Phono preamp location on rack - Does it matter?

[formdissolve]

A lot of manufacturer manuals of phono pre's I've read state to keep the preamp away from power supplies and other devices. Is this because of some EMI issue? My current pre is about 6 inches from power supplies (switch mode style) and a tape deck and I haven't heard any hum or anything. Does it actually matter?

 

[radix]

A lot of manufacturer manuals of phono pre's I've read state to keep the preamp away from power supplies and other devices. Is this because of some EMI issue? My current pre is about 6 inches from power supplies (switch mode style) and a tape deck and I haven't heard any hum or anything. Does it actually matter?

I would believe it's EMI concern, or their lawyer made them put it in there. MC, especially, is a high gain stage. The phono cable, preamp DC power cable (if external power supply) and preamp itself could pickup hum. If you are not hearing any hum, then you're good to go! Don't fix it if it's not broken.

It's likely that if you put a spectrum analyzer on there, you'd see a 50/60Hz bump at the output of the preamp. But if you don't hear it, it does not matter.

 

[MaxwellsEq]

A lot of manufacturer manuals of phono pre's I've read state to keep the preamp away from power supplies and other devices. Is this because of some EMI issue? My current pre is about 6 inches from power supplies (switch mode style) and a tape deck and I haven't heard any hum or anything. Does it actually matter?

It's sensible advice. Cartridges (especially moving coil) are the lowest signal levels you will encounter in a domestic playback system. Phono preamplifiers (especially moving coil) have some of the highest gains. Put these facts together and you have the greatest potential to pick up mains and radio interference.

 

[dualazmak]

My post here would be a kind of your interest.
- Inside of Audio-Technica AT-PEQ30 phono preamplifier, and successful DIY suppression of inaudible EMF (electro-magnetic field) interference noise: #697

 

[Balle Clorin]

It matters absolutely, also cable routing matters. You may not hear it but it I measurable.
My noisefloor in RIAA is -82db, moving it directly on top of my CD players transformer 1-2”, worsens it to -60.
I have got LED lights above turntable and the driver below; turning OFF the LED has a surprising effect, the noise INCREASE to -79dB. Shielding the bench and grounding the shield improves noise to -85db, but that is impractical

 

[GXAlan]

1) Yes, the effect is measurable
2) It might be audible, since phono preamps amplify very low level signals

You can see the effect on a DAC here. You can only imagine what a MC amp would look like.

Measured effect of cable routing/component placement

In DIY amplifier kits, there is often talk of cable routing and effects on measured performance. Here I would like to show the difference with real, premium electronics using worst case topologies. Test Setup Topping D90 MQA Belden 8423 0.8m XLR balanced cable Marantz PM-10 integrated amp...

www.audiosciencereview.com

 

[Killingbeans]

Does it actually matter?

Yes. The signal from a cartridge is very, very low amplitude and is going into an amp with high input impedance and high gain, meaning that it doesn't take much to make the SNR skyrocket.

It's sort of the diametric opposite of speakers and their cables.

But like @radix says, if you don't hear any problems, there's nothing to worry about.

 

[mash]

I'll agree with all of the posts asserting the impact and providing great detail on the measurable impact. I'll also offer up a short subjective story....

When I first got into vinyl a couple of years back, I added a turntable (VPI Traveler), cartridge (Hanna SL MC), and phono preamp (Parks Puffin) with a coax digital out into my DAC/Pre-amp (Topping D90). I immediately noticed an auditable low level hum while switched to the digital phono input. My first attempt at fixing the issue was playing with the phono grounding setup which produced no improvements. My second set of tests involved switching out cables and making sure that I had clear routing between my cable and power supplies, Again, little to no impact. Finally, (by accident while playing with the cable placement), I noticed that when I physically lifted the Puffin off of the Topping D90 (in my original setup, the Puffin sat on top of the D90) the hum completely disappeared. Turns out, all I had to do was move the Puffin 12" away from the DAC and the hum disappeared into a silent background. I haven't looked back since.

 

[mhardy6647]

Fwiw, I would look at the issue in an essentially inverted way. Put the preamp where one wishes and listen. If there's audible hum or noise, check grounding and fiddle with location (preamp and cabling) to minimize hum & noise. Empiricism is hard to beat

 

[AaronJ]

It matters absolutely, also cable routing matters. You may not hear it but it I measurable.
My noisefloor in RIAA is -82db, moving it directly on top of my CD players transformer 1-2”, worsens it to -60.
I have got LED lights above turntable and the driver below; turning OFF the LED has a surprising effect, the noise INCREASE to -79dB. Shielding the bench and grounding the shield improves noise to -85db, but that is impractical

Does this issue with the CD player occur when the CD player is not powered on? I have my SUT sitting on top of my cd player but the CD player is only ever on when I’m using it, and I haven’t noticed anything weird.

 

[restorer-john]

Many CD players keep the primary of the transformer live and only switch the secondary. The reason? Cheaper switches as they don't have to be mains rated. Or they are 'soft' switches- momentary, as the micro puts the player into a low power state when 'off'.

Transformers, power supplies, VFDs, multiplexed displays of any type (LED/LCD etc) all make a ton of noise that TTs, cables and phono front ends are very susceptible to.

Always consider where the power supplies are in your gear when you place them in any proximity to your TT and phono front end. Even the cables in the wall, light switches etc can and do affect phono stages. The order you stack your gear, the spaces between and even power leads themselves will all have a detrimental effect.

Consider you are amplifying tiny signals 1000 times (60dB) and at mains frequencies, around 10,000 times. Just 1uV of 120Hz injected noise can become 10mV going into your amp and then 250mV in your speaker. That's ~8mW and very audible.

 

[dualazmak]

Many CD players keep the primary of the transformer live and only switch the secondary. The reason? Cheaper switches as they don't have to be mains rated. Or they are 'soft' switches- momentary, as the micro puts the player into a low power state when 'off'.

Transformers, power supplies, VFDs, multiplexed displays of any type (LED/LCD etc) all make a ton of noise that TTs, cables and phono front ends are very susceptible to.

Always consider where the power supplies are in you gear when you place them in any proximity to your TT and phono front end. Even the cables in the wall, light switches etc can and do affect phono stages. The order you stack your gear, the spaces between and even power leads themselves will all have a detrimental effect.

Consider you are amplifying tiny signals 1000 times (60dB) and at mains frequencies, around 10,000 times. Just 1uV of 120Hz injected noise can become 10mV going into your amp and then 250mV in your speaker. That's ~8mW and very audible.

Yes, I fully agree with you, and this is one of the many reasons for that I use series of four (4) 6-port power strips (total 24 AC 100V power ports) where each of the 24 AC power ports has ON-OFF switch; please refer here for "startup/ignition sequences" and "shutdown sequences" in my DSP-based multichannel multi-SP-driver multi-amplifier fully active audio rig.

All of the "usually not in use" gears should be kept fully power-off (unconnected to AC power supply) in terms of possible EMI to other gears especially to phono preamplifier, even though I already applied "maximum applicable treatments/positioning avoiding EMI" on my phono preamplifier (Audio-Technica AT-PEQ30) as shared here.

 

[formdissolve]

Definitely going to reconsider my placement after all these comments. I plugged my preamp into my RME and it was definitely a lot noisier than I thought.. even just moving it around slightly helped a lot!

 

[AaronJ]

Appreciate this thread very much. Would SUT's suffer similar problems as phono stages wrt placement?

 

[MaxwellsEq]

Appreciate this thread very much. Would SUT's suffer similar problems as phono stages wrt placement?

SUTs may be worse because of the coils. I've seen expensive balancing transformers in mu-metal cases.

 

[Balle Clorin]

Easy to see the noise level on Puffins display. I can see the effect of location directly And find the best spot. Here with 26db SUT Ortofon T-5 in use at 36db gain. Turing off the preamp beside gives -86db, but I need it on of course…