Conrad Johnson LP 70/140/275 Tube rolling

A cautionary note here. Do not according to cj, replace the 6922s in the LP140M with NOS, etc tubes. It can make the amp unstable. CJ specifically matches the 6922 for the exact position in the circuit.

The other two amps, for whatever the reason, are not as sensitive. I've had my 140M and haven't played with the small signal tubes and they've run perfectly since I got them. I'm not going to play with danger :)

BTW, the biggest improvements I've heard with the amps come with cables.

Myles

Thanks Myles, I wonder why this amp is more sensitive than the others in the same series?

As long as the emission as well as the Gm (mA/V) is close to spec I don't understand this, could it be a marketing issue for CJ to make us buy tubes from them?

I am very satisfied with my new 140M, and compared to my old Premier 12 they tend to be more detailed and open, and I like that, but for some bad recordings they might sound a bit to bright.

This is why I thougt I could in a way "relax" it with tube rolling, but without loosing the beautiful sparkling top.

Ole

Hi Ole,

Glad to hear you're enjoying your cjs! The cjs work great on my ML Summits--but cjs love Maggies too because of their constant 4 ohm load. (I assume that you have had the factory set the output impedance to match your speakers eg. 4 or 8 ohms? The amps as I remember come set at the factor at 4 ohms--and with a speaker that's between the two, cj recommends the lower of the two impedance settings.

Wish could give you an answer as to why the 140 is more sensitive than it's siblings to the choice of input tubes but don't know the answer :)

As far as the sounds goes, the amp definitely is a distinct step up from the Prem 12s! It is fairly revealing and you will hear the good and the bad from your albums. But otoh, perhaps there is something else in front of the amps that is adding some brightness to the system like the front-end/cartridge or phono section? Maybe a little VTA adjustment might go a long way to making your albums sound better-esp. with the vast majority of today's MCs that are pretty VTA sensitive.

Myles

I noticed that manu seems to like to warn purchasers fr tube rolling claiming that stock tube is matching, risky to tube rolled etc. When I had my CJ Act 2.2,I emailed CJ technical support I was not encourage to change. Anyway affer having it for abt 1+ yr and after reading some postings in audiogon I went ahead and try a quad of nos tube. Wish I have ignore CJ warning. Recently I have ordered a tron seven reference, like the designer told me their is no need to change. So don't be too concern, give it a try