[mca]

I am hearing a pretty loud hum coming from my pre. I can hear it from about a foot away. Any idea what is causing this or how to stop it? I have tried the pre plugged directly to an outlet and also into a Powervar unit with the same results.

[koiman]

Mine is dead quiet.. could it be 60 cycle hum?

[ted_b]

Any hum issues I've had while owning the SWL have been outside the pre, typically a ground loop with a subwoofer or amp.  I've stayed away from cheater plugs, but have used two-prong IEC cords on my amp before.  Check things like subwoofer cables, cable tv connections or source cables too close to power cords.

[AB]

If I read you correctly, the hum is coming from the SWL's transformer. Correct?

It's probably lamination rattle in the transformer.

Google Lamination Rattle or Lam Rattle and read all about it.

From the Plinius Web site...

"MECHANICAL NOISE: Some items of equipment can directly radiate a mechanical hum or buzz. This mechanical noise almost always originates from the device's power transformer. Place your ear close to each component of your system and listen. If you hear a hum or buzz coming from within your equipment, then the noise is mechanical. 'Lamination rattle' occurs in all transformers to some degree, related to the quality of the transformer and the quality of the line voltage. If the noise intensity varies depending on the time of day, sometimes even the time of month, then it is due to the quality of the AC supply voltage in your area. In this case you're at the mercy of your energy provider."

Most pple get relief by using a "Humbuster" type device. Its circuit removes the DC from your AC.

Occasionally lam rattle isn't caused by DC but by a poorly built transformer. It can be minimized then by adding a rubber gasket/cushion beneath the transformer or simply tightening the transformer's mounting bolt. Tightening can also make it worse. It just depends, I guess.

I have also heard hum "break in". The hum is there when new and as the unit gets cycled on and off over time, it just goes away.

[HumanMedia]

The hum from my SWL 9.0 is driving me crazy also.

*This isnt ground loops from the circuit, its the physical hum from the unit itself
*Exactly the same problem if direct into the wall or through a balancing transformer (no DC offset on line)
*Ive added lots of noise absorbing chassis dampening internally
*Its been back to Modwright who addded mass to the transformers and added further chassis dampening  to the lid and is about half as bad is it was, but I can still hear it from across the room, and it is audible in quiet music 
*Mine is a 240V unit on 50hz power, but it was built for this by Modwright (even so could this be my problem?) - Maybe not if others are getting it on 120V 60hz.
*Ive tried tightening and even loosening the main transformer bolt to no avail


If anyone finds a fix I would love to know.

[bambadoo]

What tubes (5687) are you using?
Some 5687 tubes are extremely microphonic, and the slightest vibration on the preamp will cause som noise.
If you are touching the volume knob, does the hum get worse?
And my experience is that 240v - 50hz units often creates more hum.
What kind of poweramps are you using? And are they close to the preamp?

Many questions, but I have a similar problem with a 5687 preamp myself. 240v-50hz
Will try some tube rollin soon.

Best Regards

[HumanMedia]

*Ive rolled some different tubes makes no difference.

*Volume knob makes no difference

*Power amps are CIAudio D-200s which are 2 meters away (SWL buzz the same even when interconnects are not plugged in)

*No other amps I have bought locally (240v 50hz) have ever had any audible hum, this one is loud

[bambadoo]

Are those "digital" og class D amps?
I have much more hum/noise when using my preamp with class D than my other class ab (jeff rowland)
With the Rowland I can set the gain to 26 or 32 db, and at 26 I hear almost no noise.
How sensitive are the speakers? I have 4 pairs 85db, 86 db, 90db and 93 db. With the two last the noise is quite bad with the class d poweramps. I can hear it from about 5 metres away.

[Gordy]

I doubt the D-100's are the problem, especially at 2 meters.  I have 2 unshielded (wooden chassis) UcD-400's within 18-24 inches of both sides of my MW pre and the pre is dead quiet!

[HumanMedia]

Yep they are Class D.  Note also that Dan himself uses CIAudio D-200s, so if there is any general incompatibility, it should have been caught by now.  SWL buzz remains exactly the same even when I unplug the poweramps completely and switch off all other equipment (I just tried it).

Listening more closely it seems as though there is a higher buzz and a lower buzz (primary and secondary transformers?)

The most annoying is the higher buzz, so I will revisit tightening the smaller transformers down this weekend.

I cant remember what the SWL transformers use for dampening under the bolts and between the transformer and the chassis, but many transformers use cheap hard rubber and Ive even seen some vinyl material, that really doesnt do that much.  When I look inside this weekend I will measure up and see if I can replace any of it with some of that Herbie grungebuster material (washers/gaskets etc) which Ive used it before and is fantastic for minimizing vibration (deadening it without resonating).

[modwright]

What you are hearing is mechanical noise originating from the choke in the power supply I believe.  We can either replace the choke or revise the power supply circuit.  Please contact us directly or the dealer that you purchased the unit from for service.

Thanks,

Dan Wright
President, ModWright Instruments Inc.

[cody_the_cat]

Hi,
I am new to this forum since I just received my SWL9.0se not more than 2 weeks ago.  Firstly, paired with my Bel Canto eVo2 gen II power amp and Jolida JD100 tube CDP the sound is near orgasmic (hope I can say that ).  Second, my preamp is dead quiet is terms of self noise.  However, I go have an audible hum from my speakers, buy only within two feet.  In no way does the hum detract from my listening experience but it would be nice to find the culprit.  Could this be microphonics from the tubes? Thanks.

[bambadoo]

It could be or a ground loop or some vibrations from the  mains transformer that the microphonic valves pick upp.
As stated earlier I do not have a SWL9.0se but have some experience with a 5687 preamp.
Is the mains transformer placed on some damping material of any kind?

Best Regards

[transam]

Here's a good one. Is your cable hooked up to your tv or cable box and you run a pair of rca to your preamp? Try unpluging the cable going to the tv or box. I had this problem because the electric co. and cable co. used the same hole to run wires in the house. I ran a wire from my cable splitter in the basement to copper pipe as a ground.Huge difference in sound!!!