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Nobsound NS-02E Review (Tube Headphone Amp)

solderdude

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Looks like it is running on +/- 12V and so the tube will be on 24V (plate at 12V) with 2 NE5532 in parallel on the output.
Basically the G1217 Starlight but without output caps.
The 6V tube heater will be run directly from the input voltage.
A better design than the typical ones where the heater is fed through class-A output stages.
 

Doodski

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This is a noob comment, but I loved the symmetry of the components within the amp. It's a pity that it doesn't measure well for low impedance HPs.
The symmetrical layout and topography gets better too. I too am impressed by good layouts and excellent craftsmanship in finishing stuff. :D
 

LTig

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This is a noob comment, but I loved the symmetry of the components within the amp. It's a pity that it doesn't measure well for low impedance HPs.
You'd need 20 NE5532 opamps to feed a stereo 33 Ohm load. Not for this price and size.
 
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pavuol

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Speaking of symmetry, I understand car analogies are forbidden already but how is it with architecture? :)
280px-Fort_Edgecomb_Davis_Island_Maine-4.jpg
David-Sibray-at-Alberts-Chapel-1024x678.jpg
It's like a mini chapel on your desk ;)
 

magicscreen

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Thanks for the information. It's learning for me.
So, sir, starting from what impedance and sensitivity (upwards) do you think this will work fine?
I think Amir tested a passive, multi-XLR ins-outs (ports) preamp from this company and it measured very well.
For a lower cost and specific purpose, this company seems to be doing well. On eBay, they sell many products.
It has only 0.8 ohm output impedance, it is fine for low-impedance headphones.

I have a Loxjie P20. Its output impedance 47 ohm.
It sounds better than the Atom using a 300 ohm HD6XX headphone.
I bought a Grado headphone. Its only 32 ohm.
And surprise!
The Loxjie P20 has better sound with the Grado as well.
 

3125b

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Am I off base here, or is it really annoying that the input is closer to the front than the headphone output? That makes no sense ...
But apart from that, for 60 bucks this might be a fun secondary unit.
 

trl

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The Capstan

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

LTig

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It has only 0.8 ohm output impedance, it is fine for low-impedance headphones.
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.
 

LTig

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Thanks for the information. It's learning for me.
So, sir, starting from what impedance and sensitivity (upwards) do you think this will work fine?
250 Ohm and above should be fine. Lower impedance headphones could work if their sensitivity is high.
 
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milosz

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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...

Low voltage starved anode gain stages are something you see in a number of "tube" headphone amps- the Musical Fidelity X-Can V3 comes to mind. What they are doing is using the tube to color the sound in a certain, fairly predictable way in order to satisfy certain listener's tastes. Nothing right or wrong about that, it's a matter of preference. I note that although the harmonic distortion is higher than many of us who seek "transparency" in audio gear like to see, the noise level is really commendably low for a $60 headphone amp, and the power levels for driving higher-impedance 'phones is also good. So the engineering here isn't broken at all - they were going for a certain kind of sound and a certain price point, along with a certain "tube" identity which is attractive to some buyers. In a way it's kind of impressive that they can sell this for $60.

You know listening to low bit-rate MP3's through this thing might actually offer a more musical sound than a nice clean amplifier, this kind of euphonic "sweetening" can gloss over certain shortcomings in source material.

WARNING: WARDROBE ANALOGY!

Not everyone likes to wear bespoke black tie all the time- sometimes a pair of funky old jeans are called for.
 
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Ron Texas

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A tube headphone amp with switching power supplies and solid state op-amps. How strange.
 

mhardy6647

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Any pix of the innards? The output impedance suggests there's a solid state buffer on the output.
10-4
OK, took the top off:

View attachment 110263

This thing is cuter inside than out! :)

As we see there are two independent setup switching power supplies. Capacitor voltages are 16 so likely the step up value is below this. I am assuming the opamps are the front-end and the tube is the output stage.

That's the dumb way to do it, I'd opine :)
Cf. Pete Millett's low-voltage hybrid headphone amp of long ago now -- He used space charge tubes (triodes) designed to run at low voltages (for hybrid car radios at the dawn of the transistor consumer electronics era) and a ss buffer. I built a couple of these and I quite like(d) them.

http://www.pmillett.com/hybrid_head.htm

realhifiglows.jpg


EDIT:

The key phrase here is starved anode.
It is quite possible to operate a simple triode with say 12 volts on the anode. There is zip current, but you get a quite real voltage gain.
The near definitive guide is from Merlin Blencowe. PDF Here.
Yes, and thanks for sharing that document (which is new to me). Of course, us tube guys would say "starved plate" ;)
...and speaking of "proper" space charge tubes (i.e., those purpose-built to operate at low DC voltage), here's a less "scholarly" but nonetheless useful resource for us tinkerers.

http://www.junkbox.com/electronics/lowvoltagetubes.shtml

1612359078533.png
 

mhardy6647

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incompetent cathode follower
I will be integrating this phrase into my lexicon.

:)
A tube headphone amp with switching power supplies and solid state op-amps. How strange.
It's the 21st Century! We didn't get jet packs, and we can precisely target big rockets to blow up at just the right spot... but we did get these little distortion boxes.

I mean, there is a place for vacuum tube distortion -- but it's at the other end of the chain! ;)



1612359477930.png
 
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Helicopter

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Thanks for the review Amir. I find these little devices are a lot of fun to play around with, look at, and see how they sound. I don't think the mismatch or distortion are real issues because this is the opposite of something like a Schiit Heresy. The price is excellent too, for anyone that wants to have a little fun. My only recommendation for someone considering this would be to get something with a strong recommendation from the 100dB+ or even 115dB+ SINAD range and then get something like this later on, just to play around with. I have a Loxjie P20 and a Darkvoice and a whole bunch of new and vintage tubes from ebay that shipped here from all over Europe, Asia, and the US. I might get one of these too. I have some tubes that would work in it.
 
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_thelaughingman

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Definitely fun and interesting to play with these cheap tube amps. I have a sabaj pha3 and I’ve tried few different tubes from all over and fun way to get j to tube sound.
 
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The Jniac

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I will be integrating this phrase into my lexicon.

:)

It's the 21st Century! We didn't get jet packs, and we can precisely target big rockets to blow up at just the right spot... but we did get these little distortion boxes.

I mean, there is a place for vacuum tube distortion -- but it's at the other end of the chain! ;)

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.
 
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