Re: ping liz@poppyrecords

There are a lot of software products on the market but they have two major failings:

The real-time aspect was important last weekend: I was playing-in examples for presentations at the A.G.M. of a national gramophone society. Most of the records only arrived on my table 15 minutes before the presentation started, although I had been told in advance what they would be. The one of the presenters produced a record she had just been given and asked if that could be included too.

In the evening, people brought along records they would like to hear, so I only had a few minutes to look at each disc and work out what settings would suit it. (No normal 78s used the R.I.A.A. recording characteristic, so I had to work out what characteristics to use for each one.) Most were lateral recordings but a few were vertically-modulated. Several were 80 rpm and one was 66 rpm.

There is no way software with batch processing or even noticeable latency could have been used for that job.

Aye, there's the rub! No time to do that in front of an audience.

You guessed correctly - or they could be connected in parallel as long as the relative polarity was correct in each case. For coping with a mix of records it is much more convenient to have sum and difference op-amps permanently connected, then switch between them. For convenience the switching is incorporated into the equaliser:

It's a non-polarised electrolytic capacitor. I always use the pre-war German/Dutch symbol for electrolytics because it is more descriptive than the British Standard symbol. The non-polarised symbol is like two 'Dutch' electrolytic capacitors back-to-back

I use a different symbol for feedthrough capacitors, you can see some in the top row at:

The cartridge pre-amp is a low-noise design that was first used by Bell Labs for telephone line amplifiers in the 1920s, it has a combination of current and voltage feedback to ensure the correct loading without the need for a noise-generating and signal-wasting resistor. The idea was revived by the BBC for their low-noise AMC/5 microphone pre-amplifier in the 1950s. In most implimentations, including this one, it needs both side of the input signal source to float - but I have produced a variant that can work with a source that has one side earthed.

Yes, it is specified by the manufacturers to give a little bit of high frequency correction boost to the sound.

...and 1/30th of the output voltage injected into the bottom end of the cartridge.

Needle pickups have their uses - but not for stereo!