Hum from the phonoamp?

by **leifhellmusic** » 16 Jun 2006 09:23

Hi there vinyl world!

The other day when I Listened to some vinyls at a rather high volume (higher than usual) I noticed a humming sound between tracks and during more silent parts of music. In the rig I have the following gear:

Primare I21 integrated amp (new)
Sugden Optima phonoamp
Thorens TD 320 with TN2000 PSU equipped with TP90 and a Benz Micro Ace
Sony XB930 CD
Carlsson OA14 speakers
interconnects and power cords of good quality

I lifted the tonearm off track and increased the volume pot to a maximum and the humming sound was rather high (like coming from a transformer somewhere). Then I connected the CD-player (without record) and again increased the volume pot to a maximum. The humming was now clearly lower. Is it correct to deduce that the humming might be related to the phonoamp? I have tried to find some data on the Sugden phonoamp but I have not been very succesful. As I have owned some Sugden gear earlier I know they make decent amps.

I would appreciate som advice from the world and especially from those with experience of the Sugden phonoamp. Would it be reasonable to send it to someone to check the possibilities of installing some kind of filter (I am not a technician myself but I have a very good contact who have helped me before)? Or should I look for a better phono amp? The Lehmann Black box has received very good reviews and has a reasonable price.

All reactions to my questions are appreciated.

leifhellmusic

by **seppstefano** » 16 Jun 2006 09:37

Hi,
I guess the problem might be generally caused by e.g. some DC on mains, and perceived more while listening to vinyls as the phono stage has a high gain, surely higher than gains used for line.

It happens I'm experiencing a similar issue, too, and am going to arrange a DC blocker for my incoming mains on L line.

I got it while wiring some insulation trafo between my (horror) digital gear and mains, in order to reduce digital pollution of mains.

I've been suggested to try this:
2 diodes in antiparallel, and 2 electrolytic caps in antiparallel over them (6V are sufficvient, 1000 uF or 500 will do).

You might further bypass them with smaller caps and (perhaps) split the caps to reduce inductancy.

Hope that helps,

Stefano

by **leifhellmusic** » 16 Jun 2006 10:37

Thanks for answering Stefano!

Does what you suggest mean changes in the phonoamp or in the amp? As I don´t have the technical knowledge I´m wondering about "antiparallel". Do you mean connected in serie? A simple scheme would be appreciated.

Leif(hellmusic)

by **seppstefano** » 16 Jun 2006 11:11

Ciao Leif,
this means no change in phono and/or pre.

First of all, did you check to have only one device grounded? If you have more than one grounded you might have some ground loops "humming".

To remove grounding, you can insulate/disconnect the central pin of your plug(s) (either on IEC or mains).

For antiparallel I mean that you will connect the L incoming from mains to both one diode and the other, but they are oriented with different "verses".

L from mains --->|---- (paralleled with caps). L to HiFi system
----|<----

N---------------------------------------------------- N to HiFi system
G---------------------------------------------------- G to HiFi system

HTH,

Stefano

by **leifhellmusic** » 16 Jun 2006 12:03

Ciao Stefano!

Thanks again for your concern about my humming problems. As a matter of fact my villa has no grounded mains outlets (except from kitchen, bathrooms, garage and external outlets). In spite of this I use grounded plugs for my stereo gear (three connector cords and 3-poled plugs). The ground interconnect from the TT is connected to ground at the phonoamp.

I don´t now whether this might be a source for the humming. Earlier at another forum (TNT?) I put a similar question on grounding problems and was adviced to make a dedicated outlet for the stereo by using a separate ground connector attached to a copper spear in the soil in the garden. However this is not accepted in Sweden which have rather strict regulations on how to handle electricity in houses and flats.

On the net I found a device (Stop the humming filter) at

http://www.lcaudio.com/index.php?page=12

Would this be somethong to use? I happen to have such a filter at home but I have never used it.

The diodes and caps you suggest, are they put in some kind of box?

Leif(hellmusic)

by **seppstefano** » 16 Jun 2006 12:51

Ciao Leif,

leifhellmusic wrote:Ciao Stefano!

Thanks again for your concern about my humming problems. As a matter of fact my villa has no grounded mains outlets (except from kitchen, bathrooms, garage and external outlets). In spite of this I use grounded plugs for my stereo gear (three connector cords and 3-poled plugs). The ground interconnect from the TT is connected to ground at the phonoamp.

So, as far as I understand the Ground outlet for your system is completely floating... I think there will be no chance of ground loops.

leifhellmusic wrote:I don´t now whether this might be a source for the humming. Earlier at another forum (TNT?) I put a similar question on grounding problems and was adviced to make a dedicated outlet for the stereo by using a separate ground connector attached to a copper spear in the soil in the garden. However this is not accepted in Sweden which have rather strict regulations on how to handle electricity in houses and flats.

TNT... here's where we already met! The separate ground connector would be the best solution, anyway, to insulate from noises generated on ground lines by devices and by other signalling activities.

leifhellmusic wrote:On the net I found a device (Stop the humming filter) at

http://www.lcaudio.com/index.php?page=12

Would this be somethong to use? I happen to have such a filter at home but I have never used it.

As far as I can understand, this filter does something different. It aims at reducing RF polluting the mains (both generated by your system devices and incoming from mains): that's why it has coils, VDR to protect from overvoltages and X-Y caps. A good thing for your system (even if I am not so convinced of coils in the mains).

But the filters cares nothing if (but we are not yet sure) you have a DC component on incoming mains. The 2 diodes filters it at max 0,6V. The caps smoothens harmonics generated by this "clipping" operation.

leifhellmusic wrote:The diodes and caps you suggest, are they put in some kind of box?
Leif(hellmusic)

Well, being devices wired to mains, it would be better to keep them away from anybody/anything who might be harmed and/r create shorts.

If you have even a cheap multimeter you might measure DC voltage by inserting the probes in a mains receptacle. Beware: take care not to touch the metallic part of probes while measuring, only the insulated (typically red/black) plastic parts!!!!

Stefano

by **seppstefano** » 16 Jun 2006 12:56

Leif,
i beg your pardon, I didn't scroll the page...

Do definitely try the DC blocking filter...

Sorry for misunderstanding, I read only the first mains filter decsription,

Stefano

by **leifhellmusic** » 16 Jun 2006 16:07

Stefano!

Thanks a lot for your extensive answer. I will try the DC-filter from LC Audio. And I will report to the forum whether it´s a failure or success.

Leif(hellmusic)

by **leifhellmusic** » 16 Jun 2006 16:11

By the way, anyone on the forum who has experiences of my phono amp (Sugden Optima)?

leifhellmusic

by **leifhellmusic** » 17 Jun 2006 18:25

seppstefano wrote:Leif,
I beg your pardon, I didn't scroll the page... Do definitely try the DC blocking filter...
Sorry for misunderstanding, I read only the first mains filter decsription,
Stefano

Ciao Stefano,

To day I installed the DC blocking filter from LC-audio .

Unfortunately didn´t the hum disappear. It´s still there but I (might be wrong) it had a positive effect on the higher frequences which I perceived as more open. Anyway I´ll try to work on the problem and test new solutions.

by **seppstefano** » 19 Jun 2006 08:55

Ciao Leif,
you might try the antiparallel diodes + caps trick. I'm arranging it for my humming noise and will report back for next monday (I hope to manage it in the weekend),

Stefano

by **bastlnut** » 19 Jun 2006 09:26

hallo,

this could be some RF interference. look to see if there is a flourescent light, or a halogen lamp in the same power circuit as the stereo. also look that the cables are schielded and not close to any power cords.

is the Thorens correctly grounded? does it have a separate ground cable? have you replaced the original signal cable on the Thorens?
which Benz Ace do you have? low, middle, or high output?

regards,
bastlnut

by **seppstefano** » 19 Jun 2006 10:18

bastlnut wrote:hallo,

this could be some RF interference. look to see if there is a flourescent light, or a halogen lamp in the same power circuit as the stereo.

...indeed I guilty omitted this thing!

I still remember the forward leap as soon as I hard disconnected the dimmer powering the IKEA lamp.

Stefano

by **leifhellmusic** » 19 Jun 2006 10:50

bastlnut wrote:hallo,

this could be some RF interference. look to see if there is a flourescent light, or a halogen lamp in the same power circuit as the stereo. also look that the cables are schielded and not close to any power cords.

is the Thorens correctly grounded? does it have a separate ground cable? have you replaced the original signal cable on the Thorens?
which Benz Ace do you have? low, middle, or high output?

regards,
bastlnut

Hi bastlnut,

I´ve been in contact with you before and is one of those who have enjoyed your appearance at the Forum. Congrats for the 1000 posts!

Yes, the Thoren is correctlys grounded to the phonoamp with a separate ground cable. The original signal cable from the TT is replaced by a Van den Hul cable by the dealer and attached to good quality phono plugs. The Benz is a low output type.

I checked the gear using the same wall outlet as the other hifi gear. There is a halogen lamp connected to the same outlet but it is a 240 V halogen bulb so there is no transformer connected. Furthermore I tested to disconnect this lamp without any improvements. I hav also tried to move the signal cable from the TT as far away as possible from power cable. No change.

Regards

leifhellmusic