Nobsound NS-08E Vacuum Tube Headphone Amplifier Hi-Fi Valve Headphone Amp Stereo Audio Preamplifier

After reading the reviews about the tubes that come with it I went ahead and ordered a matched pair of GE JAN 5654W tubes from Riverstone Audio (after a lot of searching around these seemed like they'd be a great option for this type and I personally do love what I'm hearing so far.) Well, it's pretty much normal that the tubes that come with a tube amp should be replaced I guess, though it would be nice if more could come with excellent performers right out of the box. Naturally we buy something with slots so we can roll our own, but it would be nice if an amp came with tubes that almost no one would want to swap out. Regardless, I counted on that as part of the cost of this purchase.So far I've really been enjoying the sound. I'm debating if maybe I might even like it better than my Vali 2 despite it having a really nice tube (lots of options for the Vali 2's tube type, maybe not as many for this.) This is with a Sennheiser HD650 with the so called "KISS mod" (eg just minimal padding so you don't overdo it.) I don't have golden ears though, so YMMV. This amp is smaller than my Vali 2 which is designed more for sitting on a desk than this is (though still not exactly a huge amp regardless) so it's a little easier to move it from one area to another. The cord is very short though, so this is a problem wherever I have it (the plug doesn't really reach on my desk and needs an extension.)I have not had any problems with the recessed audio ports. Though I suppose there is no particular benefit or reason that I can think of for them being recessed. Normal 3.5mm connectors and even some adapters should fit fine in there. I think you could probably widen the recession itself using a drill and a really large bit (in reverse so it doesn't catch and pull) if it really was a problem, but I really think most things should fit without a problem and any that don't are insanely wide so will have problems with other things anyway. The connectors are -- all of them -- insanely hard to actually plug things into though. It's enough to make me worry I could loosen the jacks on the board at times and I'll probably brush on a bit of a dielectric to act as a bit of a lubricant later on (really thin ones don't actually interfere with electrical connections -- especially really tight ones like these.) The tube connectors are insanely tight though. Vacuum tubes are actually a lot tougher than people think, which is a real life saver here, but I was legitimately afraid I could break them and cut myself terribly while trying to push in the tubes I had bought. I had to just slowly work them in, wiggling back and forth a bit as I went. This worries me because it may be dangerous if anyone ever does break a tube while putting it in, but I will admit it may have an advantage in that it probably scrapes any oxidation off of the pins (since, more likely than not, people will probably be using NOS tubes with varying degrees of oxidation on the pins after all) or even holds so tightly over such a relatively large area as to more or less negate the resistance that would add even if it doesn't scrape.The only thing I do have a problem with is the volume control uses a sort of almost clicky internally notched wheel that makes the volume change in relatively large amounts. That makes it a lot harder to get just the right volume. I don't know why they would do this really. Maybe this kind of volume control is less wear and tear on the pot or something, but in the end I'm not sure if it's worth it. I'd rather have more control I think. I will say that this thing definitely has plenty of power and voltage. My headphones are the 300 ohm variety, not the 600, so I can't speak for anything higher than this, but I have plenty of volume and even on the quietest devices I own I never got the volume control higher than about 75% or so. Most of the time it was between 33-50% depending on the music's mixing and which device I had it plugged into (some have intentionally lowered outputs.) It's definitely outputting sufficient voltage from the tubes. Since these are pretty efficient headphones I can't speak for current, but it sounds like the opamp is pretty powerful too. These sorts of hybrid designs are an excellent compromise. (Of note, most of the tube sound goes into the voltage rather than the current anyway. Current *does* affect the tubes somewhat so this does ever so slightly change the coloration, but not a huge amount. These hybrid designs really are an excellent compromise.)I checked power usage because I was thinking of running this from a battery pack to a DC-DC converter outputting 6V. I don't know if anyone else is interested in doing that, but I'll at least mention my results.It's approximately 463mA most of the time (the actual volume setting doesn't make a huge difference, but if I turned it up enough it kind of hurt I read 465mA.) I guess the heaters are probably 99% of the power usage with the rest barely using much more than that. That works out to a bit under 2.8 watts of power which is pretty reasonable to work with in regards to powering via battery. (One good 18650 will probably net some 3 to 3 1/2 hours or so of play time, though I intend to use a 2x Panasonic 18650 pack for probably more than twice that.) I didn't hear any obvious noise introduced by the converter, though, again, I don't have golden ears. Oh, and for reference, the DC barrel jack is 5.5x2.5mm, not 5x2 like some might be inclined to think. I haven't tested its voltage tolerance and I don't know how directly it powers the tubes from the source. I think these use 6.3V for the heaters though, so 5V would be too low even if it otherwise worked and would cut into the lifetime of the tubes, so I recommend against that. Well, unless it provides a separated power supply to them. (I've read that supplying 20% less than the rated voltage might possibly be the most optimal, so 5.04V may actually be good, but I'm not brave enough to test this too thoroughly. Most USB power devices produce enough less than this when under load that I would recommend against them though.) Of course the other components may fail to work at too low of a voltage anyway, which I have not tested at this time.

This review is actually a simple comparison of 4 different Headphone Amps.First, I want to be clear that I am not an audiophile, not even close. I just like to listen to music, any kind of music that I feels right. So, this review just what I personally think about these products, nothing professional.Here are the 4 headphone amps (the DAC I am using is Logitech 980-000910 Bluetooth Audio Adapter, it will cost $21.98 from Amazon. And I know this is probably not the DAC you want to buy, you may want something recommend from z review or one of the most popular brand Fiio. But honestly, when I compare to those DACs under 100 USD, I just cannot tell the differenc. And the good thing about Logitech is they are Bluetooth and easy to re-pair to other devices. As I said before, I am not even close to Audiophile, that’s why I can’t tell the difference)1. Fulla 2 by Schiit: $99 plus $10 shipping, total $109.I know this is a DAC/AMP, and I know this is a solid-state Amp. But if you buy any of the Tube amp listed below, you probably will buy a DAC to pair with it, after you purchase DAC, the price will be very close. And all the tube amps I compared here are not real tube amp, they are all hybrid. That’s why I also listed Fulla 2 here.2. SMSL T2 2X6J9 Vacuum Tube Headphone Amp: $59.90 from Amazon (Total with DAC $81.88)3. Nobsound NS-08E Vacuum Tube Integrated Amp: $50 from Amazon (Total with DAC $71.98)4. Bravo Audio V2 Class A 12AU7 Tube Multi-Hybrid Headphone Amp: $66.98 from Amazon (Total with DAC $88.96)So now you know all the price, seems like all tube amps are cheaper. But…….if you bought tube amps, I am sure sooner or later you want to try tube rolling, please consider that’s also your cost on amps. That’s why I said the price of Fulla 2 is close to other tube amps.Price is the first thing I consider; the second thing is the power to drive headphones.I don’t have a lot of headphones and this review is not about headphones, so please don’t ask me any question about headphones. The headphones I am using here are Sennheiser HD600, HD6XX from Massdrop, Sony MDRV6, Sony MDR7506, Beyerdynamic Custom One Pro Plus, Audio Technica ATH-AD900X, Beyerdynamic DT 880 Premium 600 OHM, Beyerdynamic DT-990-Pro-250 OHM, Bose QuietComfort 35, Fostex TH-X00 from Massdrop, Skullcandy Hesh 2 Bluetooth, Philips SHP 9500S, and Monster NTune.NO, I don’t have Beats from Dre headphone. If you really want to know why, please GOOGLE.Some are cheap, some cost a bit more, some very easy to drive, some needs more power.Let’s say the volume knob is from 7 o’clock all the way up to 5 o’clock. This way will be easier for me to show you how every amp provides the power on the volume. Yes, I know the headphone amp drive headphone is not just about volume but also how well it controls. But again, I am not audiophile, so I don’t care about the tech issue and I don’t want to see a lot of numbers calculating here. All I care is how the music sound and how loud it can be.All 4 amps with DAC give you a good sound, but tube amps are a little bit warmer. You won’t tell the difference unless you compare them side by side.When using any headphone is under 250 OHM, you will love any of these 4 amps. They all do a good job. You won’t go wrong on any of it. So, money wise, just buy the cheapest one you can find.Any 300 OHM headphone or above, you need to start choosing. If you use 600 OHM, you can forget about #2: SMSL T2 2X6J9 Vacuum Tube Headphone Amp. You can cross it out from the list, and that’s what I did, I don’t even bother to roll the tube.On 300 OHM headphone, Fulla 2, Nobsound NS-08E, and Bravo Audio V2 all give you enough volume makes you headache if you turn the volume all the way up (your ears won’t bleed, not that loud), and I only need to turn the knob to 12 o’clock. But not SMSL T2, I need to turn all the way to 4 o’clock.On 600 OHM headphone, Fulla 2 and Nobsound need to turn to 2 o’clock to my normal listening volume, from 2 to 3 only gains a little bit, and from 3 to 5, it won’t gain any more (you can turn the knob and play back forward, nothing going to change). Bravo Audio V2 only need to turn to 1 o’clock to reach the same volume, and from 1 to 4, it only gains a little bit. And when you turn to 5 o’clock on Bravo, it did gain volume more, but it starts distortion, and I don’t like how the music sound like that. On SMSL T2, the volume is like someone whisper to your ear even you turn all the way to max, and you need to push earcup real tight to hear what they try to say, maybe good for training your listening skills and how sensitive you are to the sound, but not very good for listen to music.So, if you want to use 600 OHM headphones and you don’t want to spend a lot money to buy a High-end amp, then please choose Bravo.Now, I am going to talk about how much heat these amps will generate. Because I already cross out SMSL T2, so I only talk about the other 3. (If you really want to know, it’s the same as Nobsound)Fulla 2, you can put your hand on it or just grab it. You will only feel a little bit warmer than your hand.Nobsound, you can pretend it’s not hot and leave your hand on the case for a while and keep telling yourself it’s not hot, it’s not hot, it’s not hot………..Bravo, you can put your hand on the glass part and do the same thing as Nobsound. But I dare you to touch the heat sink, it can fry eggs!!!!!!Why we talk about the heat here, it’s a safety issue. I don’t think you want to leave Bravo on when you go to work or any other reason that you need to leave your house for more than 3 hours, it’s kind of like you forget to turn off your stove when you left your house (a very tiny stove). That means you need to power on and off every time you use it and before you leave.This is not a problem to me, but you might want to know.Then the headphone jack, Fulla 2 and bravo are both 1/4", Nobsound using 3.5mm. Personally, I like the 1/4 better.Then the input, Nobsound only has 3.5mm audio input, Bravo has both 3.5mm and RCA input, I didn’t try to plug them with different sources and start the music at the same time, I just assumed that it cannot, but you are welcome to try it and let me know how it works. Fulla 2 has 3.5mm at front and USB input on the back. I like the Fulla 2 better here, I can just connect to computer and use it.Then the external power, both Nobsound and Bravo are using external power charger. Of course, you can carry a generator with you and make it portable. but I will just use it at home.Fulla 2 just use your computer USB to power it. But if you turn the volume over 3 o’clock, you will need external power. You can use either cellphone mini usb charger at home or battery bank when goes out.Then function, Nobsound and Bravo are headphone amps only, there is no other output. Fulla 2 can use as pre-amp, DAC, and headphone amp. I use Fulla 2 connect to JBL LSR310S then LSR 305 and it works great, and from different connection on Fulla 2, you can use headphone and speakers at the same time but control the sound from computer not the knob on Fulla 2. (By the way, when you plug in headphone to Fulla 2, it will mute the speakers. But Schiit Jotunheim won’t, you have to power off your speakers or unplug the speaker cables, that’s Schiit company try to force you do some workout, not just sitting there the whole day, thank you Schiit, Jotunheim is really a nice piece of Schiit.)On tube rolling, Nobsound need a pair matching tubes, and sometimes it will cause some problem if you didn’t buy them right. Bravo just need one.I can tell you that I tried a lot of different tubes on both tube amps and honestly, I don’t feel a lot difference between tubes. I think stock tube works fine on both tube amps. If you really want to try different tubes, then I suggest Amperex on Nobsound. For Bravo, I suggest Baldwin>Sctron>RCA.Again, I really don’t think you need to spend the money on tubes. These are not real tube amps, so the sound changing is not that much when roll tubes. But…….. again……, I am not an audiophile, not even close, so………what can I say.Finally, I can tell you what I choose, but that’s only me.I keep Fulla 2 and Bravo. One for portable (Fulla 2 with computer, not cellphone, and I usually carry a battery bank with me, so I can just use that as power supply for Fulla 2, or I just plug into computer. Cellphone I use Fiio E12), Bravo in my dining room, so I won’t forget to turn off the stove when finish eating. For the price these 2 asked for, you really won’t go wrong on any of it. Personally, I like Fulla 2 better, but I just can’t say no to this cute but powerful Bravo.