[HeadphoneNewbiee]

As the title says I just got a DAC to use with my SRM-313 amplifier that makes popping noises as I connect the headphones to the amplifier.

Before I got the DAC I used to play music directly from the jack out on my phone/pc etc. and when I would connect my headphones to the amp I would do so with the power button off and then turn on the power after they were connected. This would normally not make any noise in my headphones which I guess makes sense when the power is turned off. But the thing is when I do the same with the external dac it will make loud popping/cracking noises as I connect the headphones (with the power button still off) is this a sign that I should be concerned or is it normal?

I guess i should mention that there is no problem with popping/cracking other noises after they are connected and it sounds great otherwise.

The dac that I'm using is danish audio design dac 11 with a separate psu and 2 capacitor banks

 

[ProtegeManiac]

Turn on thumps are more common in headphone amps not because of the proper higher voltage output off of a DAC (or a CDP, music server with its own DAC, etc). It's really just more common vs speaker amps as circuits designed to prevent it are not as widely used. One reason is because it's relatively easy to just unplug a headphone before switching off then plugging it in after switching it on vs say unscrewing at least two + terminals, pulling the copper out, switch on the amp, push the copper back into the terminal and now more copper fibers just fell off and will end up in the vacuum cleaner...

 

[HeadphoneNewbiee]

Thanks for the insight I did not know there was a term for this. Can it potentially be harmful to headphones?

Depending on which order i connect and turn everything on I can avoid a thump so Is there a best/proper sequence of connecting and turning everything on in general that I'm unaware of?

You call it a turn on thump but the sound it makes happens before I turn on the amp and while its amplification is set to 0. Is that "supposed" to be possible?

 

[tomb]

Thanks for the insight I did not know there was a term for this. Can it potentially be harmful to headphones?

Depending on which order i connect and turn everything on I can avoid a thump so Is there a best/proper sequence of connecting and turning everything on in general that I'm unaware of?

You call it a turn on thump but the sound it makes happens before I turn on the amp and while its amplification is set to 0. Is that "supposed" to be possible?

No, it's not. Assuming I'm interpreting your posts correctly, you might have the DAC on, but the amplifier off. If that's true, it sounds like the DAC is leaking DC. This can happen with inexpensive DACs or used DACs that have developed an offset (age drift in the electronics, capacitor going bad, etc.) The amplifier should still catch it and not pass through any voltage if it's off, however.

You could have a short to ground through the DAC, somehow. Use a DMM if you can, and measure to see if there's voltage on the headphone jack while the amp is off but the DAC connected. Disconnect the DAC and measure it again. The results should tell you if there's any errant voltage on the ground and whether it's in the amp or the DAC.

A final theory ... and I haven't seen this very often, except in the Starving Student Headphone Amplifier. There are some power supplies that allow a static charge to build up through the ground.

 

[HeadphoneNewbiee]

No, it's not. Assuming I'm interpreting your posts correctly, you might have the DAC on, but the amplifier off. If that's true, it sounds like the DAC is leaking DC. This can happen with inexpensive DACs or used DACs that have developed an offset (age drift in the electronics, capacitor going bad, etc.) The amplifier should still catch it and not pass through any voltage if it's off, however.

You could have a short to ground through the DAC, somehow. Use a DMM if you can, and measure to see if there's voltage on the headphone jack while the amp is off but the DAC connected. Disconnect the DAC and measure it again. The results should tell you if there's any errant voltage on the ground and whether it's in the amp or the DAC.

A final theory ... and I haven't seen this very often, except in the Starving Student Headphone Amplifier. There are some power supplies that allow a static charge to build up through the ground.

Edit: Would you mind explaining what a DC leakage is?
Yes you interpreted me correctly. I bought the dac setup used because It seemed like good value so maybe its because of aging. Could also be bad design but I hope not since the manufacturer appears to have a good reputation among the hifi community in my country. I don't think I know enough about electronics to troubleshoot it myself so I might just pass it on to someone with the knowledge.

But If it actually turns out there is static charge build up how would I know? The sound it makes does kinda sound like a charge being released - a little bit of static as I start to plug in the headphone and then a thumping sound as it enters fully.

 

[ProtegeManiac]

Thanks for the insight I did not know there was a term for this. Can it potentially be harmful to headphones?

Depending on which order i connect and turn everything on I can avoid a thump so Is there a best/proper sequence of connecting and turning everything on in general that I'm unaware of?

I switch on amp then source. On headphones, it's amp then source, and only then do I plug in the headphone.

You call it a turn on thump but the sound it makes happens before I turn on the amp and while its amplification is set to 0. Is that "supposed" to be possible?

If it's there before you flip the amp switch, it might be the DAC leaking an electric signal even if it's not actually decoding anything (tomb has a more detailed explanation on that).

This is less dangerous to a headphone driver than a turn on thump but try doing the same sequence, ie, switch on DAC, then amp, then plug in the headphone to avoid it.

 

[HeadphoneNewbiee]

This can happen with inexpensive DACs or used DACs that have developed an offset (age drift in the electronics, capacitor going bad, etc.)

You mentioned capacitors going bad and I realized that the dac draws power from a capacitor bank maybe it has gone bad?
When I get home I will try to power the dac with and without the bank to see if there is a difference.

 

[HeadphoneNewbiee]

Ok so I tested without the capacitor banks and it still happens. It happens regardless of whether the amp is on or off and for as long there are no headphones connected it seems to build up a charge somewhere. I also noticed a slight buzzing in the headphones (not audible while sounds are playing) that gets louder with more amplification. Maybe I made a bad gamble with this dac.

You could have a short to ground through the DAC, somehow. Use a DMM if you can, and measure to see if there's voltage on the headphone jack while the amp is off but the DAC connected. Disconnect the DAC and measure it again. The results should tell you if there's any errant voltage on the ground and whether it's in the amp or the DAC.

A final theory ... and I haven't seen this very often, except in the Starving Student Headphone Amplifier. There are some power supplies that allow a static charge to build up through the ground.

I would like to test for ground issues but I don't really know how to measure the output in particular beause its a stax plug and I have no idea which pin is for what.
If there are ground issues I'm assuming there is no easy fix and I would probably have to replace it?

 

[ProtegeManiac]

I also noticed a slight buzzing in the headphones (not audible while sounds are playing) that gets louder with more amplification.

If it gets louder when you turn it up, then it's "audible."

And even if it doesn't go up as you crank it up or you're well below the point where if cranked up you can't make out the nosie, "not audible" is more like indistinct. It's not that it isn't audible, it's just screwing with the sound without you hearing it distinct from the music. If you ever read amp and source reviews stating "blacker background with more bass slam," it's not that the bass is louder, it just doesn't have noise (nor auditory masking*) getting in the way of the bass.

Think of it like how noise gets in the way of an image - sure you can apply de-noising programs, but only to a point, because 1) your camera slows down if you use it in-cam, 2) it also slows down your computer when you're editing, and 3) your images can end up looking like it was painted by Renoir or worse, Van Gogh, instead of looking like analogue TV with a bad signal. In short, a newer sensor that actually ADCs what the lens sees with less noise at higher sensitivity** will be easier to work with.


*caused by response imbalance, ex if the treble is too loud you need to boost the bass harder to hear that; by contrast using EQ for example in some cases if most of the bass is level with 1000hz anyway, sometimes just trimming some freqs above 1000hz will make the bass more audible even if you don't boost the bass

**well not so much like back in 2011 or so when the new Sony sensor in the NEX-7 was markedly worse than the 16mp sensor in the NEX-5, or even the 12mp sensor in the Fujifilm FInepix X100, once you start working at low light and high ISO; then again, it wasn't that it was absolutely just worse ie it didn't really have way more noise - it just didn't have lower noise, but now 24mp makes that grain easier to see as more pixels can line up with the grain

 

[HeadphoneNewbiee]

If it gets louder when you turn it up, then it's "audible."

And even if it doesn't go up as you crank it up or you're well below the point where if cranked up you can't make out the nosie, "not audible" is more like indistinct. It's not that it isn't audible, it's just screwing with the sound without you hearing it distinct from the music. If you ever read amp and source reviews stating "blacker background with more bass slam," it's not that the bass is louder, it just doesn't have noise (nor auditory masking*) getting in the way of the bass.

Think of it like how noise gets in the way of an image - sure you can apply de-noising programs, but only to a point, because 1) your camera slows down if you use it in-cam, 2) it also slows down your computer when you're editing, and 3) your images can end up looking like it was painted by Renoir or worse, Van Gogh, instead of looking like analogue TV with a bad signal. In short, a newer sensor that actually ADCs what the lens sees with less noise at higher sensitivity** will be easier to work with.

Sorry I should have used other words I just ment that I didn't notice it while any music was playing. As you probably noticed I'm not versed in hifi but that is why I am here to learn

The analogy makes sense.

 

[tomb]

Sorry I should have used other words I just ment that I didn't notice it while any music was playing. As you probably noticed I'm not versed in hifi but that is why I am here to learn

The analogy makes sense.

I didn't realize the SRM-313 was a Stax Energizer. I think most of these comments, including mine, are useless. You're dealing with +or- 300 Volts (actually a 600V differential!) into the headphones. Any number of things could be going on, but it's dangerous to mess with it further in troubleshooting. Try another DAC. If that doesn't work, then have your Energizer repaired by someone knowledgeable or Stax itself.

 

[HeadphoneNewbiee]

I don't know if it matters anymore but I tried the amp with another dac in my local audio store and no problems at all. Then I tried using my dac a little more and didn't hear any noise this time so it seems like that was just a one time thing. However I was just listening to some music and decided I wanted to watch netflix and as soon that I opened the app everything went insane. My headphone litterally sounded like it was exploding every half second with ear piercing loudness to the point that I was worried that they had broke. Luckily they were fine after I used another source to check. I would say I got a taste of just how loud stax can go.
I don't think I will be using this dac anymore because it seems it is the problem.
I will be resting my ears for the rest of the day haha.

 

[TYATYA]

SRM Stax?
Can you see the internal of it?
Does anything flash when you hear pops?
(It's best to check at night)

 

[HeadphoneNewbiee]

SRM Stax?
Can you see the internal of it?
Does anything flash when you hear pops?
(It's best to check at night)

Yeah stax srm.

I have not noticed any flashing but the case is also pretty much closed. I'm not sure I want to try and reproduce it anymore though. At this point I'm just too afraid to damage my equipment or my hearing like it nearly just happened.

I don't know if I phrased my original questing correctly actually. When I read it again I realise it reads as if the amplifier itself makes a pop noise but it actually plays the sound through my headphone.
I was not sure if that was clear

 

[TYATYA]

Yeah stax srm.

I have not noticed any flashing but the case is also pretty much closed. I'm not sure I want to try and reproduce it anymore though. At this point I'm just too afraid to damage my equipment or my hearing like it nearly just happened.

I don't know if I phrased my original questing correctly actually. When I read it again I realise it reads as if the amplifier itself makes a pop noise but it actually plays the sound through my headphone.
I was not sure if that was clear

I have stax estats amp.
When led Z1Z2Z3Z4 flash I heard popping/clipping.
I know that moment beyond power of circuit