Be careful with that SUT Eugene

[worrasf]

Following a general tidy up and rearrangement of my equipment rack I noticed that whenever I operated (touched) the right channel volume knob (not the left) on the Croft 25R I was greeted by a hum through the speakers regardless of whether line or phono selected. Most curious. :rolleyes: After much head scratching I finally tracked this down to the Dynavector SUT having been placed on top of the 25R. To be fair I had thought about this beforehand but deemed that as the SUT had no power supply and the 25R no mains voltage there should be no interaction :scratch:

Having moved the SUT to it's own place on a shelf behind the 25R no more hum.

Better still, having moved it I noticed a definite improvement in stereo imaging and focus so I can only assume that there was some electrical interaction going on after all.

Steve

[synsei]

I may be talking a load of 'plums' here but SUT's contain transformers which I would think produce an electromagnetic field so it is possible that it was this which was affecting the Croft through induction, but then again I also believe we are being visited by little green men from the planet Zarg so what do I know... :lol:

[worrasf]

but then again I also believe we are being visited by little green men from the planet Zarg so what do I know... :lol:

What a daftee - everyone knows they are blue ..........:doh:

[synsei]

What a daftee - everyone knows they are blue ..........:doh:

Smurfs? :D

[PaulStewart]

What a daftee - everyone knows they are blue ..........:doh:

And they're from Barzoom :lol:

[Marco]

Hi Steve,


Following a general tidy up and rearrangement of my equipment rack I noticed that whenever I operated (touched) the right channel volume knob (not the left) on the Croft 25R I was greeted by a hum through the speakers regardless of whether line or phono selected. Most curious. :rolleyes: After much head scratching I finally tracked this down to the Dynavector SUT having been placed on top of the 25R.

I presume that you're using a dedicated earth for your SUT? If not, that's largely where the hum will be coming from. All SUTs must be earthed.

You need to run a piece of wire from the earth terminal on the back of the SUT to somewhere like underneath one of the screws on the casing of the Croft (simply wrap the bare wire around the stem of the screw, and tighten both the screw and wire up against the casing). That will provide an excellent earth contact.

Furthermore, SUTs should always be located as far away as possible from any power supply transformers. Attending to both of these factors will eliminate any hum and also improve the sound significantly! :)

Marco.

[worrasf]

Yes Marco SUT is earthed to preamp via its earth terminal I also found I was still getting some residual hum until I ran an earth lead from each of the phono plugs on the arm cable (soldered to the plug case) to the preamp this totally eliminated all noise until the topic of this thread surfaced but now all is dark and quiet :-)

Sent from my HTC One using Tapatalk

[Marco]

Excellent.

Sometimes, however, if you earth the SUT to the same terminal on the preamp, as the earth lead from the tonearm cable, you can create an earth loop, which is why I earth my SUT to the casing and the tonearm cable to the terminal post...

I find results are better that way :)

Marco.

[worrasf]

I'll give it try

Sent from my HTC One using Tapatalk

[Marco]

See what you think, dude. It's very much a system-dependent thing! :)

Marco.