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Post by freddypipsqueek on Jun 22, 2012 16:14:19 GMT
If I change an Alps 20k pot for a 100k attentuator will my White Noise Audio amp still work.
I have read up on the internet and it all appears to be down to the impedence of the source but there is no clear indication of how this can be measured. My amp is plugged into a DAC. There are also numerous posts saying the process is a bit hit miss.
I appreciate this is a vague question.
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Post by freddypipsqueek on Jun 22, 2012 16:43:49 GMT
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Deleted
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Post by Deleted on Jun 22, 2012 19:13:27 GMT
There is no simple answer. Lot's of stupid remarks and wild theories float around.
IF the pot/attenuator is too high Ohmic negative results may be: a: noise levels might go up. b: DC offset (in case it is a DC coupled amplifier with transistor input stage or tube input stage) might become higher. c: the attenuation is not 'referenced' anymore meaning if it is set to have 6dB attenuation it may well attenuate 7 dB or more in case the input reistance of the amplifier itself is lower. d: Higher sensitivity for induced hum e: frequency response in the highs region may be limited depending on the input capacitance of the circuit behind the pot.
It also has some benefits if for instance the source is high Ohmic (tube premamps for instance) or a small value coupling cap would limit the bottom part of frequency response. We are talking of relatively high output resistances in the order of several tens of kilo-Ohms
In general all modern equipment with line-out levels is very low Ohmic and can easily drive 1k to 10k loads and have a source resistance between 0 Ohm and 100 Ohm Negliable for any load higher than 1k Ohm.
Thus in most cases a lower Ohmic attenuator would be best as it has less noise, lower DC offset, higher frequency range and is no problem for modern equipment.
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Post by freddypipsqueek on Jun 22, 2012 20:49:21 GMT
Thanks Frans.
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XTRProf
Fully Modded
Pssst ! Got any spare capacitors ?
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Post by XTRProf on Jul 14, 2012 4:17:52 GMT
Hi Freddy,
What do you aim to achieve from any reading change from 20k to 100k pot? Care to share. I thought changing to a higher k pot is just for better adjustablilty of the volume?
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Post by Deleted on Jul 14, 2012 13:20:30 GMT
a volume potmeter works as a voltage divider (even in active circuits where it is situated in a feedback loop) so when the potmeter is mechanically the same it doesn't matter if it is 10 Ohm or 10MOhm it will have the exact same adjustability provided it can be driven and the circuit behind the centretap doesn't load the volpot. In essence the value of the pot is determined by those 2 primaries as well as other (bandwidth or noise) considerations.
So when a circuit is designed for 1k pots putting in a 100k pot may not be beneficial likewise viceversa.
The choice of value thus depends on many factors.
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