LOUD Subwoofer POP whe powering on speaker
Hi, I've been greatly enjoying my DINAS for the most part of two months now. Last week I added a SABAJ D2 DAC to my setup and I tidied my desk and recabled the s*** out of it. I'm not a big fan of leaving non-vital electronics powered on, so I connected both of the DINAS power supplies to a single power strip with an on/off switch and found out that when powering on the strip a loud POP can be heard (and seen!) from the subwoofers.
It scared the hell out of me the first time it happened as it was an "I might ruin my drivers" loud pop and the subwoofer goes in or out (more on that later) like crazy. I have since then made a series of tests, with the following results:
For a bit of context, my setup goes like this:
Laptop -> USB C HUB -> SABAJ D2 DAC with volume controlled preamp -> RCA out to the DINAS via RCA splitter (sub and satellite volumes at 25%
- At first I thougth the problem was caused by my DAC, as noise can be heard from the speakers if the DAC is connected but not powered, but the pop takes place even if no RCA is connected to the LEPAI amp on the DINAS.
- The pop happens on both speakers, but the cone on the left speaker goes IN whereas the cone on the right speaker goes OUT (i need to check te polarity on both subwoofers just in case I reversed them while finishing the cabinets). Silly me must somehow have reversed the right subwoofer polarity, they're both now reversed and in phase as they should be.
- The loudness of the pop does not vary with changes in the subwoofer volume pot.
- The pop happens when power goes into the amps regardless of being powered on from the amp switch or the power strip.
- It happens in other power outlets in the house and even in a different building.
Is that a normal behaviour for the LEPAI AMP? Is there any way I can troubleshoot the problem more thorougly and (hopefully) fix it?
Sounds like the inrush current charging up the board caps while the speakers are connected. Meaning that there isn't any soft start or speaker protection enabled or included.
Did they do this before, or is this a new development? I can't find any real documentation on the amp board or even a schematic, so this is basically a shot in the dark diagnosis.
@tvor-ceasar thanks for your answer. I cannot recall them doing that earlier, that's why I hoped for other DINAS owners to chime in just to know if it's a normal thing on these amps.
BTW, the right subwoofer was indeed polarity reversed, so I fixed it during lunch break.
I looked up the TPA3118D2 Datasheet - the amp chip used.
Page 15, section 7.3.3 should be a clue to what's happening. Directly from the TI PDF linked above:
7.3.3 Startup and Shutdown Operation
The TPA31xxD2 family employs a shutdown mode of operation designed to reduce supply current (Icc) to the absolute minimum level during periods of nonuse for power conservation. The SDZ input terminal should be held high (see specification table for trip point) during normal operation when the amplifier is in use. Pulling SDZ low will put the outputs to mute and the amplifier to enter a low-current state. It is not recommended to leave SDZ unconnected, because amplifier operation would be unpredictable.
For the best power-off pop performance, place the amplifier in the shutdown mode prior to removing the power supply. The gain setting is selected at the end of the start-up cycle. At the end of the start-up cycle, the gain is selected and cannot be changed until the next power-up.
What I'm getting from this is that you should go through a shutdown procedure before unplugging / removing power to avoid "power on pops". If you already do this, then there's something else to figure out.
I'll let other owners chime in for their input and experience.
@tvor-ceasar Thank you for your help, I wish my technical english was better so I could extract this precious information from datasheets myself.
If I understood correctly, signal to the amp must be muted before powering off, so the amp itself shuts down its outputs and they remain that way until the next powerup cycle.
I'll have a go and see what I can achieve by powering down the DAC/PRE before powering off the amps.
Again, thank you!
I'm glad to help if I can.
From what I read in the Datasheet, the amp itself should go through it's shut down procedure before unplugging / removing power. Since I have never used one, I don't know what that procedure would be. Is there an actual power / standby switch or button on the amp? If so, I would assume (and assuming is never a good thing 😀 ) that would put the amp through the necessary steps to power down correctly.
If you don't feel comfortable to dig into the TPA3118 board, you might consider a relay with time delay to switch on the connection between the amplifier and the loudspeaker. Many manufacturers use this by the way. If you use the power voltage of the amplifier also to power the relay to switch the loudspeaker, the loudspeaker is than connected to the amplifier after the pop is gone.
Two options that you could use are e.g. a relay with built-in time delay or delay the switching of the relay with a RC network in the coil circuit of the relay. The relay is that fed with the output of the RC, thus is activated with time delay. (Values depending on the resistance of the relay-coil etc.)
This should do the job as wel.
Hi Martin did you solved the problem with the pop? Because I'm also having that issue and would like to solve this.
Mine configuration is Laptop -> Laptop docking -> 3.5 Jack RCA splitter to the DINAS via RCA splitter
When I power off the DINAS I get an pop from the sub. Already tried different shutdown techniques but nothing helpt.
I tried every possible order for switching on /switching off components and the pop is still there, I guess it comes down to the manufacturer's 3118 implementation on this particular amp plate.
I also looked over the speaker relay approach, but wasn't sure how it would apply to a class-D amp (every relay board I looked at seemed to rely on AC power, and class D runs on DC) so that and beeing busy as hell with work and home improvement made me just leave the speakers always powered on an call it a day. I might look at it again in the future.
@arnould As I said, I didn't solve my issue with the pop. Please chime in if you manage to solve it.
Well, like I stated way up above, it sounds like the main power supply caps causing the current surge that makes the speakers go "pop". You would need a Delay circuit that would keep the speakers disconnected from the amp until the caps have settled.
I've done a general search for something ready made, and came across the Upc1237 from Banggood, which will work from 12-24VDC. That covers the voltage coming into the Lepai amps. You'll need one for each of the DINAS.
Tap the power from the switch contacts and GND so that it activates when you turn the amp on. Then wire the module in-line to the L/R, or in this case Sub/Main, OUT from the amp to the appropriate IN on the module, then from the OUT on the module to the respective drivers. Glue the module down securely and you'll be done.
You could roll your own, if you wanted, but with the sale Banggood is offering at the moment ($4.99 US + $0.90 S&H), you would be very hard pressed to beat the price.
I'll leave a few links here in case anyone is interested in learning more about how you'd go about building your own.
Mr. Carlson's Lab
Learn Electronics 555 timer search
555 timer calculator
Converting MicroFarads to Farads
Make PC Boards at home playlist
Let us know what if any of this works for you guys.
Hi this would be also the solution for me. I made an wiring schematic to be clear if I got it right.
From the Lepai amp the wire that is connected to sub connection goes to the UPC1237 IN and from the OUT connection the wire goes to the sub speaker. Correct?
@tvor-ceasar Thank you very much, I think I'll go the easy route and get me a couple of BG relays. I'll let you know how that worked out!
I finally got the delay circuits that @tvor-ceasar reccomended aaaaaaaaand... I managed to fry one of my Lepai amps. I've got a replacement on my way, so no worries about that, but I want to make sure I don't botch it again I'm trying to see what I did wrong. I wired it like this at the switch V and ground:
It worked at first, but sometime while installing the amp again it just stopped working. The power LED was blinking like crazy and the V between Vin ant GND at the switch measured at araund 4 V instead of 20V. Also one of the 3118 inside got hot like hell, so I guess somewhere in the amp must have been shorted.
I guess I'll find another spot on the amp to grab the voltage needed to operate the relay...