Leben CS600 Owners - Help

I have recently become a happy owner of CS600. I will write another post about my overall impression of its sound, but there is one minor issue. There is a very subtle hum coming out of the transformer. It does not interfere with music listening, but I can still hear it from the listening position when the music stops and the room is quiet without AC or other ambient noise. Using the Decibel app on iPhone, I tried to measure the sound level. It is not detectable from the listening position. When I place the iPhone just an inch above the top grill of the amp, the sound level goes up from 55 dB (ambient level) to about 68-9 dB. Should I call it 15 dB increase or just a noise at 69dB?

I am just wondering if this is an expected level of transformer hum for a normal CS600. Can any owner of CS600 try it for yourself and confirm? Much appreciated.
Well, I wish I could retract my posting!! (If moderator can do it, please go ahead). It turns out the noise was only happening when the amp was placed within the media rack. I live in a furnished house with a decent sturdy media furniture (I wouldn't have bought such a thing but it was still decent from audiophile standard). After I removed the silly back plate (you know, with a tiny cable hole), the amp compartment becomes a cubic-shape tunnel, with four sides blocked and front and rear surface open. This particular configuration must have generated some kind of resonance. After I took the amp out on the floor, it became dead quiet. Oh well...

If I may add a few more cents, CS600 is a fabulous amp! I am driving Harbeth M30.1 (which is also awesome!). I was a bit worried about the low rated power considering the low sensitivity of M30.1, but it was not a problem at all to fill my 5m x 7m living room (with the space behind the listener wide open). Moreover, the lush/silky midrange was quite expected, but I was most impressed about how it reproduced acoustic bass with such weight and authority! Now I understand why so many people were talking about Leben.

BTW, I had a chance to side-by-side audition CS600 with CS300X. While CS300X had the same and perhaps a bit better midrange, which was understandable at the time as my CS600 was right out of the box, CS600 clearly stood out with bigger soundstage and scale. Overall, I am so glad that I spent the extra money for more power, especially for my Harbeth.

Many Harbeth owners who are hesitant to try this low powered amp, rest assured that you will have more than enough juice, unless you want to crank up the Zarathustra.
That's a story with a happy ending. I've heard the 30.1 and would own them had they been released before I purchased the C7ES3's.

My integrated is a Rogue Cronus Magnum which I love but sometimes feel I'm missing out on some detail. I've done some minor tube rolling but I'm losing interest fast. I'm considering either a solid state integrated (Hegel possibly) or KT120's for the Rogue. I'm just not sure what I'll get out of KT120's besides more power.

I got my CS600 a month ago and have the same hum sound as you described. Thought it was defective and took it to the dealer. His demo unit also have the same hum sound. He told me that it was normal. On mine, I can only hear it when standing or sitting next to it when music is not playing.
As for speakers, I'm also thinking of getting the M30.1. Right now, my CS600 is hooked up to a pair SF Auditors. The combination sound very nice but I always hear or read about the Leben + Harbeth combination. In a few weeks, I'm going to demo the M30.1 to see if they are any better than the SF Auditors.
Glad it worked out.
I love the CS600. I had transformer hum with a previous amp and it was a deal breaker for me.
I've been thinking about trying the Harbeth 30.1.
Heard them with the Red Wine audio amp at the NY show and the sound was beautiful.
Still using the focal electra's and they sound great with the Leben too.
Listening as I write this. Tomasz Stanko Quartet, Matka Joanna on ECM.... warm and crisp at the same time.
Thank you all for the kind words and further input.

Xmuavah, I suggest that you try to place CS600 on a sturdy platform, either directly on the floor or an amp stand. I suspect that the hum will be reduced.

Oddmorning, I'm a big fan of ECM label. The M30.1/CS600 combo made some obscure (and somewhat uninteresting) ECM music come alive by rendering the live studio in front of me.

Donjr, please don't go to that route (IMHO). I heard good words about Rogue Cronus Magnum, which I'm sure is a fine product, but there's so much you can expect for the budget. I'm an expat and in my US home I have Audible Illusions M3A -> CJ MV-60 -> Proac 2.5. The system is comparable to my new system in retail price (at the time), but I never got this kind of sound. I also seriously thought about Hegel H300 as a second amp in case I need more bass and power, but I completely changed my mind now. I'm still interested in Hegel H25 DAC though.
Thanks for the suggestion on the hum noise. What tubes are you using in your CS600 and why? Have you try any other speakers before buying the M30.1? Thank you in advance.
Well, I only had it for a week, and haven't yet opened the top plate, so it's been the stock 6L6GC. I will enjoy the current setting for a while and will experiment EL34 (which I look forward to very much) after I get some clear ideas of the current sound.

I bought the speakers first so I don't have much experience with other speakers with CS600. The comparison of CS300XS/CS600 was done with Lawrence Audio Violin, driven by AMR DP-777. The results were consistent with what I have now.

My purchase of M30.1 was based on the reviews of course and also on my fond memory with P3-ES2 that I had for a while. Although it lacked the bass and scale compared to Proac 2.5, the midrange was fabulous.

So what are the improvements of the current system compared to my other Proac-based system? The key areas are:

(a) Smoother midrange/highs with reduced grain around the voice/instruments. More air.
(b) Deep deep sound stage, but this may be in part attributed to the fact that I can place the speakers well into the room (5 ft from the back wall) which was not possible in my US home living room.
(c) More "authoritative" bass. I wouldn't call it tighter, but weighty yet well defined. It's hard to describe, but it sounds more realistic without feeling muddy. I've been thinking about this matter lately. Although we all seek for "tight" bass, when you go to the jazz concert the bass sound is actually not that tight.

In my 20+ years of this hobby, the most memorable upgrade was changing Adcom GFP-555 to Melos SHA-Gold. I had never expected that a preamp alone could make such a difference. The Leben CS600 upgrade will now be put on near top of my list. Saying this in comparison with a system that is more than decent in any audiophile standards should be quite a testament. I realize I am sounding like a salesperson, but I am in no way affiliated with Leben or any companies mentioned. Just a music lover enjoying good sound.
I have owned the Leben CS600 and Harbeth M30 combo for over 3 years, had a lot of fun tube rolling (I also own the Leben RS30EQ Phono) and have tried most of the variants of 6l6s, el34s, KT tubes, of different brands, NOS or new. I think I have now come to the end of my quest with KT120 which had just burn in for 200 hours - this is as good as a major component upgrade. Now I realize the leben was actually under powered to drive the m30s fully (I listen to classical music mostly in a small 12sqm listening room, I listen quite loud). Recently I start to enjoy listening to rock music in this system, not before. I would seriously recommend anyone with my same combo to give these tubes a try.
+1 for the KT120's in a CS-600

However, as the CS-600 was not designed to use such a high-powered tube as the KT120 (the tube didn't exist when the CS-600 was designed), you can not obtain as much power as the KT120 can create.

But the amp sounds incredible in all aspects.

The Leben CS-1000P was built for the KT120s.