pHAT DAC - Wireless Audio Kit - Sound

I recently purchased a pHAT DAC - Wireless Audio Kit.
Unfortunately, I am not satisfied with the sound quality.
The heights are missing and the bass is too much. The whole thing sounds dull.
The device on the PiZero I have done with the script.
Does anyone have any advice for me?

Hi loewi,

I’m having exactly the same problem, see here: Bad sound quality with phatDAC

However no answer until now.
I’d really like to get this setup working.
Probably I will have to ask for exchange directly…

We use pHAT DAC in our office every day driving some Harmon Kardon Soundsticks and haven’t had problems with the quality. It’s a tricky issue to diagnose, since there are many factors at play, and audio quality can be very subjective!

You can ping for a return/replacement if it doesn’t meet your needs.

I’ll poke some of the other engineers to see if they can think of anything specific that might affect the audio quality, but pHAT DAC is all digital up to one end of the DAC, and just a couple of passives on the outputs- there’s very little to go wrong!

Okay testing this again at home with my Bowers & Wilkins MM1 (normally hooked up to an Apple TV) switching between my MacBook Pro and the pHAT DAC soldered right down low on a Pi Zero powered by a battery (was easier than finding another plug socket and adaptor).

I can’t discern any difference. The bass is pretty punchy with each but certainly not at the expense of the mid and low frequencies. I tend to be quite sensitive to overly bassy audio setups and spent a good 7 years listening to music every day on absolutely flat monitor headphones so I’m good (or at least I was anyway) at picking up anything trending away from this.

Of course, I can’t tell what you hear and I can’t tell you that you’re wrong. I can just say that either pHAT DAC isn’t for you, it doesn’t play nice with your speakers/amp, or that there’s somehow something wrong with your board that’s causing the bad audio quality.

Bear in mind I’ve heard the sort of thing you describe from bluetooth bookshelf speakers before; I threw them in a box and haven’t use them since. I know how flippin’ awful it sounds!

Before anyone shoots me for mentioning subjectivity; I’m not convinced such a stark bias toward the low-end could just be subjective, specially since @martymcbro has compared it to USB DACs on the same speakers.

Could you both post pictures of the soldering on your pHAT DACs?


Here is a picture of my phat dac.

I have the Phat Dac attached to my Raspberry Pi 3 where I usually output the sound to a USB sound card.
The sound over the USB sound card is good over the Phat Dac, the sound is unfortunately bad.
So it is definitely at the Phat Dac.
Please excuse my bad english it comes from the Google translator.

this is a picture of the soldering points of my phatDAC:

How does the device behave when exposing it to heat to long during soldering? Could this be a problem? I don’t think it was to long, but I have no idea how sensitive it is.

Today I also connected the phatDAC to my Yamaha RX-V681 receiver with Teufel Consono 35 Mk3 speakers.

Still no difference in sound :(


hi / i have the exact same problem

i ordered 2 phatDACs (one audio kit and one extra) / soldered both today
one works flawless and sounds clear
the other has way to much lows and little highs / sounds more like my neighbor listens to music than me

the only difference between the two - i also soldered the RCA connector to the flawed one

(tested on the same piZero, sd card, connected to my hifi amp)

also interesting: using in-ear headphones, the flawed one sounds “ok”

Could you post pictures of both?

Is the flawed one sounding bad only when connected via the RCA connector?

I noticed @loewi does not have an RCA connector populated but I’m looking for some sort of pattern here that might explain the problem.

Neither @loewi or @martymcbro have any obvious issues with soldering I can see.

@klee would you be able to return both the good and bad pHAT DAC for us to compare and test?


I already had the problem before soldering the RCA connector, using only the 3,5mm output.
To find out if the 3,5mm plug is broken, I soldered the RCA connector and tried it. It has the same problem.

I compared the bad phatDAC to a USB-DAC using KOSS Porta Pro Headphones today.
Like klee wrote, it sounds better with headphones. However I can still hear a difference, which is not so obvious as before. The phatDAC still has missing heights.

I can also return my phatDAC if this helps.

i already installed the working one behind my tv cabinet / but i will take pictures as soon as it gets a housing

here are some pics of the flawed one:

i did some more testing and it really sounds like some kind of eq issue but only when run through a hifi amp and speakers - through in-ear headphones it sounds normal to my ears - i combined the flawed one now with some usb-bowered cheap pc-speakers and it sounds normal (a litte bassy compared to the other one in the exact same setup but that could be imagination at this point)

the flawed one sounds exact the same through the jack and the RCA connector - no difference there

again: i compared the two in the exact same setups, only changing the hats between reboot
i tried 3 different pies(2xpi2b, 1xpiZero), 2 different installations of volumio, multiple jack->rca and rca->rca cables, 2 different hifi-amps (onkyo av receiver, harman kardon hifi)

i could return both but im in austria and im not sure its economical (and the working one allready is in heavy use of my wife at this point :D )

Hi There - Me Too ! - I have a Phat Dac that i bought yesterday with no HIGH Frequencies (or very little) and a distinct BASS boost. My first separate DAC.

I don’t know whats going off with this DAC - the local audio sounds better much better as it has a “full” freq range.

The PhatDac sounds muffled and all “bass” - its def got an issue. If i play same track through my macbook or my other audio gear it sounds fine and normal - but played through the Phat sounds muffled and woolly.

So…dont know what to do really is it faulty ? - is it software settings ? - i was playing a simple 44khz 16bit mp3 file using the OXM player but web audio youtube also sounds woolly too ?

Does anyone know what this could be ? - This is not an imagination or “subjective issue” - it is really a high freq missing issue it is rolling off at about 8-9khz and may also have a lump about 100hz. - Its nasty there must be a bad batch of these out there maybe with some crap passive output caps or resistors thats maybe creating a filtered effect or something ?.

all i know its not right - it should be superb crystal clear and much better than the existing on pi audio - as thats what its sold to do ! - so…? what are we doing Team sheffield - i live about 20mins from you guys lets get this sorted cuz i need to listen to our lads the Arctics at their best ;-)

FIXED IT ! - Read On :-

OK This is what’s wrong, i used my testing kit (scope multimeter capacitance testers etc)

Basically the team if sheffield have fitted 2 x 2.2nF Caps across the output of the analogue of the Chip to GND.

These in conjunction with the 470K resistors inline with the Analogue outputs unfortunately provide a very effective “LOW PASS FILTER” - (remember this from college guys) around 8-9khz cut so…

I just removed them with the Iron - tiny little surface mount caps about 2mm across - follow the tracks to the 3.5mm socket you will see them as they are the first pair you come across before the tiny 470k surface resistors. Pretty sure the PIM team just copied the Mfg’s example diagram on the chips data sheet when they made the PCB up - makes sense nice and quick way to start. - though TBH its not really the best way to get a decent sounding setup.

BINGO - crystal clear audio now - perfect sounding and now the full spectrum tested unto and above 24khz !

Have fun !

@avaproductions 470K? K?! Whoa. That sounds several orders of magnitude wrong! Would explain a lot. I wonder if the wrong reel got placed on some.

Anyone still being stumped by really bassy audio, drop a mail to paul {at} pimoroni [dot] com and we’ll get you sorted :-)

Thanks for this super tip.
Now I finally got the sound I expected.

Happy New Year

We got a ‘bass heavy’ unit back, and we found it had the wrong capacitors on the output. Someone loaded uF instead of nF for a batch of units. We’re working out how many will have been affected, but all the current stock has tested fine, which is good.

If anyone sounds like they have the ‘muffled’ problem, they can mail paul {at] pimoroni [dot} com and we’ll sort it out.

Since we’re not big or fancy enough to have component testing on our pick and place machines, we’ll be revising the test jig to look at the sound output more carefully, ideally with some nice freq. analysis, which should make it less subjective to having a tester with golden ears. Or at least not cloth ears :-)

Great ! Glad we got to the bottom of it.

Is there any way to easily identify defective boards? I’ve got one (purchased late June 2016) that sounds like it has this exact problem. The resistors are marked “471” but I can’t make out anything on the capacitors.