Phono Stage noise on my amp

excollier

excollier

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Tricky question here.
I am using gear I bought new back in 1980. The amplifier is a Panasonic SU-2800.
My problem is noise on it's phono stage, like a buzzing along with a regular "ticking" sound.
I have an Aiwa turntable which also has a built in switchable phono stage, but it was switched off as the amp has it's own phono stage. This noise has been there ever since I replaced the original Panasonic turntable that died a few years ago. This noise is very noticeable and gets louder after an lp has been played.
Last weekend I bought a Rega Planar 1 turntable (I have been promising myself a quality turntable for ages). This also produces the noise but not as loud.
To try to run a check, I plugged the Aiwa tt into a spare line input and switched on it's phono stage - there is the noise again, via a different input ( all other inputs are normally noise free) so I'm guessing - no hoping - that this noise is down to a noisy mains supply and that phono stages are sensitive to it and pick it up. No other inputs or peripherals produce this noise.
One other thing, if I touch the pivot joint at the end of the tonearm on the Rega the noise gets louder until I remove my finger, even with the turntable powered off.
I have tried other power outlets too, but no difference, and the mains leads are away from any rca/phono leads.
Any thoughts and tips on this would be helpful.

With the turntable unplugged from the amp inputs the noise changes, more of a very quiet "white noise" than a buzzing, and no "ticking". Perhaps a grounding issue as both turntables have no ground wire, where the original Panasonic tt did have one and was noise free.
 
Analoguesat

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@Vipersan might have some ideas

Static build up maybe though?
 
Vipersan

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Can't say I have any ideas without having access to the equipment ..
Having said that ..
IF the amp is producing any noise at all with no inputs connected 'white'..'ticking' or otherwise ...and is on BOTH channels ...then I would suspect inadequate decoupling in the amps internal power supply ..
IF the noise is single channel Left or Right Specific ...then one has to be suspecting breakdown of one or more components within that channel preamp/phono amp ...and only really analysis with a 'scope probing along the chain would identify the source ..
Since the Turntable has a built in Magnetic Cartridge Pre amp ...why not ignore the amps phono input ...and use one of the main amps aux inputs ..
IE let the turntable act as pre- pre amp ...thus delivering a clean 200 ..mv-ish signal to the amp via a different route..
Otherwise ..I suspect you will need a Technician with suitable gear to fault find..
best of luck ..
VS
 
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excollier

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Thanks guys, others have pointed to the method of earthing the turntable - Rega use one of the phono input leads to achieve this, and the fix seems to be as below

REGA 250 300 Tonearm modification humm-free remove signal ground

also I did connect my older turntable, complete with built in phono stage, to a spare line level input pair on the same amp and the same noise is present there too. Both turntables lack a dedicated earth lead to connect to the amp's earth point.
The original Panasonic turntable had the dedicated earth and was noiseless.

All other inputs are noise free (tuner, casette deck and cd on the aux input and the spare tape input I used to test with) until a turntable is connected.

I am trying to move to the Rega, but it has no phono stage built in, and the Aiwa with the inbuilt phono stage is far more noisy.
 
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jeallen01

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May I suggest that the problem could be the "dreaded" and "infamous" "hum loop!

That often happens (been there!) when the AV receiver and all the connected units (CD player, Skybox, etc., etc.) are all "Class II (yes "II", not "2") Double-Insulated units that don't need, and don't have, a connection to the mains supply earth conductor.

I "solved" this issue by connecting a conductor from the earth pin of a 13A plug inserted into one of the mains wall sockets to the AV receiver chassis, and then linking the chassis' of all the other units, including the t/t, to that - doing this creates an "equipotential" situation between the chassis' of all those units, which eliminates the potential (voltage) differences between the various units in the system.

Try that and see if it works.

Edited: Sorry, missed the intervening posts but they, sort of, relate the same issue/solution.
 
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Channel Hopper

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Before you start dismantling/cutting stuff, have you tried connecting the audio equipment on a different mains circuit ?
 
excollier

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Yes, I have ^^
 
Terryl

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I think it's a grounding issue, the shielding on audio leads are not that good of a conductor compared to a direct copper wire (insulated) from the turn table chassis to the amp chassis.

Ground loop maybe, but with both units in the same AC supply line there should not be a ground loop problem.

The input pre-amp stage on the phono inputs are very pron to picking up AC buzz or other noise from anything, even the mechanical noise from tone arms, you could have a possible mismatch in the impedance on the input to the pre-amp on the main amplifier, a line input isolator could help with this.

You could try one of these hummers.
Code:
http://www.instruments4music.co.uk/di_boxes__isolators/omnitronic_stereo_phono_line_isolator/24884_p.html
 
excollier

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Thanks for your thoughts on this.
Where would that item go? Between the turntable and phono inputs?
I spoke to the main distributor for Rega in Northern Ireland, the owner of Lyric Hi-Fi in Belfast. He is confused with this and we went through various ways of grounding the turntable that you would think might cure the problem but to no avail.
1.Tried connecting the outer part of the rca plug that carries the ground to the amp, directly to the earth connector on the amp - no good. 2.Connecting a wire from the tone arm to the amp's earth point - no good.
3.Earthing the amp's earth point to the mains earth pin on the power supply plug - no good.
4.Combination of 1 & 3 above - no good

strangely if I pull out the left channel rca plug from the amp, the one that carries the earth connection, the noise gets louder, but if I then connect the earth wire from this disconnected rca to the amps earth point - no noise, gone!! Plug back in and noise is back.

This is a real pain and points ever more towards a new amp :(
 
excollier

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^^ Yes it is
 
Terryl

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The isolator would go between the amp and phonograph.
 
excollier

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^^ thanks, I'll add it to my list of possible cures
 
Terryl

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You are probably looking at an impedance mismatch as the new turn table's output may be a bit different the the old one's.

Had many problems like this when revamping a stations console with new hardware, in some rare cases the old RCA cables were at fault, replacing them with new or a better grade worked things out.

Were is the turn table located? How close to the amp? Is it on a solid surface? In some rare cases the turn table's cartridge (magnetic) was directly picking up vibrations from the amps AC supply transformer, this thru the glass shelf they both were sitting on, better rubber isolation footings were used and funny noise things disappeared.

Another case was that the turn table was sitting above the amp, it was directly picking up the AC from the amps power supply, moving it a bit further away helped.

You said that this was a new turn table from Rega, have you asked them about what may be going on with this noise?

Another possibility is that the magnetic cartridge your using is not shielded and is directly picking up the hum from an outside source.

One last thing, does your amp have any type of input switching for different phono cartridge's? some do some don't.
 
A

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Out of interest what cartridge has it got fitted? And have you checked the 4 wires of the back?
 
excollier

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Rega Carbon cartridge - all good connections, and the same problem is produced by another turntable, via a different input, so this is why I tend to suspect the amp being the culprit - 36 years old. Poor grounding somewhere, as only turntables are noisy on it.

Hmm -
24v synchronous motor
The first entry level Rega turntable to use a 24v, synchronous AC motor with a new motor PCB and aluminium pulley offering low noise and better speed stability.

it must be a transformer that plugs into the wall and not a psu as such



http://www.rega.co.uk/planar-1.html
 
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A

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My project essential had an 18v motor, and some records would show it up, it's packed up on me now.

So I am running an cheap deck, but with an upgrade cartridge shure m44-7 at the moment.

But it sounds like you might need a new amp.
 
excollier

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My project essential had an 18v motor, and some records would show it up, it's packed up on me now.

So I am running an cheap deck, but with an upgrade cartridge shure m44-7 at the moment.

But it sounds like you might need a new amp.
Yeah, I think so too - although my efforts at grounding have taken the noise level down a little, so I'll have to live with it for a year until I can justify a new amp after spending on the turntable.
that's life I guess.
 
A

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I use a Maverick audio D1+ dac pre-amp, I have had the tube rolled to GE5670W the whole unit cost me £179

They also make tube hybrid amps, not tried one of them so don't know what they are like.


And I have upgraded the Dac chips to the burr-browns.

And I have changed the mode of the unit to just Dac, and not pre-amp/Dac

My record deck is plugged in to a project tube amp, in to the analogue in on the Maverick.

And that's connected to my quad elite pre-amp.

And I see the quad elite pre-amp and mono blocks on the bay for reasonable money.
 
Analoguesat

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FWIW we get some awful hums on the amp I have in the hall when lousy cheap Chinese laptop power supplies are connected to their laptops when the amp is on.

I need to redo the entire system from scratch seeing as it was put in 8 or 9 years ago at zero cost using salvaged kit picked up from various cupboards!

Have you tried ferrite rings on the transformer?
 
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