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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
bjesien
1,239 posts
 

I have e a set of NOS Mullards in both positions for just a glorious listening experience. If I want more detail and extention I have a set of Amperex that I put in the 12ax7 and Sovtek in the  EL84. I will have to try the Aperex/ Mullard combo together. 

The amp is responsive to cable changes too. I haven't tried a fuse change but I'd swear that I put a purple fuse in the Cobra will noticeable results. Never did a blind swap however. 

It's a great amp I've owned it 3 times now. A new stock EL34 that I really like is the Mullard, but never tried the new 84.

Best of luck!

oceanandmountains OP
24 posts
 

Thanks @bjesien and for sure the Leben/Klipsch combo responded to different/better cables. Not a subtle change at all.
 

BTW I can hear a slight tube buzz from the tweeter (with my ear to the speaker) with both Sovtek and Genalex tubes. Can NOS tubes reduce this noise at all or is this just part of life with the Klipsch driven by tubes?

ghasley
2,433 posts
 

@oceanandmountains it could be one of several things: 1) the new production tubes, from whom did you buy them and were they the highest grade, lowest noise offered by the seller?, 2) NOS tubes  require the same attention to detail prior to purchasing, 3) The more likely culprit could be a grounding issue. Try unplgging everything from the Leben other than the power cable and speaker cables. Is the noise still there? Is it out of both channels or just one? Does it rise and fall when adjusting the volume of the Leben. Mine are quiet.

bjesien
1,239 posts
 

Agree with ghasley, you get what you pay for.  The amp should be silent. 

oceanandmountains OP
24 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?

 

 

 

 

 

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