12AX7 - International ServiceMaster W. Germany

[Ferrari-Dude]

I was rooting through my box of preamp tubes and found 3 International ServiceMaster 12AX7/ECC83 preamp tubes. The ink is white and they state that they are made in W. Germany.

I am assuming they are rebranded; I've never heard of this brand before. On the bottom of the tube there is a 12 molded into the glass. They have a slightly larger circumference, like some RCA tubes that I have seen.

Anybody ever heard of these or used these? What are your experiences with them?

Whoever makes them, they sound great to my ear. They have zero noise or microphonics when cranked, and they have a nice smooth, creamy midrange tone.

[tonemerc]

I have used IS before and have a couple of NOS rectifier tubes from the early 60's left. They were a reseller, so that brand was made all over the free world. However, they seem to be one of the brands names that are favored by Russian counterfeiters as well. Many of the IS tubes I see on eBay are fakes.

If they sound good to you, then thats all that matters. I would be leary of paying crazy NOS prices for the IS brand though.

TM

[Ferrari-Dude]

However, they seem to be one of the brands names that are favored by Russian counterfeiters as well. Many of the IS tubes I see on eBay are fakes.

TM

I've had these tubes for probably since the late 80's and didn't realize it. Would that counterfeiting problem have been taking place as far back as then? I'm just trying to figure out if these are the real deal or not.

But, like you said, they do sound good to my ear and that's all that matters. I wish I had some more to upgrade my other heads.

[demonufo]

What do the plates look like?
W. German may well be RFT's, which have a VERY distinctive plate structure. Google some RFT ecc83/12ax7 images and compare them.
Awesome tubes, seemingly more gainy than some of the others.