# Power Tube question



## cale0906 (Apr 15, 2006)

Im looking to buy a matched set of 7581a Power tubes ........ Where ? 

Not familiar with tubes stores ....any in Canada ? :smilie_flagge17:


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## Wild Bill (May 3, 2006)

cale0906 said:


> Im looking to buy a matched set of 7581a Power tubes ........ Where ?
> 
> Not familiar with tubes stores ....any in Canada ? :smilie_flagge17:



http://www.thetubestore.com

Super people - incredibly good reputation!

:food-smiley-004:


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## cale0906 (Apr 15, 2006)

Wild Bill said:


> http://www.thetubestore.com
> 
> Super people - incredibly good reputation!
> 
> :food-smiley-004:



I emailed them .......... couldnt see 7581a Power tubes on their site 

Thanks !!

Any other places ?


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## Wild Bill (May 3, 2006)

cale0906 said:


> I emailed them .......... couldnt see 7581a Power tubes on their site
> 
> Thanks !!
> 
> Any other places ?


Found this on thetubestore.com's site:

*"Here's an interesting side note: the JAN-Philips 6L6WGB tube has the identical internal construction as the Philips 7581A tube (the industrial version of the 6L6GC tube). The difference between these two tubes is only the size of the glass bottle. Although you may not get a 7581A's 35 watts out of the 6L6WGB, you can certainly get 30 watts without any problems. These are super durable tubes made for the US military in the mid '80's. Their specs are not the same as earlier 5881 and 6L6WGB specs from the 1960's. So to get to the point, the JAN-Philips 6L6WGB tube will work perfectly in any amp requiring a 6L6GC tube. Do not worry about plate voltages over 400V with this puppy."*

With a tube so very, very rare as a 7581, you might consider this substitute. If the tubestore.com doesn't have it then you are always going to have to search far and wide and pay through the nose.

:food-smiley-004:


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## guitarman2 (Aug 25, 2006)

Also not everything is listed on their site. Best to give a call or drop an email.


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## Fader (Mar 10, 2009)

http://www.vacuumtubes.com/6l6.html

Type KT-66/7581 Tubes
The 7581/A tube is an industrial strength version of the 6L6GC which is also said to be the American equivalent to the British KT-66. The ratings 7581 are roughly the same as the 6L6GC while the 7581A has higher ratings. The 7581 has a plate voltage rating of 500 V--35 watts (5 watts more than the 6L6GC) and a screen rating of 450V--5 watts. The Philips/ECG 6BG6 that we have were made from Philips/ECG (Sylvania) 7581A parts and have the same ratings as the 7581A.

Copied from the above link.


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## WCGill (Mar 27, 2009)

http://angela.com/poweroutputtubesforguitarandhi-fiamps.aspx


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## Fader (Mar 10, 2009)

WCGill said:


> http://angela.com/poweroutputtubesforguitarandhi-fiamps.aspx


Wild Bill was right. $400 for a matched quad.


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## cale0906 (Apr 15, 2006)

Fader said:


> Wild Bill was right. $400 for a matched quad.



Yeah i know !! $200 US for 2 ...wow


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## Wild Bill (May 3, 2006)

cale0906 said:


> Yeah i know !! $200 US for 2 ...wow


The spec differences between the 7581 and a 6L6GC are "mice nuts". All that might be a concern is the plate voltage they see in your amp.

So, what IS the plate voltage? What kind of amp is it?

Often amp makers would end up with essentially the same tube under a different number, perhaps with a different pinout but many times even that was the same. The reason was that every salesman wanted the "design win". He wanted HIS tubes bought by that amp manufacturer! If he could get a tube under an "oddball" number spec'd for that amp then there was a good chance that nobody else would offer a competitive quote using that tube number. He would have 'locked out' the competition!

Now, an engineer or a tech wouldn't be fooled. To them a tube is just a tube and all they care about is the specs. It will either work or it won't.

In a big company, however, it's not the engineer who usually makes the purchasing decisions. It's someone in purchasing. If they like the price they will send the tube to engineering to get approved and then THAT's the tube number on the Bill of Materials!

If you can tell us more about your amp then we can tell you if you have to pay $400 or not!

The same situation existed for years with 6L6's and 7027's used in Ampegs. The tubes are identical inside but the pinout was slightly different. The 7027 went out of production for years and years before it was revived just a few years ago. So during those years the only choice was NOS 7027's at a ferocious price! 

Meanwhile, Ampeg had always wired the sockets in most of their amps (like V4's and V4B's) so that you could plug in either tube but unless you were a tech the sub was a little "scary". The Triode Electronics website has an excellent FAQ telling everyone not to worry but still, a lot of "newbies" still spend all that extra money for no benefit at all.

Let us know!

:food-smiley-004:


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## Rugburn (Jan 14, 2009)

My friend has an old Ampeg B-25B Bass head that runs on 7027As. It sat in delapidated shape for years, partly due to the prohibitive cost of retubing. He finally decided to get it tuned up expecting to shell out big bucks for NOS 7027s. Turned out Sovtek had just started producing 7027s again. He's one of these guys who really has a horseshoe up his ass when it comes to gear.

Shawn


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