What is the best way to replay mono LP on a stereo system?

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#21
billshurv said:
There was a thread about this fairly recently looking at the 3 main methods of getting to mono and if any of them had a real advantage. The conclusion was that a simple passive mono at line level will get you 80% of the way there and that a lot of discussions on mono cartridges forget that fact that you get noise in more than the vertical plane.



Won't stop me lusting after an old ortofon mono or using the mono MC I had made for me
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Hi billshurv.
No self respecting diyer is going to be content with 80%😀
I have been comparing stereo replay with L+R mono via Y-parallel at the tonearm plugs and the phono stage output. It's a bit more complicated on my set-up which is fully balanced from the tonearm plugs and uses balanced transformer into a balanced phono stage. Introducing two sets of balanced Y-connectors (tonearm to input transformer, phono stage to pre-amp) has the potential to upset the tonal balance due to additional capacitance and resistance. I used what I had lying around. My normal stereo hum level is usually very low but increased slightly in L+R mono even with careful cable positioning but still not audible when playing. My impression was a slight level drop compared to stereo, possibly insertion loss of the short (30cm) balanced Y-cables. Maybe that is where the small apparent hum increase comes from.
The L+R mono had the surface noise in the same central position as the music and was less noticeable as a result. On tracks with distinct pre or post echo, it was definitely an improvement to have the echo partially hidden behind the music signal instead of distinct on L or R channel as usual. As billshurv mentioned, surface noise is not completely vertical so it still is audible but much reduced and a different spectral content compared to stereo replay.
My impression is that the L+R replay was "cleaner" but with less "air", no doubt a false stereo artefact. The central image was narrow enough to not cause me to consider listening to only one speaker. Maybe if I did much listening off-axis, I would notice something amiss.
 
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#23
Bon said:
Hi billshurv.
No self respecting diyer is going to be content with 80%😀
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And yet they are! It gets complex very quickly. If you are just interested in cancelling out the vertical noise component, then a Y cable is slightly less compromised than a mono button, but more compromised than a series strapped cartridge or a proper mono (note despite marketing, a parallel strapped MM is not true mono).



But the real world is never that simple. Pano did some measurements that showed a lot of decorrelated noise that will not be cancelled in mono so there will be cases where one channel is less noisy that running in mono so for archival purposes you are better off starting with stereo and then selecting the right post processing for the record in question.



I also have an inkling, completely unproven, that you need a different speaker for mono. You don't really want a narrow line in between the speakers so a wide dispersion dedicated speaker might actually do a better job of replicating a single channel source than a speaker designed for stereo (or hopefully designed for). As I say no proof, but on my list to try one day.
 
#25
Hi billshurv.
billshurv said:
But the real world is never that simple.
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We agree there. See #13.
Bon said:
but as we are well aware, things are not always as they first seem (with vinyl).
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billshurv said:
for archival purposes you are better off starting with stereo and then selecting the right post processing for the record in question.
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An interesting suggestion. This will suit me fine because of the small number of mono recordings I am interested in. It so happens that I have a long term project to archive my LP collection at 24/192 resolution. I can not clearly distinguish between direct LP replay and a level matched 24/192 flac copy, which is close enough for me. I know Audacity has quite powerful post processing functions and the facility to choose L, R or L+R replay. This should be flexible enough to suit my purposes with no need to re-wire anything and I can keep the signal path as simple as possible. There is still a possibility that different cartridges may be more or less capable of rejecting spurious signals. I have quite a few to play with.
billshurv said:
... a wide dispersion dedicated speaker might actually do a better job of replicating a single channel source than a speaker designed for stereo
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I really don't want to go there!
 
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