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A community member
Jul 17, 2020
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Does anyone have any experience with fixing it when the volume pot goes scratchy? I have one of the originals that say THX AAA 789 without the drop logo. Any help would be much appreciated
mbvjmc
188
Jul 29, 2020
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I'm in the same boat. Mine came from the third drop sometime around Spring of last year. A month ago, the volume pot started to get scratchy. I've read that others opened up the case, carefully sprayed some doxit or electronic cleaner on the pot where the shaft meets the pot. I'm thinking about doing this soon as well, as I've done it on my Magni 3 in the past with an electronic cleaner. From my experience with the Magni pot, it is only a short-term fix, as the scratchiness came back on my Magni not long thereafter.
It appears that a cheap Chinese knockoff of an Alps pot was used in the 789's:
https://forum.hifiguides.com/t/massdrop-thx-aaa-789-linear-headphone-amplifier/32/424
A community member
Jul 31, 2020
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mbvjmcThanks a bunch for the link. It's a big help. Drop actually offered to replace my unit since the power supply is acting up as well. I didn't do it though because I have the original unit not the newer one and from what I've seen I think they cheaped out on the newer components. Luckily was able to swap out part of the cord and fix the power supply. The volume pot still scratchy every time I use it though
skylerstupid
15
Aug 2, 2020
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this is an inherent issue with ALL potentiometers and will happen with basically any pot that passes audio on any piece of professional or consumer audio gear. with the amp off; you should do a few slow, full turns back and forth. this will help spread the lubrication inside the potentiometer. ideally, do this every few months or so and it will help keep your pots better lubricated. i just do it before use and it fixes the problem
A community member
Aug 2, 2020
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skylerstupidI tried that before and it didn't seem to help. Is the lube something that is already in there or something I can add if I may ask?
A community member
Aug 3, 2020
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jgp1212Awesome. I'll definitely give it a shot. Thanks a bunch
skylerstupid
15
Aug 3, 2020
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the lube is inside the potentiometer. it is possible to open the pot to lubricate the inside, or just replace it w a new stereo pot if youre a bit savvy. i would recommend looking up a video or written explanation of how a potentiometer works. if you search for “scratchy potentiometer” plenty of articles/resources will walk you through the process
mbvjmc
188
Aug 3, 2020
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skylerstupidIt seems like the knob is part of the pot (or glued thereon). While you can desolder the pot from the PCB, you will have to break off the knob in order to completely remove the pot from the amp. Just something to consider for those who are out of warranty that are thinking about doing a volume pot replacement.
https://forum.hifiguides.com/t/massdrop-thx-aaa-789-linear-headphone-amplifier/32/424
skylerstupid
15
Aug 4, 2020
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mbvjmcso unusual for a manufacturer to glue the knob onto the pot...thx for the info, mine's been fine. only pots ive ever actually had to replace were on a vintage synth from 1977
(Edited)
Er1ckOh
28
Jan 25, 2024
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skylerstupidI hit mine with some air duster through the vents and then did maybe 10 or 15 full rotations. Seems to be working fine now. Thank you! This weekend I may get in there and give it a proper lube.
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