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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
 

Sage advice @ghasley ;) Replicating Leben’s limited edition tube set is at the top of my list. And yeah, I’m already loving the chime-like tone and want to keep moving in that direction.

Probably should also add that with the stock Sovteks and Klipsch, I haven’t experienced any brightness. So I’m also thinking NOS Amperex 12ax7s because of their reputation for clarity and, especially, dimensionality. Currently, the soundstage is tall and, according to my musician wife’s mutant ears, very deep.

The only tubes I’ve tried so far are Genalex EL84s and 12ax7 (gold pin). The difference was relatively subtle, but the graininess was definitely reduced. So smoother than Sovtek seems fairly easy/cheaply achieved.

But I’m greedy; if I can get more, I want it!
 

bjesien
1,283 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
33 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
2,487 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
1,283 posts
 

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

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