[edulov]

 
I actually found this place near me. They supposedly have 3.5 million tubes in stock, over 2000 different types, in a 7500sq. ft. warehouse. I emailed them, and they have Amperex 6688 JAN, for $7 each. I will be picking up a few on Friday.
 
http://www.thetubecenter.com/contact_thetubecenter.html

Good deal, reasonable price. BTW, 1) do not apply much force to the sides while "extracting" tubes. Just pull them up, slightly rocking back and forth 2) your new tubes will be smaller in size, its fine, do not worry

 

[edulov]

  Stumbled upon this little amp. I have a question. I saw a new amp has come out Nobsound NS-01E with similar power output as the NS-08E, but with only one tube. https://www.amazon.com/dp/B01I19SBPM/ref=psdc_537344_t2_B014FASL1A?th=1
 
Has anyone compared this one with the NS-08E, and if I am to buy one, which one should I go for, NS-08E or the newer NS-01E?
 
Thanks.

Right about this design - no info. But what worries me most is
1) A couple of posts definitely are promotional, not actual reviews
2) NOBODY, even manufacturer tells the valve reference. Never liked such behavior. 
3) Valve here must be one of the dual triodes, but which one and how many options for tube rolling will provide this reference? Since one certain tube spec is responsible for resolution, details and attack you can make a quite good prediction about sound just looking at the tube ref and manufacturer specs.
4) No board images found, so no info about electric scheme and parts. Due to the small size of the amp, the op amps have to be in small modern packaging soldered to the board (so no op amp rolling...). Since the overall sound quality heavily depends on them too, just knowing their reference might greatly help, but...
5) Just triode provide only even harmonics. Their presence is required by purists from music, but the absence or too strangled 1st and 3rd harmonics make the sound way to analytical and lifeless.
 
Ok. If you will order NS-01E, tell us about tube and make a couple of good HiRes photos of the insides.

 

[sup27606]

 
Right about this design - no info. But what worries me most is
1) A couple of posts definitely are promotional, not actual reviews
2) NOBODY, even manufacturer tells the valve reference. Never liked such behavior. 
3) Valve here must be one of the dual triodes, but which one and how many options for tube rolling will provide this reference? Since one certain tube spec is responsible for resolution, details and attack you can make a quite good prediction about sound just looking at the tube ref and manufacturer specs.
4) No board images found, so no info about electric scheme and parts. Due to the small size of the amp, the op amps have to be in small modern packaging soldered to the board (so no op amp rolling...). Since the overall sound quality heavily depends on them too, just knowing their reference might greatly help, but...
5) Just triode provide only even harmonics. Their presence is required by purists from music, but the absence or too strangled 1st and 3rd harmonics make the sound way to analytical and lifeless.
 
Ok. If you will order NS-01E, tell us about tube and make a couple of good HiRes photos of the insides.

I agree with all of your points above, and hence went for the more established NS-08E. So far I haven't regretted. Using it with the Audeze Sine. Now, compared to this one, the Cayin C5 amp sounds thin and emaciated. The sound from the NS-8E has a heft and body to it that is unmistakable. The drums reverberate and the vocals shine. Paul Simon's Dazzling Blue comes alive, and Diana Krall is just seductive now. Thanks for your response to my question.

 

[sup27606]

Whats the difference between Amperex 6688a and 6688?
Thanks.

 

[edulov]

  Whats the difference between Amperex 6688a and 6688?
Thanks.

According to the US electron tube military handbook letter "A" at the end of designation refers to the relialable version which means greater stability of electric parameters and potentially is better in everything. Other frequent letters are "JAN" used to designate military grade valves, both offering greater reliability, and longevity.
 
If you will look for Soviet (Russian) made valves, some references have the final letter -E (long life) or -ДР (-DR for long life&gold plated pins, usually military grade).
 
BTW, 6Ж9П-Е (6J9P-E) does exist! Can be found on eBay from many eastern Europe sellers. Quite cheap.

 

[cam94z28]

Just wanted to mention a weird "feature" of this amp with stock tubes. On lower impedance/higher sensitivity headphones it seems to remove bass, but on less sensitive, slightly higher impedance headphones, like my ancient Philips SHP895's, it actually adds bass, compared to a SS amp. Maybe it has a higher output impedance?
 
I haven't picked up those 6688's I mentioned yet, but my dad found a huge box (rubbermaid tote) of old NOS tubes in the attic. Crossing my fingers there are some 6688's in there, once i get my hands on it.

 

[Nrocket]

Any Master and Dynamic MH40 use with the Nobsound? I'm thinking of getting it.

 

[Audiophilic10]

Maybe this has been asked already: Any amp from this brand at similar price point without the tubes?
I saw this video about reverse-engineering it: https://www.youtube.com/watch?v=coSt5HWRvv4
Sorry to introduce controversy here, but if you jump to the end they say that basically the tubes are just forced into the design for the sake of showing tubes and without them the amp would be even cheaper and function better...

 

[sup27606]

Maybe this has been asked already: Any amp from this brand at similar price point without the tubes?
I saw this video about reverse-engineering it: https://www.youtube.com/watch?v=coSt5HWRvv4
Sorry to introduce controversy here, but if you jump to the end they say that basically the tubes are just forced into the design for the sake of showing tubes and without them the amp would be even cheaper and function better...

They didn't say the tubes are there for show. The tubes are not used for real amplification, but used as buffer which color the sound possibly by introducing some distortion. The tubes have an effect on the sound as changing the tubes change the sound profile. What engineers call better, and what audiophiles call better may be two different things, as clinically accurate may not always sound the best. Sound is very subjective. I use this amp with the Sennheiser 6xx and it sounds quite satisfying, although in certain songs, I can hear some distortion/crackling at regular volume although such instances are very rare.

 

[edulov]

They didn't say the tubes are there for show. The tubes are not used for real amplification, but used as buffer which color the sound possibly by introducing some distortion. The tubes have an effect on the sound as changing the tubes change the sound profile. What engineers call better, and what audiophiles call better may be two different things, as clinically accurate may not always sound the best. Sound is very subjective. I use this amp with the Sennheiser 6xx and it sounds quite satisfying, although in certain songs, I can hear some distortion/crackling at regular volume although such instances are very rare.

The buffer means a closed loop needed to give a higher amplification coefficient for op amps with some indirect processing of harmonics due to "how vacuum valve works". In usual HiFi-type solutions, the buffer is implemented by another op amp (mostly of the different reference) to generate reacher sound. That is why in my case I rolled both: tubes and op amps.
 
About distortions (checked in my setup):
1) Not tightly plugged PSU moved accidentally; Easy to solve;
2) USB Jitter affects USB DAC decoding - mostly. You may need some voodoo up to switching to HQ motherboard (in case of desktop)
3) EM wave mutual influence from other devices and cables. Buy HQ shielded audio cables.

 

[dr3wd4wg]

I purchased some NOS Mullard E180F tubes on Ebay (http://www.ebay.com/itm/5-Pcs-NOS-Mullard-E180F-6688-audio-radio-Preamp-Tubes-NIB-/290900841002?hash=item43bb0a922a). I have to wait till after the New Year before they ship

.  They look like early to mid 70's. Anybody else try these?

 

[joemg]

after doing a lot of googling on this, as I posted in another thread, this video shows that the tubes are only used as a buffer and not for actual amplification in these units: https://www.youtube.com/watch?annotation_id=annotation_369287791&feature=iv&src_vid=9RhD-NO0n-4&v=coSt5HWRvv4
 
That's not to say they don't sound good, but I just thought I'd spread that information so anyone considering purchasing one (as I was) has all the facts.
 
(The video shows a Xuanzu branded unit, but I believe it's just rebranded)

 

[trellus]

That's rather normal and expected at this price point. I had one of these and the tubes definitely color the sound even though they aren't doing the amplification.

after doing a lot of googling on this, as I posted in another thread, this video shows that the tubes are only used as a buffer and not for actual amplification in these units: https://www.youtube.com/watch?annotation_id=annotation_369287791&feature=iv&src_vid=9RhD-NO0n-4&v=coSt5HWRvv4

That's not to say they don't sound good, but I just thought I'd spread that information so anyone considering purchasing one (as I was) has all the facts.

(The video shows a Xuanzu branded unit, but I believe it's just rebranded)

 

[joemg]

That's rather normal and expected at this price point. I had one of these and the tubes definitely color the sound even though they aren't doing the amplification.

 
yes, I agree... but you also have units like the Bravo V1 & V2 that are true tube amps for $60/70.  Again, I'm not knocking the amp, I was a click away from buying it myself after reading reviews... but when I got all the facts, I was a little bummed out so I wanted to make sure everyone had them before making their own decision to buy.
 
After an absurd amount of research for a $50 amp, I finally just caved in and went with the Fiio E10k.  Amazon had it on warehouse deals, used, for $50.  I needed a DAC too, so there just was no beating this value for the money for me personally.  It's nowhere near as cool looking as the nobsound though, lol.

 

[edulov]

This is a hybrid amp, the amplification is made by pair op amp and valve. Other relatively cheap headphone amps with valves also are hybrid ones. Also, most of them are using triodes (pure ones). This one uses pentode as triode, but due to tube design, it gives reacher, more vivid sound.
Since I have Fiio E10K for a long time now, I made a direct comparison after a tube rolling. Everything is better, just everything, especially highs and extension and control of lows. And even after tube and op amp rolling (maybe I was lucky to buy valves really cheap) the total cost of 08E was less then Fiio's.
 
BTW, I needed a good amp for all fine hp range (32 Ohm up to 600 Ohm) with a plenty of power. Too many amps prised here actually can't drive 250 Ohm cans: they lack resolution and control. Not even counting for 600Ohm cans.