Clarifying labeling from original post. R Out and L Out are short when testing between the two little circles (+ and G). Testing the same locations on both sets of inputs are 1.9 ohms, or open, depending on the selector position.
When looking underneath, every connector except R Out looks the same. The R Out connection + and - appear to be connected underneath, whereas the other 5 rca connections are not.
When looking underneath, every connector except R Out looks the same. The R Out connection + and - appear to be connected underneath, whereas the other 5 rca connections are not.
Do you mean the ground plane on the main PCB (all the connected grounds) or the bottom blank PCB? I still don't understand why the outputs (+ and -) are shorted when the inputs are not. How does the signal get to the amp if the outputs are shorted.
The main PCB ground plane, though depending on how you construct it (metal stand-offs) it’s also connected to ground plane board.
Yellow means continuity between all points. Resistance measurements in blue. I have the LXmini crossover as a comparison, each output has 1.9 ohms across the + & -. I expected the Pre Amp output to have some resistance across the output + & -.
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two scenarios:
- your build is wrong
-your DMM is broken
ACP output - it must show ~33R, once when you fill that output cap with probes/DMM, when cans are pulled out
ACP input - it must be ~20K (value of volume pot)
https://www.firstwatt.com/pdf/art_acp.pdf
dunno for LX, lazy to search for schm, but 1R9 sounds wrong
- your build is wrong
-your DMM is broken
ACP output - it must show ~33R, once when you fill that output cap with probes/DMM, when cans are pulled out
ACP input - it must be ~20K (value of volume pot)
https://www.firstwatt.com/pdf/art_acp.pdf
dunno for LX, lazy to search for schm, but 1R9 sounds wrong
OK, I was using the Fluke wrong. I had it on the continuity measurement setting instead of the ohm setting. The outputs are 32 ohms, the inputs are 20k. The LXmini outputs are 10k. Problem solved. Sorry for any confusion.
I did
I used the unbranded LM317 to evaluate. I noticed that there was a deterioration in the signal-to-noise ratio, with the introduction of more hiss, noticeable when I use more sensitive headphones, in between the songs. It might not bother some users. It bothered me. I don't know if it would also happen with the use of reputable brand regulators. I mounted another board using J176 motorolas in place of the 2sJ74. In this case, the hiss is more audible when there is no music, something I consider undesirable. The only advantage would be the great facility to obtain 10 ma of current to feed the 2sj74.
I used the unbranded LM317 to evaluate. I noticed that there was a deterioration in the signal-to-noise ratio, with the introduction of more hiss, noticeable when I use more sensitive headphones, in between the songs. It might not bother some users. It bothered me. I don't know if it would also happen with the use of reputable brand regulators. I mounted another board using J176 motorolas in place of the 2sJ74. In this case, the hiss is more audible when there is no music, something I consider undesirable. The only advantage would be the great facility to obtain 10 ma of current to feed the 2sj74.
Wonderful Amp!
Having this amp for a few months now, its one of my alltime favorties!
I had it setup with the 32 ohm and changed to match the higher impedance cans like the HD 650's (300 ohm) and ADX 5000's at 420 ohms. Recently I went back to the 32 ohm resistors...and its just fine with the higher impedace cans...the ADX 5000 @ 420 ohms can play VERY loud....hearing damage loud.
Its one of the nicest magical pairing I have heard with these ADX 5000 dynamic driver cans....
Just Lovely Nelson!
Having this amp for a few months now, its one of my alltime favorties!
I had it setup with the 32 ohm and changed to match the higher impedance cans like the HD 650's (300 ohm) and ADX 5000's at 420 ohms. Recently I went back to the 32 ohm resistors...and its just fine with the higher impedace cans...the ADX 5000 @ 420 ohms can play VERY loud....hearing damage loud.
Its one of the nicest magical pairing I have heard with these ADX 5000 dynamic driver cans....
Just Lovely Nelson!
