LP 140M 6922 Replacement

[homey68]

I have read that CJ does a mod on the LP140M To accept other 6922 tubes. What is this mod and is it something I can do without shipping the amps to Virginia?

[AnotherJohnson]

Maybe you could elaborate on the mod your considering.

The LP140M came with 6922 small tubes and 6550 power tubes. Maybe you’re thinking about changing the 6550s to KT120s. That can be done.

I don’t think it requires anything more than bias adjustment which can be done easily as described in the owner’s manual.

[homey68]

Sorry, I should have been more explicit. I am referring to the fact that CJ doesn't recommend replacing the 6922 tubes with anything other than the Electro Harmonix that are currently in the amp. I replaced a Premier 140 with the LP140M's and using an Amperex 7308 sounded much smoother through the mid range. I would like to experiment in the LP140's with the same tubes. I keep reading that you can't replace the EH tubes in the amps. That doesn't make sense. If a tube is electrically the same, why would it not be interchangeable?

[AnotherJohnson]

I’ve seen recommendations for one brand or another, but I’ve never heard of anyone limiting the choice to one brand exclusively. A 6922 of any brand shouldn’t cause harm.

[Big Dog RJ]

Yep! If it's 6922 based and CJ only recommends that particular tube of the EH variant, they're basically telling you that the LP140M's are more suited to this tube & brand.

Similarly the case with my LP125M's, plus in the owners manual they claim nothing else would really enhance the performance of these amplifiers.

However, I've tried various versions of the 6922's/ E88CC, and ended up full circle back to the EH6922's. Again just a personal preference and one that CJ also endorse.

You may try other variants of this tube, as long as you stick with the same type, and not get too carried away with the tube rolling phenomenon...
There are no factory adjustments or mods required, as long as your tubes are within the 6922 spec.

The only mod required is when you may want to try different Output tubes, say from a 6550 or KT120 over to an EL34. EL34's being triode versions requires mods on a few resistors and bias operation. Usually done at factory but even the owner can do if handy with basic electronics and a soldering iron.

Cheers, and enjoy those fine tunes!
RJ

[homey68]

Thanks RJ, I thought I read somewhere that the amps were fine tuned for EH tubes and if you used any other tube, you might damage the amp. I thought that was really bizarre. Which one of the 3 tubes has the most influence on the sound of the amp. I know in the Premier 140, the 6922 did make a difference in the sound of the amp.
DB

[homey68]

Just finished a short listening session with the Amperex 7308 replacing the center EH 6922 in my LP140M's. What a difference in just the 2 tubes. The EH sounded pretty good, I could easily live with it. But when I installed the Amperex tubes, it was like someone lifted a veil off the speakers. To my 70 year old ears, the sound was more open and the top end was extended. The bass was more controlled but with punch. I don't have enough 7308's to replace all of them, that is why I was trying to figure out which tubes would make a difference.