[Lefoobar]

Hi Guys,

First time posting something here but I browse the forums almost everyday. I'll try to be as detailed as possible with my issue.

I recently purchased a small Tube Amp from Ebay. Unfortunately I'm having problems with the audio as suggested in the title. I get a variation of crackling, popping and scratching/hissing sounds coming out of the headphones, regardless of whether the volume is off or on. I've changed various outputs/inputs and re-seated the tube to try and fix the problem but to no avail. Also, it's probably worth mentioning that I'm a novice at electronics so the chances of me replacing internal parts of the amp are pretty slim. 

Any ideas on what this problem could be? If you need more info let me know. I'll post pics if needed. 
 
(here is the link if anyone is interested: http://www.ebay.co.uk/itm/Compatible-6Nxx-12xxx-6N11-12AU7-series-Tube-DIY-HiFI-Headphone-Amplifier-AMP-/120873666519?pt=US_Home_Audio_Amplifiers_Preamps&hash=item1c24a1c7d7)

Thanks!
- Lefoo

 

[PurpleAngel]

Also try posting this question on the website Rockgrotto, some of the people on that forum like to tinker/modifiy with those amps.
so they have some good knowledge on them.
 
You might try getting a digital multi-meter (the DT830 sells for around $7) and try balancing and fine tuning the two voltage channels.

 

[formula1]

Rockgrotto forum is offline, not sure when it will be back online. 

 

[Nic Rhodes]

Someone sold one on ebay today complaining about hum also in their advert, I find the volume pot is occasionally scratchy on these duing use but hum is down to tube / how they are connected / positioned. They are an interesting little amp that normally sells for cheaper than the one mentioned in the first sentence!
 

 

[HPiper]

All I can say is when you are buying a $25 amp made in china I wouldn't expect very much. Tell you what I have one I'll send you if you pay the shipping and it works just fine. Send me a PM. It was just to tide me over until I could afford a Little Dot and it barely even did that very well, but it does make sound come out of my phones, not noise.

 

[Lefoobar]

Hello! 

Sorry for the late response (been a bit busy). Thanks for all the replies I really appreciate it. I've ordered another tube, and have a replacement power supply on the way to see if either fix the issue. You're right though, not to expect too much with a cheap amp from China!  

@HPiper - I don't think I can PM you since I'm a new member and don't quite have that privilege just yet! Thanks for the offer, It's probably not worth the time and hassle to ship to the UK. Incredibly kind of you, though.

 

[keithsplace]

First thing I would try is new tubes.
There are several tubes that can be used in it.
I just received mine today as well, but it is new, so hopefully I will not have any issues with it.
We'll see and I'll post my review of it once I assemble it, as it was a kit.
Not that I need, but was looking for assembly instructions when I found your post, because it comes with none.
But is pretty straight forward and only requires assembly of the top bottom, mount the board, and connect the power plug.
But I have seen reviews saying some of the other tubes give better results and different colors to the sound, than the furnished
Chinese tubes. 
Actually I got the Little Bear P5

 

[Androgen]

I have two of these with the little bear branding not the muse.
they both have good tube sound but not a very great sound stage or very much instrument separation.
I paid approx $40 each at auction so there still great listening for the price.
 
I would leave it playing for a couple of days with out phones.
this is because some tubes have contaminants in them and need to be burnt off by the heater.
 
If that does'nt work try a new tube, I'd suggest buying a few different types to try.
 
Also set the voltage from ground on the rca connector, to power on the outside end of the front capacitor inside the two sets of heatsinks.
I set the voltage between 11.5v up to 16v depending on the character of the tube, type of music I want to listen to and just what sounds good to my ears.
You can do this with or without music playing. I do it with music playing so I can get it to sound right to my preference.
 
I use 11.5v for the stock chinese tube as it has a fairly high gain with less bottom end and can have too much treble at higher voltages

 

[keithsplace]

Ok 10 to 15 mins later the new Little Bear P5 is together and working.. I counted on a little burn in with the tubes would be in order.
I started listening with sound output from my PC to input to amp, to my powered PC speakers.
They are old Altec Lansing Model ACS 300.1 satellite speakers with powered subwoofer.
Amazingly there is a pair on eBay . http://www.ebay.com/itm/Altec-Lansing-Multimedia-Speakers-with-Powered-Subwoofer-Satellite-ACS300-1-/321142215351?pt=US_Computer_Speakers&hash=item4ac59152b7 today.
I got these years ago for listing to music and playing games on the PC.
They still rock, TONS of bass from such a small sub. Actually if I'm not mistaken the sub design uses two small subs in a
facing each other pattern, like a band pass set up for a car sub, only smaller but they rock. The satellites are two way, with about
a 4-1/2" mid or full range and about a 3/4" tweeter. Anyway enough about the speakers.
The amp was together in less than 10mins. Plugged in, turned on for basic smoke test. No smoke, tubes lite up, put a little music input and walla,,sound. No hums, snap, crackle or pops.  Well I will still have to wait for a descent burn in on the tubes, nice but not anything amazingly better than the sound I had. I did notice a little warble of sound, at the top of the volume not really a distortion, but kind of a pulsing kind of sound. Volume was smooth through the control, no noises to report here.
But I wasn't really expecting like night and day difference but it does seem to have a different openness on the bottom end.
We'll see and post when I get some hours on the tubes and maybe try some tube.
I think gave $27.00 total with shipping from China. First thing that I have ordered form China on eBay and actually received.
Think I have tried it twice before and not received it. Both time it got to customs in NY and it is evidently still there. From a year ago.
But eBay or  Paypal promptly refunded.