AV Fixed Volume custom level

I think you mean ‘AV Bypass’. If you set one of the inputs to an ‘AV Bypass’ you essentially by-pass the interal pre-amp section and the signal is sent directly to the power-amp section. Thus the volume is now controlled by the AV unit.

As to the noise - what you are most likley experiencing is a ground-loop noise. If I understand correctly you are using RCA inputs. If this is the case, the noise can be easily cured with an aid of an isolating transformer (typical price around EUR 15).

Dear Adam, 

Thank you for your reply. 

Yes, AV Bypass is named "AV fixed volume" in the Naim app. 

My question was if it was possible to limit the amplitude of the amplification as the default value of 100 (which is fixed) introduces too much noise.

As for the noise, it happens even when no input is plugged into the Atom, which means that the Atom is the culprit here.

This is somewhat disappointing that a built-in feature is not usable because of the hardware side. 

Ardemk,  could you try to describe this noise?  You say it's coming from the tweeter only?  So it's hiss?  Or is it more of a hum?

Fixed volume essentially opens up the taps to the power amp, so the AV amp takes over pre-amp duties. Whether this can be lowered, I don't know.  Have you asked your dealer or Naim support?

Dear Richard,

Thank you for your message and your help.

It is a hiss / white noise (illustration on YouTube here: https://www.youtube.com/watch?v=CCnCMHNyny8).

The question has been asked a few minutes ago to the support by email.

Kind regards,

Ah, if it's excessive hiss then it may be some kind of mismatch (impedance?) between your AV pre and the Atom.  Trying a different i/c might help.

The troubling thing is that it happens even when the Atom is not connected to anything (nothing plugged in aside from the speakers and the power cord naturally).

But you do realise that virtually any power amp working at full power will hiss through the speakers? This is essentially what happens when an AV bypass is engaged.

Unless of course you had an ultra-quiet power supply and lived in a Faraday's cage (i.e. your amp was isolated from any interference from the outside world).

Sure I do!

That is why I would like to limit the amplification to a custom value in order to decrease the hiss to a suitable level.

This is not a stupid question, as previously the default AV Fixed Volume value on other Naim devices was 69 (see post here https://forums.naimaudio.com/t...me-set-to-69-too-low).

ardemk posted:

Sure I do!

That is why I would like to limit the amplification to a custom value in order to decrease the hiss to a suitable level.

This is not a stupid question, as previously the default AV Fixed Volume value on other Naim devices was 69 (see post here https://forums.naimaudio.com/t...me-set-to-69-too-low).

That’s not really a uniti-gain setting - more the input trim in the previous-generation Uniti platform.
The whole point of a uniti-gain is that there is no trimming - you have the whole power of the power-amp section available. 

If it hisses at full volume, so what?  How often will you run your AV processor at 0 dB gain?

A quesiton to move this forward: what happens when you connect all as intended and run your AV processor at a normal listening level? Do you still hear the hiss?

ardemk posted:

The troubling thing is that it happens even when the Atom is not connected to anything (nothing plugged in aside from the speakers and the power cord naturally).

That's probably just the normal hiss from the amp then. Some speakers with a bright top end can make it sound brighter/louder than usual, as can certain speaker cabling and plugs, but it shouldn't normally be intrusive into music unless you listen very close up.

Thank you Adam.

The problem is that even when running the AV processor at a normal listening level you can hear the hiss in the background (I'm talking at listener's position, 3 meters away from the speakers). Otherwise it would be a non-problem!

Switching off the AV Bypass, decreasing the volume of the Uniti to 75 and counterbalancing on the AVR side is night and day regarding the output quality at equal SPL.

OK - one final test:

Could you please re-plug your front L and R speakers into your AV unit (disconnecting your ATOM from the AV unit) and turn the volume up on the AV unit (to 100% or 0dB). Is the hiss the same / different / louder / quietter?

Thank you all for your help.

Will gladly try that out to at least see how it compares.

I use AV Fixed Volume with my AV amp no excessive hiss hear, just the normal level of hiss that is the Naim signature sound but have to be right up to the tweeter to hear it.

SimonPeterArnold posted:

I use AV Fixed Volume with my AV amp no excessive hiss hear, just the normal level of hiss that is the Naim signature sound but have to be right up to the tweeter to hear it.

Thank you for sharing your experience! So in your case it is inaudible from your listening position?

I also use my Naim with an AV bypass function. And I can assure you - it’s dead quiet, even though it’s a bit of a complicated setup. 

Hence all of my questions earlier on. Have you trsted your AV amp with front speakers yet?

Good morning Adam 

It's good to hear (pun intended) that it can be dead silent! 

Thanks for asking news. I will have the opportunity to test the fronts with the AVR tonight and will keep you posted.

ardemk posted:

SimonPeterArnold posted:

I use AV Fixed Volume with my AV amp no excessive hiss hear, just the normal level of hiss that is the Naim signature sound but have to be right up to the tweeter to hear it.

Thank you for sharing your experience! So in your case it is inaudible from your listening position?

That is correct. Try switching the ground switch at the back of the unit to see if it helps. You never know!

I have just tested with the speakers connected to the AVR at full amp level (0dB attenuation), it is way worse than the Naim.

As for the floating ground, unfortunately it hasn't change anything regarding the hiss.

I guess I'm out of option... either choose the comfort of AV Fixed Volume with hiss, or manage myself the volume level per input which is cumbersome.

As the hiss is non-existent at 75 volume, the solution would have been to have a fixed volume to this value.

So that tells us that:

* Possibly your AV pre is introducing an additional level of hiss to the equation

* Mains power supply is probably ‘polluted’ with domestic equipment

Two questions:

1. Do you really listen to your ATOM at leves beyond 75 ? That seems very loud, even for a 40W amp

2. Is your mains properly earthed?

* Possibly your AV pre is introducing an additional level of hiss to the equation

No because even without any other device connected to the uniti the hiss is here!

* Mains power supply is probably ‘polluted’ with domestic equipment

Maybe, but not that many devices connected on the same electricity "branch". No improvement even if only the uniti is the only device plugged on this branch.

Two questions:

1. Do you really listen to your ATOM at leves beyond 75 ? That seems very loud, even for a 40W amp

When in AV Fixed Volume mode, from my understanding the ATOM put himself at max amplification (equals the 100 value on the volume knob). Naturally, this use case is only when the atom is receiving pre-amp signals from the AVR (for movies, tv, pc...). Line level signals from optical or web radios need only a volume of 30 and hiss is not an issue at all for these inputs.

To sum up, the hiss issue only appears in AV Fixed Volume for the Analog input. For other inputs, no problem at all as the volume is manually set to reasonable levels (30-40).

2. Is your mains properly earthed?

Yes, new building with latest norms in terms of ground. I'm pretty confident this is not a ground issue.

Thank you for your help Adam

ardemk posted:

* Possibly your AV pre is introducing an additional level of hiss to the equation

No because even without any other device connected to the uniti the hiss is here!

 

Not really - you wrote that the hiss is much worse when using speakers only with your AV unit.

Any power amp, working at full, un-attenuated power is bound to hiss.  We now know that in your room, with your mains any power amp, working at full volume hisses. ATOM is quieter, which is a testament to NAIM's build quality.

ardemk posted:

 

When in AV Fixed Volume mode, from my understanding the ATOM put himself at max amplification (equals the 100 value on the volume knob). Naturally, this use case is only when the atom is receiving pre-amp signals from the AVR (for movies, tv, pc...). Line level signals from optical or web radios need only a volume of 30 and hiss is not an issue at all for these inputs. 

Yes and no. In this setup it is your AV unit's pre-amp section that now controls the power amp in ATOM. It's your AV unit that now attenuates the signal going into the ATOM's power amp. ATOM's pre-amp is no longer in use. 

So what I don't understand is how is it possible for you to hear the hiss of the ATOMO's power-amp section when watching movies. You cannot possibly be watching them at full power, can you? You must be turning down the AV to a normal listening level. If all is connected correctly, with no ground loops, there should be no audible hiss at normal listening levels.

 

So what I don't understand is how is it possible for you to hear the hiss of the ATOMO's power-amp section when watching movies. You cannot possibly be watching them at full power, can you? You must be turning down the AV to a normal listening level. If all is connected correctly, with no ground loops, there should be no audible hiss at normal listening levels.

It's because whether there is an AVR physically connected to the ATOM or not, the hiss is present when AV Fixed Volume / AV Bypass is enabled for the analog input on the ATOM! What I do need is to attenuate the power of the power amp section (the ATOM in this use case) to decrease the hiss to an acceptable level.

I should have called the topic "Custom power attenuation when in AV Fixed Volume on the Atom" 

BTW, thank you for these discussions that sharpens my understanding in audio hardware / electronics!

ardemk posted:

 

So what I don't understand is how is it possible for you to hear the hiss of the ATOMO's power-amp section when watching movies. You cannot possibly be watching them at full power, can you? You must be turning down the AV to a normal listening level. If all is connected correctly, with no ground loops, there should be no audible hiss at normal listening levels.

It's because whether there is an AVR physically connected to the ATOM or not, the hiss is present when AV Fixed Volume / AV Bypass is enabled for the analog input on the ATOM! What I do need is to attenuate the power of the power amp section (the ATOM in this use case) to decrease the hiss to an acceptable level.

I should have called the topic "Custom power attenuation when in AV Fixed Volume on the Atom" 

BTW, thank you for these discussions that sharpens my understanding in audio hardware / electronics!

If you getting excessive hiss with nothing even connected then its either faulty or your speakers are just not a good  match to the Atom or the Atom is not a match to your speakers. I hear absolutely nothing on mine with AV fixed volume. Have to go up to the tweeter to notice anything, As a matter of interest what firmware are you on? The latest 2.6.2314 build 4658?

Hi , Just to add, I also had hiss when AV fixed volume setting on my Atom. Also present when not connected to the AV amp. Also found reducing volume helped as per the original post but not sure if this can be changed as a default. 

I have recently had a few amps in my room: Cyrus 8A, Nad C 388 both have an Av bypass mode and neither had hiss as notable as the Atom all other equipment the same. 

At present I am only running 2 speakers so I stopped using the Av amp and not sure I could live with the hiss if I had a 5.1 set up again.