2. amps-preamps
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Leben CS300XS Tube Rolling

Of course there are older threads, here and elsewhere, that cover the subject. But I’m looking for fresh takes from new users (and given how quickly used units move, I’m guessing there are a few of us around) as well as feedback from seasoned experimenters (maybe even some dating back to those mind numbingly long threads of 10+ years ago).

Some say the Leben CS300XS is responsive to different tubes, both EL84 and 12ax7. Others say only the signal tubes noticeably impact the sound. Given that versions of the amp have been around for ~20 years, this seems like something that should be already settled, but here I am…

New production or NOS and no hard budget, I’m open to trying anything anyone else enjoyed. What am I trying to achieve? Occasionally, I hear some random graininess and/or hardness at higher volumes (could this be tube related? I don’t know). Beyond that, I’m really looking for anything that brings more of the Leben’s great qualities forward (like when I added A23 cables to the mix, *everything* improved).

Speakers are Klipsch Forte IV and sole source at the moment is a Chord Qutest DAC. Thanks in advance for any advice/help you care to share.

oceanandmountains
oceanandmountains OP
33 posts
 

@ghasley I bought the Genalex tubes from Amazon thinking (mistakenly?) new production tubes, unlike NOS, would be a low risk purchase. Viva Tubes filled the order and only matched the tubes. Again, the stock Sovteks produced the same low level noise via the tweeter (the Sovtek noise might even be slightly greater than the Genalex, but I’m not sure).

As to the grounding questions: 1) the noise is present without a source connected 2) it is in both channels, same level in each 3) adjusting the volume dial does not alter the noise. The noise begins right after the red light on the Leben comes on.

Someone somewhere described the Klipsch Fortes as a magnifying glass and I’m inclined to believe that’s what I’m experiencing here: since they reflect every change in the system, I guess that means they will also find noise where other less sensitive speakers probably would not.

Thoughts?

 

 

 

 

 

oceanandmountains OP
33 posts
 

@bjesien Even with the Klipsch and ear at the tweeter?

bjesien
1,308 posts
 

Seems like the amp and probably not the tubes. The speaker can be a magnifying glass but if all the tubes are producing the same result, again, something with the amp. IMO.

bjesien
1,308 posts
 

@oceanandmountains  silent.

ghasley
2,499 posts
 

@oceanandmountains first of all, friends dont let friends buy tubes on Amazon. The good news is you can probably return them. Can you hear hiss through the headphone section?  If not, then perhaps try some low noise matched 5751’s from Brent Jesse. You dont need that much gain with those speakers. 

 

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