Matched pair - different brands

[engels]

At some point I've oredered a matched pair of 7C5's at Antique Electronics (for those of you who don't know, 7C5 is 6V6 with loktal base). Today, as I'm finishing a PP 7C5 amp I've pulled the tubes out of the boxes - the boxes look the same - and what a surprise, one tube is GE and the other is Sylvania. They ARE matched but still I wonder what the heck.

I also have a bunch of unmatched RCA 7C5's and I plan to perform a listening test.

Is it accepted to have matched pairs of different brands???

[Johan Potgieter]

Totally, Engels.

I know the appearance might disturb slightly, but that is all. Tubes of the same number should have the same characteristics irrespective of brand, and particularly with NOS from GE and Sylvania I would not have a worry.

Regards.

[tubelab.com]

It is possible that the Sylvania was made by GE or vise versa. This is not uncommon. If the tubes are of similar internal construction, don't worry about it. I have matched up several pairs of tubes of different brands.

I bought a bunch of used Russian tubes, and set out to make some matched pairs. One of the best pairs is an Electro Harmonix KT88 paired with an Electro Harmonix 6550. This is why I believe that New Sensor puts two different numbers on the same tubes.

[Johan Potgieter]

Very interesting!

The same Russian story all over again.

[tubelab.com]

The same Russian story all over again.

Russian manufacturing, but American marketing. Either way, you pay your money, and take your chances! I have bought some good New Sensor tubes, and some sheer garbage. After the bitter taste of 50% failure rate on their 300B's, I swore not to buy any more, and advised my customers to do the same. 5 years later I got a large box of used New Sensor output tubes, cheap. I have been pleasantly surprized. All of these tubes work very well, and some have passed some severe testing. I have "tested" about 6 Electro Harmonix KT88's or 6550's at 450 volts and 100 mA for several hours each in SE. All just shrug it off without even a dim glow. They sound pretty good too. I might even be tempted to buy some when I need some hefty tubes.

[Eli Duttman]

Originally posted by Johan Potgieter
Totally, Engels.

I know the appearance might disturb slightly, but that is all. Tubes of the same number should have the same characteristics irrespective of brand, and particularly with NOS from GE and Sylvania I would not have a worry.

Regards.

In the case of Locktal types, things may go even deeper. Forget the branding. How many plants actually produced tubes with Locktal bases? I would not be surprised if all Locktal tubes came from as few as 1 location.

[engels]

In my case GE is a fraction taller; the plate material seem to be a little different (Sylvania being the "blackplate" and GE something more grayish) , different internal construction and getters. Even the bases (the metal rim) look different. Definitely not from the same plant.

[Johan Potgieter]

Engels,

Yes, this is also the case with other brands, even some NOS. As a user of 6L6GCs in products I sell, I am constantly a little nervous. The classic oval shaped anodes, with larger and smaller radiating ribs either side, very large G1 radiators on the GE (goody!) but NO G1 radiating plates on the Sylvania! Then the box type anodes (black, dark grey, light grey, somme ribbed, some not) on a variery of very good (hopefully) 6L6s, some Russian 6L6GCs definitely no more than ...GBs, etc. Yet they measure the same, and one is encouraged by the statements of "tube veterans" like Tubelab.

Who knows - anything is possible these days.....

[Johan Potgieter]

Eli,

Yep, I do suspect you are on the mark.