electrical isolation of amp and other gear

I have a question about power and isolation involving an amp and other gear. Apologies if this is not the right forum.

I have (or will soon have) 3 primary audio devices:
- Pass Labs XA30.8 amp
- Lampizator Golden Gate DAC (with volume control)
- Sonore Signature Rendu SE streamer

My understanding is that that recommendation is to electrically isolate digital gear from analog gear (in terms of lines, outlets, power conditioners, etc.) However, both of the digital units that I have use linear power supplies, so I wonder if that isolation is still necessary in my case.

I also have a Furman Elite-20pfi power conditioner in which I plug some other devices (SonicTransporter that feeds the streamer as well as pro audio/guitar gear unrelated to the hi-fi system). So, with the above gear, I will have a total 4 devices to plug into the wall (the amp and DAC tend to sound better plugged into the wall then through the power conditioner).

I have 3 dedicated lines. Each one has different outlets - Furutech GTX-D NCF(R), SR Blue, Maestro. I’ll plug the power conditioner into one of them. My question is how should I group the other two? Here are some options:

- amp in 1 outlet, DAC and streamer together on 1 outlet, power conditioner on 1 outlet
- amp in 1 outlet, DAC 1 outlet, power conditioner on 1 outlet, streamer in an isolated bank in the power conditioner.

Are there other options that I should be considering? If there is no advantage to isolating gear with linear power supplies, I might as well go with the first option. At the end of the day, I’ll let me ears do the final judging. However, with all the possible options as well as the combinations of mating different pieces of gear with different outlets, there are a ton of permutations and combinations. So, I’m looking for general guidelines as a starting point.
The Furman unit you have has multiple filtered banks, so you can definitely use it for all your gear.

With the DAC, it is recommended by PS Audio, and I concur, to use shielded AC cables to keep the digital component noise emitted down. Even if you use a linear power supply ( a good idea ) DAC's are essentially computers with linear outputs. Digital tech can produce a lot of EMI/RFI which can possibly escape the power supply.
Pass Labs XA30.8 amp plugged directly into a dedicated branch circuit wall outlet. Preferably a dedicated 20 amp circuit.

Audio equipment that connects together by wire interconnects.
Make sure all dedicated circuits are fed from the same Line, leg, from the electrical panel. All from Line 1 (L1) or all from Line 2 (L2).
You can verify 100% with a multimeter set on AC volts. Also check any power conditioner to make sure the AC phase polarity on the output outlets are in phase with the other wall outlets for the other audio equipment plugged into those dedicated circuit outlets.


Years ago, I had a very expensive power conditioner with various designated outlets. In spite of all of the internal filters, the digital components still cross-contaminated the power to the other components. I also discovered that my home computer - which is in a different room and on a different circuit - also contaminated other household circuits. Digititus is far more insidious than might be expected.

After years of experimenting, now each component (analog and digital) has its own dedicated conditioner. This includes my 3 linear power supplies - each with their own conditioner - including one for the modem/router. Everything is much improved. IMO, better than sharing. Surprisingly, another dedicated power conditioner for my home computer helped significantly.

For your LPS, be sure to procure an Acoustic BBQ umbilical DC cable from grannyring.

Yeah, cross contamination is still a possible issue.

I like to use the cheapest Furman with LiFT and SMP for those digital sources.


This puts them 2 filters away from my audio, and compared to a lot of audiophile power strips, a real bargain.
erik_squires5,350 posts

03-17-2019 12:33pm

Yeah, cross contamination is still a possible issue.

And as you mentioned above, why using shielded power cords on digital equipment can’t hurt.

Though the type of shielded power cord chosen is very important. Some shielded power cords suck the air out of the music and have an effect on the soundstage not to mention can roll off the high frequencies. All making the musical sound presentation boring to listen to. Same thing as some power conditioners do.

@ erik_squires

I like to use the cheapest Furman with LiFT and SMP for those digital sources.

What exactly does the Lift switch do?

Floating the secondary winding above ground?
Disconnecting the secondary neutral ground bond from the wall receptacle equipment grounding conductor?

Is the Furman with LiFT Listed by any recognized third party electrical safety testing laboratory? Like UL?

Thanks for the responses. The power conditioner discussion is a particularly interesting one. I first thought that the isolated banks on the Furman power conditioner should do the trick. However, I found that my current DAC (Benchmark DAC3) sounded much better directly into the wall when compared to being alone on an isolated bank in the Furman. This could be for a number of reasons like a higher quality outlet on the wall (compared to the Furman) or that the filtering circuit in the Furman is degrading the signal to some degree. The same goes for my amp as well, although it is less surprising for an amp. They might benefit from a higher quality power conditioner/re-generator. I had a tried a PS Audio P10 Powerplant (amp and DAC plugged into separate banks). It sounded a bit better, but not quite enough to justify the cost. Although, I did miss it a bit after I sold it. It’s hard to forget even minor incremental improvements after experiencing them :)

A few other things about my setup:
- The power supplies are in the same chassis for all of the gear that I mentioned. So, I can’t isolate them further or use any aftermarket DC cable.
- All of the dedicated circuits are indeed ed on the same leg.
It sounds like the general consensus is that with linear power supplies, the problems of cross-contamination and the need for isolation is not as bad as with switching power supplies. However, even with linear power supplies, there is benefits in isolating digital gear.

Perhaps, one strategy is:
- Plug the amp into the amp into the wall on its own line
- Plug the DAC (Lampi Golden Gate) and streamer (Sonore Signature Rendu) into the same outlet on another line.

In order to isolate the noice from DAC and streamer further, I could use shielded cables or get a high quality power conditioner with separate banks. Any specific recommendations for these things?
That's pretty much correct.

Inside the audio devices, the two biggest sources of noise are digital processors and switching power supplies, and now, networking devices. Frequencies here are from 10kHz to GHz.So, your DAC, streamer, DSP, or Class D amps, etc. can potentially cross-contaminate.

Using a shielded cable for these reduces the chance of this noise making it elsewhere. Keeping these potentially noisy sources outside the clean zone your linear devices are on makes sense.

Linear supplies can generate switching noise from the diodes in the bridge rectifiers, but in general it's accepted this, when it exists, is of smaller magnitude, lower frequency and easier to deal with.

I’ll let my ears do the final judging.


Re: shielded vs unshielded power cords

My experience has been all over the place. Some shielded cords do suck the life out of the music – as do some power conditioners. Yet, I unexpectedly discovered a shielded cord that turbo-charges the music. My jaw nearly bounced off the floor when I first heard it. But, when I put that same cord on a different component, it was just too intense. Other shielded cords that I've tried offered presentations that were quite smooth and unfatiguing - but were just plain boring.

Generally speaking, in my experience: shielded cabling:

- doesn’t prevent digital nasties from backwashing into the rig or the house electrical grid. A good power conditioner can help stop that from happening.

- can be good as a built-in digital filter for that particular cable.

- is good for protecting that cable from emitting RFI or EMI to nearby cabling or components.

- is good for protecting that cable from receiving RFI or EMI from nearby cabling or components.

- is good for digital components.

Generally speaking, in my experience: unshielded cabling yields:

- a more lively presentation.

- better dynamics

- better harmonics

Yet, all of the above, can be nullified if the unshielded cable lays too close to a power cord or to a transformer in a component. Much depends on the rat’s nest behind your rack.

In my rig, both the digital and analog components have a mix of shielded and unshielded power cords. It took years of swapping cables to find the best synergy. Contrary to the guidelines above, I found a shielded power cord that works really well with my Class A SS amp. It’s the only cord I’ve tried where a piano sounds like a piano - a complex mix of dynamics, harmonics, tone and thunderous bass. But, the same cord sounds only okay with my source components. Go figure!


I'm with Steakster. Keep an open mind.

Shielded AC cables can pick up a lot of hash on the shielding and introduce that to the component chassis. If you're running single ended components where signal ground and chassis ground are tied together this noise can show in the output.

I found this out using a Schiit Bifrost DAC with an older unbalanced ARC preamp. On top of the ground loop hum it picked up all kinds of other RF hash. The cheap cable that came with the DAC actually sounded better than a couple of shielded AC cables I'd always been using.

Best cables were the ones with the lowest ground to AC line capacitance. There is a lot of good documentation on ground loops out there.

I'm thoroughly convinced this is related to why so many people hear differences in AC cables that shouldn't be there. It's a third interconnection between components that's normally not measured.