1060 with damaged volume pot, repairable?
- Thread starter jd3rdcoast
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jd3rdcoast
Super Member
I want to share AK member Leestereo's answer to a question I asked him in a PM regarding the tracking resistance between two Volume control pots in a dual pot arrangement. I had compared the resistance between the two potentiometers as they tracked from full CCW to full CW rotation and there were discrepancies between the two. I was curious how much it effected the output volume between Left and Right. I thought his answer was very helpful in educating me and could help others. Here is his reply:
Tracking between the volume control sections probably does contribute to the final channel imbalance, as does the balance control. However, the control inter-channel difference would have to be relatively large for it to be obvious. The resistances you report are typical of volume controls. But to evaluate the inter-channel accuracy of a volume control, one has to consider that it is a voltage divider with both a series resistance and a resistance to ground.
With the resistance measurements you have provided one can calculate the resistance to ground, e.g., with the control at 9 o'clock, the front section resistances are 257kohm & 20kohm and the rear section resistances are 228kohm and 19kohm. With a 1-volt input signal and the control at 9 o'clock, the front section would attenuate the signal to 0.072V and the rear section would attenuate the signal to 0.077V. This is a 6.7% difference and would be 0.58dB difference. Similar calculations with the 12, 1, 2 and 3 o'clock measurements, give the following percent difference between the channels: 1.1%, 5.1%, 3.2% and 1.1%, respectively. In dB, the inter-channel differences are: 0.09dB, 0.44dB, 0.28dB and 0.10dB. Considering that the "just noticeable" sound level difference is considered to be 1dB., these results are excellent.
Cheers,
Ben
Thanks Ben (@Leestereo)With the resistance measurements you have provided one can calculate the resistance to ground, e.g., with the control at 9 o'clock, the front section resistances are 257kohm & 20kohm and the rear section resistances are 228kohm and 19kohm. With a 1-volt input signal and the control at 9 o'clock, the front section would attenuate the signal to 0.072V and the rear section would attenuate the signal to 0.077V. This is a 6.7% difference and would be 0.58dB difference. Similar calculations with the 12, 1, 2 and 3 o'clock measurements, give the following percent difference between the channels: 1.1%, 5.1%, 3.2% and 1.1%, respectively. In dB, the inter-channel differences are: 0.09dB, 0.44dB, 0.28dB and 0.10dB. Considering that the "just noticeable" sound level difference is considered to be 1dB., these results are excellent.
Cheers,
Ben