RIAA vs Columbia vs Decca

Chakster, I can't agree with you on the above statement. The reason why is the labels did not choose the EQ curve. The manufacturer of the cutterhead electronics did. For example we use the Westerex 3D cutterhead and the 1700 electronics. The EQ curve is set by Westerex, not the various and many labels that used that equipment. The same is true of Neumann, who made the lathes and electronics used by many of the European labels.

If you hear differences between the labels (I know I do) its not really because of then not using the RIAA curve (every stereo LP made uses it). Its because that particular label did something to the signal prior to it ever getting to the cutter electronics. A great example is Everest, who had a special tape machine that recorded on 35 mm tape that was the same format as 35mm motion picture film. Turns out they had a bug in the EQ of the recorder that rolled off the bass at 6db/octave starting at 100Hz.

The latter sentence in your quote is simply untrue and is some sort of urban legend. If you think about it you will see why- after the inception of the stereo LP, all phono reproducers had the RIAA curve installed, with a very few preamps made that still included the older mono EQ curves. None of those older curves were used in the stereo era and by 1965 or so there were no more preamps made with the older curves. So where in the heck would the Europeans buy their preamps to play back their LPs with non-standard EQ curves?? The answer is of course that they didn't; all stereo LPs actually employed the same curves.

Reissues are most certainly RIAA. I can't imagine any modern recoding engineer using anything else.

Does anyone know of a switchable unit which can fit, say in between a phono stage and a line amplifier, to enable switching between these curves? (I have an Aesthetix phono stage feeding an Audio Research line preamp...)
Or is there an equalisation circuit that anyone knows of which can be adapted for this purpose?

Vintage, Such a device as you propose would have to operate on an already RIAA-equalized signal from the phono section. That's a whole different kettle of fish from applying an alternative equalization curve within the phono stage circuit itself. You'd be better off (less coloration, less noise, etc) just using bass and treble controls on the linestage, IMO.

Chakster, Ralph's post makes a lot of sense. But I was also wondering about the phase issues to which you refer. The very act of equalizing the signal must introduce capacitors, resistors, and, in some phono stages, inductors into the signal path. This will inevitably affect phase, whether the device or the recording is "vintage", or not.

Phase shift is removed by the act of equalizing. It was put there by the pre-emphasis network during the mastering process. So when you play it back its removed.

Vintageaxeman, The curves referred to in this thread are an urban myth, other than the RIAA curve itself. This is why you don't see switchable EQ curves on modern electronics.