Playing stereo records with mono cartridge.

[hayerjoe]

hello everyone. I hope you can help me with something I'm find quite puzzling. Sorry it's such a long post.

I have a 1958 Philips radiogram (Stockholm), it has a mono amp, the cable from the record player is ground and just one signal wire (so far so good in the mono world). However I want to safely play stereo records, obviously I'll not get any stereo effect but ive read that not only does a stereo record have signal info either side of the groove, but it also has up and down movement. Now my cartridge has a microgroove option but Q1, doesn't that mean it can just read microgroove mono records so it will miss 50% of the sound from a microgroove stereo record?

Q2 can I do any damage to a stereo record playing it with this mono cartridge and vice versa can I damage the mono cartridge by playing a stereo record through it with its up and down movement, potentially uncatered for in a mono cartridge?

Now here's the puzzling bit. I'm playing a stereo record I'm VERY familiar with (Dancing in the street - Martha and the Vandellas) to me it sounds perfect, not stereo of course but certainly not missing 50% of the audio!

I've checked the cartridge wiring thinking someone over the intervening 50+ years has converted it to play stereo records (note my research for needles/stylus suggest that a stereo needle was available for this mono cartridge and for identification purposes it was coloured red, I note my needle definitely has a 50 year old red tinge). So the cartridge has 3 wires, red carries the signal, ground is ground, and a 3rd wire is black but is ALSO ground. This 3rd wire seems to come from the opposite side of the needle (red one side, black the other, with ground separate and above them), so I thought I'll move that black wire from ground (under the deck) to the red signal wire hopefully mixing both left and right signal to go off to the amp. Result no sound at all! so I disconnected that black wire from the red cable and left it hanging (so not reconnected to ground) sound was back to being as good as ever?! very puzzling so Q3 why does my cartridge have 2 ground wires? and Q4 why with just one signal wire am I not missing half the audio from the Vandellas? (my thoughts are can this stereo needle 'read' both left and right signal and transmit a mixed signal direct to the cartridge via one wire?)

I've attached photos of cartridge (AG3016) and a stereo needle specifically for this cartridge

[hayerjoe]

OK, I found a useful post on here that provides an answer to Q3, one signal wire, one signal ground wire and an extra ground to ground the tonearm. I'll solder that back on!

[ben]

The left and right channels would be picked up together by the stylus. Maybe the extra ground is simply shielding. Many BSRs with tubular arms or metal parts on the headshell used a yellow wire for this purpose.

If you want to play stereo discs on this safely, you could buy a broken Philips headshell, gut it partially and fit a ceramic cartridge in there. I have done this. A 22gp230 head, if you can find one that works, was a later stereo compatible type (female type, later Philips ones were male)

I think Pinnacle might have made stereo headshells for these too.

Read also this thread

[Ted Kendall]

A stereo groove has the left and right modulations cut on either wall, the motion of the cutter being in a line 45 degrees to the horizontal. It follows from this that lateral motion carries the sum of left and right channels and vertical motion the difference. A mono pickup only gives output from the lateral modulation, and to that extent the system is compatible.

However, most mono pickups paid little attention to vertical motion and were quite stiff in this direction (low compliance). This caused damage to the difference signal, wrecking the disc for subsequent stereo replay. There is vertical motion even in a mono groove, known as pinch effect, and the best mono pickups had some vertical compliance, but in general this was ignored. Stereo compatible cartridges were made, having proper vertical compliance but sensing in mono, or a stereo cartridge with outputs paralleled can be used. Also, stereo records require a tip of the order of 0.7 thou, instead of the usual 1 thou mono tip.

The pickup you show plays 78rpm records (N, normal), or mono LPs (M, microgroove), so as it stands is not safe for playing stereo discs.

[hayerjoe]

Thank you Ben and Ted.

From your comments and the link Ben sent to the post about Philips cartridges I think I can now answer my own 4 questions. Q1 - it can read a stereo record and not lose 50% of audio, but due to lack of vertical movement probably loses some audio. Q2 - yes it will/can damage a stereo record due to the entire cartridge and tonearm replicating the vertical movement in the groove and this would cause excessive wear. Q3 - one ground is for the signal, the other is for grounding the entire head/cart/tonearm. Q4 - yes the needle reads and mixes both walls of the stereo groove

So I am going to get a comparable stereo cartridge and not use the AG3016

One final question out of interest. Did you see my photo of the new (nos) stylus I bought? if the old 3016 cartridge does not correctly accept vertical movement how could they sell this stylus as ok for stereo in the 60s? I've looked at the stylus thinking maybe it was thinner allow some vertical movement without raising the entire cartridge but it looks about the same thickness. Any ideas?

thanks Jo

[ajgriff]

Surely Jo's spare stylus is stereo compatible and shouldn't harm stereo records. They're still available today as listed by this vendor:

https://www.pickupnaalden.com/englis...16_GP-316_4448

Alan

[ben]

I think the problem isn't so much the stylus, as the compliance of the cartridge to which it is fitted. Then there's the old marketing or 'bending the truth' to consider...

In a nutshell: why risk it?

[ajgriff]

I take your point Ben but then I wouldn't play my stereo records on an old radiogram or Dansette regardless of the cartridge fitted. Having said that some of my stereo LPs were played using a mono Acos stereo compatible cartridge when I was a teenager and they don't seem to have suffered greatly from the experience.

I think the required compliance in the case of the AG-3016 is achieved by means of the thin twisted shank of the compatible stylus.

Alan

[Edward Huggins]

Originally Posted by ajgriff

Having said that some of my stereo LPs were played using a mono Acos stereo compatible cartridge when I was a teenager and they don't seem to have suffered greatly from the experience.

Alan

Yes, but that's the whole (er) point of using a stereo-compatible cartridge isn't it?

[hayerjoe]

thanks everyone. Whilst I agree with Alan that the new stylus is probably OK I'm still gonna take the safer route and get a stereo cartridge