12AT7 in V5 (PI) of 3 channel Dual Rectifier

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12AT7 in V5 (PI) of 3 channel Dual Rectifier

Post by phillygtr » Tue Apr 08, 2014 8:47 pm

This would be OK right? No issue with potentially damaging my amp?

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Re: 12AT7 in V5 (PI) of 3 channel Dual Rectifier

Post by dodger916 » Wed Apr 09, 2014 3:33 pm

It won't hurt; it just won't feed the power tubes with as much gusto.

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Re: 12AT7 in V5 (PI) of 3 channel Dual Rectifier

Post by crane » Thu Apr 10, 2014 12:42 am

No damages at all. Try it, it's a matter of taste.
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Re: 12AT7 in V5 (PI) of 3 channel Dual Rectifier

Post by bandit2013 » Tue Apr 29, 2014 6:07 am

There are a few tubes that are suitable replacements for a 12AX7. That would be 5751, and 12AT7. I would not go beyond 30% to 40% below nominal gain.
Typical gain factors of 12 series preamp tubes
12AX7 being 100 (nominal)
5751 is 70 (30% reduction)
12AT7 is 60 (40% reduction)
12AY7 is 45 (55% reduction)
12AV7 is 41 (59% reduction)
12AU7 is 19 (81% reduction)

Dropping too low will not be all that great. Typical replacement strategy does have limits. Say for example you have a Mark Series amp where the reverb send and return are split between two different tubes and the other triodes are used for gain stages. Dropping from a 12AX7 to a 12AT7 is okay and will alter gain structure and tone.

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