Hardware Teardown of Topping D30 DAC

[March Audio]

Well it's a cheap an cheerful DAC with a BoM of less than $30, so believe me I was not losing sleep over it. Since Amir commenting on design and parts I figured I'd point out that the layout could easily have been improved.

Thats a bit of an assumption.

 

[amirm]

Absolutely. The audio clocks 22.5792MHz/24.576MHz (of multiples thereof) should ALWAYS be as close to the DAC chip as possible.

I don't think this is the architecture Alex. I believe this is a master/slave configuration with the XMOS the master for USB. It generates MCLK for the CD4398 DAC:

XMOS needs to know the output clock rate anyway so it runs as a master, driving the CS4398 as clock, creating MCLK signal above.

Alternatively there is a CS8416 which extracts the clock from input and through a MUX drives the CS4398 as a slave just the same.

This is why there is no clock/crystal around the CS4398 at all. They are all near XMOS which is the device that needs them. It, internally then generates the appropriate master clock for CS4398.

Here is the block diagram in Amir-CAD :

The little circles are the local oscillators for XMOS as I have shown.

Again, I am just guessing at this. I have not tried to trace routes and such. Don, what do you think?

 

[DonH56]

As good a guess as any, Amir. I've not thought about it. I'd have to look up the chips and guesstimate what makes most sense at the system level, but it's a cinch that an inexpensive DAC with great performance is going to minimize components, and using the cleanest clock to drive the DAC then buffering it to everything else seems reasonable. An independent DAC oscillator is going to cost more, femtosecond jitter or not... Even 100 ps of jitter does not degrade SNR much at audio frequencies and remember (for others, I know you know this, Amir) that the impact of jitter depends upon the signal frequency, not the sampling rate (clock frequency).

 

[Jinjuku]

Amazing what $129 can get you. So we have good $100+ and a good $100- DAC's we get to choose from. Been using the Behringer as a my desktop unit to drive both active monitors and my ATH 50's

 

[FrantzM]

As always its about implementation and the effects of any actual real world design rather than audiophile dogma. The performance of clock transmission lines can be analysed and optomised. This is nothing unusual rf work.

Whack a femto clock in there, that will solve your problems any audiophile knows this.

You stole my thunder

 

[vrajcevski]

Hi,

I got the D30 - Not sure if this thread deals with repairs ( reading the text seems to say - not to try to repair - BUt - i am sucker for pain)

I had the d30 for about 7 months and lost analog out. Windows still registers the USB dvice- BUT I don't think that is where the problem is.

I did the static measurments at the test points and I can see that the Vd on the cs4398 is sitting at 2.4 V instead of 3.3. Which seems to imply that the digital part of CS4398 is simply not working - hence no sound out.

so my question - has anybody done a trace of the schematics? or DOES anybody have a schematics of the D30. My suspcion is some capacitor ( either the 10uF or the 0.1 uF going bad and shorting to ground. OR any of the elemnts in the Lm 117 circuitary.

Looking at the pictures on the previous page, one of the LM 117 ( 3.3V) is used to feed the Vd. This one gets very hot to the touch. also on the same picture, there are a group of resistors and caps circled as being in the circuit of the regulator. Is this correct?

I do have some fo the other negative voltages out of spec( -15 V is actualy more like -13.5) but the OpAmp seems to be getting good volates of +, _ 11v on the pins. so this may or may not be a problem. However I can not tell without a diagram.

I know I can try and get warranty But my attempts through Aliexpress have so far resulted with nothing and I am happy to crank up the soldering iron ( can do SMD work if needed).

another symptom - tried to use it through Optical and it does not even sync. looking at the picture above - if CS4398 is not active because of low Vd, you would not expect the optical to do anything useful.

Any suggestions or help appreciated. If this needs to go to a different thread - please let me know - or help me move it.

Vlad

 

[amirm]

Hi Vlad. I am pretty sure no schematic exists. Why not contact Topping directly and see if they will accept warranty repair?

If you don't get anywhere, I can open my D30 and make some voltage measurements you can compare. Alas, I am going on a few day trip so best time would be next week.

 

[vrajcevski]

OK, Bad to respond to one's own post - so the facts -

The Lm 1117 3.3 generating the 3.3v VD is overheating. works for a few seconds with a good voltage, then overheats - and I mean melting plastic voerheat - probably 70 degrees celsius plus.

The circuit is textbook- nothing odd, adj to ground, 2 caps in paralel with 180 ohm resistance on input same on output ( no resistance ). resistance to ground from pin 7 on CS4398 is around 460ohm ( DC conditions). the caps don;t show any shortson DC - so the ptions are caps out of spec, or lm1117 gone to oscilation generating high heat and shutting down. Could be bad lm1117. I can hear high pitch noise after about 5 seconds power even without any amplifier plugged in- more like mechanical 8 khz noise.

So next step will be to do cap and lm 1117 swap. worst option CS4398 is dead and Iit is just to much soldering in that case.

 

[amirm]

Yeh, it be loaded down and hence the reason it is getting hot and shutting down.

 

[vrajcevski]

Alas, the Seller on ali express stopped responding, so I will go directly to topping - frankly I'd be happy to get the board and do a swap myself
Thanks for listening - I love the D30 though. Temporarily I am Using Sabaj DA3 it is actually really good both phones connected directly and also going through headphone amp.

Prefere the sound of the D30 Not by much just a preference.

 

[Jimmy]

Hi, first I want to thanks Amir for all his work and knowledge sharing with the audio community.

Regarding the D30 I've noticed that in different board revisions they use different oscillators. Has someone been able to identify the black apparently programable Silicon based ones labelled as 80GFP, I'm just curious about what they are using.

Thanks.

 

[amirm]

Hi Jimmy. Thanks for the kind words. Yes, there were posts regarding different oscillators. I don't know where we landed on that though.

 

[Jimmy]

The oscillators that I refer to are the ones used in the board revision that you measured (10.1), but they are difficult to identify, they are a bit unusual since normally quartz based ones are used in this kind of application; anyway they seem to work well given the good jitter measurement results.

 

[amirm]

Here is a zoomed in version:

I can't quite read the part number though.

 

[Liberal Democracy]

Here is a zoomed in version:

View attachment 13268

I can't quite read the part number though.

80GFP ?

Possibly BDGFP

 

[amirm]

80GFP ?

That is what I read but nothing came up on a search for it. On these smaller parts often they don't put the full part number.

 

[Superdad]

Possibly BDGFP

Well now you are just reading off the eye chart at the motor vehicle department!

 

[Jimmy]

I already searched for both combinations before asking, I'm curious because silicon based oscillators aren't normally used for audio, old school quartz ones offer better specs except for resistance to vibration and temperature, and cost should be similar, so it's a pretty weird design choice.

 

[JLan08]

The only miss on this front is a front panel switch that selects between digital sources. So signals have to be routed way up there and back. This switch would have been best put in the back. I guess convenience trumped that engineering fidelity.

Thanks for taking the time to analyze! I wander if it would be worthwhile to bypass that switch with a short wire lead or two, if only one input will ever be used...

Maybe that entire STM8s business can be bypassed?

 

[amirm]

I already searched for both combinations before asking, I'm curious because silicon based oscillators aren't normally used for audio, old school quartz ones offer better specs except for resistance to vibration and temperature, and cost should be similar, so it's a pretty weird design choice.

I think the clocks are for the Xmos USB transceiver/processor. That in turn creates the clock for the DAC.