6550 Valves

[Samycasanova]

Hi there !
My knowledge in valve amps is very limited , i just started to understand the basics ...
My nephew has a guitar amp with ECC81 and 6550 Valves , and asked me to buy some to replace them . I saw several tipes of 6550 , like 6550A , 6550C , 6550ST , are they the same or are there major diferences between them ?
I want to buy , but don´t know wich ones . Can i use other kind of valves with the same bias voltages ? Which ones ?

Thanks.

P.S. Sorry my English

[Plexi]

"""http://www.timeelect.com/6550a-ex.htm"""

What amp is it? It may depend on the amp.
The 6550St ..thats the shape or some call them coke bottle.

But as for bias on them, you may have to bias the amp to the set of tubes you get.it may vary.

heres a link to show what i mean can happen.
http://www.timeelect.com/6550a-ex.htm

But if its for a mostly common amp..you can use Svetlana,or EH 6550 s'
Best to buy a matched set.
Now if you were to buy the 6550A those are going to be very expensive!
They are great tubes,and getting harder to find.
You might be able to use other tubes like KT88 etc..just have to know the amp your going to use them in.

Let us know the amp,i'm sure others will have some ideas too.

Richie

[Samycasanova]

The 6550 valves look like this . Are they 6550A , 6550ST .... any tips ?
I can replace them for others equivalent ? Wich ones ?
The amp is a "Herald VI" Made in Italy .
Thanks...