I was just given an (older) NAD 1720 stereo receiver, which I will be
using, for the time being, exclusively for headphone listening. I
notice that there is a buzzing sound which is most noticeable when the
receiver's volume knob is at "0," growing more faint as the volume is
increased to about 75% full, when it is either replaced or masked by a
fine hissing sound .

If I leave the receiver's volume at around the 75% full point
(decreasing the volume of the line in signal at source). the buzz is
barely, if at all, noticeable when music is playing, so I can live with
this minor annoyance. But I am curious what is causing this buzz, why
it decreases in intensity as the volume is increased, and if there is
perhaps a simple way to eliminate it altogether.

Thanks in advance for any helpful insights or suggestions!

I would start by replacing the main filter capacitors of the power supply.
I don't know anything about the NAD 1720 or how its power supply works, but
the biggest filter capacitors are usually the first components to go,
especially if the receiver was unused for some years.

wrote in message
oups.com...
I was just given an (older) NAD 1720 stereo receiver, which I will be
using, for the time being, exclusively for headphone listening. I
notice that there is a buzzing sound which is most noticeable when the
receiver's volume knob is at "0," growing more faint as the volume is
increased to about 75% full, when it is either replaced or masked by a
fine hissing sound .

If I leave the receiver's volume at around the 75% full point
(decreasing the volume of the line in signal at source). the buzz is
barely, if at all, noticeable when music is playing, so I can live with
this minor annoyance. But I am curious what is causing this buzz, why
it decreases in intensity as the volume is increased, and if there is
perhaps a simple way to eliminate it altogether.

Thanks in advance for any helpful insights or suggestions!

Am 1 Mar 2006 19:41:38 -0800 schrieb :

I was just given an (older) NAD 1720 stereo receiver, which I will be
using, for the time being, exclusively for headphone listening. I
notice that there is a buzzing sound which is most noticeable when the
receiver's volume knob is at "0," growing more faint as the volume is
increased to about 75% full, when it is either replaced or masked by a
fine hissing sound .

If I leave the receiver's volume at around the 75% full point
(decreasing the volume of the line in signal at source). the buzz is
barely, if at all, noticeable when music is playing, so I can live with
this minor annoyance. But I am curious what is causing this buzz, why
it decreases in intensity as the volume is increased, and if there is
perhaps a simple way to eliminate it altogether.

Thanks in advance for any helpful insights or suggestions!

HI,

I had exactly the same on a Sony amp. Didn't fix it, but i would look for a
internal ground loop. Bad capacitors i guess either on the power supply
(filter cap, big ones) or the nearby be volumen pot (very small). I also
remember having problems with ground loop and a problem with a powre
resistor somewhere between the power supply and the power amp.
It also could be bad solderig.
Hope this helps.
Lukas

"mc" wrote in message
...
I would start by replacing the main filter capacitors of the power supply.
I don't know anything about the NAD 1720 or how its power supply works, but
the biggest filter capacitors are usually the first components to go,
especially if the receiver was unused for some years.

wrote in message

Nonsense. More likely smaller vaps in the regulated power supply area,
solder connections, ground loop, the usual suspects. If the big caps were
bad, there's be a huge noise, or the thing would just blow a fuse.

Mark Z.

oups.com...
I was just given an (older) NAD 1720 stereo receiver, which I will be
using, for the time being, exclusively for headphone listening.

snip

wrote in message
oups.com...
I was just given an (older) NAD 1720 stereo receiver, which I will
be
using, for the time being, exclusively for headphone listening. I
notice that there is a buzzing sound which is most noticeable when
the
receiver's volume knob is at "0," growing more faint as the volume
is
increased to about 75% full, when it is either replaced or masked by
a
fine hissing sound .

If I leave the receiver's volume at around the 75% full point
(decreasing the volume of the line in signal at source). the buzz is
barely, if at all, noticeable when music is playing, so I can live
with
this minor annoyance. But I am curious what is causing this buzz,
why
it decreases in intensity as the volume is increased, and if there
is
perhaps a simple way to eliminate it altogether.

Thanks in advance for any helpful insights or suggestions!


If you are using headphones, what impedence are they? If they are 8R
or in that parish try putting a resistor in series with channel, say
about 330R. What you are hearing could just be amp noise with the
headphones effectively connected across the speaker output.

The fact that it decreases with line input level tends to suggests it
could be coming from the source.

But as others have said the biggest likely culprit is a problem with
earthing, either a bad earth on the volume control or something
external. Since it is NAD I might presume you live in the UK? If so
make sure only ONE item of your hi-fi has an earth connection in the
mains plug. I know others will chastise me for suggesting removing
earths but it is often the only way.


--
Woody

harrogate3 at ntlworld dot com

I would start off by replacing the main filter caps in the powersupply, and
also the decoupler caps before and after the voltage regulators.

The best way to find the defective caps, is to use an ESR meter to test
them.

--

Jerry G.
======


wrote in message
oups.com...
I was just given an (older) NAD 1720 stereo receiver, which I will be
using, for the time being, exclusively for headphone listening. I
notice that there is a buzzing sound which is most noticeable when the
receiver's volume knob is at "0," growing more faint as the volume is
increased to about 75% full, when it is either replaced or masked by a
fine hissing sound .

If I leave the receiver's volume at around the 75% full point
(decreasing the volume of the line in signal at source). the buzz is
barely, if at all, noticeable when music is playing, so I can live with
this minor annoyance. But I am curious what is causing this buzz, why
it decreases in intensity as the volume is increased, and if there is
perhaps a simple way to eliminate it altogether.

Thanks in advance for any helpful insights or suggestions!

"harrogate2" wrote in message
...

If you are using headphones, what impedence are they? If they are 8R
or in that parish try putting a resistor in series with channel, say
about 330R. What you are hearing could just be amp noise with the
headphones effectively connected across the speaker output.

I second that. It may be just that the headphones are so efficient that
he's hearing low-level hum that would be unnoticeable in speakers.

Thanks to all for your comments and suggestions!

Here are the specs for the headphones I'm using:


Beyerdynamic DT801

Impedance (Ohms) 250
Sensitivity (dB) 94
Max Power (mW) 175Max
SPL (dB) 116


I should add that the buzz reaches its minimum point not at 75% volume,
but actually at around 50%, and the buzzing is much more pronounced in
the left side than in the right. The audio is coming from my G4's line
out, and there is no buzzing when the headphones are plugged in
directly to the computer.

Any further comments and suggestions are looked forward to and
appreciated!

wrote in message
oups.com...
Thanks to all for your comments and suggestions!

Here are the specs for the headphones I'm using:


Beyerdynamic DT801

Impedance (Ohms) 250
Sensitivity (dB) 94
Max Power (mW) 175Max
SPL (dB) 116


I should add that the buzz reaches its minimum point not at 75%
volume,
but actually at around 50%, and the buzzing is much more pronounced
in
the left side than in the right. The audio is coming from my G4's
line
out, and there is no buzzing when the headphones are plugged in
directly to the computer.

Any further comments and suggestions are looked forward to and
appreciated!


Ah, you didn't say you were feeding it with a computer!

There is no real need for a computer PSU to give a well smoothed
output - well regulated yes but not 'clean.' Therefore it could be the
supply line to the audio card being dirty, it could be being passed
through your audio card earthing (common) line, it could be the effect
of your amp being earthed having the co-ax screen connected to the PC
and earth current flowing, or (most likely) it could be pick-up from
any one (or more) or a number of different clocks within the machine.

IMO the most likely source is you video card which you can check quite
easily. Just go into the video setup and change the frame refresh rate
of your monitor and see if the pitch of the buzz changes with it. If
so the simplest solution might be to relocate the sound card (assuming
the video is AGP) to a different PCI socket further away. If the sound
is embedded on the motherboard then try a separate sound card and
again insert it as far from the video card as possible,

If that is not the cause try disconnecting the screen of the co-ax
plug at the PC end and let the amp and PC carry earth continuity
through the mains. Beware that if there is no mains earth continuity
this may cause a very loud buzz so keep the amp volume well down when
you try it.

Don't give up - it just takes time and a lot of fiddling!


--
Woody

harrogate3 at ntlworld dot com