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 Post subject: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Tue Nov 08, 2011 8:15 am 
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Victor III
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F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
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Location: Italy
..emporary pick-up cartridges.

Gentle fellows,

some time ago I read on a specialised tech article about phono preamplifiers that a 78 stereo cartridge (they usually are stereo indeed, and only rewired for mono) it is possible to play vertical cut records provided that "some" phase is inverted. However, the author completely failed to mention which phase, where and how.

I lately did some experiments with a Grado 78 cartridge and the only Edison Diamond disc that I own, but failed to hear anything. So I thought to ask some questions to fellows who may have travelled this road before.

1) Is it really necessary to invert a phase to hear something? Shouldn't a stereo cartridge reveal some signal anyhow on vertical cut groves? Only TRUE mono cartridges made for horizontal cut should stay mute on vertical cuts, correct?

2) In case, which phase should be inverted, and how does this translate into the colour code of the standard four leads wiring all contemporary cartridges?

3) How should one expect the final volume of Edison's Diamonds be, compared to the avarage 78s recordings? Almost the same, much quieter, louder...

4) Are significant problems of equalisation expected, or should the RIAA network compensate well enough the recording equalisation?

Thank you and have a nice day!


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Tue Nov 08, 2011 5:43 pm 
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Victor II
Joined: Thu Jan 08, 2009 6:03 pm
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A stereo cartridge is designed to respond to both lateral and vertical modulation. If you play an Edison DD or other vertical modulation recording with a stereo cartridge and listen thru a full stereo playback system, you will hear the recording but the sound will be out of phase between the two speakers. This will sound strange with sound coming from the two speakers but no image seeming to come from the space between the speakers. If you play a lateral mono recording such as other typical 78rpm records on this same stereo system, you will hear the recording and the sound will be in phase and sound natural from the two speakers. This may be adequate if you are only casually interested in listening to the vertical recordings.

In order to hear the sound of a vertical recording with minimum surface noise from the record, you need to combine the two signals coming from the cartridge into one signal. If you parallel- or series-connect the cartridge outputs, you will transform the cartridge into either lateral-only or vertical-only responding, depending on the particular connection. This will reduce the unwanted surface noise from the modulation direction that you don't want to hear.

Parallel connection of the cartridge outputs such that you hook the + or 'hot' connections together and the - or 'ground' connections together will result in the cartridge becoming lateral-only responding which is correct for most 78rpm records. To make the cartridge vertical-only responding, connect the 'hot' terminal of one cartridge output to the 'ground' terminal of the other channel. Similarly, connect the other two cartridge pins together. Then use only one cable (not the original two) to carry the signal from the cartridge to the amplifier. If your cartridge has only three output pins, connect one side of the output cable to one of the 'hot' pins and the other side of the cable to the other 'hot' pin and remove any cable connection from the third pin. This will allow you to play vertical modulated records such as Edison DDs and Pathé Sapphire records with minimum surface noise created by the lateral direction.
Collecting moss, radios and phonos in the mountains of WNC.


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Tue Nov 08, 2011 7:05 pm 
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Victor IV
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"Did you ever stop to think that pleasure is a duty?" (Victor sales pamphlet)
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Correct me if I'm wrong, but there should be no RIAA equalization applied to any of the Edison acoustically-recorded discs. I used a flat pre-amp when making transfers and apply a turnover curve later for various makers' electric recordings.
The turnover curve for Edison Laterals is listed in my restoration program as 500hz, but I don't know if that applies to the late electric Diamond Discs also.
Bob
"Comparison is the thief of joy" Theodore Roosevelt


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Tue Nov 08, 2011 8:42 pm 
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Victor IV
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Here is a simple diagram to wire the stereo cartridge properly for vertical recordings. The output is mono of course. You could use a "Y" adapter to feed a mono signal to both channels of your pre-amplifier.


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Wed Nov 09, 2011 8:03 am 
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Victor III
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F. Depero, "Grammofono", 1923.
Joined: Thu Feb 24, 2011 4:19 am
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Location: Italy
Thanks everybody for your interesting insight. Let me translate the content of the previous posts in terms of colour codes and wiring.

First of all, if I remember correctly no signal manipulation happens inside the turntable unit, so the four leads go directly to the RCA output plugs, correct? I think that the connection table is as follows:

RED --> R channel + --> Central pin of right (RED) RCA jack
GREEN --> R channel GND --> Shield of right (RED) RCA jack
WHITE --> L channel + --> Central pin of left (WHITE) RCA jack
BLUE --> L channel GND --> Shield of left (WHITE) RCA jack

Please correct me if the above is wrong.

Now, as all of the four contacts are still available at the RCA jack end, a rewiring for vertical cut at that end should also be possible. I think it's better to work at that end, as headshells receptacles are extremely tiny and very easy to break: the less they're touched, the better.

Let's also skip the point concerning the MONO wiring and let's keep the groove noise in STEREO (amplifiers usually have a mono/stereo selector, and I prefer to use that one, unless I have no choice).

This said, is it sufficient to INVERT the wiring of one of the two RCA plugs to hear a in-phase sound read by a vertical cut groove? That is: should I connect the right shield of the RCA jack to its plug, and the wire that was connected to the plug at the shield, leaving the left jack untouched?


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Thu Nov 10, 2011 6:46 pm 
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Victor II
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Marco, what you are suggesting MAY work, but there is a good chance that it will not. The reason is that the two ground (cable shield) connections appearing at the RCA connector ends of your cables are probably connected together somewhere inside the turntable. In which case, switching the shield and hot connections at the RCA plug will only short out one channel of the cartridge. This will cause no harm to the cartridge, but it won't get you the desired result. Furthermore, even if your shield wires are not connected together inside the TT, switching the hot and ground on one cable may result in considerable hum being added to your signal. It's better to do the wire switching at the cartridge to avoid these problems. The diagram shown in VintageTech's post puts the two cartridge outputs in series and out of phase, which will be correct for playing vertical modulation.

Bob, you are correct that RIAA equalization was not employed in the recording of either acoustic or early electric records. But I find it acceptable for listening. It's easy to use because it's readily available, and it provides some treble cut shelving which tends to reduce surface noise while improving the bass content of acoustic recordings. There really isn't any 'CORRECT' EQ to use when listening to acoustic recordings. They were recorded with whatever mechanical resonances in the recorder struck the fancy of the recording engineer that day, resulting in wild variations from one studio and day to another, and none of this was documented. So just use your tone controls or a graphic equalizer while listening to doctor the sound to suit your taste.
Collecting moss, radios and phonos in the mountains of WNC.


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Thu Nov 10, 2011 8:15 pm 
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Victor V
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Aren't Grado 78 RPM carts already jimmy rigged for mono lateral playback only? Assuming the cart is already jumpered inside for mono may change the game plan that one would use to use a stereo cart for vertical cut records. Or perhaps not. :?


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Fri Nov 11, 2011 3:54 am 
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Victor III
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@ gregbogantz: Thanks, I've already thought about that and already had in mind to inspect the connection PCB inside the turntable to verify that the shields stay separate. The matter to which I was step-by-step trying to bring the conversation is to find a point where a channel can be phase-inverted without too much noise being injected into the circuit. Where is the signal at a sufficent level already, and on a convenient impedance to avoid significant noise injection? Perhaps the connection between the preamplifer and the power stage?

@ Wolfe: I don't think so. When switching from STEREO to MONO there is a clearly detectable difference, so I assume Grado 78 is a true stereo cartridge.

However there's still this mistery record that outputs no sound. A standard diamond 78 needle, although perhaps not perfect, should read Edison Diamonds well enough to produce an audible sound, shouldn't it?


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Fri Nov 11, 2011 10:24 am 
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Victor III
Joined: Sun Sep 05, 2010 10:56 pm
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Marco Gilardetti wrote:
@ gregbogantz:
However there's still this mistery record that outputs no sound. A standard diamond 78 needle, although perhaps not perfect, should read Edison Diamonds well enough to produce an audible sound, shouldn't it?


Yes, a standard diamond stylus (either for 78 or LP) should easily be able to read and produce music from an Edison Diamond Disc, or a Pathé (type) vertical recording. I have transferred literally hundreds of my diamond discs using a common Stanton 681 cartridge on a Mirachord turntable, wiring the channels out-of-phase and feeding the mono signal thru a Y-adaptor to both stereo channels of my preamp. Some discs play back better with the 78 stylus, some better with the LP stylus. If you are not getting sound, you have just wired up something wrong. The Edison recordings will play back with somewhat less volume, but not so much that you can't get sound, by any means. You will just have to turn up the volume on your amp a notch.


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 Post subject: Re: Playing Edison Diamonds (or other vertical cut) with cont...
PostPosted: Fri Nov 11, 2011 8:08 pm 
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Victor V
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Yes. Most any size 78 stylus or even an LP stylus should retrieve something from a vertical cut Edison disc, regardless, if the wiring is correct.


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