looping issue HELP!

[tragwag]

I'm embossing polycarbonate with sapphire, normal ~2 mil groove depth, specific problem was with 224 LPI feedscrew

for the past few months I've had a few customers come back after getting their records saying "the record sounds great until it hits this one loop and gets stuck"
For a while I couldn't replicate the problem on my technics 1200 (on any setting), or my cheap portable crosley player.
Then one copy looped on my crosley, so I could finally figure out the issue.
I found no groove bunching, no overmodulation, no scratches or anything visual.

I changed out the feedscrew anyway, and the problem went away on my crosley player.
I've stuck with that feedscrew since, but I'm still getting complaints here and there.

The first few instances of this issue, every client had the Audio Technica LP60 turntable.
I chalked up the looping to this table having no weighted tonearm or skate control.
It was odd because every person noted that the cut tracked fine, so the groove depth is alright.

But now a few folks with other tables are having the same issue.
I keep a test cut here to check on my crosley, and inspect but there are no apparent issues.

I do mention on my site that not every player can play lathe cut records well, but I would like to get to the bottom of this if it's something I can fix.
HELP!

[Cubed]

Hey, I'm not an expert and might be a dumb ass at this but I do have a good understanding on machinery.

Stupid question, how are you visually inspecting the disc with the looping and does the looping happen on same diameter of the other discs?

Does the carriage slide easily when the feed is not engaged? Does the feed knife that contacts the lead screw have any "play"?

Does the old lead screw have any visual defects that may be the reason it was changed?

I'm still learning here and trying to help so sorry if the questions are newbie-ish.

[powerstrip]

I tried that very thing with terrible results. 224 is very tricky, especially with polycarbonate.

I hate to sound defeatist, but It seems that no matter what you do for quality control at home (I do the same thing., test on a tech 12, and test on a cheap GE portable player.), someone out there will have the perfect balance of needle shape, wear, and weight to accommodate the needle skidding all the way across the record. It's just not the same as a cut. I gave up on makrolon, that stuff is just horrible to me. still have a bunch of PIAPTK blanks just sitting around...

You basically have to pack these things with a disclaimer and a digital backup...

[opcode66]

Never had these complaints when i was cutting one-off dubs. I think the process is more repeatable and less prone to variance on a Neumann. My only issue cuttting poly was with chip pickup. But, I resolved that.

[tragwag]

Yeah I do have a disclaimer on the site, and include a card with the records, but I can't help but feel bad when the band or label ordering the records have that certain turntable that can't play it. Then they wonder how they'll be able to sell them if they can't play them

I'm visually inspecting the disc with my microscope which is 40x
I lube the carriage weekly, and adjust the feedscrew knife so it can move freely.
Though that may still be the issue, I'd have to kinda take it apart or totally adjust things.

I find it difficult because most people hear what the records cost and want to jam it with as much time as possible.

thanks for the help all, I'll get back if I find any resolution with this.

[opcode66]

Nearly every one-off dub I did was 20+ minutes per side. So, I feel you pain on that one. Especially if there is an error in the cut half way through the second side. Now, that is a pain in the ass! One of the main reasons I stopped. Not enough return to make it worth my time. Sooooooo much happier now that I stopped doing dubs and focused on my inventions.

[Graham B.]

I've occasionally received similar feedback after testing records on three separate turntables, one of which is a crappy Numark portable with no adjustment capabilities. Everything looked good, sounded good and played through here but some people's turntables are different. I've had people make adjustments to their set up and correct the problem. I had another person refuse to touch their tone arm and just had to accept one spot on the record didn't track right. It's been very few and far between for me but it seems like an almost inevitable problem with so many variables in playback systems out there. I've also explained before people order the potential playback issues that can accompany their records. Some people's understanding of what they are getting is different than others. As long as I'm employing a standard of quality control and actually rejecting and remaking defective records I feel like acknowledging "user error" is a rare but inevitable problem that's out of my control. It sucks but there's only so much a person can do to ensure what's going out is good.

[tragwag]

yeah absolutely.

Just to test it, I played THE ENTIRETY OF EVERY RECORD for one current job, and I found out of the first 5 or so, 2 had loops in them.
When looking at the spot, I noticed it wasn't a regular issue where a whole groove is touching or there's a scratch.
It looked like a simple stylus lift, almost instantaneous. I can only assume it was some debris that got in the way and caused the playback needle to slightly jump out of the groove and not fall back in.

After the initial 5 or so, every copy was totally fine all the way through.

Though I can imagine on a 224 LPI job (this test was a 160 LPI job) the issue would be more severe and any small amount of debris could derail the playback on a cheap table.

Thanks all for the help and advice, I'm hoping this is the issue.

[opcode66]

Are you using an elliptical EQ to avoid out of phase audio around 250 Hz and below? If not, this can happen with loud enough audio. It excites the stylus enough to jump it right off the record. Wiggles right out of the groove.

[tragwag]

Are you using an elliptical EQ to avoid out of phase audio around 250 Hz and below? If not, this can happen with loud enough audio. It excites the stylus enough to jump it right off the record. Wiggles right out of the groove.

Huh, that might be it? I thought because I summed everything to mono in the computer, I would avoid that issue.

[markrob]

Hi,

If your are cutting mono, its not an issue.

Mark

[opcode66]

I thought you were talking about the VR which is a stereo unit. You sum to mono before cutting on the VR?

[tragwag]

VR cuts are all solid, this issue is with embossing on the presto units. everything summed to mono in the computer for the presto, but VR cuts are stereo.

[Steve E.]

When you're using a mono head, phase can't possibly be the issue, because the walls of the groove are not being cut independently. Even if the signal "phased out" for a moment when you summed to mono, this wouldn't make the head lift.

In my old home, I found that walking on the floorboards near my presto could cause an out-of-hearing-range low frequency bump that could bounce the head off out of the groove. A dashpot could help that, and better insulation (Sorbothane under the metal frame) could help, too.

Debris could make the head lift, too, but that's less likely with embossing.

[tragwag]

I believe I've found the issue after months of testing and swapping feed screws, etc.

Over-modulation!
But specifically, in my cutting setup, over-modulation of low-mid frequencies.
With my 92B amp, the meter reads up to 0db (ref +4 dBu)
When cutting, I implement the I-RIAA curve in the computer, before the amplifier.
What I see on the meter is HEAVILY favored towards the high end due to the RIAA, so the deciding factor in the overall level of my cut is the high frequency sounds. (normally hi hats, vocal sibilance, etc)

What was happening in this case (a very mellow acoustic track), I was over-modulating the groove but pushing too much low-mid, even though the high end was still below the 0db mark.

Keep in mind, this is 6N/1D head, sapphire embossing on polycarbonate, 224 LPI feedscrew,
while striving for playback on the cheapest of turntables (Crosley portable player, no weight on tonearm)
My technics 1200 had no problem playing the louder cut.

Worth mentioning is how the problem would present itself. Rather than a skating issue, like most cheap players and embossed lathe cuts, this was showing up as a looping issue. Lately it would seem the needle would hop out of the bottom of the groove, and land on the wall sounding crappy and distorted out of nowhere. (like embossed cuts do sometimes on the needle drop)

Earlier I had written off over-modulation because I couldn't see any crashing grooves through the scope.

hope this helps out others
whew!

[Steve E.]

So, if the grooves aren't crashing, what IS happening? Is a "next" groove deforming the shape of a prior groove without breaking its wall? Have you been able to locate any sort of visual representation of a problematic groove?

[tragwag]

So, if the grooves aren't crashing, what IS happening? Is a "next" groove deforming the shape of a prior groove without breaking its wall? Have you been able to locate any sort of visual representation of a problematic groove?

That's the thing with the embossed groove, there isn't a visual symptom.
The needle isn't hopping from one groove to another, it's hopping from the proper position in the groove, to the wall of the groove.
This can show up as looping, or skipping, or the overly distorted playback if it continues to track the wall.
Sometimes on the needle drop with lathe cuts, it'll ride the groove wall and you can just tap it into the right position in the groove.
The louder low/mid levels are causing these unweighted tonearms to hop onto the wall.

That's the only thing I can imagine being the issue as there are no scratches or crashing grooves.

[Steve E.]

Do you mean it is riding the horizontal "land" between and above the grooves?

[tragwag]

I believe I may have solved this issue once again, more specifically.
I was having looping issues with 80s style hardcore punk,
this style calls for really saturated lows and low mids in the drums, guitars and bass.
When I reduced the low end more significantly, the looping issue went away.
Instead of reducing the overall volume like I did before, I just reduced the low end, and the cut tracks 100% on the cheap crosley player I have here.

I hope this thread can help others in the future!