Tube rolling

[turntable]

What do the Conrad Johnson owners or tube owners buy when tube rolling?

cj indicate that for their power amps small tubes need to be replaced every 1500 hours and power tubes every 3000 hours.

My prem8a's are well and truly due to be retubed as it has been 2 years and well and truly over 3000 hours. The amps are sounding a bit thick and lacking extension compared to when with new tubes.

I really did not want to spend $1800 on power tubes alone from cj. 16 x 6550 are expensive and another $400-500 on input tubes.

I see that Svet 6550 Winged C tubes are not available and the moment due to issues at the St Peters plant.

I decided to give the Tung Sol 6550 reissue tubes bought from Jim Mcshane for $99 per quad. Bargain.
I bought two sets of input tubes. Some GE 5751's. I bought a set of EI 6FQ7 and a set of Mazda 6FQ7's from Upscale Audio.

It will be interesting how they sound compared to the stock cj tubes.

[Tonepub]

Are you sure you are reading that right... Small signal tubes usually last 5000-10000 hours

[turntable]

Go to their web site, it has it there. I have also spoken to Lew in the past.

The amps drive the small tubes quite hard.

I believe the pre amp tubes may last longer, as there was no real difference in sound when I changed those last week and they had around 3500 hours i would guess.

[Puma Cat]

For the newer C-J gear I've owned, I've stayed with the stock tubes for the most part. I did roll some Ediswan CV2492s into the input tubes in my LP70S, and I do prefer them to the stock EH6922s, but the amp still sounds great with the stock 6922s.

For my Premier 11A, which is similar to your Premier 8A, I personally liked the Genalex Gold Lion KT88s more overall than the 6550s, though the bass was not quite a tight as with the 6550s. Your tastes may be different.

I was also using a mix of GE Jan 5751 and Mazda 6FQ7 input tubes in my Premier 11A, so it sounds iike you and I were identically matched on those tubes between our respective amps.

You are correct that the CJ web site says power amps small tubes need to be replaced every 1500 hours and power tubes every 3000 hours; I too have heard that C-J amps tend to drive the small tubes quite hard.

[Tonepub]

I've never had that experience with any of the CJ amps I've owned. Just talked to Ed at CJ this morning and for the record, CJ does NOT "drive their input tubes quite hard." They just tend to be over conservative with their estimates.

He told me that if your amp still sounds good, the tubes are still good and that much of this will depend on the tubes that you have in those positions. Obviously some of the Chinese and current Russian tubes do not have the lifespan that the better NOS tubes do, or something like the Gold Lion, Psvane or EAT tubes, so those of you spending the money for upgraded tubes should not have to count on replacing your tubes at the 1500 hour mark.

Lew Johnson has always told me that he feels the two input tubes affect the sonic character of their amplifiers much more than the output tubes, and again, that's been my experience with each one of the CJ tube power amps I've owned and reviewed.

It's too bad that we don't get the chance to do a "long term test" as Car and Driver does. It would be interesting to run a few amplifiers, and take the tubes out at regular intervals and run them on a tube tester to see how they are degrading at 200, 500, 1000 and 2000 hours. Not enough hours in a day to do all that!

[Puma Cat]

Thanks, Jeff, this is very helpful info.

[turntable]

I don't disagree with you Jeff. My system has done probaly around 3500 on the stk tubes in the last 2 years. All I know is that my system is sounding a little flat and lacking extension and I noticed that about a month ago. or maybe all my teflon caps have finally stopped breaking in :scratch2:

I swapped the ART tubes with a new set of 6922's and no real change in sound.

I had some original GE tubes that Jack English ( remember him?) had used prior to selling me the prem 8a's. I decided to use those as an interium before I receive my new tubes. Swapping to used GE input tubes did not change the sound that much. Swapping in the GE 6550's gave a large differecne in sound and it opened up. Was that the GE tubes being newer or the sound of the GE tubes ? not sure.

When I get the new tubes, I'll put the power tubes in first and listen, then the input tubes.

Yes, it would be good to do a long term tube test. All I need is a tube tester:D

[Tonepub]

That's definitely the sign that the tubes need to be changed...

The variation in tubes by brand is huge. Let us know what you find out!