Denon F-109 mini system how to ground without buzz?

DaveJazz

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I have read various posts on this forum & others re earthing for electrical safety, grounding for RFI, and signal (audio) ground etc! I do know a bit about electrics as I do building and car electronics, and built computers. I hope you will take some time to read my post below and give any firm solutions!

I have been in contact with Denon customer service who passed it on to their office in Germany, who then gave a reply. This reply though proved that they did not understand a thing and they contradicted themselves! I am getting nowhere with them as they don't know that they don't know!

This is the original problem that I sent to Denon;

I have the three F-109 units (amp/tuner, CD, Network player) which are all
interconnected for total system control for power off & system remote as
per Denons instructions. The units are all double insulated dessign (so no earth for electrical saftey).

My problem is that I can (occasionally) get a small static charge when I touch
them. I know that the units are not electrically earthed as "double
insulated", & are therefore "floating" in relation to true
earth which is 0v. Therefore you get static when you touch them as you are now
"grounding" (equalising the potential) the units! I have measured
with a digital multi-meter a voltage of around 90AC when connecting one probe
to the hi-fi (in standby mode) & the other to a good ground (radiator in
the room or the earth in the mains spike & RFI filter block extension which
the hi-fi is connected to). This are normal expected values.

Normally to stop this occurring you "ground" the metalwork which then
makes it relative to earth or 0v!

So I undid a back casework screw on the Amp/Tuner & attached a 2.5mm dia
cable which I then connected to the earth on my mains filter extension block. I
also connected a wire from the Network player to the same screw on the Amp, and
another wire from the CD to the same screw on the amp. Now all of the three
units are at the same potential, and all now measured 0AC voltage as all now
earthed, so no potential difference! Great!. No, not quite, as now I noticed a
faint electronic component buzz (unit in standby & buzz does not transmit
into speakers when operational). After much disconnecting of wires etc I traced
it down to coming from the back power side of the Amp unit! I removed the earth
connection & the buzzing stops! All three units can still be connected, but
as soon as I connect to "Ground" is comes back! I re-did the test
using different earthing points etc to eliminate bad earth etc., & still
the same result!

Also I noticed doing continuity checks that the CD Player and the Network
Player cases are isolated from their PCB boards and the signal - ground of the
co-ax out. But the amp case seems to be connected to the signal - ground of the
co-ax via the PCB board!

I know that the above is a bit long & technical but I would like to be able
to "ground" the F-109 hi-fi to get rid of static, but without the
Amp/tuner buzzing! Also I am trying to get as much RFI grounded (so far not
picking anything up through the speakers or the new F-109 system) as my
neighbour is an amateur radio nut (radio ham), and has a nice transmitter
aerial in his garden!!

I got a silly email back from them and sent them further info answering their email! I can not even re-send/reply or even open the "report" on their website!

This is further

I am
fully aware of what ESD is (voltage potential difference between two objects)
and I reiterate that when I connect a multimeter between the radiator in the
room (or other good earth) and any of the three cases that I get an AC voltage
reading of 90V. This is because the three units ARE NOT connected to EARTH!! If
they were then the reading would be 0V as that is “Earth”. If I already had a
direct connection through the Hi-Fi to “Earth” as you state that “There
is already a proper earthen point to the ground.” Then I would not be getting a
reading of 90ACV between the cases and an existing common earth!





The three unit cases ARE NOT directly connected together! Again if you connect
a multimeter between any combination of the three cases, you will find that
there is ONLY direct continuity between the Network player and the Amp/tuner
cases, even with ALL cables connected! Also there is about 3.16ACV difference
between the cases themselves, connecting the multimeter between one case and
the next, with or without all the cables connected!




What
“cinch” inputs?? You have co-ax RCA (phono style) for the digital signals, and
then a 3.5mm mini jack for the remote control system interconnects!




The
FM?DAB antenna IS NOT grounded! There is no need as it is internal (loft
mount), in fact in a normal domestic situation I have never seen an antenna
connected to earth! If I use your supplied antenna it would still not be
connected to Earth! Even if I disconnect the antenna from the Amp/Tuner and
reconnect my made up Earth lead to a good earth and the Amp (therefore only one
earth point and NO loops), I still get the buzz! If the antenna was causing
problems I would be getting noise etc on the Tuner through the speakers! I am
NOT getting any noise from the Tuner, in fact I am getting max strength (no.8)
on all my FM and DAB stations without any noise/interference!! I have never had
any noise in my antenna systems!




As
for ground loops, all units are double insulated (no earth), with only one
power connection as the CD player is daisy chained off the Amp, and the Network
player is daisy chained off the CD player. Even with the antenna disconnected
(therefore nothing external) the buzz appears!




All I
want to do is to have the cases at “ground” (0V), so no difference between the
cases and “earth”, and no difference between the cases themselves (best way to
stop ESD, etc), and without what sounds like an electronic component getting
agitated on the power side of the Amp! The noise DOES NOT transmit to the
speakers! It is a buzzing sound coming from the Amp/Tuner unit only, and coming
from the rear “power” side of the case. P.S I am having trouble getting to grips with your forum posting format as the other forums that I post on (cars) are a bit easier and have built in auto spell check etc. Many thanks if you can understand and help!!!.






 

ID.

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When I was at school we used to skuff our shoes along the carpet to build up static electricity and then zap one another. We also observed that we got the best sparks when we would discharge using a metal cabinet.
 

DaveJazz

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Err....yes I am real......and the post is real........................

i'm sorry if the post is a bit strage but I tried to cut and paste two emails into the forum with strange results!...................oops!

Might have to cut post out and re-do in word then re-post......................all the info is there anyway
 

davedotco

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DaveJazz said:
So I undid a back casework screw on the Amp/Tuner & attached a 2.5mm dia cable which I then connected to the earth on my mains filter extension block. I also connected a wire from the Network player to the same screw on the Amp, and another wire from the CD to the same screw on the amp. Now all of the three units are at the same potential, and all now measured 0AC voltage as all now earthed, so no potential difference! Great!. No, not quite, as now I noticed a faint electronic component buzz (unit in standby & buzz does not transmit into speakers when operational). After much disconnecting of wires etc I traced it down to coming from the back power side of the Amp unit! I removed the earth connection & the buzzing stops! All three units can still be connected, but as soon as I connect to "Ground" is comes back! I re-did the test using different earthing points etc to eliminate bad earth etc., & still the same result!

Also I noticed doing continuity checks that the CD Player and the Network Player cases are isolated from their PCB boards and the signal - ground of the co-ax out. But the amp case seems to be connected to the signal - ground of the co-ax via the PCB board!

This is the 'system' ground, all the PCBs are connected via their interconnects to the amp PCB, which is connected to earth, this is correct.

The amplifier casework is earthed as the voltages involved are quite high, the other units operate at lower voltages and so the cases can be left to 'float'. If the static bothers you connect the cases of the 3 units as above but do not connect another wire to the mains ground.

The cases are earthed to each other, they are earthed to the amp PCB, which is earthed via the mains lead. That should sort it out, everything earthed once and once only.

Though why you are worrying about this is beyond me.
 

DaveJazz

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Maybee I didn't make it clear in my first post.......................

All the three cases are double insulated (no requirement for earth connection for electrical safety) ..........................That includes the Amp!

So there is no connection to mains earth via a power lead anywhere in the system as Live & Neutral are only connected (fig 8 connector on back of Amp), this is Denon UK spec.

Therefore as there is no exsiting Earth connection there can not be a "ground-loop hum".

I want to "earth" using a single point "star" (to make the system at 0V earth to reduce potential for static discharge) but get a faint buzz of a component from the amp case only. The buzz does transmit into sound through the speakers (so not hum)..........it is the sound an electrical component makes when agitated the wrong way.

I have already connected all three cases together (as you have just mentioned) which makes them all at the same potential and gets rid of the 3.16ACV difference between them, and no buzz..................just as soon as i do an earth connection (the ONLY earth connection in the whole system) a component in the amp case buzzes!

I just like metal casework earthed...............also stops it attracting lots of dust if grounded properly!!
 

DaveJazz

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In fact you got me thinking...........................

I wonder as they are are only using L + N if they are treating "ground" on the PCB as N??............In fact most incoming mains is single core with the steel armor proving the path for the combined netral and earth!........By connecting a seperate earth would then create a "loop"...................which would agitate an electronic component without the noise transmitting through the speakers!.....................hmmmmmm..............

Also connected my "earth" back up to the amp case but fitted via an ESD wall plug (uk mains plug with earth connection only with 1megaohm resistor.....................and NO BUZZ!!!!!!......................Have read on other forums people fitting 10ohm resitor between the case and the "earth".......also with a capacitor as well!.........................any thoughts????..............:?
 

DaveJazz

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Think I have managed to solve it................:pray:

Found out that the Amp has a "Protection Circuit" which prevents damge to components from overload & excess voltage.......or if the speaker cables + or - touch the rear panel/casework of the amp!

I recon that by connecting an earth to the casework caused the protection circuit to think it should trip (it was not fully tripping) as in my house (as is fairly common) the earth at the incomer is the same as the Neutral (combined N & PME I think it's called). So I was getting an earth/neutral loop!

Anyway I carried on with the ESD plug I have which caused the "buzz" to lessen. Ended up using a variety of different resistors, & finally got the "buzz" to go at about 4.5M Ohm. So I ended up connecting a seperate 5.6M Ohm (to make sure) resistor to each of the three cases. Then a short (8") piece of wire from each of the three resistors. The three wire ends where then joined together and a single earth wire was taken from this join to the earth pin of a 3-pin UK plug. Everything was soldered and heat shrunk. No "buzz" and not as much ESD or dust!

Found out that ESD testers for ESD protection kits work in the rage of 0.75M Ohm to 35M Ohm! So by effectivly wiring up the three cases to a 5.6M Ohm ESD kit isn't that high but does stop the protection circuit components "buzzing". I wonder what the electronices in a "Russ Andrews" earth connection block are?
 

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