Nobsound NS-02E Review (Tube Headphone Amp)

[magicscreen]

No, it's not. Low output impedance and high current delivery are not necessarily related.

In this case the low output impedance stems from lots of local negative feedback in the output stage. Yet an opamp is not able to deliver lots of current.

I do not understand.
The Jds Labs Atom has similar low output impedance and opamp output stage. So the Atom cannot deliver enough current?

 

[amirm]

Amir, given the horrible results why the choice of the doubtful Pink Panther instead of the one with straight head cut?
;-)

Because subjectively it sounds good with high impedance headphones.

 

[solderdude]

back to science, either Amir wasn't using the right tube or it needs some more time to burn-in or his AP needs to be recallibrated

View attachment 110302

As usual these manufacturers are lying through their teeth.
It looks like 2 NE5532 are used. Most likely as unity gain buffer circuits or with say 2x gain and buffer circuit.
Datasheet says: 40mA (max. 60mA) short circuit current.
Let's go for max 50mA while still being able to put out some voltage.
Two opamps in parallel (it is a dual opamp, 2 opamps in one DIP package) = 100mApk =71mArms
71mA x 32 Ohm = 2.3V = 160mW in 32 Ohm
Fits Amir's measurements like a glove.

 

[solderdude]

I do not understand.
The Jds Labs Atom has similar low output impedance and opamp output stage. So the Atom cannot deliver enough current?

The output resistance in opamp circuits does not determine the max output current.
The current limiter in the used opamps does.
For the NE5532 this is low (see my previous post) and the output resistance can be very low (feedback)
The Atom uses high current output buffer (LME49600) with a 250mA current limit so it can provide much more power than the 80mA of this amp.
With 250mA pk you can get 180mArms x 32 Ohm = 5.6V = 1W.

 

[GrumpyOldMan]

For US$60 I'd buy this as a windowsill ornament. If it can make some sound, that's just a bonus.

 

[BostonJack]

Speaking of symmetry, I understand car analogies are forbidden already but how is it with architecture?

Spoiler: octagon symmetry

It's like a mini chapel on your desk

Or, if the case were pentagonal, it could induce Satanic influences on the sound.
Perhaps leading to a darker sound that some might prefer.

 

[MC_RME]

FWIW: Devices like this intentionally use a standard tube follower circuit at much too low operating voltage - to intentionally generate loads of second harmonics. Second harmonic alone is as good as inaudible even at several percent. And it has nothing to do with the original tube sound or the way tubes distort when used correctly. Using the tube as low voltage FX stage is not new, has been used like this for at least 20 years, even in 'pro' devices for studios...

 

[mhardy6647]

Those are all transistor-based distortion. The Marty Robbins thing was actually a bass guitar plugged into a broken channel on a channel strip, not a tube amp.

ostensibly a bad transformer (and some issues with noisy or just weird transistors) -- yes, I just actually saw that!
Still, one can make vacuum tubes produce some interestingly euphonic noises, even if Marty & Co... umm... didn't.

 

[mhardy6647]

FWIW: Devices like this intentionally use a standard tube follower circuit at much too low operating voltage - to intentionally generate loads of second harmonics. Second harmonic alone is as good as inaudible even at several percent. And it has nothing to do with the original tube sound or the way tubes distort when used correctly. Using the tube as low voltage FX stage is not new, has been used like this for at least 20 years, even in 'pro' devices for studios...

PAiA "Tube Head" preamplifier, e.g.
I've always wanted one of those...

https://paia.com/proddetail.php?prod=9305HSRP

https://worldradiohistory.com/Archive-Radio-Electronics/90s/1994/EN-1994-06.pdf

 

[trl]

First off, I find the brand name hilarious. I wonder if anyone has pointed out this potential for puerile snickering to the (probably) very serious Chinese engineers and businesspeople behind the Nobsound line of audio goods...

Well, NOBSOUND and DOUK AUDIO are doing (selling) very good passive switchers. We had one of these switchers recently measured here and it was about perfect. I also have a TRS-TRS NOBSOUND switcher similar with the one from the above link and it works flawless, although the TRS plugs are not the best in class, but I don't care much, as I don't disconnect plugs often; all I care is the middle switcher knob to last during time.

 

[fordiebianco]

First off, I find the brand name hilarious. I wonder if anyone has pointed out this potential for puerile snickering to the (probably) very serious Chinese engineers and businesspeople behind the Nobsound line of audio goods...

I have quite a collection of Nobsound/Douk Audio tube gear. I have all of them serviced by my local amplifier repair shop (specialising in tube kit) before using them, as I am always a bit suspicious around the built quality and safety. They nevertheless all pass and sometimes even create a bit of a raised eyebrow and a headscratch by those wizened tube masters (particularly the 6P1 power amp created quite a stir).

I am never expecting a sonic revelation from them, but they are great to look at from my reading corner and drive my KEF 105.1 nicely and sometimes even make them sing. Then it's back to my Loxjie A30.

With other words, the anti-thesis to the gear championed on here.

 

[tomchr]

back to science, either Amir wasn't using the right tube or it needs some more time to burn-in or his AP needs to be recallibrated

View attachment 110302

Heh... Ten bucks says the THD spec was copied from the NE5532 data sheet. 0.06% sounds right for a tube, assuming you don't push it too hard.

I bet the difference between channels is due to differences in the tube itself. It's very likely that the voltage/current starved operation of the tube in this amp puts the tube at an operating point that's very sensitive to device characteristics.
I have seen the THD of tubes improve through the first few hours of use, but usually not by more than a few dB.
It could also be a defective or 'aged' (i.e. worn out) tube. After many hours of use the electron emissivity of the cathode just isn't what it used to be. That usually takes years of use, though.

Tom