Author Topic: One for hi-fi buffs  (Read 733 times)

Redlight

  • Enjoying life in the slow lane
One for hi-fi buffs
« on: May 02, 2020, 03:56:32 pm »
I wonder if anyone can explain something rather odd that bugs me with my stereo set up.

In a nutshell - one speaker always seems slightly louder than the other.

I'm using a NAD 3020e amp that has served me well for more than 30 years. On headphones, there's no discernible difference in volume between the channels but when I use the speakers the left always sounds slightly louder.  I've checked the polarity on the connections and the speaker cables are about the same length, give or take a foot.

Any suggestions?
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Gattopardo

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  • Overseaing the building of the death star
Re: One for hi-fi buffs
« Reply #1 on: May 02, 2020, 04:22:11 pm »
Swap the speakers over, see if it continues.

nicknack

  • Hornblower
Re: One for hi-fi buffs
« Reply #2 on: May 02, 2020, 04:28:52 pm »
Dodgy connection in a switch/pot on the Nad. At least that's what does it on my 40 year old Sansui. Switch cleaner and a good waggle.
<edit>memo to self: always fully read before replying. I don't use headphones so I'm not sure if my response is useful. But you could still try any switching to speaker connections.
There's no vibrations, but wait.

Re: One for hi-fi buffs
« Reply #3 on: May 02, 2020, 04:30:27 pm »
Once you have ruled out the equipment, as Gattorpardo and nicknack suggest, then my thoughts turn to the positioning of yourself and the two speakers (you did say stereo). If your room has no or very little acoustic treatment then:
A, you could be sitting in a null or a peak,
B, the speakers might not be equidistant from the side walls, or
C, the acoustics of the room might not be even, for example, if you have a brick wall to one side and a plasterboard wall on the other side. This would allow some frequencies to have a difference response and sound louder or softer on one side.

Re: One for hi-fi buffs
« Reply #4 on: May 02, 2020, 04:34:23 pm »
Dodgy connection in a switch/pot on the Nad. At least that's what does it on my 40 year old Sansui. Switch cleaner and a good waggle.
<edit>memo to self: always fully read before replying. I don't use headphones so I'm not sure if my response is useful. But you could still try any switching to speaker connections.
This is what I had on my Harman Kardon Amp.
Switch cleaner sorted it out.
Clicky

Re: One for hi-fi buffs
« Reply #5 on: May 02, 2020, 05:23:30 pm »
First thing to do is swap the channels over. Does the imbalance follow?

Wombat

  • Is it supposed to hurt this much?
Re: One for hi-fi buffs
« Reply #6 on: May 02, 2020, 05:40:31 pm »
Have you had a hearing test lately?  It might be you!  I've evidently had uneven hearing damage for quite some years.  From the frequencies that have suffered, I'm more inclined to attribute it to the racing two stroke motorcycles than the Led Zeppelin...
Wombat

Re: One for hi-fi buffs
« Reply #7 on: May 02, 2020, 06:06:00 pm »
According the the circuit diagram that I found online, there are a couple of switch contacts between the amplifier outputs and the speaker.

One is the headphone socket switch, which shuts the speakers off when the headphones are plugged in. If there is some resistance in those contacts, it will have the effect that you described. There is a 220 Ohm resistor in series with the headphones, so small amounts of resistance will make little difference to the headphones.

There is also some component (labelled A-25, numbered E401 and E402 here:- https://www.vintage-radio.net/forum/attachment.php?s=c63081e6ad7f311d57f98be8f0dd511d&attachmentid=50583&d=1304439057) which I don't recognise, but it has to take the full speaker current.

I can't see other components that would reduce the volume without distortion.
Quote from: Kim
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Feanor

  • It's mostly downhill from here.
Re: One for hi-fi buffs
« Reply #8 on: May 02, 2020, 06:20:00 pm »
E401 and E402 are thermal cutouts.

I've had more than a few of these beasts on the bench over the years, most recently about 3 months ago!


Re: One for hi-fi buffs
« Reply #9 on: May 02, 2020, 07:55:58 pm »
FWIW some headphones are much higher impedance than the nominal 8 ohms (I'm looking at you, Mr Sennheiser).  And there may be something else that limits the output into the headphones.  This means that they draw less current and a bad connection in the speaker path is much less likely to affect the output to the headphones than the speakers.

IIRC the NAD3020 does not have a 'speaker switch'; if so, the usual arrangement is that when headphones are used the speakers are switched out of the circuit by the headphone socket itself, i.e. pushing the jack into the headphone socket opens contacts in the socket which disconnect the speakers. These contacts are remade when the jack is removed; well that is the idea anyway....this arrangement isn't 100% reliable IME.  The headphone socket would be the first place I'd look for that bad contact.

(ps I see much of the above is covered by Diver300 above; sorry for duplicate post)

cheers

Redlight

  • Enjoying life in the slow lane
Re: One for hi-fi buffs
« Reply #10 on: May 02, 2020, 09:44:27 pm »
Thanks for all of the advice so far.  In answer to the question about swapping the speakers - yes, I've tried swapping the connections so that the left channel on the amp is hooked up to the right hand speaker and vice-versa, and it makes no difference. The left is still louder.

I hadn't thought about having a hearing test, but I think what I'll do is get a second opinion on what I'm hearing, since it may be a while before I can get a test.  I'm intrigued at the suggestion that the composition of the walls might have an effect. The left is close to a very solid exterior wall and the right placed at the same distance from a single brick interior wall. Quite how I fix that, apart from a lot of trial and error, I don't know, but it could be fun.

The technical information is intriguing but well beyond my limited abilities so I will resist any urge to open up the amp and start fiddling around. There's a very good hi-fi shop (from where I bought my current turntable and speakers) just down the road, so if the problem persists I will drop the amp in there when it re-opens. I'm sure they will try to sell me a new amp and, since the incumbent is 31 years old I might stand a chance at persuading Mrs Redlight that the purchase is justified :-)
Between the Disney abattoir and the chemical refinery

Re: One for hi-fi buffs
« Reply #11 on: May 02, 2020, 09:48:38 pm »
Thanks for all of the advice so far.  In answer to the question about swapping the speakers - yes, I've tried swapping the connections so that the left channel on the amp is hooked up to the right hand speaker and vice-versa, and it makes no difference. The left is still louder
[/quote]

The left speaker, or the speaker connected to the left channel?

Mrs Pingu

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Re: One for hi-fi buffs
« Reply #12 on: May 02, 2020, 09:49:24 pm »
Did you swap the speakers around?
Do not clench. It only makes it worse.

Redlight

  • Enjoying life in the slow lane
Re: One for hi-fi buffs
« Reply #13 on: May 02, 2020, 09:50:23 pm »
Did you swap the speakers around?

No - but I'll try that tomorrow. All I've done so far is swap the connections on the amp.
Between the Disney abattoir and the chemical refinery

Redlight

  • Enjoying life in the slow lane
Re: One for hi-fi buffs
« Reply #14 on: May 02, 2020, 09:51:34 pm »
Thanks for all of the advice so far.  In answer to the question about swapping the speakers - yes, I've tried swapping the connections so that the left channel on the amp is hooked up to the right hand speaker and vice-versa, and it makes no difference. The left is still louder

The left speaker, or the speaker connected to the left channel?
[/quote]

The left speaker, which is now relaying the signal from the right hand channel on the amp.
Between the Disney abattoir and the chemical refinery

Kim

  • Timelord
Re: One for hi-fi buffs
« Reply #15 on: May 02, 2020, 10:06:44 pm »
Thanks for all of the advice so far.  In answer to the question about swapping the speakers - yes, I've tried swapping the connections so that the left channel on the amp is hooked up to the right hand speaker and vice-versa, and it makes no difference. The left is still louder

The left speaker, or the speaker connected to the left channel?

The left speaker, which is now relaying the signal from the right hand channel on the amp.

That (assuming you haven't touched the input to the amp) suggests the problem is downstream of the amp.  Therefore the speakers, the room, your ears or your brain.
Careful, Kim. Your sarcasm's showing...

Mrs Pingu

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Re: One for hi-fi buffs
« Reply #16 on: May 02, 2020, 10:28:42 pm »
So testing:
Try listening with your back to the speakers
Swap the speakers round
In that order before you get a hearing test :)
Do not clench. It only makes it worse.

Re: One for hi-fi buffs
« Reply #17 on: May 02, 2020, 11:13:06 pm »

That (assuming you haven't touched the input to the amp) suggests the problem is downstream of the amp.  Therefore the speakers, the room, your ears or your brain.

so no excuse for buying new kit then.

[Unless it is new speakers, new house, rewired brain...etc....]

cheers

Re: One for hi-fi buffs
« Reply #18 on: May 02, 2020, 11:48:10 pm »
Mrs. Pingu, can I ask what you are listening to for testing purposes and if this is music (as opposed to pink noise) whether you are familiar with the recording and the stereo placement of the instruments and vocals?

Valiant

  • aka Sam
    • Radiance Audio
Re: One for hi-fi buffs
« Reply #19 on: May 03, 2020, 12:03:13 am »
If you've swapped the speakers and outputs and the seem to not make a difference, it could be that some of the capacitors are loosing their capacitance and may need to be replaced soon. Entirely normal for something of that age.
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Re: One for hi-fi buffs
« Reply #20 on: May 03, 2020, 12:11:29 am »
Thanks for all of the advice so far.  In answer to the question about swapping the speakers - yes, I've tried swapping the connections so that the left channel on the amp is hooked up to the right hand speaker and vice-versa, and it makes no difference. The left is still louder

The left speaker, or the speaker connected to the left channel?

The left speaker, which is now relaying the signal from the right hand channel on the amp.

That (assuming you haven't touched the input to the amp) suggests the problem is downstream of the amp.  Therefore the speakers, the room, your ears or your brain.
Or following the same logic as the thread about TV reception, the cable could be faulty.
Quote from: Kim
Paging Diver300.  Diver300 to the GSM Trimphone, please...

Kim

  • Timelord
Re: One for hi-fi buffs
« Reply #21 on: May 03, 2020, 12:24:47 am »
GPWM.  Always suspect wiring.  Especially if it's connected with those crappy speaker terminal things.
Careful, Kim. Your sarcasm's showing...