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Low frequencies bad in one channel - Tube amp

orwak

Member
Hi

I have a Leben 300F with one problem, when playing test tones around 60Hz you clearly can hear that the sound level is much less in one channel than the other. (I have been switching all tubes back and forth and so no problem there, also replaced all of them with new tubes). When the frequency is above 100Hz or something the output seems the same in both channels.

I previously had one output tube with a short which burnt a grid resistor that I replaced(with same value), could some other part have been damaged so it could cause the low frequency problem in one channel?

(A very odd thing is that the shorted output tube was the first tube in left channel, and the frequency problem is located in the right channel).

Any tube specialists with an idea about this?

Regards
Orwak
 
Have you swapped your speaker cables over to make sure you haven't taken out a driver in one of them?
 
Have you swapped your speaker cables over to make sure you haven't taken out a driver in one of them?
Yes, no problem with the drivers. The sound is normal above 100-150hz and upwards, the problem is just obvious below 100Hz. I have switched around every possible cable so my guess its internal in the amp.
 
Sounds like a capacitor issue.
Coupling cap or cathode resistor bypass cap with too low a value. The 2nd one is more likely as it's usually an electrolytic.
 
Exactly the same thing happened to me for years. No bass from my right hand speaker so bass players were always left of centre no matter what the LP. I tried everything from azymuth to inventing a balance control for my Sugden A21SE, all to no avail. In the end it was my hearing - my right side audio nerve was on its way out due to a Schwannoma (floating benign tumour like ball of dead cells which grate against the audio nerve as it passes through your skull on its way to your brain)and the problem started with the lower frequencies ( Uncommon, it´s usually the highs apparently). I am now stone deaf - zero, zilch in my right ear so I face it to the rear wall when I am listening to music and my left ear towards the speakers just to get a semblance of a central image. I sincerely hope this is not your case and would urge you to visit your doc just to check. I still appreciate tonal information but stereo is a thing of the past for me. Apparently, according to Wikipedia, Schwannomas can form in your penis too, which at my age, might have been a slightly better option as I do try to use my system every day !

P.S. Do I win a prize for using the word penis in a hifi forum ?
 
Exactly the same thing happened to me for years. No bass from my right hand speaker so bass players were always left of centre no matter what the LP. I tried everything from azymuth to inventing a balance control for my Sugden A21SE, all to no avail. In the end it was my hearing - my right side audio nerve was on its way out due to a Schwannoma (floating benign tumour like ball of dead cells which grate against the audio nerve as it passes through your skull on its way to your brain)and the problem started with the lower frequencies ( Uncommon, it´s usually the highs apparently). I am now stone deaf - zero, zilch in my right ear so I face it to the rear wall when I am listening to music and my left ear towards the speakers just to get a semblance of a central image. I sincerely hope this is not your case and would urge you to visit your doc just to check. I still appreciate tonal information but stereo is a thing of the past for me. Apparently, according to Wikipedia, Schwannomas can form in your penis too, which at my age, might have been a slightly better option as I do try to use my system every day !

P.S. Do I win a prize for using the word penis in a hifi forum ?


No prize for the word penis but a massive prize for using it every day

Good luck stay safe.
 
Got the amp back from service and the sound problem in one channel is fixed!
Problem was another grid resistor, in addition to the one I changed, that was damaged in the bad sounding channel, I had not seen this as it was a super tiny burn spot.
/Henrik
 


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