They are my boards. See the article I wrote below:
Making a Single Rail Linear Power Supply! – audiosy.net
Hi folks!
I have problems with my ACP+ high frequency response. I find the treble in quite a few recordings to be too harsh so my ears start bleeding. Don't have this problem when I connect my headphones directly to my Dragonfly Red. I used exactly the parts that were suggested, resistors are Dale except R12, R13, R16 and R17. Can this be the problem? Or can someone tell me how I could shoothen out the highest frequencies a bit? Thanks a lot!
Regards from Vienna,
Johannes
I have problems with my ACP+ high frequency response. I find the treble in quite a few recordings to be too harsh so my ears start bleeding. Don't have this problem when I connect my headphones directly to my Dragonfly Red. I used exactly the parts that were suggested, resistors are Dale except R12, R13, R16 and R17. Can this be the problem? Or can someone tell me how I could shoothen out the highest frequencies a bit? Thanks a lot!
Regards from Vienna,
Johannes
I think you have to tell us what headphones are in use.
Could they have an exaggerated top end.
Or maybe the Dragónfly's top is rolled off in a big way and you never noticed this.
But the first thing would be to plug several different phones, if possible, and compare.
The ACP+ has an extended but flat FR and is not adding anything, especially in the top octaves. The resistors you mention determine the idle current through Q6 and do not affect FR.
So back to headphones.
This is all part of the fun.
Thanks for responding so quickly! I have tried both of my headphones, which are Sennheiser HD595 and RHA T20i. I agree that the Dragonfly might have rolled off highs and the ACP+ is probably very flat. But still to my ears it is hard to listen to some music that has by recording maybe lots of high frequencies. I really like the sound signature of the Dragonfly and also I enjoy the ACP+ a lot - I feel dynamics are really fun and also spaciousness and stage. So I ask myself how can I achieve keeping the ACP+ in the audio chain while preventing to hurt my ears. Any suggestions on that?
Is it possible that because of the lack of distortion you are listening too loudly? It is an easy trap to fall into. Also, you may want to adjust the gain volume of the pc and the volume of the acp in that you may want to lower the pc volume a little if there is enough gain in the acp to ensure nothing is being over driven
Maybe you are right. But still I am not considering the volume to be up too much. I could turn the digital source down a bit but then the humming becomes louder. Which is kind of another problem I will have to solve at some point. Interestingly when I detach all RCA plugs and turn up the volume completely there is a humming on the headphone output which is getting louder once my hand is getting closer to the volume knob (not even touching!). As it touches it, it's very loud. Whereas when I touch one of the side caps C6-C9, it almost disappears. I have asked this a while ago and got an answer too, but still no multimeter at hand (arriving soon). Anyone have a suggestion?
Q5 (top) has 1k gate resistor, R10. The bottom one Q6 does not have one, either add one there between gate and source pins (maybe it helps) - or some have placed a 220pf between gate and drain of the input LSJ74 (I stored that idea as "ACP all mosfet" diagram, but of course can't find the original on the web
).HF drives you crazy. . .
Hello,
I could use a hand. I built the ACA+ and am experiencing rhythmic power surging throughout the whole board.
I see 24.8 V at the power jack and checking the voltage at the switch the surge voltage is about 3V.
I have replaced both the Caps and Resistors in the power supply portion of the board, without a change.
Thank you for any help
Take care
I could use a hand. I built the ACA+ and am experiencing rhythmic power surging throughout the whole board.
I see 24.8 V at the power jack and checking the voltage at the switch the surge voltage is about 3V.
I have replaced both the Caps and Resistors in the power supply portion of the board, without a change.
Thank you for any help
Take care
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