Describing that "ON" noise in old SS equipment - diyAudio
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Old 19th December 2009, 06:18 PM   #1
6f6 is offline 6f6  United States
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Default Describing that "ON" noise in old SS equipment

How would one describe the "ON" noise that one usually gets in 1970's era solid state equipment electronics? I just put my McIntosh C-28 preamp up for sale at Ebay; I described the sound as "white noise"- kind of like air draining out the hose from an air compressor. This is not hum or squeal- I know what causes those. Would this be more accurately described as "transistor noise"? Do you guys use other words to describe it?
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Old 19th December 2009, 06:21 PM   #2
dhaen is offline dhaen  Europe
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Faulty?
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Old 19th December 2009, 06:33 PM   #3
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White-noise and Pink-noise is used to make measurements on loudspeaker, in equipment electronics is used to SNR for measure noise
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Old 19th December 2009, 06:37 PM   #4
6f6 is offline 6f6  United States
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Not faulty, just old. All the old SS equipment make this sound, its not a bad part, I'm guessing that it is an issue stemming from the interelectrode capacitances of older BJT transistors- they charge and discharge and create a very low noise floor
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Old 19th December 2009, 06:47 PM   #5
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Has it been re-capped?
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Old 19th December 2009, 06:51 PM   #6
dhaen is offline dhaen  Europe
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Sorry 6F6 that was just my odd sense of humour...
However, I'm still not sure what you mean. I do remember when this "ilk" of kit was new, but don't remember any strange noises, except in the occasional badly designed one. I doubt there's anything iffy about the McIntosh's design.
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Old 19th December 2009, 06:53 PM   #7
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Quote:
Originally Posted by 6f6 View Post
Not faulty, just old. All the old SS equipment make this sound, its not a bad part, I'm guessing that it is an issue stemming from the interelectrode capacitances of older BJT transistors- they charge and discharge and create a very low noise floor
Electrolytic capacitors should be aged, filtering the power supply is not good as when the equipment was new...
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Old 19th December 2009, 07:18 PM   #8
6f6 is offline 6f6  United States
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No, I did not recap it. I know that leaky electrolytics usually cause hum.
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Old 19th December 2009, 07:35 PM   #9
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Yes is hum, not is this noise that you have?
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Old 19th December 2009, 08:11 PM   #10
6f6 is offline 6f6  United States
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Not hum. If there was hum, I would have replaced the electrolytic caps. My guess here is that it is transistor or resistor noise. This noise may have very well been present 30 years ago- it is very common to classic 1970's solid state equipment. I guess that I'm a bit picky; I DIYed a tube-based preamp and tweaked it until nothing could be heard with the volume all the way up.
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