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Preamp tubes in power amps

I’ve had tube gear for a decade but never, until recently, looked into how it functions or how to optimize it. So, my basic question is, my Rogue Magnum M-120 monoblocks have their power tubes, and then also a couple of 12AU7s and one 12AX7.

Would replacing those with NOS higher end tubes like a Seimens or a Mullard have much benefit?

Or would my tube budget be better spent replacing the new production 6922s in my BAT VK-3i with some higher end NOS tubes?

I figure I can’t afford to replace the power tubes until they die. But looking to see where the best bang for the buck would be on the preamp tube side of the equation.

Thanks to all who answer the actual question!
jji666
tomcy6's avatar
tomcy6
2,638 posts
 
I’m not familiar with your components, but you want to first upgrade the input tubes or voltage gain tubes, same thing, I think. As to whether the preamp or amp would have the most impact, I’d guess the preamp unless the tubes in your pre are not used for voltage gain and are in the amp.

That’s unfortunate about the 7DJ8s, but it shows why you need to talk to the manufacturer. 7DJ8s are often used as subs for 6922s these days.  Did you talk to Upscale about the problem?


jji666 OP
601 posts
 
Thanks again.  Yes I did tell Upscale about the issue.  They tested all the tubes and sent the survivors back to me, but I haven’t used them as the only 6922 sockets I have are in the BAT.  I can’t put them back in there.

The only gripe I have about Upscale was his statement about 7DJ8s being a perfect substitute ...”trust Uncle Kevie on this one.” Not “make sure this is ok with your gear.”

Oddly, Victor at BAT seemed skeptical that changing tubes would have much impact.  

tomcy6's avatar
tomcy6
2,638 posts
 
See if you can get Viktor to talk to Upscale or get an email from him stating the 7DJ8 is not suitable for his preamp and pursue the matter with Upscale.  Did Upscale know that you planned to use the tubes in a BAT pre?

Some manufacturers advise that you can't do better than the stock tubes because that's what they designed the pre or amp with, others encourage tube rolling. I guess unless you hear from someone who has the same components and had success tube rolling, I'd follow the manufacturer's recommendations.
jji666 OP
601 posts
 
Thank you. This is helpful advice.

Upscale didn’t know. I don’t think they should be quite so certain in their marketing materials that 7DJ8s work anywhere.  But I couldn’t say that there was anything specifically said to me, or omitted, that was a problem with Upscale. I ordered several sets and had ruined most before Kevin could respond. The tubes DID sound good...

The issue was years ago, and so I’m not going to pursue it with them now. It comes up mainly because at that time I decided not to try NOS tubes in this preamp again. But now that I have it available to my best amp/speaker combo again, I am again wondering if some NOS would add magic.
sandthemall
544 posts
 
The signal is much smaller/more delicate at the preamp. So it follows that any change will have a greater impact there rather than the amp.
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