaker systems.
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Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
20 years old I'd have to look up a schematic.. Some complimentary Hitachi parts for the bass amplifiers and ordinary bipolar for the treble amps. I got a pair of surplus Crown amps (500 watts into 8 ohms and 1,000 into 2-5 ohms) intending to tri-amp but never got around to it. Too many interesting things to do and never enough time.
The Crown amps were a steal for ~$150 each - never used and intended to go into an MRI for hospitals as "gradient" drive amplifiers, but they are stock Crown audio amps, weighing in at >100 lbs each. No meters on the front.
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