Hello and a first question.

[m_u]

Hi all,
I've been reading ASR for over a year now. Great topics, measures and suggestions, now my audiophile friends hate me haha.

The idea to register came yesterday because I found a weird behavior with my setup.
Speaking of wich.

Martin Logan motion 40 speakers, DEQX hp-3 preamp, MarchAudio p252 amp, Acoustic signature wow turntable and arcam rphono phono preamp.
Everything was piled on top of each other - deqx at the bottom, MarchAudio p252 amp on top of deqx, Rphono preamp on top of an amp.
Yesterday I noticed a low frequency switching noise out of the speakers. I was able to hear it if my ear was relatively close to the speaker. When I moved Rphono preamp away about 40cm left of the top of the amp - the noise was gone.
It is definitely not deqx as I tried moving rphone closer to deqx and even put it on top of the left side of the deqx (where it has a toroidal transformer) and the swithing noise was not there. Noise became stronger only if I moved rphono closer to MarchAudio p252 amp

1st photo - how it was
2nd photo - how it's now

Can this somehow be fixed or it's a known problem of p252 modules (because if it really is that it's not good)?

P.s. sorry for the photo quality.

 

[RayDunzl]

Phono preamps have a lot of gain (amplification) of very small signals.

Typically 40dB for MM and 60dB for MC cartridges.

40dB = 100x, and 60dB = 1000x the input signal.

It shouldn't be placed where it or its wiring could pick up noise from other devices or wiring.

Just move the phono pre to the quieter location.

 

[m_u]

Just move the phono pre to the quieter location.

I had that explanation in my mind that it's probably picks up switching noise from a switching power supply and amplifies it.

 

[March Audio]

I had that explanation in my mind that it's probably picks up switching noise from a switching power supply and amplifies it.

Exactly as Ray says. Its not an unusual circumstance with a phono section being placed close to another item (transformer) and you need to keep them physically separated.

One question, is the DEQX RCA or XLR output?

 

[Blumlein 88]

I know I'm just piling on. But these other guys have told you exactly right. Welcome to the forum m_u.

 

[RayDunzl]

I had that explanation in my mind that it's probably picks up switching noise from a switching power supply and amplifies it.

My preamp sits on top of and the amplifiers on either side of this monstrosity:

I have measurable 60hz and harmonics, but it isn't audible at full volume, so, I haven't worried about it.

Besides, as a pre-millenial, I still like the look of the bottom shelf of the rack - the, uh, power station.

A big heavy 45x16x11 inch lump of antique iron.

 

[m_u]

Well, currently it's 15cm away from deqx and 37 cm away from p252. Can't hear any noise with my ear almost touches the speaker.

Exactly as Ray says. Its not an unusual circumstance with a phono section being placed close to another item (transformer) and you need to keep them physically separated.

One question, is the DEQX RCA or XLR output?

RCA unfortunately

 

[m_u]

My preamp sits on top of and the amplifiers on either side of this monstrosity

I think that if your amps have linear power supplies you will not hear anything as it's a switching power supply noise (like something is switching something with a constant amplitude)

 

[March Audio]

Well, currently it's 15cm away from deqx and 37 cm away from p252. Can't hear any noise with my ear almost touches the speaker.

RCA unfortunately

RCA isnt a problem so long as the cable is wired correctly. Is it one of our adaptor cables or something else?

 

[m_u]

RCA isnt a problem so long as the cable is wired correctly. Is it one of our adaptor cables or something else?

You wired an rca to xlr cable so I presume it is lol

 

[March Audio]

I think that if your amps have linear power supplies you will not hear anything as it's a switching power supply noise (like something is switching something with a constant amplitude)

Im afraid this isnt the case. The transformers in linear power supplies also emit magnetic fields (50/60Hz hum) which can be picked up by other components in close proximity.

 

[m_u]

Im afraid this isnt the case. The transformers in linear power supplies also emit magnetic fields which can be picked up by other components in close proximity.

Yes, but the sound was not like a constant low level noise or constant hum, it was like a fast clicks or like a trigger double kick drum around 180pbm with 16th notes

 

[March Audio]

Yes, but the sound was not like a constant low level noise, it was like a fast clicks or like a trigger double kick drum around 180pbm with 16th notes

Sure , I understand , just trying to explain that the fundamental issue is not something exclusive to SMPS although the resultant noise may be different in nature.

 

[m_u]

magnetic field noises are everywhere and I know how they sounds. I remember how I could tell if somone was watching tv at their house being myself of the street, because I could hear high frequency hum from crt tvs