New Cartridge Causing Intermittent Popping

It might be the stylus design!!

Line Contact / Linear Contact / Special Line Contact / Fine Line

The cross-section of a Line Contact stylus can be regarded as an Ellipse taken to the extreme and with straight vertical edges (rather than round) for deeper groove contact, as illustrated below.

The Line Contact stylus shape can be considered a later variation of the Stereohedron stylus (with its four slivers shaved off, it is sort of a double elliptical) as patented originally by Pickering in 1973.

Patented in 1978 in Japan by inventor Junshiro Ogura, the Line Contact stylus is shaped such that it allows maximum vertical contact with the groove walls whilst having a small front-to-back contact. This kind of stylus is almost always fitted with a nude diamond. Compared to Conical Styluses (that due to their rounded shape only touch the groove walls in one vertical spot, thus more easily wearing them out on that depth), Line Contact styluses can make slightly worn records (when worn as a result of the use with conical or elliptical styluses) sound almost pristine. This is because the larger vertical area can now be modulated by previously untouched areas of the groove walls.

The variations such as Linear Contact, Special Line Contact, and Fine Line all represent further refinements of the principle, usually adjusting the shape of the shank and/or the width of the contact area. The variations with the narrowest contact area such as Ortofon’s Fine Line, Audio Technica’s Line Contact, and the more generic Special Line Contact achieve the most accurate results with the best high-frequency response and lowest distortion. All the variations have in common that the stylus wears more evenly which results in a longer stylus life.

In general, the more precise the stylus shape, obviously, the better it is at picking up high frequencies but also the better it is at picking up small defects in the pressing or very brief noise spikes. Compared to the simple Stylus shapes, the Line Contact and more advanced designs require records that are cleaner and in better condition to be played mainly noise-free. But in my book a little playback noise here and there certainly does not stand in the way of my musical enjoyment, and even if so, usually, it’s nothing a record cleaning machine can’t fix.

6.  Swapped tubes. No difference.

7.  Replaced headshell leads with super snug fitting heavier gauge.  Let's see! I will note that the last cartridge (before the Ethos) that used this headshell and leads fit more snugly.  

I'm optimistic this is the issue.  Loading, gain, cleanliness of record, etc. made no difference. 

I'm 5 minutes into a new side and no popping --fingers crossed!

Thanks @yogiboy ! I agree that this stylus type has real potential to be noisier. This is a loud popping sound--not necessarily what I associate with surface noise. 

I noticed the headshell lead wires were particularly loose and didn't allow me to snap them more snugly with surgical pliers or needlenose.  Now, I just replaced them and there's no popping--thusfar. 

The past few months, I grappled with an intermittent loud pop issue in my office 2ch setup (new 2nd system). The pops were singular, but LOUD. Startlingly so. Even louder than the peak music levels. I went through all the usual suspects -- record cleanliness, static discharge, phono stage overload margins (tried 5 different phono stages). Nothing helped. Turned out it was AMP clipping, caused by severe low frequency feedback.

The KAB rumble filter stopped it (an easy solution), but I went ahead and really fixed the issue with proper turntable isolation -- which was not easy, mind you.

I’m not sure that’s what you’re grappling with here, but thought I’d mention it because this almost drove me insane. Does you incidence of pops always correspond with musical peaks / crescendos? That’s probably amp clipping. At first I was SURE it had to be static discharge, but then I started to notice the POPs were more likely to happen at the same point of certain tracks (where it was loud and especially bass-heavy), and only when the volume was high. A good example is the opening of Elvis Costello’s "(What’s So Funny ’Bout) Peace, Love, and Understanding" track on "Armed Forces", and Foo Fighters "There Is Nothing Left to Lose" (at many points on this album lol).

It seems unlikely a change in cartridge and could cause amp clipping, but it’s possible the new cart could have a generally stronger LF response (or even a peak in the wrong area), or exhibits a different resonant frequency with your tonearm, or even encourages you to use the system at a slightly higher volume than before.

@mulveling ,  As usual, you are so conscientious!  I'm glad you chimed in.  Even if this doesn't fix my issue, it's important to note. 

New headshell lead wires helped --a bit. But I still have it and it is as you describe. A LOUD pop. I've never had that before with this table, phono pre and numerous carts and amps.  I'm going to make a few adjustments. I also have subwoofers (REL T9is) that are barely on.  I mean set around 30 hz and volume so low that they are nearly undetectable. Let me turn them off.