Strange knocking recorded when transferring records

[Drew]

Greetings;

I wanted to ask the collective minds about a strange phenomenon I've discovered when I transfer records to see if anyone has experienced this or may know where to point me in troubleshooting this. After I transfer a record, when listening back to the file, sometime around the second 1/2 of a record side, I hear a soft knocking sound during the softest parts of the record (mostly in between songs) and cannot understand what is causing this. The cadence appears to be timed with the rotation of the platter. This does not show up at the start of the record though
This happens with most any record I play and is very intermittent in nature; sometimes I hear it only once, other times I hear it multiple times (even replaying the same record side). I'm very pleased with this TT overall but this knocking drives me nuts and it creates more work for me in the process. I have also experienced this on one pass and then it disappears on the next pass (same spot on the record).

As I bought this turntable used a few years ago, I noticed the sub platter did have a chunk missing from it but am not sure if this would cause the knocking I hear.
As stated, this is an MMF 5.1 fitted with an Ortofon 2M Blue cartridge, acrylic platter and a cork mat (both Music Hall). At first, I noticed the issue with just the acrylic platter installed but now hear it with the original metal platter also.


I can provide a short clip if that would help.

Thanks for the help...

[Craig Maier]

Hi Drew,

I can think of two possibilities. One - if it is a record changer, there is a trip mechanism that (when not properly maintained) can create a noise once per revolution of the record as it resets the mechanism. Two - if the tone arm is set too heavy with regards tracking, the stylus on the cartridge can actually bottom-out producing such a sound. If this is the case, reduce the tracking force a bit and see if it goes away.

Craig

[Marc Hildebrant]

Drew,

The missing piece in the sub platter sounds like a starting point to your problem. Can a picture be taken to show us ?

Marc

[Drew]

Hi Craig;

I think your suggestion regarding the tonearm did the trick. Interesting though, all the research I did when I set up the tracking pointed to 1.8g for the recommended force, including Music Hall and Ortofon. I thought about that as a possibility initially, but blew it off because of that. Silly me.

It took some experimenting, but I think I now have an optimal setting for that arm; I had to back it down to 1.5g and so far it appears to be remedied.

Good call... and thanks for the help on this.

Marc; I took a closer look at the sub platter and it appears the belt rides about 1/4 inch above the chunk that is missing, but I might ask Music Hall of they sell a replacement one anyway.

[Craig Maier]

H Drew,

Glad to learn that it is now working ok for you.

Craig

[klimbo123]

Hi Craig;

I think your suggestion regarding the tonearm did the trick. Interesting though, all the research I did when I set up the tracking pointed to 1.8g for the recommended force, including Music Hall and Ortofon. I thought about that as a possibility initially, but blew it off because of that. Silly me.

It took some experimenting, but I think I now have an optimal setting for that arm; I had to back it down to 1.5g and so far it appears to be remedied.

Good call... and thanks for the help on this. Lucky Patcher 9Apps VidMate

Marc; I took a closer look at the sub platter and it appears the belt rides about 1/4 inch above the chunk that is missing, but I might ask Music Hall of they sell a replacement one anyway.

yes i think the suggestion of craig maier is good and very helpful