[cyphervld]

Hello all,
 
I have just built my very own can tube amp using a PCB model bought on Ebay from a seller that I have bought my previous amp from. Basically, it consists of a 12AU7 tube in series with a JRC 4556 Op=Amp so that it can be run off of a 12V DC supply with just 1A. 
 
My problem is that the amp only works well at relatively low volume, if I even try to make it a bit louder (but not as much as to blow my ears off) the bass becomes very distorted and there is a significant loss in volume. I can't figure it out. The tube seems to be operating just fine. Might it be that it isn't getting enough current to sustain higher volume? What shoiuld I look into? 
 
Thaks in advance!

 

[Sempertiger]

I'm curious if you have any test equipment available. specificly a multi meter, function generator and O-scope. Without looking at what a clean signal is doing as it goes through the circuit, I'ld just be speculating.
 
But in case you don't, let me share some thoughts. Since you are talking about a single tube and op-amp, I'm assuming that this is a mono amp. If this is the case then you could have a degraded tube, or a faulty op amp. If it's a multi channel amp, then I'm curious if the problem exists in both channels.
 
If I didn't have any test equipment, and the amp is either a mono amp or you are finding the problem exists in a single channel, then I would try replacing the appropriate tube with an other one. If that doesn't solve the problem, then try swaping out the op-amp, if it's easy. If that doesn't solves the problem then you probably have a powersupply issue.
 
If you don't have any replacement tubes or op amp, or the previous steps didn't help, then I would try to power the amp with a power source that can provide more/better current. I would probably use a car or motorcycle battery with a 10amp inline fuse. If this solves your problem then you are probably starving your amp by having a power supply that isn't putting out it's rated power, or it's simply not big enough. Eithe way it needs to be addressed.
 
If none of these issues fix it, then we need a multi meter at the least, and a schematic of your amp.
 
JS
I

 

[cyphervld]

I do have a mulltimeter, I have tried with another opamp and the result is the same. The opamp is dual and so is the 12AU7 triode so the amp is stereo. Unfortunately I don't have a replacement valve since they are pretty scarce as is over here and I am not going to pay 50$ on ebay for one. I can't upload the schematics to easily since it;s  in a protected PDF file.. 

 

[wz2000]

Sounds like the amp isn't supplying enough current. This could be caused by the power supply or the design of the amp itself. What headphones are you using? I once built a somewhat similar amp and it could only drive some more efficient headphones, while more power hungry phones would distort just like you said.

 

[Sempertiger]

at this point I would try the battery idea. if you still have the issue, then i'm affraid you either need to spend the money for another tube, or like wz2000 said, your amp might be too small for the drivers you are trying to push with it.
 
Short of removing each component and testing it, if the battery idea doesn't solve the problem, then you have an issue with your amp. Namely, it's either too small or you have a faulty component/s. I would try plugging in some smaller drivers. a cheap set of earbuds for example. if you still have the issue with the earbuds, then you most likely have a faulty component. if the earbuds sound good, then your amp is too small for your original phones. Be careful not to mistake overdriving your earbuds with amp noise.
 
If you have a bad component, try looking in your area for a tube tester. It won't be easy to find, but I would start with an old TV repair shop. if you can't find a shop that has one, start asking around for an old tv or radio repair man, retired, that might still have some of his gear.
 
good luck.

 

[cyphervld]

The tube does work, because if it didn't I wouldn't have any sound. And I can see the heaters worrking. Would a tube tester show me if it's not running optimally? I can try getting another tube from where I bought this one since it's pretty close to home and maybe I can get a replacement. I will post some pictures tomorrow with the build. 
 
As far as cans are concerned, I tried it with a pair of Microsoft VoIP phones first so I don't fry my better ones and then I tried with my Shure SE 115's. They boyh do the same, and this amp is supposed to power any impendance headphones anyway. 

 

[Sempertiger]

Honestly, I would try the battery first. Tubes typically just stop working, but they can degrade resulting in symptoms you are experiencing. A tune tester will tell you how well your tube is working.

I keep bringing up the tube because it is the most likely component to fail, but like wz2000 said I think yor power supply is starving your amp. By hooking it up to a battery, you isolate the amp from the power supply.