7025 WA tubes in TA-30

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Kerry Brown
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7025 WA tubes in TA-30

Post by Kerry Brown » Thu Feb 16, 2017 2:45 pm

Two of my friends are using 7025 WA tubes in their amps instead of 12AX7's. I'd like to try some in my TA-30 but wondering if I need to change all six or just V1, V2, and V3? I'm looking for a little warmer, fuller sound from the Vox and the Tweed voices. Currently all six preamp tubes are Mesa.

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Authorized Boogie
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Re: 7025 WA tubes in TA-30

Post by Authorized Boogie » Thu Feb 16, 2017 2:55 pm

7025's were a low noise 12AX7, however later the 12AX7-A was introduced with the same low noise construction - deeming the 7025 designation obsolete.
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Re: 7025 WA tubes in TA-30

Post by bandit2013 » Fri May 26, 2017 8:15 pm

Not sure about the TA amp. There are some 12AX7 tubes that will provide a change in character. All depends on the circuit of the preamp for the tube position you change. I found the Mesa SPAX7 seems to have a bit of roll off on the top frequencies. It is essentially the same tube a the 12AX7A stock tube.
There are some other variants in the 12AX7 family, short plate like the Mesa tube generally have the least influence from mechanical vibration. Medium plate tubes like the 7025 (generally the Chinese variant has a medium plate) also the Tung Sol, Mullard CV4004, EH12AX7, Svetlana (all from the same company but difference character in tone ) to the long plate Mullard RI 12AX7, as well as the JJ ECC803s. Warmer tubes would be the Mullards or the ECC803s but that all depends on the tuning of the circuit the tube is in.

Believe it or not the Mesa stock tube is dark sounding in one amp (Roadster) or the RA on the clean channel but bright and grinding on the hi/lo as well as balanced and masterful with the TC-50 and JP-2C. Tonal character you will hear from the tube is dependent on the circuit that is using it. In some cases you may not even notice a difference.

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