Experience with DC Offset blocking devices, eg Isotek EVO 3 Synchro - anyone.?
- Thread starter Yanntoe
- Start date
Hi Yanntoe,
Some time ago I read about reasons for hum where the person who described the problem found the source of his troubles to be a set of 12V lights with dimmer switch.
And so have you tried disconnecting everything electric in your house?
From my experience I have a naim 5si that had a hum coming through the speakers. To remedy this I ran a wire from ground to RCA socket on the back of the amp. I am in the UK and using three prong socket seems to be easy to apply. I do have transformer hum though for which will be getting an ATL DC blocker box.
Some time ago I read about reasons for hum where the person who described the problem found the source of his troubles to be a set of 12V lights with dimmer switch.
And so have you tried disconnecting everything electric in your house?
From my experience I have a naim 5si that had a hum coming through the speakers. To remedy this I ran a wire from ground to RCA socket on the back of the amp. I am in the UK and using three prong socket seems to be easy to apply. I do have transformer hum though for which will be getting an ATL DC blocker box.
Yanntoe
pfm Member
Thanks sq225917 - I would infer from this that "stuff" on the mains can get "into" the circuitry of e.g. amps. Whatever "stuff" is getting into mine , it seems to induce mechanical hum in the transformers - so, "stuff" gets as far as the transformers. As there's a corresponding hum from the speakers I suspect that the "stuff" that makes the transformers vibrate is the same stuff as that which causes the speakers to hum. I have no internet traffic on the mains from my domestic set up - perhaps the neighbours do. I did have a look and, whilst not an expert in such matters, there seems to be iec inlet filters on some of the offending equipment.
I'd be interested to hear, Ivelin, how you get on with the DC blocker. Concerning linking an earth from the socket to the RCA outlet - I guess you are linking the ground (outer contact of the RCA) to earth via a modified RCA connector ... or? don't know why but that causes a little bit of concern for me - i know. .... I'm a wimp. There are no dimmers in the house and I have removed every electrical circuit from the house except the HiFi ring.
I'd be interested to hear, Ivelin, how you get on with the DC blocker. Concerning linking an earth from the socket to the RCA outlet - I guess you are linking the ground (outer contact of the RCA) to earth via a modified RCA connector ... or? don't know why but that causes a little bit of concern for me - i know. .... I'm a wimp. There are no dimmers in the house and I have removed every electrical circuit from the house except the HiFi ring.
Hi Yanntoe,
Answering your question: Yes, it is a wire with a modified RCA (keeping the outer ring part) from the outer casing of an unused RCA to ground (earth). You can see this topic here:
https://community.naimaudio.com/t/naim-5si-hum-sonos-zp90/5743/17
Post #17 shows the adapted wire.
If you check the socket, where you will plug it, making sure that ground is not live then there is nothing to worry about. On the same topic, have you checked the earthing of the sockets where your hifi is connected?
Answering your question: Yes, it is a wire with a modified RCA (keeping the outer ring part) from the outer casing of an unused RCA to ground (earth). You can see this topic here:
https://community.naimaudio.com/t/naim-5si-hum-sonos-zp90/5743/17
Post #17 shows the adapted wire.
If you check the socket, where you will plug it, making sure that ground is not live then there is nothing to worry about. On the same topic, have you checked the earthing of the sockets where your hifi is connected?
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Yanntoe
pfm Member
Thanks Ivelin,
I think the only way to do this would be via a casing screw as there are no spare RCA inputs on the amps (i.e. they are monoblocks and have a single RCA input each. Or I might be able to add the passive pre back into the system and add an earth to one of RCA's on that...... Not really sure how I would check for DC on the mains socket - is that as simple as setting the test meter I have to DC and checking between the live and neutral on the incoming mains.
I think the only way to do this would be via a casing screw as there are no spare RCA inputs on the amps (i.e. they are monoblocks and have a single RCA input each. Or I might be able to add the passive pre back into the system and add an earth to one of RCA's on that...... Not really sure how I would check for DC on the mains socket - is that as simple as setting the test meter I have to DC and checking between the live and neutral on the incoming mains.
Hi Yanntoe,
Sorry my mistake, I meant have you checked the earth of the sockets where the system is connected? (I will correct my post above)
The earth check you can do with a multimeter by measuring Phase to Neutral then Phase to Earth and then Neutral to Earth. A good example is PN=240V, PE=240V, NE less than 2V (assuming you are in Europe)
If you ran a wire to a screw on the case this is for main earth which is for electrical safety and hopefully your amps are already built with it. Running the wire to an RCA is, I think, eliminating ground loop, which is one of the main reasons why speakers hum/buzz.
Sorry my mistake, I meant have you checked the earth of the sockets where the system is connected? (I will correct my post above)
The earth check you can do with a multimeter by measuring Phase to Neutral then Phase to Earth and then Neutral to Earth. A good example is PN=240V, PE=240V, NE less than 2V (assuming you are in Europe)
If you ran a wire to a screw on the case this is for main earth which is for electrical safety and hopefully your amps are already built with it. Running the wire to an RCA is, I think, eliminating ground loop, which is one of the main reasons why speakers hum/buzz.
Yanntoe
pfm Member
OK SO results of the Ivelin test
PN continuously cycling between 251 - 253V
PE continuously cycling between 251 - 253V
NE 1.3 to 1.5V
In terms of DC over the PN then we have continuously cycling between plus 0.1V and minus 0.1V. that's if the multimeter really reads DC (when DC is selected) across the AC contacts - I can never convince myself that it's not an "artefact" - however it's the best I can do!
Does that shed any light on things?
PN continuously cycling between 251 - 253V
PE continuously cycling between 251 - 253V
NE 1.3 to 1.5V
In terms of DC over the PN then we have continuously cycling between plus 0.1V and minus 0.1V. that's if the multimeter really reads DC (when DC is selected) across the AC contacts - I can never convince myself that it's not an "artefact" - however it's the best I can do!
Does that shed any light on things?
Arkless Electronics
Trade: Amp design and repairs.
I hope no one's going to get hurt messing with mains 240V here...
Your OP says the amps, but the rest of the thread makes it somewhat unclear... Does your hum come from the amp itself, or your speakers?
If the former, and especially if it changes or fluctuates slightly during different hours of the day, I would be confident that a DC blocker would fix it. I am amazed at the difference the cheap one I bought from ATL makes.
If the former, and especially if it changes or fluctuates slightly during different hours of the day, I would be confident that a DC blocker would fix it. I am amazed at the difference the cheap one I bought from ATL makes.
Hi Yanntoe,
Just to let you know that I got my DC blocker (2 weeks ago). The Naim amp seems to have calmed down and the hum/buzz is almost gone. The impact of the DC blocker is such that now the noise from the amp doesn't fluctuate and is constant through out the day and night. I am much happier with the Naim and also find it a lot less annoying when idling. The remaining hum I will attribute with the almost 250V mains and less than a perfect transformer; I think with the higher mains voltage the transformer saturates which leads to the mechanical hum and maybe increased temperature.
Regarding measuring the DC I read somewhere that only a multimeter is not enough and, as NRG has commented previously, a cap and a resistor circuit is the way to do it. I will reiterate NRG's advice, unless you know what you are doing don't do it.
Let us know if you have sorted out the hum.
Just to let you know that I got my DC blocker (2 weeks ago). The Naim amp seems to have calmed down and the hum/buzz is almost gone. The impact of the DC blocker is such that now the noise from the amp doesn't fluctuate and is constant through out the day and night. I am much happier with the Naim and also find it a lot less annoying when idling. The remaining hum I will attribute with the almost 250V mains and less than a perfect transformer; I think with the higher mains voltage the transformer saturates which leads to the mechanical hum and maybe increased temperature.
Regarding measuring the DC I read somewhere that only a multimeter is not enough and, as NRG has commented previously, a cap and a resistor circuit is the way to do it. I will reiterate NRG's advice, unless you know what you are doing don't do it.
Let us know if you have sorted out the hum.
https://avahifi.com/collections/accessories/products/humdinger-dc-line-blocker
This works, from personal experience.
This works, from personal experience.
Yanntoe
pfm Member
Thanks Ivelin, thanks Firedog.
Great that it all works in reducing "casing" hum - I might have a go with either the ATL or Humdinger options, but having had an e-mail chat with ATL , he doesn't have anything to eliminate the problem I describe - suggests getting isolation transformers.
The cost of isolation transformers is sufficiently high for me to wonder about scrapping the whole HiFi, getting used to the idea that high-end kit isn't going to get on well here, and just going for a few cheaper all-in-one solutions. It's a pity, but I probably don't listen enough to justify spending £000's on the system.
Oh and in response to the concerns about killing myself by connecting dangerous wiring concoctions to the mains, a) thanks for the concern, b) I'm pretty circumspect when it comes to mains supply, and c) it's all protected by RCD/MCB etc. so even if I get it wrong, whist the HiFi might fry, I'm likely to be OK . Now, where did I put my dismembered OTL Valve amp .......
Anyway many thanks everybody.
Great that it all works in reducing "casing" hum - I might have a go with either the ATL or Humdinger options, but having had an e-mail chat with ATL , he doesn't have anything to eliminate the problem I describe - suggests getting isolation transformers.
The cost of isolation transformers is sufficiently high for me to wonder about scrapping the whole HiFi, getting used to the idea that high-end kit isn't going to get on well here, and just going for a few cheaper all-in-one solutions. It's a pity, but I probably don't listen enough to justify spending £000's on the system.
Oh and in response to the concerns about killing myself by connecting dangerous wiring concoctions to the mains, a) thanks for the concern, b) I'm pretty circumspect when it comes to mains supply, and c) it's all protected by RCD/MCB etc. so even if I get it wrong, whist the HiFi might fry, I'm likely to be OK . Now, where did I put my dismembered OTL Valve amp .......
Anyway many thanks everybody.
The hum through your speakers sounds like either a ground loop with another nearby device, or a crappy unshielded interconnect running next to a noisy mains lead. Have you fiddled with unplugging things etc to try and alleviate it?
Hi, I have the smaller ATL unit that is the 2v option and wanted to get your opinion. My Nap 250dr was humming like crazy and this was down to the transformer which has been replaced by Naim. I have the smaller ATL device which has stopped the fluctuating hum that could be heard when a hairdryer or similar item is on in the house. My nap 250dr now doesn't hum audibly from the listening position. However my hicap dr does have an audible hum despite going through the smaller atl dc blocker. Do you think this larger device or the large sojstrom device would help this situation. Note the hum doesnt fluctuate it is a pretty consistent hum from the hicap.
Thanks in advance
Cereal Killer
432
Hi - I’d say yes it should work, my amp has 6 toroidal transformers in it; 2x 700va, 2x 100va, 1x 50va 1x 10va. There’s also over 400,000uF of capacitors in it. this all goes the SJ03/2x20a CM filers.
Smaller DC blockers do work but have a limit of around 4/500va.
alternatively the ATL one I previously linked too should work well and comes prebuilt.