Good point.
Yes, my main test for both pots will be on the speakers.
Will report. Until then enjoying DCG3 very much on headphones tap.
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Salas DCG3 preamp (line & headphone)
I can’t fully disable such PSU since Khozmo pot relay is NO and will be not engaged for signal in. However, I used external PSU (I have nice old linear regulated lab type HP) and saw exactly same symptom. It is definitely on attenuator that something is messing up its output. It is nice device conceptually (based on Nikitin attenuator developed in 60’s), but it’s very challenging one and I definitely can’t recommend it to the forum. No any noise on DCG3 when I use not motorized Apls or Goldpoint. More troubleshooting is on the way....
I can’t fully disable such PSU since Khozmo pot relay is NO and will be not engaged for signal in. However, I used external PSU (I have nice old linear regulated lab type HP) and saw exactly same symptom. It is definitely on attenuator that something is messing up its output. It is nice device conceptually (based on Nikitin attenuator developed in 60’s), but it’s very challenging one and I definitely can’t recommend it to the forum. No any noise on DCG3 when I use not motorized Apls or Goldpoint. More troubleshooting is on the way....
Just finished and tested my boards from the group buy. Every thing went flawlessly thanks to teabag and his excellent parts matching. I have 5.2 ma flowing through the LTP and 113 ma through the output stage. Offset on both sides is 0.1mv .Heatsinks are warm to the touch. I am impressed with the bandwidth. A square wave at 100KHZ is perfect.
Use the post's #452 rig but with 7V PSU and J113. Vary source resistor or JFET until Id=5mA. Approximately.
In spite of all my attempts and use of all advised known methods, I do still have these main 60Hz picks coupled. I made 0.3mm copper cage all-around attenuator and placed permalloy shield around output RCAs. I succeed to reduce amplitude below hearing detectable level and I believe I'm going to leave that unit as is for now.
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Many PSUs there. What is the red raw PSU board for? What about the oxidized RCA contacts maybe also playing a role? You didn't do too bad in the end though.
Is there supersonic noise rise in the card at 192kHz sampling rate? Because the THD & THD+N numbers in the last two charts seem more than what meets the eye inside the audio band pictured. Possibly lower sampling rates or another measurement software give better figures?
Is there supersonic noise rise in the card at 192kHz sampling rate? Because the THD & THD+N numbers in the last two charts seem more than what meets the eye inside the audio band pictured. Possibly lower sampling rates or another measurement software give better figures?
In did, it is DC blocker based on R. Elliott concept. No buzz from tranys. Salas, your right and it is quite disorganized layout inside for RF/EMI hygiene.
About oxidized on RCAs… It is silver plated and Ag2O is bad but still conductive. It might be not Oxide on my RCAs and yes, I’ll clean it today to see if any change. Thanks for that tip. I listened to it yesterday by connecting it for my NAD M5 with Audeze LCD-2. It’s SQ is very good and I can’t hear any imperfection that might come from these 60Hz picks.
I’m sure if I’ll go to 48kHz bandwith on ARTA, THD will be in 0.004*% level and THD+N will be just a bit higher. BTW, RMA is still showing an “Excellent” score now.
Question to ARTA, why it is not like a oscilloscopes, measuring with what is set on screen (or test limit) and do go way above for what with allow. ��
Well, I have another thing to ask.
As I mentioned, I have full separation between L&R channels now and only point where L&R GNDs meet each other is headphone jack GND. That point is going to Earth with 10R lift (R.Elliott lift style) . When I connect AKG K701 (63R), all is totally fine. When I connect Audeze (70R), I have hum. Hum is totally disappears when I connect interconnect cables to pre-amp output (cables are in air on the other side). What is your opinion about that?
About oxidized on RCAs… It is silver plated and Ag2O is bad but still conductive. It might be not Oxide on my RCAs and yes, I’ll clean it today to see if any change. Thanks for that tip. I listened to it yesterday by connecting it for my NAD M5 with Audeze LCD-2. It’s SQ is very good and I can’t hear any imperfection that might come from these 60Hz picks.
I’m sure if I’ll go to 48kHz bandwith on ARTA, THD will be in 0.004*% level and THD+N will be just a bit higher. BTW, RMA is still showing an “Excellent” score now.
Question to ARTA, why it is not like a oscilloscopes, measuring with what is set on screen (or test limit) and do go way above for what with allow. ��
Well, I have another thing to ask.
As I mentioned, I have full separation between L&R channels now and only point where L&R GNDs meet each other is headphone jack GND. That point is going to Earth with 10R lift (R.Elliott lift style) . When I connect AKG K701 (63R), all is totally fine. When I connect Audeze (70R), I have hum. Hum is totally disappears when I connect interconnect cables to pre-amp output (cables are in air on the other side). What is your opinion about that?
You are right. I looked at the letters on it now and it says DC Trap For Toroidal transformers indeed. Alex maybe had DC in his mains and his TXs hummed (?)
But its could also be dangerous to touch and adding loop area to propagate AC mains field inside the box. Maybe better not to have such if not strictly necessary in the first place.
ARTA measures and integrates all you can expand to left and right of the audio band portion it initially displays. Sampling rate chosen is the actual restriction. The FrHigh & FrLow buttons found at the right hand border let you control extension of frequency display.
Maybe because those cans have different scheme. Like one has common return wire and the other separate return wires. In any case you should try see what happens without lift, or refer to chassis somewhere else. I don't know exactly why because its not a typical config this one. Has powered extras. But I haven't met hum between Sen Y style separate return and AKG common return single side cable for instance. Either in several DCG3 builds I had seen live or by any previous reports here.
In some builds I had to shield the IEC mains inlet to null hum.... I see you left the mains wires free in your box......