some info:
1. I was measuring the resistance between in and out of the channel. (example: L+in and L+out).
2. The relays I used are Omron G6S-2 DC12 (https://mouser.com/datasheet/2/307/en_g6s-1128313.pdf).
3. I was initially powering the attenuator using with a 15V 2A 30W SMPS.
4. The attenuator has a 7812 regulator to bring down the voltage to 12VDC. It also has a 7806 to bring down the voltage further to 6VDC (6VDC is used to power the 2 ICs)
5. After a certain rotation of the rotary encoder, the resistance between the L and R channels are highly out of sync. maybe 50% off (example: L+in/L+out could be measure 8Kohms while L-in/L-out could be 4Kohms)
6. I replaced the SMPS with a V+/V- linear supply (using a 48VA 2x15VAC 1.6A transformer) I'm using for another project. I tapped to the unregulated +VDC after the 1st capacitor (around +26 VDC without load). After the replacement, the problem I was having disappeared.
questions:
1. could the SMPS be defective?
2. maybe my SMPS does have enough juice to power the attenuator? (though I did some quick math based on the relay coil ratings and it seems to be more than enough (11.7mA x 12VDC x 16 relays = around 2.25W))
3. Can I perhaps parallel SMPS output?
4. Maybe the problem be elsewhere?
Thanks!
1. I was measuring the resistance between in and out of the channel. (example: L+in and L+out).
2. The relays I used are Omron G6S-2 DC12 (https://mouser.com/datasheet/2/307/en_g6s-1128313.pdf).
3. I was initially powering the attenuator using with a 15V 2A 30W SMPS.
4. The attenuator has a 7812 regulator to bring down the voltage to 12VDC. It also has a 7806 to bring down the voltage further to 6VDC (6VDC is used to power the 2 ICs)
5. After a certain rotation of the rotary encoder, the resistance between the L and R channels are highly out of sync. maybe 50% off (example: L+in/L+out could be measure 8Kohms while L-in/L-out could be 4Kohms)
6. I replaced the SMPS with a V+/V- linear supply (using a 48VA 2x15VAC 1.6A transformer) I'm using for another project. I tapped to the unregulated +VDC after the 1st capacitor (around +26 VDC without load). After the replacement, the problem I was having disappeared.
questions:
1. could the SMPS be defective?
2. maybe my SMPS does have enough juice to power the attenuator? (though I did some quick math based on the relay coil ratings and it seems to be more than enough (11.7mA x 12VDC x 16 relays = around 2.25W))
3. Can I perhaps parallel SMPS output?
4. Maybe the problem be elsewhere?
Thanks!
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Usualy a SMPS supports some level of overloading with no problems. I tested them when at job at 2x normal rated load for few minutes. So discard SMPS issue.
Perhaps relays are failed and the give rise to internal resistance or the divers of them can't place full voltage across the coil (BJT lacks 1V when saturated, at 6V it is a 17% loss). Use MOSFET to drive relay coils (2N7000, BS170 or BS250 are fine). For audio, use a 0.047uF across the coil and reversed bias diode to supress BEMF in the coil and noise induced into signal path.
Perhaps relays are failed and the give rise to internal resistance or the divers of them can't place full voltage across the coil (BJT lacks 1V when saturated, at 6V it is a 17% loss). Use MOSFET to drive relay coils (2N7000, BS170 or BS250 are fine). For audio, use a 0.047uF across the coil and reversed bias diode to supress BEMF in the coil and noise induced into signal path.
You say 2 IC's. Is the left and right driven separately? Maybe something fishy with the chips driving the relays. That should be easy to check. Just measure which relays have coil voltage when they are out of sync. Should be the same. I could see using separate drivers if you plan on adding a balance control.