Low volume from power amp

[PK1]

I recently started to build a better audio system than the average AVR, and started with an Arcam PA240 power amp that I came across that was a very good deal, so I bought it. I took a pair of CSS-Audion Triton 1TD-X speakers that I had around to start the system with, and then bought an Eversolo DMP-A8 as an all-in-one streamer/DAC/Preamp. Having enough to start playing music, I connected everything together but noticed that I needed to put the volume at very high levels (over 70%) on the Eversolo just to get close to "normal" listening levels. It all felt very low and subdued. I moved the amp's gain to 31db (from 25), with no noticeable difference. This was the same situation using either XLR or RCA connections. As a point of reference, the same speakers used with an Arcam SA20 integrated amp (or a Wiim amp for that matter), would start to get plenty loud just at a third of the volume, but not with the Eversolo. I could barely hear anything below 50% volume, and then approaching normal listening levels at over 70%, but even then certainly not "loud".

Thinking that perhaps there may be a mismatch with the Eversolo and my power amp, I returned the Eversolo and ordered a separate DAC and Pre-amp. The DAC is a SMSL SU-10, and the pre-amp is is Ladder Bach. I received the DAC today, but the Ladder Bach hasn't even shipped yet so it will be another few weeks. Since the DAC has a volume control on it, I connected it directly to the power amp to give it a try but had exactly the same issue: volume level at 70+% levels start to approach normal listening levels. To feed the DAC I am using an iPad pro connected directly to its USB-C input.

Wondering if the lack of a preamp might be the issue, I researched this for a while but everything that I could find about connecting DACs directly to power amps returned discussions around "quality of sound" but not "volume" so it doesn't seem the lack of a preamp is necessarily the cause of the issue that I am describing. Since I won't have my preamp for another few weeks to see if it makes a difference I thought I would ask the question here to see if there is something that I am overlooking or other things I need to consider to match the components of the system.

For reference, the PA240 power amp has an input impedance of 10K ohms. The SU-10 has an output voltage of ~5V (higher than many I have seen), and while I couldn't find its output impedance specs anywhere online, the lower model which is the SU-9 has an impedance of 370 ohms with the XLR connection (based on tests on this site). Not sure if the SU-9 and the SU-10 are similar in that regard, but thought I'd mention it.

Appreciate any insights.

 

[Chromatischism]

All I can think of is to ensure the source and DAC are at 100% volume. I lent a coworker recently an Apple dongle, who said he wasn't really impressed with the sound. I asked him how he controlled the volume, to which he said he didn't want to take the iPhone past 30-50%. That meant the aux device he was outputting to had to work too hard to amplify the signal.

 

[PK1]

Before I connected everything I max’ed the volume on my iPad but didn’t really check it again during my tests.

After I got your response I checked to be sure and it was at 1/3 of the volume! Tried to change it but it doesn’t do anything. I see the volume control slider on the Apple Music interface, but it doesn’t respond to any input. When I disconnect the USB-C cable volume immediately goes to max, but when I connect it again it goes to zero, but the volume level remains at where it was before (low).

What gives??

The first time I connected the USB cable to the DAC a window popped up on my iPad asking whether I was connecting to a headphone or “other device”, and I chose other “other device” (why lie!) but in hindsight I think this may be why I don’t have control over the volume.

Not sure how to change this as it doesn’t ask me this question again.

Thoughts?

 

[antcollinet]

iPad asking whether I was connecting to a headphone or “other device”, and I chose other “other device”

If you'd selected headphone, this might make sense. Ipad/Iphone (at least in europe) is requried to limit max high volume on headphones to protect hearing.

With "other device" or even better ; "Speaker" there should be no such restrictions. If I were you Id check what it is currently set to - It'll be in settings, but not sure where. I know where to find it for bluetooth devices, but I don't have any USB devices to try.

 

[PK1]

If you'd selected headphone, this might make sense. Ipad/Iphone (at least in europe) is requried to limit max high volume on headphones to protect hearing.

With "other device" or even better ; "Speaker" there should be no such restrictions. If I were you Id check what it is currently set to - It'll be in settings, but not sure where. I know where to find it for bluetooth devices, but I don't have any USB devices to try.

I definitely selected “other device”, but I can't find where to change it. Google searches haven’t helped. Still working on it…

Edit: found it, it’s under Settings=>Sounds=>Headphone Safety. From there I chose “forget all USB devices”, then selected headphone. While the volume then increased to half way (instead of a third), no sound played. Selecting “other device“ allows music to play, but can’t change the volume. I’ll keep searching but if anyone has any ideas feel free…

 

[PK1]

Alright, tried a few more things: used both USB-C and USB-B inputs, different cables, as well as “headphone” and ”other devices” and volume control remains locked In every case. What used to happen before is as soon as I’d connect the USB cable the volume would go to zero and then grey out, but 10-15 seconds later it would show approx 1/3 volume but still greyed out. Now it just goes to zero as soon as I connect the cable and stays there (doesn’t show 1/3 any more). Can’t explain what changed, but it still plays at the same low volume level.

After thinking about this a little, on “other device” wouldn’t the iPad send out digital information? If so, the volume setting would be irrelevant. The problem is that the same thing happens in headphone mode so I’m at a loss and haven‘t been able to find any information on this through my searches.

So back to my original issue, this may not be something related to the volume setting being too low on the iPad, it’s probably something else. Since the same thing happened with the Eversolo, I am starting to wonder if there is something wrong with my amp.

 

[antcollinet]

wouldn’t the iPad send out digital information? If so, the volume setting would be irrelevant.

No, the iPad is probably implementing digital volume control. Do you have (or can you borrow) a computer you can connect to the amp instead?

 

[PK1]

No, the iPad is probably implementing digital volume control. Do you have (or can you borrow) a computer you can connect to the amp instead?

Are you saying that the iPad sends electronic signals related to playback volume to the DAC instructing it what volume level to play? Just want to make sure I understand this. Not understanding how this works I would have thought that the iPad only sends music data electronically which the DAC then converts to analog and any volume controls would be in the DAC.

To your other question, yes, I connected a MacBook to the system and while the volume control doesnt freeze as it does on the iPad, the playback volume level is equally low even when the volume setting on the MacBook is at max. Effectively no difference between the iPad and the MacBook.

I also connected an Android tablet to the DAC, same thing, maybe even slightly lower volumes. At this point the only thing that I can think of that I haven’t tried is installing a preamp in the system, which what I am waiting to receive.

What is surprising to me is that given the higher than average output voltage of the DAC (I think it’s 5.1V) I would have thought I’d have the opposite effect (louder), which is not the case. But I also don’t profess to be overly knowledgeable in electronic matters.

 

[antcollinet]

Are you saying that the iPad sends electronic signals related to playback volume to the DAC instructing it what volume level to play?

That is possible over USB for some DACs.

However, it is also possible (more likely IMO) that the IPAD is changing the digital signal to reduce the volume of the actual encoded music before sending to the DAC.

Either way - the way to find out if there is a problem with the amp or not is to use a different (ideally computer) source, as you have done.

What is surprising to me is that given the higher than average output voltage of the DAC (I think it’s 5.1V)

Hang on - I thought you were connecting directly from the Ipad to the amp USB input.

If there is a DAC in the way you need to check it's settings as well. Is *it* outputting a lower volume for some reason.

 

[PK1]

Hang on - I thought you were connecting directly from the Ipad to the amp USB input.

If there is a DAC in the way you need to check it's settings as well. Is *it* outputting a lower volume for some reason.

It’s a power amp, it doesn’t have a digital input. The set up is: iPad to DAC to power amp.

I have checked all the DAC settings, can’t find anything related to volume output. I have turned off all the filters, etc., to no avail.

 

[staticV3]

However, it is also possible (more likely IMO) that the IPAD is changing the digital signal to reduce the volume of the actual encoded music before sending to the DAC.

The default, systemwide iOS/iPadOS volume control is unable to control software volume when using USB output.

If the connected DAC supports UAC2 hardware volume control, then the volume rocker will continue working like always.

If the connected DAC does not support UAC2 control, then the volume rocker will cease to function and volume will be locked to 100%

If the connected DAC has a broken UAC2 implementation, then it's possible that the volume rocker will appear to be working, but the volume won't actually change.

 

[antcollinet]

It’s a power amp, it doesn’t have a digital input. The set up is: iPad to DAC to power amp.

I have checked all the DAC settings, can’t find anything related to volume output. I have turned off all the filters, etc., to no avail.

Sorry - got this thread mixed up with another one.

 

[antcollinet]

The default, systemwide iOS/iPadOS volume control is unable to control software volume when using USB output.

If the connected DAC supports UAC2 hardware volume control, then the volume rocker will continue working like always.

If the connected DAC does not support UAC2 control, then the volume rocker will cease to function and volume will be locked to 100%

If the connected DAC has a broken UAC2 implementation, then it's possible that the volume rocker will appear to be working, but the volume won't actually change.

In this case the volume rocker is not working, but is showing either 0 or about 1/3rd. Something not right.

 

[antcollinet]

It’s a power amp, it doesn’t have a digital input. The set up is: iPad to DAC to power amp.

I have checked all the DAC settings, can’t find anything related to volume output. I have turned off all the filters, etc., to no avail.

So you've turned up the volume with the remote to 0dB? Have you reset the filters to default (you shouldn't have filters off)

Do you have a multimeter you could use to measure the voltage out of the DAC?, and then the voltage at the speaker terminals. This should tell you instantly where the problem is.

 

[PK1]

The default, systemwide iOS/iPadOS volume control is unable to control software volume when using USB output.

If the connected DAC supports UAC2 hardware volume control, then the volume rocker will continue working like always.

If the connected DAC does not support UAC2 control, then the volume rocker will cease to function and volume will be locked to 100%

If the connected DAC has a broken UAC2 implementation, then it's possible that the volume rocker will appear to be working, but the volume won't actually change.

To be clear, the volume controller on the DAC works, in that it increases and decreases volume, but the volume levels are much lower than “normal“. Meaning that to listen at normal volumes, I need to be close to the max volume setting on the DAC, even then it sounds… dim or not full.

On the other hand the volume setting on the iPad freezes the minute I plug in the USB, which is what you’re explaining above. So effectively the iPad does its job sending music data (since it plays music), but somehow because of the DAC, some setting, or maybe even the amp itself, the volume output is low.

 

[PK1]

So you've turned up the volume with the remote to 0dB?

Do you have a multimeter you could use to measure the volume out of the DAC?

I achieve normal listening volumes around -25, -30db on a scale of -100 to +2, so I‘m about 70-75% of max volume just to get to normal volumes, but even then it sound dimmer and less full than the levels I get on the Wiim amp at much lower volume settings.

It’s a good idea to check the output voltage, I’ll do that. In the meanwhile, could there be something wrong with the power amp? I have only tried it with this DAC (SU-10) and previously with an Eversolo A8. I’m wondering maybe the amp is the culprit, but can’t think of what. It does, after all, “amplify” but volumes are lower.

 

[antcollinet]

I achieve normal listening volumes around -25, -30db on a scale of -100 to +2, so I‘m about 70-75% of max volume

No, that is not 75%

With dB, then each -6dB is half of the voltage. Each -10dB Is 1/2 the "perceived" volume.

So with -30dB, you are already at 1/8th of the maximum perceived volume, and about 1/32 of the maximum voltage output. So if your max voltage output is 5V then at -30dB you are at 0.15V

I think this misunderstanding might be your problem.

 

[staticV3]

To be clear, the volume controller on the DAC works, in that it increases and decreases volume, but the volume levels are much lower than “normal“. Meaning that to listen at normal volumes, I need to be close to the max volume setting on the DAC, even then it sounds… dim or not full.

On the other hand the volume setting on the iPad freezes the minute I plug in the USB, which is what you’re explaining above. So effectively the iPad does its job sending music data (since it plays music), but somehow because of the DAC, some setting, or maybe even the amp itself, the volume output is low.

I'd try connecting to the DAC not via USB, but via Toslink or Coax using one of these:
https://www.audiosciencereview.com/...amp-suggestion-apple-music.53486/post-1934048

 

[PK1]

No, that is not 75%

With dB, then each -6dB is half of the voltage. Each -10dB Is 1/2 the "perceived" volume.

So with -30dB, you are already at 1/8th of the maximum perceived volume, and about 1/32 of the maximum voltage output. So if your max voltage output is 5V then at -30dB you are at 0.15V

I think this misunderstanding might be your problem.

Certainly not debating you as you are clearly more knowledgeable than I in this, but asking the question so that I can understand what you are explaining:

At -100 the volume is muted, that is the minimum, and +2 is the maximum (102 db range total). As I turn the volume up, I get to -30 which is 70db higher than the minimum (or ~70% of the volume range) just to get to normal listening levels. With other systems, at 30-35% of the volume range the system is plenty loud.

Unless the volume range isn’t linear, which I doubt, I don’t understand how at -30 I’d only be at 1/8 of output volume.

 

[PK1]

I'd try connecting to the DAC not via USB, but via Toslink or Coax using one of these:
https://www.audiosciencereview.com/...amp-suggestion-apple-music.53486/post-1934048

That's interesting, I didn't know these things existed. Since I am planning on using a preamp I'll wait to get it and try it to see if it addresses things, if not I'll try this solution.

For educational purposes, why would this make a difference vs. the USC connection?