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    Building, troubleshooting and testing of these amplifiers should only be
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YAMAHA 12AX7A/7025-HELP-anyone seen that before?

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siemionet

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Joined 2018
Hi,
I have few 12AX7A/7025 valves with YAMAHA logo. These were taken in 1994 from Soldano or Rivera amp. Not sure today which one. Almost unused. Does anyone have any information about these valves? They sound really good. Just replaced RUBY 12AX7AC5HG+ and RUBY 12AX7AC5HG in my VOX AC4 HW for these YAMAHA. Thanks in advance...
 

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Lingwendil

Lingwendil

Member
Joined 2008
siemionet said:
If these are also RUBY so they have much thicker glass and sound "much better" than RUBY 12AX7AC5 HG+ and RUBY 12AX7AC5 HG made recently. I would rather expect that newer would sound better due to improvement in process of production....
Click to expand...

I have found the opposite in nearly everything tube related... The "best" seem to be cold-war era production european, at least as far as ruggedness and specifications...

I think Ruby is a "middle of the road" brand, not bad, tend to be okay most of the time. I had really bad luck with them for 12AT7 a while back, very microphonic and poor section matching, but everything else I tried from them was good. They are usuallytested and "gone through" chinese tubes. I hear that many may be rebranded russian surplus, but all of the ones I've handled look like chinese construction (not a bad thing, so long as they are done right) so quality can be a broad range. As a rule i tend to avoid most chinese tubes, simply because the specs are all over the place (worse than surplus russian!) and you may have to go through a bunch to pick out the better ones, but with Ruby, someone else already dug through the pile for you :)

That reminds me, I still have a stash of Ruby power tubes of various types (guitar shop buyout) that I need to look at.

Also, FWIW, these look similar to a Sovtek 12AX7WA that I have on hand as well, although the plate stampings look different.
 
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siemionet

Member
Joined 2018
That’s true. Maybe Russian military. Theese are good quality. I have some old Russian EL84 and these sound like 130% of any other tube :) Also tubes made in Poland Telam/Polam EL84 sound great. I remember in 70’ Polam produced bulbs for different companies (Philips, Osram etc.). They all came from the same factory with different logos, inside different boxes to different countries. I’m curious if that applies to valves/tubes as well. Most likely yes..
 
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