Pontus turn on “thump”

[gjpmho]

Hi,

I recently acquired a Pontus I and hear a thump through my speakers when I turn on the Pontus from standby mode. I measured a voltage spike at the Pontus RCA outputs. Is expected and by design?? I have the latest USB and FPGA firmware installed. I know the easy workaround is to turn on the DAC before the amp. Thanks.

 

[Wolf11Man]

The cost of an audio gear design rises with the competence of the developer. If you can not copy an existing design and don't want to spend the money a good circuit designer will charge, you end up with components that "thump" on start up, shut down or both. Simply a case of "we can not do it right and because of that don't care".
A mute circuit is very basic electronics, but you got to know the basics...

 

[gjpmho]

thanks for your response, makes sense unfortunately. It seems this is par for course with Denafrips DACs? Am I wrong? The Pontus also has a mute button but I think that is a digital switch at a later stage. I suppose it’s safe to say there’s nothing wrong with the DAC besides missing a mute relay circuit? I’m not seeing at other issues, and tbh music sounds amazing to my ears.

 

[Wolf11Man]

Today you can "design" a lot of well working audio gear by simply combining integrated parts using the example shematics of data sheets. Not to mention the very common Asian practice of copying and stealing the work of others. Then a layout program will do most of the work. If you did not completely screw up, the pcb will work. No need for decades of learning, try and error, reading complicated books etc until you become a real specialist who knows what every part of a cirquit does. Which comes handy for countries without a many decades long history of audio culture, but the desire to flood the world market with cheaply build products. Some get the edge to sell their stuff at elevated prices, mostly because of marketing and valueable external looks.

 

[gjpmho]

Today you can "design" a lot of well working audio gear by simply combining integrated parts using the example shematics of data sheets. Not to mention the very common Asian practice of copying and stealing the work of others. Then a layout program will do most of the work. If you did not completely screw up, the pcb will work. No need for decades of learning, try and error, reading complicated books etc until you become a real specialist who knows what every part of a cirquit does. Which comes handy for countries without a many decades long history of audio culture, but the desire to flood the world market with cheaply build products. Some get the edge to sell their stuff at elevated prices, mostly because of marketing and valueable external looks.

I’ve spoken with two Pontus owners who swear they haven’t experienced a voltage spike on start up. Be careful out there with your biased assumptions and sweeping generalizations. There’s snake oil all around in the audiophile business. Let’s dig in to your response a little more. Do you have any evidence you can share? Folks copy and steal from each other all the time. Microsoft copied from Apple, Apple copied from Xerox etc. I am convinced there’s something wrong with my unit, and this is not by design. Aesthetics are also part of the audiophile business, and I am enjoying the sound signature from this DAC. Or were you just looking for low hanging fruit to target Asian audiophile businesses?

 

[Wolf11Man]

Today you find design flaws in all price categories. Also allmost everything comes from Asia, not only manufacturing, but also designing whole assemblies is cheaper there. Even the once succsessfull idea, design it in North America, Japan or the EU and have it build somewere behind a rice field, has become too expensive. So design is outsourced as well. You sketch what you want and send it away...
As a comparison, this may lead to a situation of someone, who never drove a car, designing a chassis and suspention. The "fine tuning" is then done in the software. What do you do if the "fine tuning" is not sufficient, because of design flaws and a container full of your new product is already shipped? You sell them and hope no one cares. If someone does, you blame it on a "one time defect". Maybe tell him how to work around the problem and keep on selling. If complaints are not too violent, you don't even fix it in the next production run, because of cost.
Brands appear and vanish, this is a part of the game called capitalysm. Small brands don't have the resources for years of development or product recalls. Produce cheapest, sell at the highest price you can get, in a market of subjective appreciation and snake oil dripping from any component. If you talk DAC's, all of them use one or a few of a limited number of integrated cirquits. Any difference in "sound" should be subjective or based in the surrounding circuits which are based on very usual components. These have be connected properly.

For your DAC, have it fixed by the seller. If not possible, turn it on in a different sequence. There is nothing else you can do.

It is good design practice to have the output muted by a relais (best) or semiconductor (cheapest). If there was a schematic of your DAC, someone could verify, but this will be a trade secret of highest priority. Higher than the option to repair it when it fails or has a problem like yours.
The level of the "thump" will depend on your amplification chain. Some may never experience it, because they switch on DAC and Amp at the same time, with the muting of the amp masking the voltage spike. I prefer to have volume down until switching on or off my gear.

 

[gjpmho]

Oh Ok I see the bigger picture. Apologies. I’ve emailed the manufacturer with a video demo and description of the thump. I measured a 1VDC spike across L and R signal to gnd from the RCA output.The manufacturer says it’s a fault, but I’m not seeing a mute circuit.

I’ve verified the digital power supply stays on in standby mode. Pressing standby turns on the analog power supply. I can live with the thump, is a 1VDC spike something to be concerned about? The DAC Output voltage (signal ended) is 2Vrms.

 

[gjpmho]

Turns out after more research this thump is inrush current, and typical for any audio component that does not have a mute relay. This is by design and a 1VDC spike is okay in the scope of things: RCA analog out is usually 2VRMs. Still a reminder to turn on your audio source before the amp and turn off amp first…

 

[gjpmho]

Oh Ok I see the bigger picture. Apologies. I’ve emailed the manufacturer with a video demo and description of the thump. I measured a 1VDC spike across L and R signal to gnd from the RCA output.The manufacturer says it’s a fault, but I’m not seeing a mute circuit.

I’ve verified the digital power supply stays on in standby mode. Pressing standby turns on the analog power supply. I can live with the thump, is a 1VDC spike something to be concerned about? The DAC Output voltage (signal ended) is 2Vrms.

1 VDC is ok. I would not buy a $2K DAC that does not have a mute relay. This should be commonplace at this price point. For example Schiit Audio DACs have a mute relay, which they talk about in their FAQs.

 

[Wolf11Man]

The mute circuit could be made from a transistor as well, even as these are a "no go" for high ender and often disabeled when gear get's "tuned".
So the mute circuit activating these semiconductors that pull the output to ground could be defective. If it exists.

 

[Sokel]

Anything more than a few mV VDC (ideally zero) at a gear's output is not ok. At all.
An output of 1VDC at the source's output will be amplified just fine as any other output resulting in many volts at the speakers inputs.

One may be lucky and the next stage has blocking caps, etc, but that's far from ideal, that's because a measure like that is for preventing faulty gear to destroy it.
1VDC is enormous.

 

[gjpmho]

The mute circuit could be made from a transistor as well, even as these are a "no go" for high ender and often disabeled when gear get's "tuned".
So the mute circuit activating these semiconductors that pull the output to ground could be defective. If it exists.

Muting works when I press the mute button.

Anything more than a few mV VDC (ideally zero) at a gear's output is not ok. At all.
An output of 1VDC at the source's output will be amplified just fine as any other output resulting in many volts at the speakers inputs.

One may be lucky and the next stage has blocking caps, etc, but that's far from ideal, that's because a measure like that is for preventing faulty gear to destroy it.
1VDC is enormous.

I’m talking about the voltage spike through RCA output when the DAC is turned on. I think you're referring to the idle voltage at the output. Which is fine at 2mV.

 

[Wolf11Man]

Sorry, I didn't know it was such an expensive DAC. I would have said it a little more carefull if I had seen the the price tag of 2395 Euros before posting. I have never heard before of Denafrips.
Anyway, the reality in the high end business is not allways gold plated.

 

[Sokel]

Muting works when I press the mute button.

I’m talking about the voltage spike through RCA output when the DAC is turned on. I think you're referring to the idle voltage at the output. Which is fine at 2mV.

Turn-on, turn-off, idle, it doesn't matter.
No DC should ever be present at the outputs.

Something is way faulty in there.

Edit: Something can also be be faulty about the whole rig, sub-optimal grounding for example. Check it on its own to see.

 

[gjpmho]

The mute circuit could be made from a transistor as well, even as these are a "no go" for high ender and often disabeled when gear get's "tuned".
So the mute circuit activating these semiconductors that pull the output to ground could be defective. If it exists.

Ok. Thanks.
The mute button mutes audio as expected.
I will try and trace the signal from the mute button on the control panel.

 

[gjpmho]

Turn-on, turn-off, idle, it doesn't matter.
No DC should ever be present at the outputs.

Something is way faulty in there.

Edit: Something can also be be faulty about the whole rig, sub-optimal grounding for example. Check it an its own to see.

look up inrush current.. many audio components that do not mute during startup will produce DC spikes. That is why many people turn on the audio source before their amplifier… The Pontus has large capacitor banks which doesn’t help.

 

[Sokel]

look up inrush current.. many audio components that do not mute during startup will produce DC spikes.

I have built a gazillion audio thingies with no muting (but I do prefer a nice relay at my nice ones) .
The ones that outputted DC was either my fault (usually a voltage missing somewhere or a reversed diode, etc) or bad stuff like broken components.

Inrush current stays at check when everything else is ok.
Imagine if it was the norm at power amps for example!

 

[Wolf11Man]

Just for a try, connect a simple ground wire between the DAC and the amp or pre-amp it feeds. This should put the cases on the same potential.

 

[gjpmho]

I have built a gazillion audio thingies with no muting (but I do prefer a nice relay at my nice ones) .
The ones that outputted DC was either my fault (usually a voltage missing somewhere or a reversed diode, etc) or bad stuff like broken components.

Inrush current stays at check when everything else is ok.
Imagine if it was the norm at power amps for example!

Normal power amps that do not have a mute relay usually thump, right?

 

[gjpmho]

Just for a try, connect a simple ground wire between the DAC and the amp or pre-amp it feeds. This should put the cases on the same potential.

The voltage spike was measured on the DAC was disconnected from the amp with the amp powered off.