Technics SL1500C hum through external phono??

[Entrigo]

one ground/earth = no hum
two ground/earth - hums with multiple earth loops


View attachment 8415

View attachment 8414




Ground Loop Hum

A ground loop hum occurs when there’s a difference in electrical potential (voltage) between different components in your audio setup. This difference can create a loop, leading to unwanted electrical interference manifesting as a low-frequency hum or buzz. Turntables, like many audio devices, are susceptible to ground loop hum.

Multiple Ground Paths: If your turntable and other audio components are plugged into separate power outlets or grounded differently, ground loop hum can occur

OK but how do you get out of it?

And could it be the preamp causing the issue? The turntable plugged into line in using its preamp is silent. Plugged into the Rega amp phono using line out is silent. But plugged into the Moon preamp with TT line out and into the Rega line in - hum...

 

[daytona600]

OK but how do you get out of it?

Take the technics back your dealer for advice or can you try another another phono stage or Turntable

 

[Entrigo]

OK but how do you get out of it?

Take the technics back your dealer for advice or can you try another another phono stage or Turntable

No need. Got a Rega Elex-R yesterday and as said above, the Technics through the Rega phono in is silent ... Save of course the obvious hiss.

So it wasn't the Technics after all. Returned the Moon today and right now really enjoying some low level Beethoven, after having played the White Album earlier on today at significantly higher volume (before playing some CDs and streaming - just to check the amp works as expected).

Now can't wait for tomorrow morning to blast some proper punky / rocky stuff.

 

[daytona600]

Glad you sorted out the hum

 

[Entrigo]

Glad you sorted out the hum

Thank you. I did for a few minutes consider digging a little deeper into the issue thanks to the very helpful diagram you shared. Out of principle, as I really wanted to get to the bottom of it.

But I honestly spent so many hours in the last couple of weeks on this that I just couldn't... So I packed up the Moon and posted it without looking back!

 

[Al ears]

OK but how do you get out of it?

And could it be the preamp causing the issue? The turntable plugged into line in using its preamp is silent. Plugged into the Rega amp phono using line out is silent. But plugged into the Moon preamp with TT line out and into the Rega line in - hum...

If you plug into a phono preamp then you should not be using line out on the turntable.
Is this actually what you are doing?
I am confused by this explanation of yours.

 

[Entrigo]

If you plug into a phono preamp then you should not be using line out on the turntable.
Is this actually what you are doing?
I am confused by this explanation of yours.

Sorry no, I got myself confused with all the various permutations.

It was of course TT line out to amp line in using the TT preamp and TT phono out to phono in of either preamp or amp to use an external phono...

 

[Entrigo]

Now I was reading that the Elex-R has 220pF capacitance and this is to keep hum at bay.

On the Moon I was using either 0 or 100pF to tty and remain within the 100-200pF recommended for the AT carts.

Could that have been the issue?

 

[Entrigo]

Now I was reading that the Elex-R has 220pF capacitance and this is to keep hum at bay.

On the Moon I was using either 0 or 100pF to tty and remain within the 100-200pF recommended for the AT carts.

Could that have been the issue?

P.s. I am probably at over 300 now but can't really hear this much increase in brightness.

So if it is about lower capacitance causing the hum, I would need to be very careful about buying an external phono and just be happy with my set-up...

 

[nopiano]

Now I was reading that the Elex-R has 220pF capacitance and this is to keep hum at bay.

On the Moon I was using either 0 or 100pF to tty and remain within the 100-200pF recommended for the AT carts.

Could that have been the issue?

I have never heard of capacitance in this context affecting hum. All it does is change the HF response of the cartridge.

See the graph in the second post here…

Quick Question About Preamp Capacitance

My preamp's capacitance can be set at 100pf or 200pf. I'm not sure how that relates to my phono cartridge or system? Any info would be appreciated.

forums.stevehoffman.tv

 

[Al ears]

I have never heard of capacitance in this context affecting hum. All it does is change the HF response of the cartridge.

See the graph in the second post here…

Quick Question About Preamp Capacitance

My preamp's capacitance can be set at 100pf or 200pf. I'm not sure how that relates to my phono cartridge or system? Any info would be appreciated.

forums.stevehoffman.tv

Quite so.

 

[daytona600]

Capacitance in phono stage + phono cables add together for total in Pf 100-400
Adjust loading on your phono stage to suit MM cartridge

Incorrect loading too much or too little can make HF sound brittle to Soft
MI moving iron cartridges - Grado , Soundsmith , Nagaoka are not affected at all by Capacitance

 

[Rui]

In this situation that i refer the turntable from Po-Ject that the non existance of a ground wire created a hum, of corse , like many other times in the past non wired ground turntables always had problems and that might be related with the standart electrical system provided in each country, i think, as after a ground wire installed none as this last Pro-Ject turntable had the hum efect of double ground wired , but the next model of the same design came with it, but all is good now, i also two years ago in December aquired a Rega turntable and i´m happy with it no noise under, maybe the quality of the building is related with that, also thankfull for all knowledge i wasn´t aware of before reading here in the coment section all information given`, thank to everyone that contributed with aditional information here in the forum.

 

[Entrigo]

Well. Hopefully final update.. Just got a Pro-ject S3B and it also sounds silent, just like the phono stage of my Elex-R.

So it looks like it was really a freaky coincidence of two faulty ex-demo units (the Rega Fono and the Simaudio Moon).

 

[Fandango Andy]

Hello wise forum-dwellers!

Going mad and would really really appreciate some expert tech advice!

Posted a week or so ago about this issue, thinking the problem was either with my amp or the phono stage but now I think it might be the turntable.

The lowdown:
Over the last couple of months, I ran my Technic TT through different phono options. All of this bar using the Technics own preamp produce a hum. This at full volume is roughly 40dB. As in, measuring around 75dB in total, with a background noise level of 35dB - measured in front of the speakers with a meter app on my phone (it's not scientific, I am a heathen etc so please bear with me).

Combinations tried follows:

• TT through Rega Fono MM into line in of my Marantz PM7200 amp - hum
• TT through Simaudio Moon 110LP into line in of Marantz - hum
• TT through Marantz phono in - hum (though quieter - but then the Marantz sounds MUCH quieter than any of the two external phono - whatever the reason, at the same volume knob position/distance/record playing, it reads nearly 30dB quieter than the Moon)
• TT through Moon into line in of a brand new Fosi mini amp - hum
• TT using own preamp into line in of Marantz - SILENT!

I also tried:
switching off all electrics, double grounding (extra metal wire from ground of Moon to ground pin of next electrical socket), moving away from amp, sitting on foam isolation pads, plugging Moon into extension from next door's socket, swapping RCAs around. Nothing. Also no hum from any of the other channels of the amp.

So:

1. Could it be the turntable phono out signal path or connections that is the problem?
2. Or some other issue in the connection between the TT and the external phonos?
3. Has anyone with a Technics SL1500C which has a similar issue?

I appreciate a proper answer is hard just on paper, but would really appreciate some insights before I take my 'baby' to my local shop - as they have a 4 weeks lead time - and I would rather avoid being without for 4 weeks and them saying "nothing wrong with this"...

Thanks!

Other than the "double grounding" you don't mention grounding. If you haven't already try this:

Unplug everything in the room. To ensure no interference. Plug the amp, preamp and turntable into the same extention lead. Ground the TT to the main amp.

If it works turn everything else in the room on one by one to see if the hum comes back.