I Just bought this amp and I noticed that the tubes in the power amp section for v-2 and v-3 are suppose to be 12BH7'But mine are 12AT'S.Are these proper substitutes?The v1 is suppose to be a 12DW7 And mine is a RCA MADE IN JAPAN 7247.I've read that that is a proper sustitute or is it? Here is my tube list and if anyone would like to comment or recormend on what I should change,It would be most helpful.Thanks Gravyman. PREAMP SECTION. V1 SYLVANIA 12DW7/V2 RCA 12AX7A/V3 SYLVANIA 12DW7/ V4 EI 12DW7/V5 JAPAN/PRO COMM ''There is no numbers on this one.POWER AMP SECTION- V1 RCA MADE IN JAPAN 7247/ V2 RCA 12AT7/ V3 NO NAME 12AT7/ V4-V9 ARE 6146 GE AND RCA
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Tube advice for 1970 SVT BLUELINE
- Thread starter GravyMan
- Start date
I think you would want to bring that to a proper tech, those are so cool, it's not worth saving a few bucks and wondering if it's 'all sorted out'. I don't think the 12AT7 is a proper substitute for a 12BH7, my book does not list it as an acceptable substitute. I'd get 12BH7s. Hopefully you have a good tech near you.
My local organ shop, tube experts since the '50s, recently sold me some 7247s. They told me it took some digging for the right substitution book, but the 7247 is a proper replacement for a 12DW7. I understand that the 12DW7 is half low gain, half higher gain, like if you took half a 12AU7 and hald a 12AX7.
And I just checked my tube substitution handbook, it also lists the 7247 as a sub for the 12DW7, - now I don't know why the organ shop had a hard time figuring it out.
My local organ shop, tube experts since the '50s, recently sold me some 7247s. They told me it took some digging for the right substitution book, but the 7247 is a proper replacement for a 12DW7. I understand that the 12DW7 is half low gain, half higher gain, like if you took half a 12AU7 and hald a 12AX7.
And I just checked my tube substitution handbook, it also lists the 7247 as a sub for the 12DW7, - now I don't know why the organ shop had a hard time figuring it out.
- Feb 16, 2008
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7247's, as stated above, are a direct substitute for a 12DW7, but 12AT7's are NOT a substitute for a 12BH7. i'd recommend getting some NOS philips/sylvania's since they're still available at reasonable prices and much better quality than the reissues.
I think there is a modification procedure in an tube amp book that talks about swapping the 12BH7's for 12AT7's.
It did involve some wiring changes and adding a cap, I believe.
Definitely have the amp checked out because you do not know what someone may have done inside to make 12AT7's work.
Strange that those tubes were changed but it still has 6146's in it...
I think the 12BH7 change did have to do with changing the 6146's so you really want to make sure what is going on inside.
It did involve some wiring changes and adding a cap, I believe.
Definitely have the amp checked out because you do not know what someone may have done inside to make 12AT7's work.
Strange that those tubes were changed but it still has 6146's in it...
I think the 12BH7 change did have to do with changing the 6146's so you really want to make sure what is going on inside.
Tone difference won't really come into it, the 12BH7 is in the Power section. Take the amp to a tech and ask if he knows why the 12AT7's have been put there.
