Topping NX7 with a digital piano

[Phoney]

While there are no specs on them, internal headphone amplifiers in digital pianos are usually not great. People are reporting issues with both high and low impedance headphones. My suspicion is that the amps are usually not very powerful and they might also have a high output impedance on top of that. I have a Roland FP-30x and decided to go with a Topping NX7, as people recommended using an external amp. I am using my DT770 Pro 80ohm for this purpose. So, I tried for fun to use the piano output and I did actually get sufficient volume, but I had to play at 90% volume or more. I really felt like the sound improved significantly when using the NX7 instead, but surprisingly I had to use high gain at around 12 o' clock. I'm not sure wether that's normal or not, I just thought that the DT770 would be very easy for the NX7 to drive, and while max volume was loud, it didn't really hurt my ears.

But then I started thinking; does it make sense that the sound improved by connecting another amp to the internal one, when the internal one had high impedance output? What is the effect of the original amps impedance output when I use the headphone output for the NX7, does connecting a NX7 nullify that issue and then the NX7s own low impedance output will drive the DT770 properly? It's just a bit hard to understand how a signal that didn't sound good to begin with (even with sufficient voulme) can turn into a "cleaner"/better one when amplified, but I'm sure there can be an explanation for it. Otherwise I could be imagining things, but the difference just seemed a bit obvious, even on lower volumes. I do know that a high output impedance can mess with the sound of dynamic HPs. Another question is if I'm running the risk of damaging anything by using an amp on top of another amp? Maybe a silly question, but ChatGPT (which is allways right) said that this could damage the amp somehow.. And lastly I assume that the logical thing is to use max volume on the piano when connected to the NX7 as a preamp?

I hope that I posted this in the right forum category, I apologize if not.

 

[staticV3]

does connecting a NX7 nullify that issue and then the NX7s own low impedance output will drive the DT770 properly?

When you have poor impedance bridging (High output impedance, low load impedance), then you can improve the signal by putting an additional Amp between source and headphone.

The Amp presents a much higher load impedance to the piano, therefore improving the impedance bridging from the piano.

And with the external Amp's low output impedance you in turn improve the impedance bridging to the headphone.

 

[Phoney]

When you have poor impedance bridging (High output impedance, low load impedance), then you can improve the signal by putting an additional Amp between source and headphone.

The Amp presents a much higher load impedance to the piano, therefore improving the impedance bridging from the piano.

And with the external Amp's low output impedance you in turn improve the impedance bridging to the headphone.

Thank you! Good to know that I probably wasn't just imagining things.

So I'm guessing that there's absolutely no issue to this solution? I assume that ChatGPT is not exactly right on this one, or didn't quite understand the question.

 

[restorer-john]

Chat GPT is confused.

I imagine Chat GPT is fake, like the Wizard of Oz, except using 100,000 Indians in a giant computer call centre all trying to answer millions of requests.

 

[nerdstrike]

Since you now have a headphone amp, I would imagine you'd be much better off taking the line out than using the headphone interface. That's what you'd do if you were connecting to studio hardware certainly. The only reason not to would be if there was some binaural stuff going on, but I don't think Roland leans into that...

Does the manual make any suggestions?

 

[Phoney]

Since you now have a headphone amp, I would imagine you'd be much better off taking the line out than using the headphone interface. That's what you'd do if you were connecting to studio hardware certainly. The only reason not to would be if there was some binaural stuff going on, but I don't think Roland leans into that...

Does the manual make any suggestions?

I'm not sure if it's possible. The only input I have on the NX7 is though aux, and I don't think I can use the R/L output which is supposed to be used with amplified speakers?

 

[staticV3]

The only input I have on the NX7 is though aux, and I don't think I can use the R/L output which is supposed to be used with amplified speakers?

Yes you can. Though special care should put on the cable pinout. Is the R/L output differential or single-ended? You can check that with a cheap multimeter.

 

[Phoney]

Yes you can. Though special care should put on the cable pinout. Is the R/L output differential or single-ended? You can check that with a cheap multimeter.

I'm not sure if it's worth the hassle to buy a cable for it, the sound is quite good and more than loud enough using the headphone out. So if that's just for potensially better performance or power, it's not really needed. I do hear some noise at max volume on the NX7, but that's beyond reasonable listening levels.

 

[nerdstrike]

I see the NX7 is smaller than I imagined... Two 1/4" to single 3.5mm would need adapters... May not be worthwhile as you say.

W.r.t. instrument volume control, it occurs to me that we don't know the distortion characteristic of the onboard amp. On line out you'd probably set it to 90% or so (clipping paranoia).

 

[Rja4000]

Is the R/L output differential or single-ended?

Given the drawing above, I'd said balanced (differential), since they draw TRS jacks for the speaker cables.
But it doesn't matter much, since the NX7 input is unbalanced anyway.

A cable like this would work.

Sommer Cable Basic HBA-3S62 0,9m

Y Audio Cable Length: 0.9 m, 3.5 mm Mini jack stereo to 2x 6.3 mm jack mono HICON plug, Colour-coded 6.3 mm jack plug, Colour: Black, 5 Year manufacturer's warranty

www.thomann.de

 

[staticV3]

Given the drawing above, I'd said balanced (differential), since they draw TRS jacks for the speaker cables.
But it doesn't matter much, since the NX7 input is unbalanced anyway.

A cable like this would work.

Sommer Cable Basic HBA-3S62 0,9m

Y Audio Cable Length: 0.9 m, 3.5 mm Mini jack stereo to 2x 6.3 mm jack mono HICON plug, Colour-coded 6.3 mm jack plug, Colour: Black, 5 Year manufacturer's warranty

www.thomann.de

That's the thing though. If the output is TRS Balanced, and you plug in that cable you sent, then you'll short Cold to GND, which can damage the electronics.

 

[Rja4000]

That's the thing though. If the output is TRS Balanced, and you plug in that cable you sent, then you'll short Cold to GND, which can damage the electronics.

Well, in theory, yes.

But if that's the case, that's a serious design issue, since most users will have no clue and eventually plug the wrong cable.

 

[restorer-john]

That's the thing though. If the output is TRS Balanced, and you plug in that cable you sent, then you'll short Cold to GND, which can damage the electronics.

If a TRS balanced output on a device is 'damaged' by a TS short, then it is faulty by design and not fit for purpose. TRS is always going to get 'shorted' everytime somebody plugs in a TRS connector in any case.

If these stupid manufacturers would do what they are supposed to do and pad out with 200-600R resistors, none of this BS would be a problem.