Y adapters to sum to mono...where to connect the ground?

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tateharmann
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Y adapters to sum to mono...where to connect the ground?

Post by tateharmann » 14 Mar 2018 04:02

Hello,

I have a little Y adapter setup to sum stereo down to mono and when I went to connect it I realized that I had no where to connect the ground coming out of the TT ( JVC L-A55). So my little adapter setup went between the TT and preamp but I connected the ground to the ground terminal on the preamp. Does that sound right? Also, I seen some that solder some passive resistors into the cables - would I expect to get any increase in sound quality if I do that? I'm comfortable soldering and have the equipment to get it done - just curious.

My "summing" cable setup is two Hosa Y adapters connected together: a female RCA stereo to male 1/4'' mono connected to a 1/4'' female mono to stereo RCA male.

Searing75
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Re: Y adapters to sum to mono...where to connect the ground?

Post by Searing75 » 14 Mar 2018 04:54

Why are you going mono? Does your preamp not have a left and right input on the back? Would be very odd if it didn’t?

Yes, tt ground goes to the ground terminal on the back of the preamp.

And, no, don’t solder any resistors into your cables, or anywhere for that matter. If you do this, you will lose high end. This is done to increase the loading of the cart used at times. What cart are you running?

antennaguru
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Re: Y adapters to sum to mono...where to connect the ground?

Post by antennaguru » 14 Mar 2018 06:40

Back to Back Y adapters work well to sum the left and right signal from your tonearm cable to your phono stage when playing mono source material (only). I do this myself with the my dedicated 78rpm tonearm/cartridge, on the way to my non-RIAA phono stage, since even though it is a stereo phono stage and the tonearm is wired for stereo, the phono stage lacks a stereo mono switch. Summing will cancel out much of the noise and even the channel balance for mono records. Some people prefer to use shorting leads wrapped on the back of the cartridge which is a different way to accomplish the same thing, though possibly less easy to remove to return to stereo.

Yes, the single ground wire goes from the chassis of the turntable and/or tonearm to the binding post on the phono stage, as it normally should - unless you find you get a ground loop with it connected and it sounds quieter disconnected.

WRT using additional resistors I am wondering what you are considering that for? There would be no need to do so unless your phono stage is being overdriven by your cartridge and you need to attenuate the signal to avoid clipping distortion in the phono stage, though that would seem unlikely. If that was the case you could use various Tee or Pi resistor configurations as attenuators.

Possibly you are trying to resistively load your cartridge to achieve different frequency response? This can also be done using Y adapters as well, but in a non-summing configuration where you build up some RCA plugs with various resistors across them to experiment with different loading on your cartridge, by placing additional resistance in parallel with your cartridge. The limitation here is that you can only achieve lower loading than you have.

If you do use resistors for either of these applications it is important to remember to use metal film or wirewound resistors for these applications and not simple carbon resistors, to minimize intermodulation distortion for a lower noise floor.

Hope this helps!

tateharmann
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Re: Y adapters to sum to mono...where to connect the ground?

Post by tateharmann » 14 Mar 2018 14:23

antennaguru wrote: Yes, the single ground wire goes from the chassis of the turntable and/or tonearm to the binding post on the phono stage, as it normally should - unless you find you get a ground loop with it connected and it sounds quieter disconnected.
Perfect thank you!
antennaguru wrote: WRT using additional resistors I am wondering what you are considering that for? There would be no need to do so unless your phono stage is being overdriven by your cartridge and you need to attenuate the signal to avoid clipping distortion in the phono stage, though that would seem unlikely. If that was the case you could use various Tee or Pi resistor configurations as attenuators.

Hope this helps!
I've seen a number of schematics that include resistors in them as you are basically shorting out the output. Maybe this is most important for higher output devices, though, like a 1/8'' smartphone headphone jack? I guess in those applications is mostly where I've seen resistors used.

Any rate - using my little summing device here has made vast improvements in the playback of a mono copy (a rather bad one) of Getz/Gilberto on Verve so I'm happy with it :)

antennaguru
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Re: Y adapters to sum to mono...where to connect the ground?

Post by antennaguru » 14 Mar 2018 14:59

Glad that using the back to back Y adapters is working for you! It really does Help when playing mono records, both in reducing surface noise and evening channel balance!

Back in the "golden" era when records were our primary quality music source the electronics manufacturers used to give us really useful features in our preamps such as a really good "Phono Stage", a "Mono Switch" to sum the channel balance for mono records, a "Subsonic Filter Switch" to calm down the woofers/subwoofers on warped records, and a "Balance Control" with a central detent (off position) to shift the central image when needed, which have one by one disappeared from many modern preamps because only some people use only some of them, some of the time - so now no one gets these sometimes very useful controls any of the time in the quest for minimizing cost/complexity and being competitive. No one argues these were all useful features when they existed and being defeatable they didn't hurt the sound. However, "Simple Defeatable Tone Controls" were also useful to touch up the frequency balance of certain recordings, but again another useful feature that got eliminated over time for the same reasons with little objection from us under the guise of simpler purer circuitry, ignoring that the defeat switch gave us that as well...

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Re: Y adapters to sum to mono...where to connect the ground?

Post by JDJX » 14 Mar 2018 16:06

I've seen a number of schematics that include resistors in them as you are basically shorting out the output. Maybe this is most important for higher output devices, though, like a 1/8'' smartphone headphone jack? I guess in those applications is mostly where I've seen resistors used.

Any rate - using my little summing device here has made vast improvements in the playback of a mono copy (a rather bad one) of Getz/Gilberto on Verve so I'm happy with.
Yes, resistors insure that any pre amp is "happy" with summing both channels.
Also, summing both channels does indeed make mono LPs sound better.:)

This is the resistive stereo to mono converter that I built...
strero to mono.jpg
(34.11 KiB) Downloaded 227 times
resmonoxx1.jpg
(215.89 KiB) Downloaded 217 times

tateharmann
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Re: Y adapters to sum to mono...where to connect the ground?

Post by tateharmann » 15 Mar 2018 02:22

antennaguru wrote:Glad that using the back to back Y adapters is working for you! It really does Help when playing mono records, both in reducing surface noise and evening channel balance!

Back in the "golden" era when records were our primary quality music source the electronics manufacturers used to give us really useful features in our preamps such as a really good "Phono Stage", a "Mono Switch" to sum the channel balance for mono records, a "Subsonic Filter Switch" to calm down the woofers/subwoofers on warped records, and a "Balance Control" with a central detent (off position) to shift the central image when needed, which have one by one disappeared from many modern preamps because only some people use only some of them, some of the time - so now no one gets these sometimes very useful controls any of the time in the quest for minimizing cost/complexity and being competitive. No one argues these were all useful features when they existed and being defeatable they didn't hurt the sound. However, "Simple Defeatable Tone Controls" were also useful to touch up the frequency balance of certain recordings, but again another useful feature that got eliminated over time for the same reasons with little objection from us under the guise of simpler purer circuitry, ignoring that the defeat switch gave us that as well...
Yea I agree completely there!

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Re: Y adapters to sum to mono...where to connect the ground?

Post by tateharmann » 15 Mar 2018 02:27

JDJX wrote: Yes, resistors insure that any pre amp is "happy" with summing both channels.
Also, summing both channels does indeed make mono LPs sound better.:)

This is the resistive stereo to mono converter that I built...
Oh yea! Yours was one that popped up when I was searching for this. My question on yours and others is that there doesn't seem to be consistency on the ohm rating of the resistors used so can I just use anything less than 1k or something? I imagine too big a resistor would kill the signal completely and too small wouldn't do much of anything?

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Re: Y adapters to sum to mono...where to connect the ground?

Post by JDJX » 15 Mar 2018 05:17

I can just say that 680r seems to be a good value.
It only restricts volume a negligible amount but, gives adequate resistance. :)

tateharmann
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Re: Y adapters to sum to mono...where to connect the ground?

Post by tateharmann » 15 Mar 2018 14:21

OK awesome thanks - some day I will have to build one of these :) Some day I also will just buy a mono cartridge haha...but until then..

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