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12BZ7 ///12AX7

Could not finda  topic for tubes, so am using amps section.
After making the amazing discovery of the E80CC as sub for AU~~E80CC blows away every/all AU's, including the *Holy Grails/Siemens,Tele's*.
http://www.r-type.org/exhib/aaa0426.htm
at least in my Defy7, the swap was more than just significant, the Defy came to life from the grave.
I found the Siemens to bea  miniscle superior to Philips = both are equal IMHO, and the valvo Red label E80's going for $$$$$$$$$$ is a scam. Don't buy into it. 
Right now that tube  is going for $50/each. When word gets out  ~~Super Tube~~~the price will rocket, as that tube is not being produced any longer. 
I've loaded up on the Philips label.

so i figured,, maybe there is a  
~~Super Tube~~ for the AX..
After days/weeks of research,,i found this
12BZ7
https://www.radiomuseum.org/tubes/tube_12bz7.html


*Big Boys*
So  ordered a  bunch off ebay, and will arrive next week
Will post a  review.
can not find much on the INET about the 12BZ7,, anyone have experience with this tube?
mozartfan

Showing 5 responses by mulveling

mulveling's avatar
mulveling
1,774 posts
 
@chinacat
The 5751 silver plates, as you mentioned, are very revealing. However in my system it was revealing to the point of being BRUTAL. Including an excess of high frequency energy. I liked the effect for up to 30 minutes at a time, but then it became too fatiguing to continue. The 12ax7 had the better, more natural balance. However the 5751 was very exciting at first, especially with certain recordings.

Then, of course every system and set of ears is different! To add some context, my Tannoy Canterbury GR speakers often don’t do well with upstream gear having any excess treble energy. I am glad you enjoy the tubes, regardless!
mulveling's avatar
mulveling
1,774 posts
 
Well 12au7 suck, so it’s not uncommon for folks to find a different sub type that blows all the best 12au7 away. Many tubes operate similarly to a 12au7 and do it better. 12ax7 is a better sounding tube albeit with a very different use/purpose, and you may have a much harder time finding a sub to beat the greats.
mulveling's avatar
mulveling
1,774 posts
 
I'm not sure how the extra current capability of the 12bz7 over 12ax7 would be an advantage? Most designers place 12ax7 for their gain, not current. They're never reasonably going to be asked to drive a hard load, so you're perhaps not gaining anything meaningful. However the 12au7 is often used as a driver or follower, and I've always heard improvements by subbing in the much stouter 12bh7.

Yes, you have to be careful that you have enough overhead for the extra heater current draw. Always consider the component. For a preamp with 6x 12au7, yeah you're probably in trouble subbing 12bh7's and doubling the heater requirements. For my Rogue Apollos with 4x 12au7 and 12x KT120 - well more than 90% of the heater current is sucked down by the power tubes and an extra 0.3A per 12bh7 didn't pose a problem. And yes it sounded a lot better too!
mulveling's avatar
mulveling
1,774 posts
 
Try some "used test strong" Telefunken 12ax7 when you get a chance. They’re solid all-rounders, and relatively common on the 2nd hand markets. But favorite 12ax7, by a good margin, has been the Mazda silver/chrome plate. Unfortunately they’re rare and expensive ($350+ a pair), and they have a bit of extra energy up top - so won’t be ideal for systems that need a push towards a relaxed top end.

Also I like those RCA tall black plates pretty well, but think the Mazdas are much better.
mulveling's avatar
mulveling
1,774 posts
 
The Tele ribbed plates aren't as warm as the smooth plates - you may like those better. Surprised you didn't like the Mazdas, but systems change and optimal tube selections can change over time - are you sure they weren't the 5751 silver plates? Those were awful lol. 
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