Any idea what tube these are?

[N0WEK]

I got these some time ago in a big assortment of tubes. The only identifying marks are:

SYO
56B

on the metal base ring.

The straight wall envelope suggest European.

Any ideas?

[KF7WWW]

I can't be sure but they look like EL34's better known as 6ca7's.

[DMOD]

They may well be Mullard EL34 / 6CA7 and the SYO-56B is a date code.

[N0WEK]

They may well be Mullard EL34 / 6CA7 and the SYO-56B is a date code.

Good call guys!

Date code reads "Feb 1956"

Thanks!

http://www.tube-classics.de/TC/Tubes/Valvo%20EL34/EL34.htm


    Eindhoven, NL    

Dec. 1954 - 1956 (1957?)
            
Philips Valvo EL34 6CA7 with black metal base Einhoven SY0 SYO SYN code    

Code: 5XX SY0 or 5X SYN

Identified by:

- one piece disc getter

- black metal base

Comment:

Very rare. SY0 Samples found from 54K until 56F, but also one from 57A (Jan. 1957) and SYNs: 5D and 5F

[Jim/WA2MER]

Before you put those in the junk box or install them in your Apache (or whatever else uses them), do yourself a favor and go to eBay to see what people will pay for used Amperex or Mullard metal base EL34s.

[N0WEK]

Before you put those in the junk box or install them in your Apache (or whatever else uses them), do yourself a favor and go to eBay to see what people will pay for used Amperex or Mullard metal base EL34s.

Yikes!!!

I guess I should test these and list them over there. $600 for a used pair?

The upside of Audiophools!

Thanks!

[Jim/WA2MER]

Crap, I posted the wrong message! I meant to offer you $10 for the pair