One intermittent channel during mono embossing

[FFrankensteinRecords]

The past few days I've been battling this issue where one channel (the left speaker) is fading in and out. I'm even more perplexed because I'm cutting on a mono system. It can occur at any point but usually waits until about halfway through to record to show up. I'm cutting with a mono Presto 1C head on a Y series lathe. I can't see any abnormalities visually on the record. When it happens the other speaker sounds normal but the left speaker fades in and out with each revolution. I've switched amps and styli, tried every manner of angle adjustment, weight change, Cleaned the feedscrew etc and nothing has cleared it up. I've heard it on all my playback turntables. I've also heard some cuts that sound okay on one turntable but then sound messed up on another. It's driving me crazy that I can't figure out what is causing it, I've probably burned up 15 blanks or more testing and making adjustments.

Any ideas?

[markrob]

Hi,

That's pretty crazy. For that to happen, the cutter stylus would have to move in a 45 degree angle rather than side to side. Can't see that happening with a 1C. Can you post a sample of the problem? Also, I microscope picture of the groove would be helpful.

Mark

[FFrankensteinRecords]

Here is a video illustrating the problem as best I can:
https://youtu.be/zHHm_eWzHNI

Here is a video I took with my microscope camera of the grooves in a couple different places on the record, starting in the middle where it happens most often.
https://youtu.be/vSzXEDx71p8

[markrob]

Hi,

Is it possible you are actually riding between the grooves? Given the pitch and due to some "horns" formed due to embossing, maybe you would only get one side of playback. Just a thought. Anybody else have a clue?

Mark

[FFrankensteinRecords]

I'm familiar with them and I don't think it's horns, unless they're interferring in a way I've never encountered before.
I think it's in the cutting somehow and not the playback. I have a playback turntable that is a little fast and doesn't occur exactly with each revolution there, it's slightly off indicating to me that its occuring at the speed it was cut at.
Pretty much the only things I havn't changed are the cutterhead, the lathe itself, and the parametric EQ. Everything else has been changed all around and basically ruled out to me.
I'll rule out the EQ for sure later tonight, but it's my least suspect. I don't have another cutterhead to try but I have another lathe I could get out of storage. I just can't imagine what could be happening in the head to cause this. And the fact that it can sound okay on one turntable and bad on another leaves me really puzzled.

[EmAtChapterV]

I'd look closer at your playback system first, to be honest. The only stereo signal I've ever managed to accidentally cut with a mono system was rotational movements when cutting high level subsonic test tones (20 to 30 hz) with a Fairchild 541A that wasn't mounted completely level. Midrange stereo separation on a Presto 1C should be physically impossible with the construction of that head.