Re: sylvainia 6ca7 WTB: two pairs

[mike s]

On Saturday, May 14, 2011 1:34:39 AM UTC+1, shawn s wrote:
> need two pairs of tubes for my altec amps
>

I'm curious, do they have to be that type? In the UK we call the equivalent type EL34. Used to be made by Mullard and the like. EL34 is still manufactured in Russia I think and relatively cheap.

[Phil Allison[_3_]]

"mike s"
shawn s wrote:
>> need two pairs of tubes for my altec amps
>>
>
> I'm curious, do they have to be that type?
> In the UK we call the equivalent type EL34.
> Used to be made by Mullard and > the like.

** The Sylvania 6CA7 is a rather different tube to the EL34 made by Mullard
and others - the structure is different and the electrical characteristics
quite different.

I used a fair number of them in the 1980s for guitar amp repairs - but soon
found they were not happy in 100 watt Marshall amps. The screens would glow
very brightly at full power and the tube soon expired. What I found was
that the screen supply must not exceed 400 volts with them.

In amps that had a screen supply voltage between 360 and 400 volts, the
performance and longevity were both excellent.

Probably the nearest tubes in current production are the " big bottle" 6CA7
by Electro Harmonix and the JJ KT77.


..... Phil

[Big Bad Bob]

On 05/14/11 15:46, mike s so wittily quipped:
> On Saturday, May 14, 2011 1:34:39 AM UTC+1, shawn s wrote:
>> need two pairs of tubes for my altec amps
>>
>
> I'm curious, do they have to be that type? In the UK we call the equivalent type EL34. Used to be made by Mullard and the like. EL34 is still manufactured in Russia I think and relatively cheap.
>

saw some interesting forum comments 6ca7 vs EL34. Apparently this is a
common issue.

http://www.marshallforum.com/workbench/16651-6ca7-vs-el34.html

http://www.thegearpage.net/board/showthread.php?t=448991

http://vintageamps.com/plexiboard/viewtopic.php?f=13&t=27871&start=0

(google search "6ca7 vs el34" showed a LOT of responses, >18000)