Where do classical vinyl records get their rumble from?

To All,

While I may have been impetuous and inaccurate about exactly which mono designed cartridges use two balanced mono coils and which use a single, both designs exist. And both designs can be considered a true mono cartridge. My determination for a true mono design is based on the differences between a strapped stereo cartridge and one that is built from the ground up, for strictly mono.

The Hana mono cartridge is described as a true mono, single coil cartridge that can be used on a stereo pressing without damaging the record.

Here is AI’s response to the single coil to dual coil mono design approach;

Two Coils vs. One: Traditional true mono cartridges rely on a single coil. However, cartridges described as having "left and right mono coils" typically feature dual moving coils (like a stereo cartridge) internally wired or angled to respond only to horizontal movement. This dual-generator configuration allows the cartridge to present a balanced load to your preamp, avoiding the ground-loop hum issues that can sometimes occur when bridging a single-coil mono cartridge to two stereo inputs.

The Audio Technica AT33 Mono as recommended by Jonathon Carr on an earlier Audiogon post. The AT 33 Mono has two distinct, horizontally oriented coils.

@goofyfoot 

The distinction between true mono cartridges and those that are not, pertains to whether a stereo cartridge was strapped. This has been discussed in past Audiogon posts to great detail

Rather than trawl through umpteen posts, I asked ChatGPT, which of course has already trawled through Audiogon posts  while building its Large Language Model!

Strapping a cartridge refers to internally wiring the audio pins of a stereo turntable cartridge so that both channels output the exact same signal, converting a stereo cartridge into a mono player. [1, 2]

How It Works

• The Pins: The back of a standard phono cartridge has four pins: Left (+ / -) and Right (+ / -).
• The Strapping: A small wire, solder, or connector physically bridges the positive pins together and the negative pins together.
• The Result: Rather than outputting separate left and right stereo signals, the cartridge combines the audio data into one single, centralized signal, mimicking a true mono setup. [1, 2, 3]

Why People Do It

• Better Mono Playback: Playing vintage mono records using an unstrapped stereo cartridge can create annoying, out-of-phase surface noise. Strapping eliminates this and reduces background noise and rumble. [1, 2]
• Cost Savings: True mono cartridges can be expensive. Strapping an affordable stereo cartridge allows you to achieve the benefits of mono playback without buying specialized equipment. [1, 2, 3, 4]
• Modern Convenience: Many manufacturers offer mono cartridges that are factory-"strapped" for plug-and-play compatibility with standard stereo amplifiers. [1, 2]

As a bit of an aside, current DS Audio optical cartridges cannot be strapped, because two of the four wires carry a DC voltage to power the Light Emitting Diodes in the cartridge. 

Also a bit quirky is my Soulnote E-1 Ver2 Equalizer, which acts as a phono stage for MM and MC cartridges, as well as being an equaliser for DS Audio optical cartridges.  It has a switchable low-cut filter designed to mitigate the audible effects of warps, but the filter only operates on MM and MC inputs .

The Soulnote is also a bit unusual because it does not use any negative feedback.  Negative feedback improves distortion numbers in the frequency domain, at the expense of smearing signals in the time domain.

I get the sense that every 'quirk' in the Soulnote has been carefully thought through by the designers, so it is no accident that the extended bass from optical cartridges is kept intact.  Also, there is no mono switch - that is left to the pre-amplifier 

When I think about my vinyl playback systems, there are three critical components. I would like my turntables and cartridges to be neutral, minimising added noise and coloration.  Against this quiet background, the Soulnote phono-stage / equaliser seems to make an astonishing difference though I have no rational way of apportioning the plaudits.

@goofyfoot 

This dual-generator configuration allows the cartridge to present a balanced load to your preamp, avoiding the ground-loop hum issues that can sometimes occur when bridging a single-coil mono cartridge to two stereo inputs

It is a bit early in the morning for me, but I cannot see why a single coil (with two wire connections) cannot also present as 'balanced' to a phono stage with suitable mono input.

Another quirk of the Soulnote is that it can accept balanced or single-ended input from MM and MC cartridges over either XLR or RCA connections.  Balanced or single-ended operation is configured by a rear panel 'bridging' switch and the user cannot mix-and-match from the front panel.

@richardbrand I would avoid any strapped stereo cartridge, as it's no different than using a stereo to mono splitter. Also, so many cartridges today build their mono cartridges from the ground up that strapped stereo cartridges are becoming a thing of the past. As to why some designers opt for two balanced mono coils and some for one coil appears to be subjective. Anyway, I'm beginning to regret I said anything but my suggestion was just out of curiosity. Even if you did play those particular records with a mono cartridge and the anomalous noises disappeared, I'm still not sure what you could do about it.

@goofyfoot 

"Even if you did play those particular records with a mono cartridge and the anomalous noises disappeared, I'm still not sure what you could do about it."

Since all mono laquears are cut with stereo cutting heads these days the need for a "mono" cartridge is moot, the groove pitch and every other factor is the same as stereo. Simply switching your phono preamp or integrated to mono sums the vertical stereo stylus excursions completely canceling them out and eliminating the surface noise that's picked up. A surface that's already quiet might not show any audible improvement noise wise by doing so.

Using an MM stereo cartridge that has the option of a spherical stylus, with what I believe is a .7 mil radius for ancient mono vinyl would be more than satisfactory in this case