Hum and dc blocker after 6 months on hicap and 250DR

Hi,
I have an hicap DR and a 250 DR, both happily humming.
this didn’t bother me while the music was playing, but was quite annoying during the night and in the early morning silence.
Effective solution was to put 2 IFI DC Blocker: 1 standard for the hicap and 1 + for the 250
after 6 months and several connections and disconnections, I would like to share my experience:
DC blocker on hicap DR does not affect sound quality at all
DC blocker on 250 DR kills some of the dynamics, sound is less natural, bass is less deep
so for the time being I disconnected the DC blocker from the 250 and kept just the one on the hicap
I prefer to let 250 hum, being compensated by better level of sound performance
there are several debates on this topic, my experience is that on power amp defenetely dc blocker has an impact on SQ, on Hicap it doesn’t.
Hope this might be helpful

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You could also try a higher end DC blocker. After all the IFI is super small which I assume can limit the choice of components like size of capacitors for improved dynamics and such.

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IFI do a ‘+’ version for higher-draw power amps etc. May be worth trying if you can get one to dem.

Oops, apologies. I see you already have the + one.

@Gruido71

Try swapping the DC Blockers over.

I had two standard ones on my 250s. Virtually stopped all the hum, without having a detrimental affect on the SQ.

DG…

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What is causing the DC interence in the first instance?

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This is a nice question… hard to say

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Sure I will !

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It may just be a naturally noisy transformer.
This is indicated by an unchanging hum volume and tone, whereas DC on the supply would come and go and that causes the transformer hum to vary.

Most DC ‘Blockers’ that I’ve designed and made (or just borrowed to try) do reduce hum level to some extent, but in my case it never totally fixed the low and steady hum.
My design unit supplied was not connected to a single device like the iFi’s, it powered all the system, amp, streamer, tuner and x2 PSU’s, it did give a small improvement to SQ.

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Thanks for the replies people.

I ask because I have a ground loop with a HT connected in my system and had previously wondered whether the DC blocker on the HT amp would prevent the issue?

Made me also think whether another component in Gruido’s system could be the root cause of the issue?

iFI also do a Ground Defender that you could try.

With a GND Defender at the IEC power input, it will intelligently detect and remove the ground loop at the component.

Behind this, the GND Defender:

** Intelligently breaks DC ground loops to eliminate ground loop hum*
** EMI shielding is retained*
** Equipment Safety is unaffected (not a ground lift – so maintains equipment safety ground)*

If multiple ground loops exist, more than one GND Defender may be required.

The GND Defender is smarter than the average ground lift. By a long way.

Not tried this as I haven’t had this particular issue, but did have transformer hum and, their DC Blocker worked well.

Something to consider. A lot of places do 30 day returns, so worth trying with nothing to lose.

DG…

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Oh yes. That’s what I was thinking of… :+1:

thanks all. something strange is that I was keeping the whole components in a sideboard and they were deadly silent. finally I moved them in a dedicated rack and the hum begun. the wall plug changed, but the new one it is strictly connected to the previous plug, being an arm of the same wire. maybe it’s just a coincidence maybe not. my fridge hums as well, but I think it’s something different.

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That’ll be caused by your hifi.

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Yebbut it’s frigid so shouldn’t let itself be affected by these kind of things.

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I would throw another spanner into the works here. Since I’ve improved isolation on the Naim power supplies I have noticed less humming. No im not suggesting that isolation fixes the cause of the hum which is DC offset but better isolation does reduce vibration and therefore resulted in a lower noise floor in my system.

what are you using to isolate your components?

I have many levels of isolation on my rack but the final ebony wood pieces made a surprising difference that I didn’t expect.

I got the idea from a Quadraspire Q plus reference review. The author stated that even on a Quadraspire Reference X hifi rack the small isolation feet improved the midrange even further. I’ve had a similar effect in my system with these affordable indoneasian ebony feet.

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Thanks, this is very interesring. I found discs with 3 spheres wirking well. They contribute to sound definition especially under the streamer. Which are the noticable effects of your isolators?

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Lower noise floor which translates to a more calm presentation. Treble glare is reduced from my digital signal. (Analogue does not exhibit this)

Midrange resolution improves along with bass. The bass on some tracks appears to be more powerful and on some slightly less. My explanation is that it is now better controlled. It’s nicely balanced. Powerful & tight, yet it still produces the bounce and warmth that you want. Please note these difference are NOT night and DAY but you will notice them. More like a 10 percent shift in the sound presentation.

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Thanks, very interesting