[davejansen]

I have received the replacement tubes earlier this week and wanted to give you a small update now that I've had a chance to spend some time with the amp and new tubes.
 

 

 
The tubes look rather old because of the half washed out prints on them and sprayed-on paint (or whatever it is), but they're not scratched or dinged or anything. The Chinese tubes that came with the amp look better because they're new, but the difference is, quite honestly, not very big. They're a funky looking tube, anyway. But none of this really matters of course, we're here for the sound.
 

 
I replaced the Chinese tubes with these and flipped the amp on and left it there for about 20 minutes or so before I gave it a first listen. While I believe burn-in is important, I also just really like to listen to music while I work, so I don't mind experiencing the burn-in with the tubes, so to speak. Interestingly enough, too, there was an immediate sound quality difference when compared to the Chinese tubes. I'm not a pro in any sense of the word when it comes to describing audio (or experiencing it for that matter), but I'll try my best to put in words what I felt/heard.
 
Especially as I keep using these tubes, I notice they produce a more open sound, with more separation between instruments. The booming feeling of the Chinese tubes is much less here, too, and seems to keep getting better as more hours are put into these tubes. With certain tracks the playful placing of instruments works really well with these tubes when compared to the Chinese ones, which I really like.
 

 
Overall I'm very happy with the setup. I'm glad I went for the Russian tubes, the difference is both noticeable and a clear improvement, to my ears anyway. If you end up going for this amp, I recommend you get replacement tubes too, if only just to experience the difference (and choose whichever one you prefer). I bought mine here, it cost me about $30 shipped to get these.
 
Hope this helps! Feel free to ask me any questions if you have them. I'll try my best to help out.
 
-Dave

 

[Nympho]

Has any one changed the blue tube wire connectors? They seem incompetent.

 

[borrego]

Has any one changed the blue tube wire connectors? They seem incompetent.

Those blue wires are running at 280V and get very hot from the FU32 tubes. Typical PVC/PTEE cable jackets will get melt down because of the temperature. I won't bother replacing those.

 

[Nympho]

I am new to tube amps and i have a fluttering sound in my right headphone is that normal burn in?

 

[Lorspeaker]

not burn in....jus a fly gotten trapped in your right cup...

 

[Nympho]

I think the tube may be going bad, I switched the the two RCA 832A and the problem moved to the left headphone.

 

[JustinBieber]

Switch one tube into another socket. If the flutter sound goes into the left channel then one tube is messed up.
 
If you're talking about this amp, you can grab 832A pairs of tubes on eBay. I imagine it sounds better than the cheapo Chinese tubes this amp comes with.

 

[borrego]

The 832A tubes on ebay are not new tubes (judging from the tube pictures where there are carbon deposite inside the tubes). So one is betting to get a good used pair of 832A.

The best price/performance tube rolling will be to rewire the central tube socket to run 12.6V filament voltage and replace the 6N2 tubes with 5751 tubes. Thus will give the best sound improvement.

If one think the FU32 tubes are "cheap" and inferior, the 6N2 tube will be worse.

Personnally I think the FU32 tubes are perfectly fine, sound performance vise. The best upgrade will be to use 12.6V 5751 tube replacing the 6.3V 6N2. I have checked with the manufacturer directly and it was also their upgrade recommendation.

 

[DavidK35]

You can get replacement USA NOS tubes dirt cheap @ http://www.vacuumtubes.net/prices.htm
 
$7ea.

 

[borrego]

  You can get replacement USA NOS tubes dirt cheap @ http://www.vacuumtubes.net/prices.htm
 
$7ea.

 
Wow. If it is really USD7ea for NOS 832A then it is indeed dirt cheep. I just send them an email asking the shipping cost.

 

[Nympho]

  Follow up on the previous post, the amp with the following modification:
Tube:
Chinese Beijing FU-32 -> RCA 832A
Chinese Beijing 6N2 -> JJ 12AX7 (including Filament connection mod on the amp)

Cap:
Replace the unmarked ceramic 0.1uF cap with Bennic 0.33/400V FPP cap
 
A bit of tidying up of the connections, such as the cap is now wired directly across the input and power tube, instead of going back to the bus, routed round and round and then to the power tube.


After about 16 hours of continuous operation, the thing cleared up quite a bit, it is much better than what it was without modification.   I will swap in the Chinese FU-32 tube in a moment and see how much difference did that tube make.
 
====Edit====

Swapped the original FU-32 for about an hour, and couldn't stand the muddy sound.  Swapped back RCA 832A, and it already sounds better within a minute of powering up.

is the unmarked ceramic caps the green ones or the white ones with brownish ends?

 

[Maniac]

White one with brown ends.
 
Just tap them with something hard, I use my ring (platinum) and it will sound a bit like two pebbles hitting one another, and that's ceramic.  Plastic will sound dull.

 

[Nympho]

  White one with brown ends.
 
Just tap them with something hard, I use my ring (platinum) and it will sound a bit like two pebbles hitting one another, and that's ceramic.  Plastic will sound dull.

Thank you very much. Just got my hakko soldering iron today, so i can start practicing before i even try to change them.

 

[Maniac]

  Thank you very much. Just got my hakko soldering iron today, so i can start practicing before i even try to change them.

Good luck, the wiring can be simplified by applying simple logic.  Something like "does this line need to go back and forth for absolutely no reason..."

My advice on this amp is that due to the cheapness of the amp, DO NOT drop uber expensive parts in it, it is going to be a waste of your money.  Try out cheap and good parts by all means, save the high end parts for other stuff.

The amp is limited by the output transformer, and there really is no point going too far when you are limited by the output transformer.

 

[Nympho]

  Good luck, the wiring can be simplified by applying simple logic.  Something like "does this line need to go back and forth for absolutely no reason..."

My advice on this amp is that due to the cheapness of the amp, DO NOT drop uber expensive parts in it, it is going to be a waste of your money.  Try out cheap and good parts by all means, save the high end parts for other stuff.

The amp is limited by the output transformer, and there really is no point going too far when you are limited by the output transformer.

I have been thinking hard of keeping the idea of using the FU32 and changing to a 12ax7, then taking out the stereo outputs, and creating my own design. But I still have a lot to learn before I can start on such a big project since I dont have any electronic experience. After I read through a few books I got I can start planning. Also I dont think I'll need 2 output transformers if I go w/o the stereo outputs.