[glynnw]

Wanted a couple of inexpensive KT120 tubes for a Conrad Johnson MV75a-1 amp that mostly sits on a shelf, but I want it usable.  Best deal was a pair of Tung-Sol KT120s on Alibaba.  HMMM!  Russian tubes from China.  OK, I'll gamble.  They arrive.  Are shorter, glass is different, interior parts are smaller, base is different, different color on bottom piece.  But what the heck, let's see if they work.  They do and they sound fine, paired with a real pair of Tung-Sols.  So I will use them until something obvious goes wrong. I wish they would just use the real name of the Chinese company making them.  But I am a bit surprised that it was so easy to buy what I assume to be counterfeit goods thru Alibaba.

[FullRangeMan]

Any photo?
Power handling should be smaller.

[mick wolfe]

The MV-75A1 was designed for 6550's. Back in the day I used Ei KT90's as well. The KT120 is a different animal, but I assume you've done your homework and found that the KT120 is compatible.

[FullRangeMan]

120 will drain more cathode current from the PS than the 6550.

[glynnw]

First, none other than Bill Thalmann has said KT120 tubes are fine here.

Second - these 2 are currently working together as one channel in MV75.  Any idea who made the one on the right? 

[FullRangeMan]

Wow, incredible fake tube, obviously this tube not a KT120, plate are too small, plate seems came from other smaller tube as KT88 or 6L6, so this tube dont have the 120 parameters.
Russian builders dont made this kind of trick.

[FullRangeMan]

This your tube plate seems to be very similar to this KT88 images>

[FullRangeMan]

these 2 are currently working together as one channel in MV75.
I dont know who is this Bill, but since these fake tube are so electrically different from a regular KT120 I would dont mix these tubes in the same amp. IMO.

[mick wolfe]

First, none other than Bill Thalmann has said KT120 tubes are fine here.

Second - these 2 are currently working together as one channel in MV75.  Any idea who made the one on the right? 

The tube on the right looks similar in physical appearance "only" to a Genalex Gold Lion KT88 or a Mullard 6550/KT88. New re-issues in both cases. It's clearly not a Tung-Sol KT120. A total fake on many fronts. Even the new Tung-Sol 6550 looks nothing like the "Tung-Sol 120" pic on the right.

[mick wolfe]

these 2 are currently working together as one channel in MV75.
I dont know who is this Bill, but since these fake tube are so electrically different from a regular KT120 I would dont mix these tubes in the same amp. IMO.

Bill Thalmann was my go-to guy when I had CJ gear. I believe he's now retired or at least thinking about it. A very reliable source and an excellent technician in my experience. With that said, while he might endorse a nice matched quad of Tung-Sol 120's, I doubt he'd ever endorse the clear mismatch shown in the pic.

[glynnw]

Counterfeits no longer in amp.  I just wanted to see if they biased correctly and worked with the existing tubes.  In both cases the counterfeits worked well, but I agree that continuing to run them is a gamble.  Maybe they'll be part of a new art project.

[Whitespider]

Bill Thalmann was the first employee hired at Conrad Johnson.  In his 20 years at Conrad Johnson, he was originally the sole technician, later the senior technician, and finally head of development and technical director.  Bill went on to establish Music Technology Repair Center which just this month closed shop as a brick and mortar storefront.

[audio.bill]

... But I am a bit surprised that it was so easy to buy what I assume to be counterfeit goods thru Alibaba.

Alibaba regularly sells lots of counterfeit goods, there are knockoff cables and components some of which carry the original brand names at a fraction of their normal price.

[Tyson]

Those tubes are definitely KT88's and not KT120's.

[glynnw]

Paypal just issued me credit for the fake tubes. Took a couple of months and some bitching, but once I got thru to a human there he understood and said they were familiar with the issue of Alibaba and fake goods and I got a refund.

I still have the tubes.  Uh, anyone want a pair of KT120s?  (Just kiddin)

[S Clark]

Glad you got it going.  I've got 4 basically new KT120's if you decide you need more.