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Civilian 6n2+fu32 tube headphone amp - Page 3

post #31 of 104
How does the sound quality compare to some of the other amps around? What would you guys say it's similar to, or not?
post #32 of 104
Thread Starter 

Full rounded sound with sweet treble, makes my AKG's sing. Had to give up on the Fostex phones they developed a fault & the supplier failed to fix the problem. Would like to try Sennhesers when funds permit.

post #33 of 104
post #34 of 104

I just purchased this from cart100.com and got some 832a vacuum tubes off of ebay. My question is, can a 12au7a work in this? or do you need a 12ax7? thanks

post #35 of 104
Thread Starter 

Cannot use any "12" series, unless you rewire it (I posted a schematic in an earlier post) . Without rewiring

you need to use a "6" series, 6AX7 & 6AT7 both work.

post #36 of 104

Thanks. I actually cancelled the order after hearing from another source that the internals on this amp are of really low quality. It's powerful and I fear it could ruin expensive headphones. It does look super cool though.

post #37 of 104
Thread Starter 

IMO you should not listen to fearmongering rumours, unless it comes from multiple sources.

I have had zero issues with mine. Good luck.

post #38 of 104
Originally Posted by ag8908 View Post

Thanks. I actually cancelled the order after hearing from another source that the internals on this amp are of really low quality. It's powerful and I fear it could ruin expensive headphones. It does look super cool though.

You get what you pay for, and sometimes you get more! Especially from China.
post #39 of 104
I'm interested in picking one of these up. I'll replace the cheapo Chinese tubes and probably replace the knobs to something prettier.

Does anyone have any feedback powering these with the HE-500 or a different pair of planars other than the Fostex? Any background noise, hum, channel imbalance, or any other issues? Info on this are scarce and anything would be appreciated.
post #40 of 104

Just chiming in here as there really isn't a whole lot of information available on these amps (nor an actual product name, it seems).


I've picked up one of these to power my Thunderpants (modified Fostex T50RP) at work. Having previously used the surprisingly capable Little Dot 1+ for this very duty, I wanted to try something else and this amp caught my eye for both its looks and pricetag, along with it being a tube amp. I have actually purchased replacement tubes that were recommended by someone else but have yet to receive them, so keep in mind that my initial impressions are for the stock amp and only after having listened to it for about 15 hours or so.


For the sake of completeness; I listen to music from my iMac (using iTunes), using optical out connected to a iBasso D10 Cobra as a DAC, to which the amp is connected. In the photos you see me use a very flimsy 3.5mm to rca cable, that's because my proper cable is currently on its way in.



I think the amp looks pretty nice as-is, but can definitely see room for improvement. The knob is fine but it feels plastic-y so replacing the knob itself could be nice. The big power switch on the left makes a proper FLICK sound when you turn it on or off, which I kind of like, but it feels decidedly "homemade." The outside of the headphone jack is plastic and it shows, but you sort of not notice this once you have your headphone plugged in (which is why I have the thing anyway), so it doesn't bother me.



The amp, as was mentioned before, gets quite warm. When you adjust the volume you can feel a very apparent glow coming from the big tubes, which slightly light up too, if you look carefully / at an angle. I immediately gave it a listen when I received the amp and listened for about three hours straight, and could notice a rather obvious change in sound quality in that time. It seems quite apparent that this amp (or its tubes, actually) benefit greatly from burn-in. I want to reserve my opinion on the stock tubes until I get the other set (these, in case you're curious), but my initial impressions compared to my memory of the Little Dot 1+ with this headphone is that the bass is a bit more muffled, less punchy. I want to write an addendum to this once I have received and listened to the other tubes, though.



The amp matches quite well with the modified Fostex T50RPs that I'm using (Smeggy's Thunderpants), though I wish it had a little more power. Whereas I had plenty of room left on the Little Dot 1+ with these headphones, with certain albums I have to push it over 75% to get it to a good volume level. On the specs listed it supported headphones ranging from 32 to 600 Ohm, but no further information was listed.


That said, they perform admirably. I get the right volume even though I have to crank the knob up more than I'd prefer, but at the same time I notice no obvious sound distortion. I actually don't even notice any hiss or background noise, even when not playing any music. Even with the Little Dot 1+ I'd hear background hiss at higher volumes, so in that sense this one is, somehow, better.



Overall I like the amp. While it won't win any awards or probably won't get past a proper review from someone who knows what the hell they're talking about, I like it. It sounds good, it looks unusual in a good way, and it's a pleasure listening to it. Combined with the Thunderpants it gives a nice sound that doesn't tire your ears (I listen all day, every day, so that's important for me), and there's plenty of room to play with this amp, either by putting in some more expensive tubes or by replacing some parts to make it look even better.


I bought mine through Aliexpress for $240 shipped. They even offer 110v and 220v models, which I'm not sure other places offer too.


Hope this helps others that have stumbled upon this intriguing little amp. Please feel free to shoot me a question if you have any.

Edited by davejansen - 8/19/14 at 11:44pm
post #41 of 104
Thread Starter 

Look forward to your review when you have the replacement tubes (NOS I presume).

You will notice a big difference after a burn in of 3 days,

24 hours will get 90% of it.

post #42 of 104

Any clue how this amp may sound with DT990 250OHM on NOS tubes?

post #43 of 104


these tubes are cute..... :P

post #44 of 104

I'm still waiting on my replacement tubes, but I received the 3.5mm to RCA cable I ordered from China a couple of days ago.


Having listened more to the amp throughout the week, I'm enjoying the sound it produces for the most part, though I'm increasingly curious how different things will sound with the tubes I've got coming in. They're by no means fancy ones so I can honestly say I have no idea what the result will be. With these tubes and my headphones bass is quite boomy, more-so than when I used these headphones with the Little Dot 1+ or a cheap Korean-brand HiFi amplifier before. When comparing it to the iBasso D10 Cobra (seen in the photos used just as a DAC) using as an amp, too, I have to say the combination doesn't work very well with my headphones. The Fostex has some pretty sharp highs, and the D10 seems to amplify that, giving it a rather uncomfortable sound. It's far less with this amp, but again, I'm curious what will happen with the replacement tubes.


Overall I tend to listen to more active music at work (where I have this setup), which is why I was looking for something with a bit more "oomph" bass-wise, as compared to my home setup.


A small photo update, mostly focussed on the new 3.5mm to RCA cable. You'll also notice the optical cable bought from the same shop.



Thanks for reading!

post #45 of 104

I received the "Deluxe" edition of the amp today. I purchased the amp directly from the manufacturer store in China. I also had the amp modified to have 12.6V filament power supply to use 12AX7 tubes.



The deluxe edition of the amp uses aluminum case, and slightly more powerful power supply transformer. According to the manufacturer store, it shall give better dynamics and "sense of space".



For those who are interested: the output transformer of this amp (pictured above) have the following output impedance settings: 10ohm when connected to 32ohm headphones, 14.5ohm when connected to 64ohm headphones, 42ohm when connected to 300ohm headphones, and 64ohm when connected to 600ohm headphones. Inductance of output transformer is measured at 17.58H at 100Hhz, and 15.7H at 1kHz.


Other advices from the manufacturer:

1. The amplifier can "auto detect" the headphone impedance and use the corresponding output transformer settings (I have no idea how but the output transformer picture does have 5 output wires)

2. Modification to use 12.6V filament has to be done with special attention to avoid A/C current noise.

3. Don't bother to swap FU32 tubes with Russian GY32 tubes, the FU32 is better

4. Upgrade FU32 to 832a tubes will result to better treble details. The rest will be similar

5. The blue wires connecting to the FU32 tubes are with 280V. Thus one must handle those wire with extreme care to avoid electric shock

6. Proper initial "burn-in" for the tubes should be tuning on the amp listening for approximately 2 hours, then turning off and let the tubes ti cool down, then listening to 2 hours... till the sound more or less settle. It will usually take approximately 20 cycles.


My observations:

1. The design concept of this amp is to use the cheapest/most widely available tubes in China to make a good sounding amp. Both the 6N2 and FU32 tubes costs around USD2.2 each in China

2. All FU32 tubes available on the market are NOS. The most recent production was done in early 90's, with some date back to 1959. So even new FU32 tube is at least 20 years old.


Link to the manufacturer shop on Taobao: http://item.taobao.com/item.htm?spm=a230r.1.14.5.wERvfJ&id=35905011085&ns=1#detail

Edited by borrego - 9/12/14 at 2:00am
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