What is recommended volume level for Source, Preamp and Power amp?

vbutani

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I recently bought Swara tube preamp and O&B audio SS2150 A/B power amp and trying different combinations of volume levels in all the devices.

My setup:
LG G8x Mobile to play FLAC/Apple lossless files >> Swara tube preamp >> O&B Power amp >> Dali Blue 6006 Floorstanding speakers

I observed that setting full volume on power amp causes humm sound which is only audible going nearby speakers when there is no music playing.

I dont know what is the recommended volume level for each device to reduce noise and get best possible sound out of it?

Please advise.

Thanks.
 

sandeepmohan

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I observed that setting full volume on power amp causes humm sound which is only audible going nearby speakers when there is no music playing.
Are you sure you can adjust the gain on your power amplifier? Its usually on the pre amp.
Ideally; you want the pre amp volume level around the 40% mark, where its at the listenable level.
You adjust or reduce the gain on your source according to the above.
Listen for hum with only the power amplifier connected to your loudspeaker. If its not there, then its likely coming from your pre amplifier, cable linking your mobile device to the pre amplifier. Diagnose step by step.
 

Yelamanchili manohar

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I recently bought Swara tube preamp and O&B audio SS2150 A/B power amp and trying different combinations of volume levels in all the devices.

My setup:
LG G8x Mobile to play FLAC/Apple lossless files >> Swara tube preamp >> O&B Power amp >> Dali Blue 6006 Floorstanding speakers

I observed that setting full volume on power amp causes humm sound which is only audible going nearby speakers when there is no music playing.

I dont know what is the recommended volume level for each device to reduce noise and get best possible sound out of it?

Please advise.

Thanks.
Preamp at max, and power amp till where it doesn't distort :)
 

vbutani

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Are you sure you can adjust the gain on your power amplifier? Its usually on the pre amp.
Ideally; you want the pre amp volume level around the 40% mark, where its at the listenable level.
You adjust or reduce the gain on your source according to the above.
Listen for hum with only the power amplifier connected to your loudspeaker. If its not there, then its likely coming from your pre amplifier, cable linking your mobile device to the pre amplifier. Diagnose step by step.
Thanks for the details, I tried following:-
(Yes, the gain control is available on my power amp.)

I checked for humm by only connecting to power amp, humm is present. I tried changing cables and observed that humm varies on the cable. It seems my EP to RCA cable and RCA-to-RCA cable are culprit as they're very basic cable.
I will try other cables to eliminate humm issue.

I am still not clear on volume level part.
Is it good idea to keep mobile (digital) source volume at 100% and use pre amp volume which has remote control, but in this case I have to turn down gain on power amp to 20-25% as it will be more loud and not at listenable level.
if power amp is set to 20-25% gain, is there any chance speakers are not getting enough current to drive speakers fluently?

I hope I am not creating confusion here!

Thanks
 

Yelamanchili manohar

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Thanks for the details, I tried following:-
(Yes, the gain control is available on my power amp.)

I checked for humm by only connecting to power amp, humm is present. I tried changing cables and observed that humm varies on the cable. It seems my EP to RCA cable and RCA-to-RCA cable are culprit as they're very basic cable.
I will try other cables to eliminate humm issue.

I am still not clear on volume level part.
Is it good idea to keep mobile (digital) source volume at 100% and use pre amp volume which has remote control, but in this case I have to turn down gain on power amp to 20-25% as it will be more loud and not at listenable level.
if power amp is set to 20-25% gain, is there any chance speakers are not getting enough current to drive speakers fluently?

I hope I am not creating confusion here!

Thanks
Hi butani :)

1. Do you have your components plugged into different plugs in the wall. This could cause the hum you're experiencing. Best is to use a power extension board and everything into one.
2. Please keep your mobile phone volume at 100%. We certainly don't need any digital volume attenuation at this stage.
3. Coming to the preamp and poweramp, try starting at 50% on both, and, then tweak from there. The knob you have on the power amp, is not a volume control. It is a gain knob. The more the gain, then more the distortion. So you really have to experiment with preamp volume level and poweramp gain level to see where it sounds best to you,
 

Yelamanchili manohar

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Thanks for the details, I tried following:-
(Yes, the gain control is available on my power amp.)

I checked for humm by only connecting to power amp, humm is present. I tried changing cables and observed that humm varies on the cable. It seems my EP to RCA cable and RCA-to-RCA cable are culprit as they're very basic cable.
I will try other cables to eliminate humm issue.

I am still not clear on volume level part.
Is it good idea to keep mobile (digital) source volume at 100% and use pre amp volume which has remote control, but in this case I have to turn down gain on power amp to 20-25% as it will be more loud and not at listenable level.
if power amp is set to 20-25% gain, is there any chance speakers are not getting enough current to drive speakers fluently?

I hope I am not creating confusion here!

Thanks
Hi butani :)

1. Do you have your components plugged into different plugs in the wall. This could cause the hum you're experiencing. Best is to use a power extension board and everything into one.
2. Please keep your mobile phone volume at 100%. We certainly don't need any digital volume attenuation at this stage.
3. Coming to the preamp and poweramp, try starting at 50% on both, and, then tweak from there. The knob you have on the power amp, is not a volume control. It is a gain knob. The more the gain, then more the distortion. So you really have to experiment with preamp volume level and poweramp gain level to see where it sounds best to you,
 

vbutani

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Hi butani :)

1. Do you have your components plugged into different plugs in the wall. This could cause the hum you're experiencing. Best is to use a power extension board and everything into one.
2. Please keep your mobile phone volume at 100%. We certainly don't need any digital volume attenuation at this stage.
3. Coming to the preamp and poweramp, try starting at 50% on both, and, then tweak from there. The knob you have on the power amp, is not a volume control. It is a gain knob. The more the gain, then more the distortion. So you really have to experiment with preamp volume level and poweramp gain level to see where it sounds best to you,
Super! This will help in setting up right volume for my setup!

I made sure that all components are plugged in same extension however it's same issue but I think using good shielded cable may solve the problem.

Thanks @Yelamanchili manohar
 

girishtd8262

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Hi butani :)

1. Do you have your components plugged into different plugs in the wall. This could cause the hum you're experiencing. Best is to use a power extension board and everything into one.
2. Please keep your mobile phone volume at 100%. We certainly don't need any digital volume attenuation at this stage.
3. Coming to the preamp and poweramp, try starting at 50% on both, and, then tweak from there. The knob you have on the power amp, is not a volume control. It is a gain knob. The more the gain, then more the distortion. So you really have to experiment with preamp volume level and poweramp gain level to see where it sounds best to you,
It sounds good if you keep high vol on source. preamp or power amplifier side start from lower bol keep it at your regular listening level.leave some good headroom for the amp to work.
Lower vol on amp makes sound to be more clearer.this is my observation
 

jls001

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Digital volume control in the phone throws away bits. So keep it full at all times unless there's no other volume control in the chain.

Keep the volume control of your power amp also full.

Control the volume from preamp. Volume control is traditionally done at the preamp stage, specifically at the input of the preamp before the signal from the source reaches the active electronics of the preamp.

Alternately, you can also try playing music without the preamp in the chain since your power amp has volume control.

You can choose your preferred sound from these two options.
 

amrutmhatre90

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Digital volume control in the phone throws away bits. So keep it full at all times unless there's no other volume control in the chain.

Keep the volume control of your power amp also full.

Control the volume from preamp. Volume control is traditionally done at the preamp stage, specifically at the input of the preamp before the signal from the source reaches the active electronics of the preamp.

+1 Volume should be controlled at Pre Amp but full power amp attracts noise and hiss, if the speakers are sensitive then it is more than audible.

The practice I follow is, source volume, pre amp half and then adjust the gain at power amp till it gets loud enough to reduce volume.
Pre amp needs more than 25% also to sing to its glory.

One can try keeping the pre amp volume full and then adjust the power amp till it is loud enough which you sometimes listen to but loud. Then just play with pre amp volume to make changes daily and not touch the power amp gain.
This way no guest at home can blow your speakers even if they increase the pre amp volume to full:D
 

reachkalyan.kr

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I checked for humm by only connecting to power amp, humm is present. I tried changing cables and observed that humm varies on the cable. It seems my EP to RCA cable and RCA-to-RCA cable are culprit as they're very basic cable.
I will try other cables to eliminate humm issue.
Humm can report for several reason.
IMHO ,Humm should not be present if only power cable and speakers cables are connected in the Poweramp.
Remove the RCA cables at the Poweramp side and try to isolate.
 

jls001

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The practice I follow is, source volume, pre amp half and then adjust the gain at power amp till it gets loud enough to reduce volume.
Pre amp needs more than 25% also to sing to its glory.
A clarification about the terms "gain" and "volume": gain is the amount of change (amplification) of the amplitude of the incoming signal. Whether it's preamp or power amp, this ratio (namely, the voltage of output signal, Vo/the voltage of input signal, Vi) is usually fixed. In rare cases there might be a toggle switch which allows selection of two different gains. What the volume potentiometer does is reduce the value of Vi. If Vi is reduced the Vo is also reduced by a corresponding ratio, namely, the gain.

So "volume" and "gain" are two different things and must not be interchangeably used.

Also, most power amps do not have volume control though some do have gain selector switch.

Not trying to be pedantic:)
 

keith_correa

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This is not a simple question and the answer to your question is not simple too. Gain and volume are different animals. Simplistically, gain is a load at the input while volume affects the output. What is the output impedance of your pre? Your manufacturer should be able to tell you that. Based on that, your amp manufacturer should be able to tell you what the ideal gain setting should be kept at the amp.
The volume pot is a resistive element so the more it is opened up the better the sound. So once the gain on the amp is determined and fixed, you don't play around with that any more. You play around with the pre volume and the source volume to determine what is best sounding for YOU!

Edit: I see Joshua beat me to it. :D
 

Kannan

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@vbutani from the specs, I see that the amp has input sensitivity settings of 0.5 V and 1.5V.
The volume control on this power amp it is only an attenuator, to be used only if you do not have a dedicated preamp.
Since you have a dedicated preamp, set it to full (no brainer here).

Of course put the digital output full on your LG source aswell.
Try both 0.5 and 1.5 volt sensitivity on the power amp.

Go with the sensitivity that offers a wider bandwidth on the volume pot of the preamp. I guess with modern DACs pushing out 2 volts, 0.5 should be good enough on the power amp, but try both settings
 

mbhangui

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This is not a simple question and the answer to your question is not simple too. Gain and volume are different animals. Simplistically, gain is a load at the input while volume affects the output. What is the output impedance of your pre? Your manufacturer should be able to tell you that. Based on that, your amp manufacturer should be able to tell you what the ideal gain setting should be kept at the amp.
The volume pot is a resistive element so the more it is opened up the better the sound. So once the gain on the amp is determined and fixed, you don't play around with that any more. You play around with the pre volume and the source volume to determine what is best sounding for YOU!

Edit: I see Joshua beat me to it. :D
Both Keith and Joshua have expained it well. This is exactly the reason I have a Nelson Pass B1 in my chain. The B1 allows me to floor the accelerator of my power amp. Here is what Nelson says and uses the analogy of flooring the accelerator and still driving the car at 55 mph :)

So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.

I suppose if I had to floor the accelerator to drive 55 mph, maybe I’d think the life was being sucked out of my driving. Then again, maybe I like 55. Nice and safe, good gas mileage…

Is impedance matching an issue? Passive volume controls do have to make a trade-off between input impedance and output impedance. If the input impedance is high, making the input to the volume control easy for the source to drive, then the output impedance is also high, possibly creating difficulty with the input impedance of the power amplifier. And vice versa: If your amplifier prefers low source impedance, then your signal source might have to look at low impedance in the volume control.

This suggests the possibility of using a high quality buffer in conjunction with a volume control. A buffer is still an active circuit using tubes or

transistors, but it has no voltage gain – it only interposes itself to make a low impedance into a high impedance, or vice versa.

If you put a buffer in front of a volume control, the control’s low impedance looks like high impedance. If you put a buffer after a volume control, it makes the output impedance much lower. You can put buffers before and after a volume control if you want.

The thing here is to try to make a buffer that is very neutral. Given the simple task, it’s pretty easy to construct simple buffers with very low distortion and noise and very wide bandwidth, all without negative feedback.

Ask @sachu888 if he has the boards for PASS B1 or the the version without the coupling capacitors. It is a wonderful device to match your source with your power amplifier. It has a volume control and has a unity gain.
 
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vbutani

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Humm can report for several reason.
IMHO ,Humm should not be present if only power cable and speakers cables are connected in the Poweramp.
Remove the RCA cables at the Poweramp side and try to isolate.
Thanks for your opinion, I checked as you suggested and found no humm in the power amp when connected without RAC and just power cable and speakers.
 

vbutani

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This is not a simple question and the answer to your question is not simple too. Gain and volume are different animals. Simplistically, gain is a load at the input while volume affects the output. What is the output impedance of your pre? Your manufacturer should be able to tell you that. Based on that, your amp manufacturer should be able to tell you what the ideal gain setting should be kept at the amp.
The volume pot is a resistive element so the more it is opened up the better the sound. So once the gain on the amp is determined and fixed, you don't play around with that any more. You play around with the pre volume and the source volume to determine what is best sounding for YOU!

Edit: I see Joshua beat me to it. :D
Output impedance on pre amp is 280 ohm. the power amp has gain input selection of 0.5v (High gain) and 1.5v (Low gain).
My source has capability of max 1.9v and I am sure Pre amp output will be same around 2v.
Let me try with volume pot, but it seems I have lot of power now! :)
 

vbutani

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@vbutani from the specs, I see that the amp has input sensitivity settings of 0.5 V and 1.5V.
The volume control on this power amp it is only an attenuator, to be used only if you do not have a dedicated preamp.
Since you have a dedicated preamp, set it to full (no brainer here).

Of course put the digital output full on your LG source aswell.
Try both 0.5 and 1.5 volt sensitivity on the power amp.

Go with the sensitivity that offers a wider bandwidth on the volume pot of the preamp. I guess with modern DACs pushing out 2 volts, 0.5 should be good enough on the power amp, but try both settings
@Kannan you're right, I have checked with the power amp designer as well and he suggested the same.
The volume attenuator provided is useful while directly connecting source without pre amp.
Though I will try both settings.
 
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