Review and Measurements of the Topping D70 DAC

[Majestyk]

I really wanted to try out the D70, thinking it could be an upgrade, but it wasn't. There was a little bit of increase in resolution with the D70, with slightly better separation between the instruments, but it definitely lacked general punch, bass was recessed (yet the A20H does not have artificially boosted bass), there was a bit of lack of treble extension and the soundstage sounded a tiny bit narrower. That was a big no for me. I could not enjoy the music as much. I'm not a believer in dac burn-in, so I'm going to send it back for a refund.

This is near identical to my findings comparing the D50 with an anther DAC (one of which is no longer relevant). Like you, I was really hoping the D50 would be superior and I had no bias against it. So thanks for posting this, it has saved me some $$$ since I was thinking about getting the D70.

 

[777]

So, the load of the LME49720 is 420ohm in parallel with 23nF+22ohm.

From this is the problem, lack of punch, byte and air. The op-amps are loaded too heavy or if they want low noise, then the op-amps are too weak, those need current buffers.

 

[JohnYang1997]

Have anyone measured 420ohm load with 49720? I bet no one. If anyone measured will know there is zero issue with that.

 

[777]

Have anyone measured 420ohm load with 49720? I bet no one. If anyone measured will know there is zero issue with that.

Really ? You talking about wishful thinking not about real electronics.

 

[JohnYang1997]

Really ? You talking about wishful thinking not about real electronics.

I have measured lme49720 with various load. It gives less than 0.0001% thd for 200ohn load. Not sure why hpa4 has high distortion with 600ohm. That's also not the case in lme49720 datasheet.

 

[JohnYang1997]

And the specified output level on the last two graphs? And gain circuit?

 

[JohnYang1997]

The input impedance is too high. It casues common mode distortion.

10k input impedance distortion vs frequency posted by johnc in Ti.

 

[JohnYang1997]

Not only that +20dbu is 7.75Vrms. That's too high for reference. You only need 2Vrms in normal situations. Tho 7V shouldn't be an issue according to datasheet either. That's probably also implementation problem.

 

[777]

I have measured lme49720 with various load. It gives less than 0.0001% thd for 200ohn load. Not sure why hpa4 has high distortion with 600ohm. That's also not the case in lme49720 datasheet.

Have you measured LME49720 at 0.0001% ? Can you measure that tinny distortion ? Did you have AP like Amirm ? If you look at the schematic, at 20khz there is an aprox. 200ohm equivalent load impedance, without next stage (xlr to rca conversion) connect it. The output capacitor is 24nF+22ohm. Why would you do that ? Why would you do that at 2x of gain ?

Ok, you can do that with a simple op-amp. Maybe the THD is small indeed but you must to expect at that kind of remarks about sound. It's not too clever to force the limits of the components. You can not use your car at the limit all the time just because the datasheet telling us "it's ok". Or maybe that is a chinnese philosophy ?

 

[JohnYang1997]

Have you measured LME49720 at 0.0001% ? Can you measure that tinny distortion ? Did you have AP like Amirm ? If you look at the schematic, at 20khz there is an aprox. 200ohm equivalent load impedance, without next stage (xlr to rca conversion) connect it. The output capacitor is 24nF+22ohm. Why would you do that ? Why would you do that at 2x of gain ?

Ok, you can do that with a simple op-amp. Maybe the THD is small indeed but you must to expect at that kind of remarks about sound. It's not too clever to force the limits of the components. You can not use your car at the limit all the time just because the datasheet telling us "it's ok". Or maybe that is a chinnese philosophy ?

Do you have any idea of what 24nf mean? Also that's called engineering not dreaming.

 

[777]

Do you have any idea of what 24nf mean? Also that's called engineering not dreaming.

Yes, 47nF in series with 47nF.

 

[777]

Again, this is real engineering not wishful thinking. Engineering with facts, with measurement of the complete and final product, not optimistic datasheet specifications. Again, it is not a clever design to load the humble op-amp with a veavy load. This is not a characteristic for a highend gear. Sometimes, the small price is not the target. Topping can do the perfect job if they want.

 

[JohnYang1997]

Again, this is real engineering not wishful thinking. Engineering with facts, with measurement of the complete and final product, not optimistic datasheet specifications. Again, it is not a clever design to load the humble op-amp with a veavy load. This is not a characteristic for a highend gear. Sometimes, the small price is not the target. Topping can do the perfect job if they want.

Fisrt of all. lme49720 has more than 50ma current output capability. Loading 2Vrms with 200ohm is 10ma average and 28 ma peak. What's the deal with 470ohm that's less than 10ma peak? No issue. It's not pushing to the edge/limit. I wouldn't think it unless over 35ma.
Secondly, I have personally measured lme49720 with 32 100 200ohm. I didn't see distortion at 200ohm. It's clean.
Thirdly, according to datasheet, with 600ohm it has 0.00003% at 10khz at 5Vrms and 0.00005% at 8Vrms. (already proven hpa4 measurements being irrelevant) There is absolutely no reason that 470ohm 2Vrms loading will cause distortion. The nF capacitor is in the ultrasonic range and it's very high in hundred khz range. How much energy could be in there, even in a dac? It wouldn't cause any loss in performance. Just like we use 4.7ohm // to 100nF in amplifier output to stabilize the amplifier. It's not a 4.7ohm loading. If you don't know something, would you not pretend to know? It's very very normal circuit. If you want to prove me wrong get d70 and mod it to your liking and post me the improvement in measurements.

 

[JohnYang1997]

To simply prove to you that it's irrelevant. How much distortion do you see at high frequency? -120db. Does it rise at higher frequency? No. The opamp is not the issue.

 

[777]

You measured LME49720 ? With what device ?
0.00005% at 8Vrms ? Did you know which is the voltage supply in Topping supply ? 11Vdc.
4.7ohm//100nF ? Really No men, Boucherot cell, aka Zobel circuit has eventually 4.7ohm + 100nF. The capacitance at the output of the amplifiers or op-amps has more meanings. If you do not have minimum in series resistance the op-amp will has problem with phase margin, with stability. Maybe 22ohm is enough or maybe not for a low gain without any compensation circuit. I'll see that in a simulator.

In my opinion is not right to use two AK4497 for achieve ultra-low-noise and use at the limit one op-amp for that. Logically, if you use 2 x AK4497, then you must put the half values of the resistors and double values of the capacitors from the AK4497 datasheet to achieve all the low noise of the two AK4497. Topping didn't do that. How much is engineering and how much is marketing ? D70 is a very good dac but it could be better, one of the best. Maybe next time when the price will be a little higher.

 

[JohnYang1997]

You measured LME49720 ? With what device ?
0.00005% at 8Vrms ? Did you know which is the voltage supply in Topping supply ? 11Vdc.
4.7ohm//100nF ? Really No men, Boucherot cell, aka Zobel circuit has eventually 4.7ohm + 100nF. The capacitance at the output of the amplifiers or op-amps has more meanings. If you do not have minimum in series resistance the op-amp will has problem with phase margin, with stability. Maybe 22ohm is enough or maybe not for a low gain without any compensation circuit. I'll see that in a simulator.

In my opinion is not right to use two AK4497 for achieve ultra-low-noise and use at the limit one op-amp for that. Logically, if you use 2 x AK4497, then you must put the half values of the resistors and double values of the capacitors from the AK4497 datasheet to achieve all the low noise of the two AK4497. Topping didn't do that. Hoew much is engineering and how much is marketing ? D70 is a very good dac but it could be better, one of the best. Maybe next time when the price will be a little higher.

yeah 4.7+100n. I think I meant load//(4.7+100n).

 

[JohnYang1997]

You measured LME49720 ? With what device ?
0.00005% at 8Vrms ? Did you know which is the voltage supply in Topping supply ? 11Vdc.
4.7ohm//100nF ? Really No men, Boucherot cell, aka Zobel circuit has eventually 4.7ohm + 100nF. The capacitance at the output of the amplifiers or op-amps has more meanings. If you do not have minimum in series resistance the op-amp will has problem with phase margin, with stability. Maybe 22ohm is enough or maybe not for a low gain without any compensation circuit. I'll see that in a simulator.

In my opinion is not right to use two AK4497 for achieve ultra-low-noise and use at the limit one op-amp for that. Logically, if you use 2 x AK4497, then you must put the half values of the resistors and double values of the capacitors from the AK4497 datasheet to achieve all the low noise of the two AK4497. Topping didn't do that. How much is engineering and how much is marketing ? D70 is a very good dac but it could be better, one of the best. Maybe next time when the price will be a little higher.

What I wanted to say was the loading isn't the problem. It's only depending on the current. Not voltage. 2V from d70 is non issue. When I brought up zobel network, I wanted to say it's not a loading the output. Saying 22ohm+47nF or 23nF counts as loading is wrong. So basically both of yours original statements are wrong.
Also I used o2 as platform to test all different opamps. I modified the circuit so I can measure opamp in both parallel and nonparalleled configurations. And ap can measure as low as -160db harmonics. You don't need that good to measure sub -120db. Right level will be even better than -120db.

 

[JohnYang1997]

I wasn't talking about noise. Or dual 4497 or anything related.
I was only talking about your impression that that's the end of the world after seeing 470ohm loading for lme49720. It genuinely looks like you never seen a DAC circuit or opamp measurements. Now I know that you do. However still 470 is not significant loading for 49720 and small capacitor in series with resistor doesn't count as loading. These two are only thing I had problem with.
And there isn't a problem. No lack of punch or bit or air. It doesn't need buffer nor the load is too heavy.

 

[cglin222]

I recently got one off drop, but I can't set it to DAC only mode.
I tried to press the physical power button and sel button but that don't do anything, power button do turn the unit on/off, just not when sel is pressed.
however using sel button and remote power button on/off while hold sel, still don't see the menu
What am I doing wrong?

Thanks

 

[BDWoody]

I recently got one off drop, but I can't set it to DAC only mode.
I tried to press the physical power button and sel button but that don't do anything, power button do turn the unit on/off, just not when sel is pressed.
however using sel button and remote power button on/off while hold sel, still don't see the menu
What am I doing wrong?

Thanks

Turn it off with switch on back.
Push the sel button and hold.
Turn power on with switch on back.