Conrad Johnson Amp with ESL9s

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Bartonfields

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Long time lurker... First post and a question about my set-up and amp suitability, hoping someone can help.

I have a home cinema and listening room combined, with a pair of Classic 9s up front which are driven by a Conrad Johnson Premier 11 power amp.

I’ve never really had any issues until recently having upgraded my cinema processor to a Lyngdorf MP-40 and whilst running room perfect calibration I noticed a little distortion. I don’t run my cinema very loud, but the calibration processes required the volume to be turned up a little higher than normal and that’s when I noticed some distortion and the little red LEDs on the power amp were flashing. its possibly a question for members in the Conrad Johnson forum, but I‘m wondering if I should be considering upgrading to a higher powered amp anyway? I’m now concerned that I’m already getting close to the limits with this amp and wondering if there much headroom left. Here are the specs, what do you guys think?

Power: 70 watts RMS per channel.
Sensitivity: 950 mv to full power.
Small Signal Distortion: Less than .1% at midband.
Phase: Phase correct (non-inverting).
Frequency response: 20Hz to 20KHz +0, -.5dB Hum and noise: 98dB below full power output.
Input impedance: 100K ohms.

If I were to upgrade to another tube amp what minimum specs should I be looking at to safely run the ESL9s.
 

Big Dog RJ

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Oh dear! I just came across this only now... wondering why no one bothered to reply.

I'll reply to you in a bit, just listening to some fine tunes. CJ gear with CLX's, mighty fine!

I guess my reply may be too late but nonetheless some useful info. Cheers, RJ
 

Big Dog RJ

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Ok here goes, 50cts worth...

First of all, CJ tube gear is solid! Their power supplies are extremely well designed and the highest quality parts are used throughout, even in their entry level gear all the way upto their Art series gear. This is one of the best tube gear that money can buy, and the other being ARC (Audio Research Corp). Apart from the many others... it's basically CJ & ARC that have been the hallmark of legendary tube gear, so they're in a class of their own!

I've owned the Premier 11A and every Premier line of CJ all the way upto the Prem8A's. They're built to very high standards and simplicity in circuit design that was based in the 50's and 60's, they set the bar really high since then, that many struggle to keep up. There's absolutely no issue with the Prem11 driving the ESL 9's.

I've used the Prem11A to drive the following speakers full range, no sweat:
Maggie's MG3.5/r, MG3.6/r
Martin Logan CLS IIz
Infinity Renaissance 90's & Ren 80's
B&W Matrix 801
Thiel CS7 version 1
Energy Veritas version 1
ProAc Tablet's and Response 1s

The Prem11A didn't flinch one bit! Of course on really loud passages, the LEDs would flicker/ flash but that's normal. It drove all these speakers with ease and it was a beautiful sound.

Now, regarding the LEDs flashing, that could be due to several aspects:
1. How old are the tubes? Especially the Output tubes... anything more than 5 - 6yrs in operation would require changing including the small signal tubes (input & driver / phase inverter tubes).

2. Check the output tube bias. Once you've set the bias properly, as a final adjustment- turn the bias down just very slightly, a tiny small turn anticlockwise which you should feel in your finger tips. This will ensure that the idle current is stable and will not flicker again, unless you go really loud...

3. When you mentioned that after you placed in a new signal processor, you had to turn things up quite a bit and that's when you noticed the LEDs flashing on the prem11... this to me sounds like the Output tubes are weak, hence requires changing.

4. Most people power up tube gear and leave it on for 30mins to warm up... then they fiddle around for another 15mins before sitting down to listen... this is basically 45mins of wasted tube life! Tubes don't require extensive warm up, all they require is about 15mins tops to really settle in and the soundstage depth opens up nicely.

5. Once tube gear is powered up, it's meant to be left on for a certain period of time, at least 3-4 hours of quality listening. If after about an hour or so the gear is switched off then after 30mins again powered back on, this on / off cycle is what kills tubes! If you're not going to listen for a certain period of time totally engaged in the music presentation then there's no point owning tube gear.

If you're considering higher power tube gear from CJ, ARC, VTL, Manley Labs, Jadis, Cary and so on, anything in the range of 50w and above will drive the ESL 9's with ease. CJ tube gear is Class AB power rated, there is Class A power within the first few watts, about 5-10% then it switches into Class AB in ultra linear mode. It only takes a handful of watts and pure high current and stable voltage to handle stats efficiently.

Power ratings really means nothing! You can have amplifiers rated at 100s & 100s of watts but they can't handle reactive loads typically found in stats. Their power supplies are inadequate. Whereas CJ tube amplifiers have no issues with stats, and they can handle impedence loads of less than 1 Ohm.

So depending on your listening habits and music tastes, you really don't need anything more than 70w of pure tube finesse. If you really believe that your speakers require more headroom then any tube gear with more power will do nicely, although you would never use anything close to its rated power output. Remember, it's all to do with high current capacity and stable voltage that fully grips and controls stats. That's why Class A output amplifiers with just 30w to 60w of Class A sound superb with stats!
So anything rated in the region of 100w in Class AB tube amplifiers will do just fine. You'll never require anything more.

Hope that helps and terribly sorry for the very late reply. Damn, half the year has almost gone!
Cheers, RJ
 
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ttocs

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I also missed this. sorry.

You mention about noticing distortion after calibration. I'd look specifically at this point. Turn off the calibration and see if the distortion goes away.

Calibrating our stats is not always successful. When I first began using Dirac 8 years ago, I found it to be problematic with higher frequencies in the Left and Right main speakers (back then I had the Vista), so I wasn't able to use it for music, but did use it for HT. Now, with the current Dirac, I only use it for my 11A up to 400Hz, but full range for all the other speakers. I just am not fully satisfied with letting the stats be calibrated above 400-500Hz.
 

Big Dog RJ

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Ttocs, that's great advice mate. He should loom into that.

Speaking of the OP, I'm not even sure if he's seen our messages... it's been since Dec 2021, that's quite a while back. Hopefully, he comes across it sooner or later. I was just wondering why would he require any more power than 70w of Class AB from CJ, which is supreme tube finesse... his Prem11 is fine!

Would be interesting to learn how it turned out, maybe a different type of amplifier was already purchased.

Cheers, RJ
 
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