Hi,
I have built a Slone's OptiMOS with SMD implementation of the low-power part on a double layer PCB 160 mm x 50 mm. Input transistors are BC850C / BC860C, the SMD version of 2N5551 is MMBT5551, driver transistors are 2SC3421 / 2SA1358, output is "standard" 2SK1058 / 2SJ160. Powered by +/- 50V. The output transistors are biased to approx. 40 mA without signal.
It sounds great - very good detail, powerful bass.
The problem with it is I get an audible noise when listening at lower signal levels. If the CD player is not playing, nothing is to be heard, but when it starts, at low volume levels, noise is to be heard as high as the signal. I am afraid my amp is ringing... but unfortunatelly I don't have an oscilloscope.
I would be glad to hear some ideas what could cause such a noise, and what could I try in order to find out what is happening.
Thanx!
I have built a Slone's OptiMOS with SMD implementation of the low-power part on a double layer PCB 160 mm x 50 mm. Input transistors are BC850C / BC860C, the SMD version of 2N5551 is MMBT5551, driver transistors are 2SC3421 / 2SA1358, output is "standard" 2SK1058 / 2SJ160. Powered by +/- 50V. The output transistors are biased to approx. 40 mA without signal.
It sounds great - very good detail, powerful bass.
The problem with it is I get an audible noise when listening at lower signal levels. If the CD player is not playing, nothing is to be heard, but when it starts, at low volume levels, noise is to be heard as high as the signal. I am afraid my amp is ringing... but unfortunatelly I don't have an oscilloscope.
I would be glad to hear some ideas what could cause such a noise, and what could I try in order to find out what is happening.
Thanx!
Which book did G.R.S. publish the OptiMOS design in? I have his Tab Electronics book and his High Power Amplifiers book, and he doesn't give names to the amps, though in the final design of the latter book, he refers to it as an optimized MOSFET design. Is this one, or is it published in the book I don't have?
..Todd
..Todd
As all the friends suggested check all of that, plus you could lift your inputs ground by connecting a 10 Ω resistor from inputs ground to ground. Also instead of the resistor you can put the same way a thermistor like a keystone CL 60. It has exactly the same resistance and is for 6A. Thermistors also can be used as surge supressors if you connect it on the primary of the transformer.That is from the great Nelson Pass. Check also your wiring if it passes close to the transformer it picks up noise.I hope gave you an answer.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.