LP66S New Owner Questions

[Dsper]

Hi,

I have finally made the move to my first tube amp and it is a LP66S. It is paired with a 17LS2 preamp and, for the first time in a while, I am listening to music and not my speakers.

Current tubes are Sovtec Reflector 6992s and Penta KT88s. Of course, I am already thinking about tube rolling but do not want to screw up the amp doing something stupid. I am hoping that other owners would share some information or direct me to a thread I may have missed.

Regarding the input tubes, does one have to change all three tubes or can just one or two tubes be replaced?

If you can change just one 6992, for example, what position should be changed for most impact - V1, V2, or V3?

Regarding the power tubes, I assume that one should never mix 6550s with Kt88s. But is it safe to mix different brands of the same type of tube?

For example, could I change out just two of the Penta KT88s with, for instance, two Mullard KT88s?

If this is not okay, why so?

If this is okay to do, in what positions (V4, V5, V6, and V7) should the two new tubes be placed for maximum sound impact?

I am obviously a newbie here and would appreciate any and all advice!

Thank you, Dsper

[admin]

I admittedly don't have too much experience with the LP66s but if you plan on tube rolling, I would change V1-V3 all at the same time and/or V4-V7 at the same time. As for which ones will have the most effect on the sound,... I think that is tough one to answer. The output tubes are most likely going to have an overall bigger effect but I think this will depend on what kind of tubes you plan on using as there are tubes that are very similar and different.

Best approach in my opinion is getting advice from previous owners (which is what you are currently doing), calling CJ themselves for advice, and then contacting your tube dealer of choice for recommendations. We have had discussions/recommendations on the latter here on CJO.

[AnotherJohnson]

If you’re asking “am I going to blow something up,” the answer is “not likely.”

If you’re asking “can I improve the sound by aggressive tube rolling,” I think the answer is still “not likely.”

There’s really no reason to stray from the tube types that were used in the OEM design. The LP66S was very well thought of. I like the basic LP concept, which, at least in the case of the more powerful LP amps, involves a triode on the input side and an ultra linear pentode on the output side. All of my experiences with CJ over many years have been that the recommended tubes work wonderfully. Why waste money and time chasing something else?

Naturally, others may disagree. As usual, YMMV

[Big Dog RJ]

Ah! Another wonderful LP66s, marvellous amplifier.

At one point when CJ introduced this line, I was not quite sure where exactly they were going, since subsequently right after with not much of a gap, there was quite a line up to choose from - MV60/SE, LP66S, LP125M, LP140m, LP260m, LP275M'S, and now of course the new Classic series. So many customers would ask me where does the LP66s sit having such a wide selection and nearly the same sound? I would get confused myself but later it became clear... just go with the one that suits your speakers, your room and most of all what you can afford, that's about it! Don't worry about the specs, yep pretty much the same mate. That CJ musicality and quality signature sound towards high quality recordings is all present, getting the most from those quality recordings is what's it all about.

In terms of tube rolling and trying different tubes vs brands, you can certainly venture out with no harm. However, my sincere advise, keep the same brand with the same type, better not to mix incase there may be variations in tube specs, and there are.

Better still, if you want "best" sound, try to order matched pairs. In the case of the LP66S, all you require is 4 output tubes. You can order quad (4) matched sets from CJ, Tubestore, TubeDepot or Upscale Audio. CJ charges a premium price for carefully matched quad sets of output tubes for your amplifier and this will be the best sound.

As AJ has stated, tube rolling doesn't give a big improvement. There are definitely small changes but nothing very significant as compared to changing or upgrading gear...

As for the input and driver tubes, try to get what CJ recommends for this particular amplifier. Although we can recommend many varieties, you may not like these, and may prefer something that CJ recommends, that would be the starting point. Just make sure when ordering, you are getting your monies worth from trusted and reliable suppliers. There are far too many doggy ones these days claiming to be the ultimate in tube quality... be aware!

As for the LP66S, you already mentioned that you're enjoying the music and not getting caught in the gear. This means you're totally engaged in the music and it's a captivating experience, in which case why change at all?
Just sit back and enjoy to the fullest!

Cheers mate, RJ