4 questions re. Denon PMA-600NE amplifier.

[Iolo]

I'm very impressed with the high quality of sound produced by my new Denon PMA-600NE amplifier (bought last week from Peter Tyson), but before I can relax and enjoy it I would be most grateful for help with the following four questions, please.

1. The amp came with two "short-circuiting pin plugs" in the two phono input sockets on the rear of the amp. I've removed them in order to insert the R & L jacks from my Internet Radio in the amp (the resulting Internet radio reception through the Denon is excellent). I've stored the two "short-circuiting pin plugs" in an envelope but am curious as to what they are for. There's no explanation in the Denon's manual, only a note warning that they should never be placed in the audio output Recording sockets.

2. Over part of the grille on the top of the amp there's a rigid, clear, plastic sheet which has ventilation holes in it which are aligned perfectly with the ventilation holes of the grille (in the metal case of the top of the amp). This plastic sheet (about six inches by three inches in size) is attached to the top of the amp by four plastic clips which have been clipped to four of the holes of the grille in the metal case of the amp. It would not be easy to remove this plastic sheet, so I assume that it is not to be removed. What is the purpose of this plastic sheet, please?

3. I've used the bass, treble, and balance knobs on the front of the amp to produce the sound and balance I want, but I've been curious to hear the intended sound of the tracks I play, and the intended sound of the soundtracks of TV programmes I watch. So I've pressed the "Source Direct" button on the front of the amp while playing the TV, while playing tracks bluetoothed from my smartphone, and while playing the Internet radio. In each case I have found that switching on "Source Direct" loads about 75% of the volume onto my left speaker, so that only a little sound can be heard from the right speaker! Surely that's not what the producers of the music and programmes intended. The only difference between my left and right speaker is that the speaker cable from the amp to the left speaker is about two metres shorter than the cable from the amp to the right speaker. Does this difference in cable lengths account for the left speaker receiving greater volume?

4. I have positioned the amp on top of my DVD player in the space underneath my TV. The grilles in the two sides of the amp have plenty of space in front of them; there are two cable holes (about 2" in diameter and about 18" apart) in the back of the cabinet, directly behind the amp (so there is an air-flow at the back of the amp); and the door of the cabinet will always be open when the amp is switched on (as shown in the photo below). But when I place my hand in the space between the grille on the top of the amp and the wood of the cabinet above the amp I find that the air in that space is quite warm, due to the heat produced by the amp. Is this warmth normal? (I imagine some users may place a turntable or other equipment on top of the amp.)

 

[Gray]

I'll start you off with an answer to question 1.
The idea behind shorting plugs is to electrically close the inputs to prevent noise - more worthwhile on the high gain phono inputs - but you don't want them shorting any outputs.

 

[Al ears]

Regards question 3 you mentioned having played with the balance control. Is it moved to the left?
Asking because some Source Direct buttons only effect the Tone Controls and not the Balance.
The difference in speaker cable length is nothing to worry about.
as to Question 2, no idea but if it was meant to be removed it would say so in the manual.

 

[Gray]

4) If they do, user's shouldn't be placing anything on top of the amp.
It will be normal to feel warmth above the amp (even in free space).
I'd be happier to see as much of an opening at the back as you've got at the front - a 2 inch hole isn't much.
Having said that, some people box amps in worse than you have - too much heat build- up does nothing for longevity though.

 

[Iolo]

Regards question 3 you mentioned having played with the balance control. Is it moved to the left?
Asking because some Source Direct buttons only effect the Tone Controls and not the Balance. The difference in speaker cable length is nothing to worry about.

I started out with Source Direct switched on, but found that nearly all the Balance was loaded onto the left speaker and that the sound coming from the left speaker was also heavily bassy, so I switched Source Direct off and then was able to lessen the level of bass and equalise the balance between the left and right speakers by turning the Balance Control almost all the way in favour of the right speaker! But I find that effect odd. I believe that the only difference between my two speakers is that the left-speaker's cable is about two metres shorter than the right-speaker's cable.

as to Question 2, no idea but if it was meant to be removed it would say so in the manual.

I wonder if the purpose of the plastic sheet is that if the top of the amp becomes too hot the plastic would react in some way, indicating that a heat problem needs attention?

 

[Gray]

Your balance issue needs addressing.
(It's not related to speaker cable length).
Is it the same with all sources?

 

[Iolo]

Your balance issue needs addressing.
(It's not related to speaker cable length).
Is it the same with all sources?

Yes, regardless of whatever is the source, having "Direct Source" switched on diverts about 75% of the volume to the left speaker. (It's just struck me that this may relate to my having to turn the Balance Control about 75% towards the right speaker when "Direct Source" is switched off. )

I wonder if the Balance Control needs adjusting inside the amp, which would unfortunately mean having to pack the amp up and sending it back for examination and perhaps repair.

Perhaps I should firstly try attaching a different pair of speakers - which also have wires of equal length?

 

[Gray]

Yes, regardless of whatever is the source, having "Direct Source" switched on diverts about 75% of the volume to the left speaker. (It's just struck me that this may relate to my having to turn the Balance Control about 75% towards the right speaker when "Direct Source" is switched off. )

I wonder if the Balance Control needs adjusting inside the amp, which would unfortunately mean having to pack the amp up and sending it back for examination and perhaps repair.

Perhaps I should firstly try attaching a different pair of speakers - which also have wires of equal length?

The first thing to do is swap the speaker cables at the amp terminals.
See if the symptoms change sides.

Most unlikely the amp is faulty - and even if it is, you're not going to accept any repair offer.

 

[Al ears]

Your balance issue needs addressing.
(It's not related to speaker cable length).
Is it the same with all sources?

doesn't sound right at all does it. Wonder if speakers worked OK with his previous amp.D

Do the speakers sound correct with all Tone Controls and Balance switched to the dead centre position and the Source Direct off?

 

[Gray]

doesn't sound right at all does it. Wonder if speakers worked OK with his previous amp.D

Makes you wonder 🤔
I think he's saying that the imbalance needs massive correction, regardless of source direct switching.

 

[Iolo]

The first thing to do is swap the speaker cables at the amp terminals.
See if the symptoms change sides.

Yes! Gray, that's clever. Of course that's the thing to do! I will try that tomorrow.

Most unlikely the amp is faulty - and even if it is, you're not going to accept any repair offer.

Gray, even if Denon say "Send it back to us!" do you think I should just stick with the amp as it is? I agree that as the amp is at present, having to turn the Balance Control 75% to the right to get equal balance, the amp produces satisfying sound. Are you saying that if the balance is wrongly set inside the machine it's not worth having anyone fix the balance - because other problems could develop in transit or during the repair?

Wonder if speakers worked OK with his previous amp.

Yes, "Al ears", the balance between the speakers worked as it should with the previous amp's Balance Control.

Do the speakers sound correct with all Tone Controls and Balance switched to the dead centre position and the Source Direct off?

"Al ears", with Source Direct switched off the volume balance is only equal when the Balance Control knob is turned 75% to the right (in favour of the right speaker), well beyond the central position. And with Source Direct switched on the balance is about 75% in favour of the left speaker - and of course one can't alter the balance because Source Direct knocks out use of the Balance Control knob.

 

[Al ears]

Yes! Gray, that's clever. Of course that's the thing to do! I will try that tomorrow.

Gray, even if Denon say "Send it back to us!" do you think I should just stick with the amp as it is? I agree that as the amp is at present, having to turn the Balance Control 75% to the right to get equal balance, the amp produces satisfying sound. Are you saying that if the balance is wrongly set inside the machine it's not worth having anyone fix the balance - because other problems could develop in transit or during the repair?

Yes, "Al ears", the balance between the speakers worked as it should with the previous amp's Balance Control.

"Al ears", with Source Direct switched off the volume balance is only equal when the Balance Control knob is turned 75% to the right (in favour of the right speaker), well beyond the central position. And with Source Direct switched on the balance is about 75% in favour of the left speaker - and of course one can't alter the balance because Source Direct knocks out use of the Balance Control knob.

Are you sure it does? As I said some only work on the Tone Controls.
Either way there is something wrong with that amp.
I would return it.

 

[Iolo]

Are you sure it does? As I said some only work on the Tone Controls.

Yes, sure, by way of my experience of the Source Direct button, and by what the manual confirms, as follows:

"Adjusting the tone:
1 Press SOURCE DIRECT on the main unit to turn off
source direct mode.
The SOURCE DIRECT indicator turns off.
2 Turn the BASS, TREBLE and BALANCE knobs to adjust
the tone. "

and

"Playback in source direct mode:
The signal does not pass through the tone adjustment circuitry (BASS,
TREBLE and BALANCE), resulting in playback of a higher sound
quality"

 

[Al ears]

Yes, sure, by way of my experience of the Source Direct button, and by what the manual confirms, as follows:

"Adjusting the tone:
1 Press SOURCE DIRECT on the main unit to turn off
source direct mode.
The SOURCE DIRECT indicator turns off.
2 Turn the BASS, TREBLE and BALANCE knobs to adjust
the tone. "

and

"Playback in source direct mode:
The signal does not pass through the tone adjustment circuitry (BASS,
TREBLE and BALANCE), resulting in playback of a higher sound
quality"

I see, thanks for clarification

 

[Gray]

Gray, even if Denon say "Send it back to us!" do you think I should just stick with the amp as it is? I agree that as the amp is at present, having to turn the Balance Control 75% to the right to get equal balance, the amp produces satisfying sound. Are you saying that if the balance is wrongly set inside the machine it's not worth having anyone fix the balance - because other problems could develop in transit or during the repair?

You only bought the amp last week lolo.
With the balance control in its central position, there should be equal volume from your speakers (regardless of the 'source direct' switch position).
Forget all about the extra 2 metres of speaker cable. If it were 200 metres, it still wouldn't give you the imbalance.
You say your speakers were OK with a previous amp so that does suggest a problem with this new amp.
If you confirm it to be faulty, under no circumstances should you stick with it, nor have anybody repair it. The retailer (not Denon) is your first port of call.
You should accept nothing less than a brand new replacement. As an alternative, the retailer might offer you a full refund, in which case you can buy from elsewhere.

 

[Al ears]

You only bought the amp last week lolo.
With the balance control in its central position, there should be equal volume from your speakers (regardless of the 'source direct' switch position).
Forget all about the extra 2 metres of speaker cable. If it were 200 metres, it still wouldn't give you the imbalance.
You say your speakers were OK with a previous amp so that does suggest a problem with this new amp.
If you confirm it to be faulty, under no circumstances should you stick with it, nor have anybody repair it. The retailer (not Denon) is your first port of call.
You should accept nothing less than a brand new replacement. As an alternative, the retailer might offer you a full refund, in which case you can buy from elsewhere.

Hear, hear!

 

[Iolo]

Re. my third question re. the apparent loading of "balance" on the left speaker at the expense of the right speaker, this afternoon I did numerous tests: swapping over the leads from the amp's left and right outputs; attaching different speakers; attaching different wires; and testing the two sets of speakers in different locations in the room.

In the end I was reminded of the extraordinary processes of experimentation which sound specialists have to go through in dealing with acoustics in certain concert halls! After hours of experimentation I proved to myself that there's nothing wrong with either of my two sets of speakers, nor the amp, nor the wiring.

The "problem" was the different immediate environments of the two speakers. The environment of the left speaker was enhancing its volume, while the quite different environment of the right speaker (on the other side of the considerably large room) was reducing it.

The solution has been to locate the right speaker differently. For example, one change is that while the left speaker remains in the same position on the floor (though actually separated from carpet by a layer of granite tiles), the other speaker is now sited about 12" above the sea of carpet beneath and in front of it.

I now have near-equal balance between the two speakers when the amp is in "Direct Source" mode. And by turning the Balance Control a little to the right, with "Direct Source" switched off, I now have perfect balance.

So that particular problem has now been solved.

My thanks to those who tried to help!

 

[Gray]

The solution has been to locate the right speaker differently.

The sooner you get both speakers on stands with tweeters at ear height (equally distant from your ears), the sooner you'll start to appreciate that amp even more than you do now

 

[Iolo]

The sooner you get both speakers on stands with tweeters at ear height (equally distant from your ears), the sooner you'll start to appreciate that amp even more than you do now

Ha, ha! Yes! I'm sure that'd be the case. I have to say that for £359 ("Peter Tyson", Carlisle, matched the cheapest price elsewhere) the quality of sound of this Denon is magnificent. Even music bluetoothed to it (from two rooms beyond the living-room, where the Denon is) is magnificently reproduced. It's a joy for me, at 67, to hear my life's music collection presented so marvellously!

 

[Gray]

It's a joy for me, at 67, to hear my life's music collection presented so marvellously!

It's all about the music (at least it should be).
The hi-fi is just a means to an end.