It was something that I couldnt get around with my old experimental chassie. To many possible interfering factors so I set it up on a new plank. I added 100k pot and RCAs some day ago, and I am going without strange stuff like chokes during testing to make sure I dont mistake B+hum for EMI interference or oscillation etc.
This is just a linear filter and resistor anode follower. Anode with 10x probes and output over 100 resp 33 k output on 1x probes on pics
This is just a linear filter and resistor anode follower. Anode with 10x probes and output over 100 resp 33 k output on 1x probes on pics
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Yes, I did some quick measures after mounting pot and RCAs. First soundcard after calibration then DUT with 100 K pot set for no gain.
Got Alps 20 K plastic, 50 K blue and 70 K Black I think. Putted 100 k blue in as a start. It could be. I hope to find out by controlled change process istead of just mount evry possible fault source and reverse engineer as I tried before.
"What Is the Process of Elimination?
The process of elimination is simple. If you read a question on a test and don’t know the answer, then instead of looking for the right answer (which you don’t know), you look for the wrong answers. If you are lucky, you will be able to identify all but one of the answer choices as wrong and eliminate them, giving you the one correct answer."
The process of elimination is simple. If you read a question on a test and don’t know the answer, then instead of looking for the right answer (which you don’t know), you look for the wrong answers. If you are lucky, you will be able to identify all but one of the answer choices as wrong and eliminate them, giving you the one correct answer."
About the Arta measures I'm beginning to think that the 50 Hz mountaintop has something to do with my comps/ soundcards grounding relative my different DUTs grounding.
My suspicions is because they show up on every DUT I have tested and also that the 6V6 is dead silent in company with my self-built EL84 PP but slightly hummy with a lended 6L6 PP that someone else has built.
6V6 now has audioground star that connects to PSU star that connects to earth/chassieground via 35 A diodebridge parallelled with a 5 ohm NTC.
My suspicions is because they show up on every DUT I have tested and also that the 6V6 is dead silent in company with my self-built EL84 PP but slightly hummy with a lended 6L6 PP that someone else has built.
6V6 now has audioground star that connects to PSU star that connects to earth/chassieground via 35 A diodebridge parallelled with a 5 ohm NTC.
I went another step and mounted the SSHVs today. With those set on 0,400 V = 40 mA per channel my recent choice of tranny and GZ34 gives me 346 volts DC after filters so I set B+ to 325. All measures are on probes 1X.
First pic is on dual 8K2 resistor dummy to average the voltage to the SSHVs. Some mains/temp variations but the filtered rail seems nice.
I have seen some tendencies to 50 Hz hum on some takings on one channel tho. You can see it on pic 2, where the SSHVs are in and the circuit also. Channel 2 shows some signs of 50 Hz interference.
So I did some minor changes on the ground solderings. I moved one return from one side of a solderstand (ca 10 mm copper) to the other. And the tendensies seemed to (almost) go away
Pic 3 (channels switched sorry)
Sensitive stuff
First pic is on dual 8K2 resistor dummy to average the voltage to the SSHVs. Some mains/temp variations but the filtered rail seems nice.
I have seen some tendencies to 50 Hz hum on some takings on one channel tho. You can see it on pic 2, where the SSHVs are in and the circuit also. Channel 2 shows some signs of 50 Hz interference.
So I did some minor changes on the ground solderings. I moved one return from one side of a solderstand (ca 10 mm copper) to the other. And the tendensies seemed to (almost) go away
Pic 3 (channels switched sorry)Sensitive stuff
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