Higher bias usually reduces Xover distortion, this may be due to slower switching at higher currents preventing the output from tracking the NFB loop as accurately. Too much loss of speed will cause instability which is why I moved to FETs as the Miller cap is much smaller to attain stability.
Are referring to back in the day or current offerings?
In the current data sheet by onsemi, they are described as high power audio transistors.
Edit: just see a couple new posts with open devices and discussion (had not updated the thread in my browser, it seems).
Let me read.
Process distributions in general have gotten tighter over the years, but the bottom of the barrel is still the bottom of the barrel. Anything else is still better.
If you’re using those you don’t really worry about the optimum bias, because there is usually enough else wrong with it.
If you’re using those you don’t really worry about the optimum bias, because there is usually enough else wrong with it.
Hi mz543578854,
Back in the day. "New" devices are probably fakes. I don't care, they are garbage parts.
If my name is going on a repair or new build, garbage parts aren't allowed. It just isn't worth it both for reliability or reduced performance. If someone wants something that poor in a repair or build, they can go somewhere else. I don't need the trouble.
Back in the day. "New" devices are probably fakes. I don't care, they are garbage parts.
If my name is going on a repair or new build, garbage parts aren't allowed. It just isn't worth it both for reliability or reduced performance. If someone wants something that poor in a repair or build, they can go somewhere else. I don't need the trouble.
It would come down to devices closest to capacitance, Ft and beta to the originals. If you can't find anything close, I'd default to MJ21194 /MJ21196 devices. Sometimes the higher voltage ones are less expensive or more available. The 405 isn't a "normal" amplifier design.
The Quad used very early parts, so anything today will require you to stabilize the amplifier, and you'd probably end up with higher performance. Even the beta vs current being more constant is going to help, but test for oscillation at higher currents too. The LM301 is something worth looking at, I'd look at bipolar input op amps first, an NE5534A might be very good. Expect to do some high frequency compensation there.
The Quad used very early parts, so anything today will require you to stabilize the amplifier, and you'd probably end up with higher performance. Even the beta vs current being more constant is going to help, but test for oscillation at higher currents too. The LM301 is something worth looking at, I'd look at bipolar input op amps first, an NE5534A might be very good. Expect to do some high frequency compensation there.
I was referring to the current MJ15015/16 by OnSemi. You can get them from Mouser. What do you mean by fakes?
https://www.mouser.de/ProductDetail/onsemi/MJ15015G?qs=HVbQlW5zcXWKXfGMBnUQFA==
I would never consider using any MJ15015 or MJ15016 devices. Not even if I had some for free.
I once had to use them in warranty repairs, supplied by the distributor in audio amplifiers. They are garbage devices.
I once had to use them in warranty repairs, supplied by the distributor in audio amplifiers. They are garbage devices.
Any of those alternate devices you listed wahab would work well.
I would rather use currently manufactured devices from an authorized distributor these days. Back in the day we were more worried about factory "floor sweepings", or rejects. They were supposed to be destroyed, so were rare. The semiconductor supply was relatively safe. Later TV Horizontal output transistors were showing up as fakes, and the famous Sony SG613 SCR. Then remarking machines became available and the market exploded with remarked parts. Today, all that garbage is still floating around in addition top counterfeit devices. It just isn't worth the risk to buy anything you don't know exactly how they cane to be in your hand.
I would rather use currently manufactured devices from an authorized distributor these days. Back in the day we were more worried about factory "floor sweepings", or rejects. They were supposed to be destroyed, so were rare. The semiconductor supply was relatively safe. Later TV Horizontal output transistors were showing up as fakes, and the famous Sony SG613 SCR. Then remarking machines became available and the market exploded with remarked parts. Today, all that garbage is still floating around in addition top counterfeit devices. It just isn't worth the risk to buy anything you don't know exactly how they cane to be in your hand.