1955 Traviata in Stereo - The Transfer to Digital
I'll try and address some of the issues you've raised – I've not had the opportunity to discuss these details elsewhere so I hope you oblige a longish blog.
The transfer from LP to digital
I actually transferred the recording myself from the best parts of two LP copies – specifically I will offer the FLAC version at 24bit 44.1kHz (I think that the higher-than-CD bit rate sounds better, while I'm personally not convinced that 88.1kHz and 96kHz are necessary).
What makes this transfer different
Regarding the left/right differences, I came to the conclusion it is genuine stereo by a process of elimination. I've considered factors like DC offset, azimuth issues, phase inversion and no matter how I look at it, it does not quite act like an ordinary monophonic signal.
DC offset is not a big issue here – the start of the Prelude looks like this (Top=Left channel, Bottom=Right channel)
If DC offset was an issue, it could look something like this amplified example (from an unrelated recording) where the signal is not centred.
I've been asked about phase and it's role: I also suspected azimuth and phase inversion, at least initially, but in practice they look different as well.
Why I think this is something special
A test I use is to boost the mid signal, then boost the side signal even more and mix them together. This can make it very obvious if there are phase issues.
With a genuinely mono recording, for example an LP transfer of de Sabata's 1953 Tosca, when the signal was tested the channels are visibly very unequal.
Here the left channel (top) is louder (+6dB) and the right channel (bottom) is affected because the signals have a lot in common but are a very different polarity.
The phase cancellation in bass and treble is visible in this meter:
In this example, everything in the bottom half of this graph is affected which here is everything below 300Hz and above 1700Hz.
What I am looking for in a recording
When applying the same test to a contemporary official stereo recording, Medea recorded with Callas and Serafin at La Scala, we can see that the sides are pretty evenly matched
...and the signal is not being cancelled out by phase problems...
La Traviata 1955 - couldn't see the wood for the trees?
Keeping that in mind, when I tested the 1955 Traviata recording it, like the stereo reference above, shows channels which have a fair balance (the right side is just 0.5dB louder) unlike the mono example which was over +6dB louder on one side
Also like the stereo example, the phase is not cancelling out – the signal is just louder and wider which is what you expect from stereo...
As unexpected as it was given the age and provenance of the recording - I still can't really explain the mechanics - I think the recording sounds better than ever in this transfer.
Examples you can hear for yourself
Given all this writing, let's listen to examples of both my transfers and transfers off the internet which - as far as I've been able to tell- have exclusively been described as mono: I have applied the widening process to them all.
NB If I proceed with any of these operas in the future, I will make my own LP transfers but I wanted a quick way of providing examples just now
The examples used are:
1955 - Traviata “Addio del passato” with Callas, di Stefano, Bastianini at La Scala, my remastering from LPs
Stereo starts at 0:00 then Mono starts at 03:29
Then other records which have piqued my interest
1958 – Turandot with Nilsson and di Stefano at La Scala – my LP rip, no noise removal
Stereo starts at 07:00 then Mono starts at 08:38
1959 - Pietra del Paragone with Cossotto et al at Piccola Scala – Original from Youtube *Some distortion on original*
Stereo starts at 10:17 then Mono starts at 13:05
1959 - Tosca with Tebaldi, di Stefano and Gobbi at La Scala – Original from Youtube
Stereo starts at 15:54 then Mono starts at 18:48
1960 – Poliuto with Corelli, Callas, Bastianini at La Scala – my LP transfer for sale on my site - https://revitalizedclassics.co.uk/collections/digital-downloads-for-sale-in-the-eu-and-uk/products/revitalized-classics-donizettis-poliuto-maria-callas-and-franco-corelli-in-genuine-stereo
Stereo starts at 21:39 then Mono starts at 25:09
1961 - Fedora with Tebaldi and di Stefano, Sereni at Naples – Original from Youtube
Stereo starts at 28:36 then Mono starts at 30:47
1962 - Ugonotti 1962 with Sutherland, Corelli, Simionato etc at La Scala – Original from YouTube
Stereo starts at 33:00 then Mono starts at 35:37
I hope you enjoy these examples and I believe you will notice both stage movements and aural depth which cannot be explained, in my opinion, just by the idiosyncrasies of tape decks, turntables etc.
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