Turntable Wiring Confusion

[Vdubguy99]

Good Evening Brothers and Sisters!

I recently acquired a couple turntables from a family member and while getting one of them ready noticed a nick in the RCA cables that appeared to be soldered into the back of the deck. I tested it out and it played fine but decided to replace the RCA wiring inside anyways. I bought the best RCA cable I could find at a local tech shop and immediately noticed the twisted pair inside was significantly smaller than the original. The original wiring on the Hitachi HT-40S looked almost like stranded lamp cord and it had no inner foil jacket for noise suppression at all. I got out my soldering equipment and went to town carefully connecting one wire at time. I ran continuity checks when I was finished to make sure I didn't have anything crossed and connected it up to my ONKYO TX-DS454 receiver to the Phono and ground connections to find unbearable hum. There was no hum when I tested it originally which leads me to believe I have chosen incorrectly for the type of cable I used. I am a little confused how the original lamp cord type wire was good enough and I installed something i thought would be better but it made it worse.

I was hoping somebody here could educate me on the correct type of wiring needed for this application and if it has been addressed already in another post, I sincerely apologize. I hope i can figure this out because the hum is terrible at any level past 30% volume. Is the wire I used too small? Is there a specific resistance or capacitance wire I should use?

Thank You everyone

 

[TLS Guy]

Good Evening Brothers and Sisters!

I recently acquired a couple turntables from a family member and while getting one of them ready noticed a nick in the RCA cables that appeared to be soldered into the back of the deck. I tested it out and it played fine but decided to replace the RCA wiring inside anyways. I bought the best RCA cable I could find at a local tech shop and immediately noticed the twisted pair inside was significantly smaller than the original. The original wiring on the Hitachi HT-40S looked almost like stranded lamp cord and it had no inner foil jacket for noise suppression at all. I got out my soldering equipment and went to town carefully connecting one wire at time. I ran continuity checks when I was finished to make sure I didn't have anything crossed and connected it up to my ONKYO TX-DS454 receiver to the Phono and ground connections to find unbearable hum. There was no hum when I tested it originally which leads me to believe I have chosen incorrectly for the type of cable I used. I am a little confused how the original lamp cord type wire was good enough and I installed something i thought would be better but it made it worse.

I was hoping somebody here could educate me on the correct type of wiring needed for this application and if it has been addressed already in another post, I sincerely apologize. I hope i can figure this out because the hum is terrible at any level past 30% volume. Is the wire I used too small? Is there a specific resistance or capacitance wire I should use?

Thank You everyone

It should be screened cable. I think someone else did something improper and got away with it.

How is/was the turntable chassis grounded?

You need to check for proper wiring right back from the cartridge. The screen are the grounds.

My guess is you have got lives and grounds mixed up.

Also it is best to not ground the turntable chassis through the cartridge cable screens, but ground the turntable chassis to the premp or receiver directly.

There may also be muting switches in the cartridge connection, since this is an auto return turntable. So you may need a service manual to look at the circuit.

Your problem though is definitely not your cable selection. You have made a mistake somehow.

 

[slipperybidness]

Good Evening Brothers and Sisters!

I recently acquired a couple turntables from a family member and while getting one of them ready noticed a nick in the RCA cables that appeared to be soldered into the back of the deck. I tested it out and it played fine but decided to replace the RCA wiring inside anyways. I bought the best RCA cable I could find at a local tech shop and immediately noticed the twisted pair inside was significantly smaller than the original. The original wiring on the Hitachi HT-40S looked almost like stranded lamp cord and it had no inner foil jacket for noise suppression at all. I got out my soldering equipment and went to town carefully connecting one wire at time. I ran continuity checks when I was finished to make sure I didn't have anything crossed and connected it up to my ONKYO TX-DS454 receiver to the Phono and ground connections to find unbearable hum. There was no hum when I tested it originally which leads me to believe I have chosen incorrectly for the type of cable I used. I am a little confused how the original lamp cord type wire was good enough and I installed something i thought would be better but it made it worse.

I was hoping somebody here could educate me on the correct type of wiring needed for this application and if it has been addressed already in another post, I sincerely apologize. I hope i can figure this out because the hum is terrible at any level past 30% volume. Is the wire I used too small? Is there a specific resistance or capacitance wire I should use?

Thank You everyone

Work with TLS and take his advice and he will get you set straight.

But, I wanted to add my 2 cents--Personally, if I were going through the trouble of replacing soldered RCA cables from a turntable, then I would choose to install RCA JACKS so that I could then use any RCA cables that I want.

Something along these lines:
https://www.parts-express.com/parts-express-chassis-mount-rca-jack-pair--091-1120

 

[Vdubguy99]

Thank you both for your advise. I will have another look at it tomorrow. I know there is a chassis ground that runs to the transformer and I will make sure that didn't get disconnected. I have also thought about the the RCA jacks but the plastic on the record deck is really flimsy. Not sure if that will work.

I will let you know what I find. Maybe i will take some pics of it.

Thanks again

 

[slipperybidness]

Thank you both for your advise. I will have another look at it tomorrow. I know there is a chassis ground that runs to the transformer and I will make sure that didn't get disconnected. I have also thought about the the RCA jacks but the plastic on the record deck is really flimsy. Not sure if that will work.

I will let you know what I find. Maybe i will take some pics of it.

Thanks again

Yeah, those RCA jacks were just a simple example, there are other types available. Or, you could always add some sort of re-informent plate, etc.

No biggie, I'm just saying if I'm going to that trouble, then I'm installing jacks.

 

[Swerd]

Work with TLS and take his advice and he will get you set straight.

Yes, I agree. TLS Guy would certainly know.

I also know for certain that I've never altered the cables on any turntable. The phrase "If it ain't broke, don't fix it" applies here.

But, I wanted to add my 2 cents--Personally, if I were going through the trouble of replacing soldered RCA cables from a turntable, then I would choose to install RCA JACKS so that I could then use any RCA cables that I want.

There is a good reason why turntable manufacturers have avoided installing RCA jacks, instead of the hardwired cables 3 to 4 feet in length. They don't want owners to use longer cables.

A typical moving magnet pick-up cartridge generates a low voltage signal, roughly 2.5 to 5 mV. (Moving coil pick-ups generate even lower voltages.) These weak signals are prone to picking up noise (RFI or EMI) or loosing high frequency audio signals via cable capacitance. The longer these cables are, the worse these problems can be.

Only recently RCA jacks have appeared in new turntables, but only in those that have built-in phono stage preamps. These preamps boost those low voltage signals to about 150 mV, similar to the analog audio line level signals from other sound source devices other than turntables. At these voltage levels, the audio signal is much less prone to interference from RFI/EMI or loss via capacitance, at much longer cable lengths.

 

[slipperybidness]

Yes, I agree. TLS Guy would certainly know.

I also know for certain that I've never altered the cables on any turntable. The phrase "If it ain't broke, don't fix it" applies here.
There is a good reason why turntable manufacturers have avoided installing RCA jacks, instead of the hardwired cables 3 to 4 feet in length. They don't want owners to use longer cables.

A typical moving magnet pick-up cartridge generates a low voltage signal, roughly 2.5 to 5 mV. (Moving coil pick-ups generate even lower voltages.) These weak signals are prone to picking up noise (RFI or EMI) or loosing high frequency audio signals via cable capacitance. The longer these cables are, the worse these problems can be.

Only recently RCA jacks have appeared in new turntables, but only in those that have built-in phono stage preamps. These preamps boost those low voltage signals to about 150 mV, similar to the analog audio line level signals from other sound source devices other than turntables. At these voltage levels, the audio signal is much less prone to interference from RFI/EMI or loss via capacitance, at much longer cable lengths.

Yup, I know this, as long as you have this knowledge, go for the jacks. In general, I would hope that people that have the skill set to install the jacks also have the sense to know what cables and what length to use, but of course that may not be the case.

That's one of the things that I don't like about the SL1210--the integrated RCA cables! RCA jacks are just a cleaner look, and give you options.

 

[Swerd]

Yup, I know this, as long as you have this knowledge, go for the jacks.

I had hoped you understood this, but it is the reason why turntable manufacturers avoid doing that.

It also indirectly tells us what manufacturers believe the answer is to the audiophile questions that never go away:

"If I change the existing audio cables for something of better quality, will the sound improve? Why don't manufacturers already do that?"​

The answer is NO (of course). Even when the audio signal is most vulnerable, at very low voltage, shielded cable of what looks like pedestrian quality is good enough. Going to cables constructed more expensively than 'good enough' does not result in improved sound quality.