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Post by zone47 on Dec 5, 2006 11:26:27 GMT -7
critical spot for tone shaping? *looking at a Dr. Z Prescription amp* ... how about V2 ? ..and V3 is the phase inverter?... so it must be balanced. ... so put your best NOS tube in V1, correct?
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Post by rhythmeister on Dec 5, 2006 11:44:19 GMT -7
I'll take a crack at this. There is a big difference b/w the old Prescription (Rx) and the new one (Rx ES). The new one has a 12AX7 in V1, an EF-86 in V2 and another 12AX7 in V3. In this setup, the quality of the EF-86 in V2 will be critically important as well as what you put in V1. The EF-86 has over twice as much gain as the 12AX7, so it will make a great impact on the tone. Plus, NOS EF-86 tubes are pretty much essential (unless the new EH offering proves to be great and reliable). If I owned this amp, I'd look for a NOS 12AX7 for V1 and a NOS EF-86 for V2.
Now in the old Prescription, V1-V3 were 12AX7 tubes. In this case, I agree that your best sounding NOS tube would usually go in V1 as it will impact tone greatly.
Cheers, Blair
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Post by mudskipper on Dec 5, 2006 20:19:39 GMT -7
critical spot for tone shaping? with all things being equal. it is a good assessment. and putting your favorite tube in V1 position would be a great start. then tweak the PI tube. just remember that your "best NOS tube" may *not* be your "most favorite".
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Post by anacephalic on Dec 8, 2006 14:12:17 GMT -7
eis righten v1 and v3 on. i spent a few hours moving my collection of ax7s around betwin my RX and different tubes in different places had profound effects and they weren't always what i expected based on what i assumed the better tube was. v2 had less impact though even there i ulimately came up with a favorite tube. i really need to try a nos 5751 or two and the mullard reissue 12ax7. in one of the harmony central reviews for the RX there was a suggested tube swap to turn the beast into a pseudo tweed. i always thought that would be kinda fun too.
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