Mannevond
New Head-Fier
- Joined
- Aug 5, 2009
- Posts
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Hi
I got my hands on a few LM49720HA opamps (TO 99 metal capsule), and got this crazy idea that I should test it in my CMoy. First ghetto style attempt was to just cut the legs to length and pop it in the IC socket. Worked out well, sounded ok but I broke one of the legs when swapping between that and the others I normally use. So I decided to mount a new one on a small piece of proto board and solder the legs to make it more sturdy and easy to fit.
Problem now is that it gets VERY warm when playing loud, and still quite warm on moderate volumes. This did not happen with the one I broke. Legs were a bit shorter than on the protoboard one. After a while there is some noise as well, as if it was picking up RF or something, but I think it is something else. Only happens when I have played for a while and the heat has built up. Turning it off for a few seconds gets rid of it until the opamp gets warm again.
Is this oscillation? I have decoupling caps connected directly to the DIL8 socket, but they are a bit further away from the IC than they are when using standard DIL8 ICs, since I have mounted it on my ghetto adapter. Would it help to move the decoupling caps closer to the IC? There is space on the protoboard...
My CMoy has input caps, 2*470uF/25V power caps, 18V power supply, rest is more or less standard. Gain is set to 11, but considering lowering since it is way too loud long before it starts distorting around one o'clock on the volume control.
I really want this one to work. The sound is very nice until the opamp gets warm and starts the noise show...
I got my hands on a few LM49720HA opamps (TO 99 metal capsule), and got this crazy idea that I should test it in my CMoy. First ghetto style attempt was to just cut the legs to length and pop it in the IC socket. Worked out well, sounded ok but I broke one of the legs when swapping between that and the others I normally use. So I decided to mount a new one on a small piece of proto board and solder the legs to make it more sturdy and easy to fit.
Problem now is that it gets VERY warm when playing loud, and still quite warm on moderate volumes. This did not happen with the one I broke. Legs were a bit shorter than on the protoboard one. After a while there is some noise as well, as if it was picking up RF or something, but I think it is something else. Only happens when I have played for a while and the heat has built up. Turning it off for a few seconds gets rid of it until the opamp gets warm again.
Is this oscillation? I have decoupling caps connected directly to the DIL8 socket, but they are a bit further away from the IC than they are when using standard DIL8 ICs, since I have mounted it on my ghetto adapter. Would it help to move the decoupling caps closer to the IC? There is space on the protoboard...
My CMoy has input caps, 2*470uF/25V power caps, 18V power supply, rest is more or less standard. Gain is set to 11, but considering lowering since it is way too loud long before it starts distorting around one o'clock on the volume control.
I really want this one to work. The sound is very nice until the opamp gets warm and starts the noise show...