Wrong place for that discussion, I think. 😊www.diyaudio.com/community/threads/help-with-w-one-ladder-relay-attenuator-remote-control.427834/#post-8028818
Patrick
Patrick
I’ve got a pair of ACA monoblocks and in process of gathering all the parts for a My_Ref FE amp. I know the ACA’s need the preamp, but what’s the opinion on using the DCG3 with possibly a gain switch to use it for both? Would it be easy to put a pair of RCA outs for passive volume control of the My-Refs utilizing the volume control and iSelect in a DCG3 pre? Trying to think of the best way to do this so I don’t have to be swapping cables all the time if I want to switch amps. I’d originally thought of using a Mesmerize, but I’m not sure it’d work with the ACAs.
Hi, its possible to tap from the i-select for no gain outputs, but it would be preferable to also add a unity gain capable op-amp buffer stage in-between. To isolate the rest and potently drive the interconnects. A gain switch wired to the front panel is possible to pick up noise because in the feedback path. The DCG3 can't be set to less than 6dB gain anyway.
Thanks Salas. I’ll have to think on that. I really want to utilize the selector source options for both amps. I know I can direct in (no preamp) with the My_Ref, but I’d like the ability to switch sources. A single preamp/selector would be ideal, but maybe not the best option in the end in this situation. I’m not sure if 6dB gain will be too much for the My_Ref, although I might be able to adjust the input on the amps slightly to help with that situation. That’s one reason I thought a gain switch would possibly be useful. Still lots to learn.
If on the fly gain changing is not required, but to use different power amps between time periods, you could alternatively install female pins to can swap R6 resistor values for different gain setting.
Test run SSLV 1.3 Shunt reg + DCG3, all test points OK, dc offset normal. The heatsinks are only slightly warm, bias 110mA. I am satisfied 🙂
@Salas Before inserting the dc servo into the socket I trimmed both channels to about 1mV after 15 min. After inserting the dc servo and cold dcg3 one channel shows approx 25mV, after settling the temperature for approx 10min it drops to 3mV, the other channel is still below 1mV. Is this deviation OK, I would rather blame it on the manufacturing deviation of the AD823 😡
If I would like to try another operational amplifier on the dc servo position for peace of mind, which do you recommend from the available ones?
@Salas Before inserting the dc servo into the socket I trimmed both channels to about 1mV after 15 min. After inserting the dc servo and cold dcg3 one channel shows approx 25mV, after settling the temperature for approx 10min it drops to 3mV, the other channel is still below 1mV. Is this deviation OK, I would rather blame it on the manufacturing deviation of the AD823 😡
If I would like to try another operational amplifier on the dc servo position for peace of mind, which do you recommend from the available ones?
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Hi, no, 25mV is not normal after inserting the servo op-amp. Even if it settles to 3mV eventually. 1mV right away or below is normal. Like in the other channel.
Short each line input to GND first to make sure it isn't about interference. Check that the servo chip in the high offset channel is inserted with the right orientation and its pressed down in the socket properly.
If the situation doesn't change, swap the AD823 servo chips between channels to see if the high offset follows one certain chip or not. If it does, then its a rogue op-amp sample.
The inexpensive ubiquitous TL072CP added some noise vs modern better spec types in my lab tests but it still controlled offset well for a comparison. And it didn't interfere with the tone in a bad way.
Short each line input to GND first to make sure it isn't about interference. Check that the servo chip in the high offset channel is inserted with the right orientation and its pressed down in the socket properly.
If the situation doesn't change, swap the AD823 servo chips between channels to see if the high offset follows one certain chip or not. If it does, then its a rogue op-amp sample.
The inexpensive ubiquitous TL072CP added some noise vs modern better spec types in my lab tests but it still controlled offset well for a comparison. And it didn't interfere with the tone in a bad way.