Let's share secrets of Lamm 6C33C tubes

I don't know Lamms, but my experience with Eastern-sourced tubes is the opposite of Jedinite24. Of around a dozen shipments of 6C33C totaling 50 tubes I received one tube with broken glass. Do expect a 10-25% failure rate over the life of this tube. My experience with arcing out of Eastern-sourced tubes is about the same as with BAT-sourced tubes.

Jedinite24, and everyone else here:

One way to reduce arcing on otherwise new tubes is to light up the filaments of the tube without applying B+ to it. Leave it in this state for at least 4 days and nights.

This process is called preconditioning and should be done with any new power tube that has not been used before (if it has been used, preconditioning will not do any good).

**Preconditioning will double the life of any power tube.**

It will also substantially reduce arcing failure that otherwise occurs shortly after installation, due to the tube being unhappy about being shipped. You can see that this is a big deal. I may be giving away a little secret here; this may be why the more expensive tubes seem to hold up better. (It appears that the process of preconditioning uses the filament heat to cure the cathode coating, which otherwise can flake off the cathode fairly easily which is the cause of arcing failure.)

If your amplifier does not have a Standby function (Standby on most tube amps is where the filaments are lit up but the B+ power supply is not running), this might be difficult to pull off. But setting up almost any power amplifier with a Standby switch is a fairly simple matter, although one that should only be done by a qualified technician.

6c33c does need testing/matching in BAT. The nature of "balanced bridge" dictates matched by plate voltage offset.

Call Victor and he should be able to explain in-depth if needed.

Hi Maril555

I don't know the answer to the V1 vs V2 question but I thought I'd share with you my horrendous experiences with buying those cheaper 6C33C tubes that are often listed on popular auction sites.

Often times the sellers of the 6C33C tubes are overseas and they don't give a damn about packaging. Even sellers with high feedback just wrap them up in bubble wrap put in box, and drop it off in the mail. I had a set of 4 tubes come in a box that looked like a soccer team kicked the box around. The ones that do survive the trip you are lucky if they will work of test well. Out of 8 tubes I purchased 2 were good enough to use in my amps. Others arced, died a quick death or were just plain DOA.

Lamm and other US sellers may charge more for these 6C33C tubes but I believe they have to go through a lot tubes to get decent ones for their gear. I really wouldn't buy 6C33C tubes unless they were tested. Too many things can go wrong if you get a bad set. I blew the fuses in my amps how many times buying these cheaper 6C33C tubes. I was lucky I didn't damage my amps or speakers. I got real lucky and scored Lamm tested 6C33C tubes from an estate sale at a very decent price. Each box did have a specific V marking but in my case that didn't matter to me. There was no documentation with these tubes stating why each tube had a V marking.

I don't know the exact answer to your question (I do have the same ML-2 amps).
What I do know, that 6c33c don't need testing and matching in many applications, and only a few manufacturers do that.
I know for a fact, that BAT does it, and LAMM, of course.
I would guess, that the difference b/w V1 and v2 tubes, is that one reguires testing and maybe matching, and the other one doesn't.
For example- V1 position requires higher tolerances and v2 doesn't. Hence, if you flip them, then your V1 will be out of tolerance.
In the end- this is the same tube, and out of the factory variances are not that huge.
The last thing- I'm buying from LAMM to be safe :)
I would love to know an exact answer to this as well.
The other tube in these amps, that needs frequent replacement is 6n6p- Vlad claims he tests and matches them, which is reflected in the asking price.
This tube is readily available elsewhere for much less, so I wonder...

Cmon' Share the secret! or any thing you think is interesting!