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Post by bloozeman on Dec 16, 2015 18:44:09 GMT -7
So just curious. I've read that you can substitute a 5751for a 12ax7 tube and it will give you a little more headroom. So is it possible to replace all 3 12ax7 tubes in a maz Jr for the 5751 and have more gain and headroom? Specifically in a NR model? Is that possible?
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Post by cap10toons on Dec 16, 2015 19:19:49 GMT -7
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Post by cap10toons on Dec 17, 2015 8:24:46 GMT -7
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Post by John on Dec 17, 2015 10:50:32 GMT -7
It should be possible as the 5751 is close to a 12ax7. But tone/feel may be a little 'different'.
When I had my Maz Jr, I used a 5751 in V1. And if I 1) turned the mids down 2)didn't turn the (preamp) volume up to much 3) turned the cut and treble up pretty far....it was my "Stangray Jr" when used with normal/vintage output tele pickups.
No, it didn't have quite the beefy firm bottom end. No, it didn't have quite the percussive response (because it lacked the ef86) No, not quite the shimmering highs...
But it was darn close. And the advantages to me were 1) I could get some breakup if I wanted (which I usually wanted at least a little..and 2) I could turn the mids up if I wanted. (which I usually did)
I never tried the 5751 in any other position. The amp sounded like a low volume stangray, so I just left it with the 5751 in V1.
Dang...writing about this is making me miss that amp!
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Post by zpilot on Dec 24, 2015 6:09:49 GMT -7
Yes, it is possible and I've tried it but personally I like my MAZ best with the 12AX7LPS phase inverter it came with. Another option you might consider is a 12AU7. It's a lower gain tube and Ampeg used them for a PI in some of their amps. I believe it was the V4 and V2. I always thought they were fantastic amps.
And I believe there are some NOS 12AU7's for sale on the BST site at a good price. They should last a lot longer than new production.
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zeno
Junior Member
Posts: 63
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Post by zeno on Dec 24, 2015 7:20:41 GMT -7
I replaced the stock 12AX7 in (V-1) in my MAZ 18 jr several months ago with an N.O.S. RCA black-plate 5751 & haven't looked back. Not only was there a significant increase in headroom, but when it does saturate, the breakup is "creamier" & much less "fizzy". Seemed that it really opened up the MAZ. Definitely no loss in bass response or anything like that. However, I'm running the RCA with two N.O.S. Polam El84's in the power section and (to me) the overall improvement in tone over the stock tubes is fantastic. So much so, that I had my buddy in Warsaw, Poland send me several more matched pairs of the Polam's. I'm going to get another RCA black-plate 5751 for back up at some point, but It's my understanding tubes in the V-1 position usually last a long time.
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Post by bloozeman on Dec 24, 2015 8:06:06 GMT -7
Hmm, wondering if this would work well for the Maz 8 and give it more headroom by changing to all 5751??
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zeno
Junior Member
Posts: 63
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Post by zeno on Dec 24, 2015 9:16:46 GMT -7
Hmm, wondering if this would work well for the Maz 8 and give it more headroom by changing to all 5751?? Ha! I had the same idea . However, my home practice amp is a Vox AC-4 C1-12. Although the quality is not the same as the MAZ 8, I think the board is similar. Anyway, the Vox is just a little 4 watt tube amp that came with 2 Chinese 12AX-7's & 1 Chinese El-84. Typical Vox chimey tones but break started with the volume just past 9 O'clock turning to a muddy, overdriven mess past noon. Anyway, I replaced the Chinese 12AX-7's with JJ-5751's & the lone EL-84 with an old, NOS Amperex 6BQ5 (el-84) I had lying around. Holy Cow! The amp got (Much) louder & much cleaner in usable volume well above noon. Vox chime that shakes the walls & now breaks up later with a greater saturated tone from this cheap little amp. It's fun to experiment, and it's weird how a cheap tube upgrade makes such positive differences!
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Post by dergit (Markus) on Dec 25, 2015 6:57:22 GMT -7
Interesting. I have a few nos Philips 5751s lying around that I like in v1. Had never thought of replacing the LPS (or the Mullard reissue in my maz 8) in PI but I like what I'm hearing in cap10toons video! Will give them a spin soon!
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Post by zpilot on Dec 30, 2015 6:33:30 GMT -7
Hmm, wondering if this would work well for the Maz 8 and give it more headroom by changing to all 5751?? Ha! I had the same idea . However, my home practice amp is a Vox AC-4 C1-12. Although the quality is not the same as the MAZ 8, I think the board is similar. Anyway, the Vox is just a little 4 watt tube amp that came with 2 Chinese 12AX-7's & 1 Chinese El-84. Typical Vox chimey tones but break started with the volume just past 9 O'clock turning to a muddy, overdriven mess past noon. Anyway, I replaced the Chinese 12AX-7's with JJ-5751's & the lone EL-84 with an old, NOS Amperex 6BQ5 (el-84) I had lying around. Holy Cow! The amp got (Much) louder & much cleaner in usable volume well above noon. Vox chime that shakes the walls & now breaks up later with a greater saturated tone from this cheap little amp. It's fun to experiment, and it's weird how a cheap tube upgrade makes such positive differences! Mercury Magnetics sells a really nice upgrade mod kit for that Vox AC-4. It includes new transformers and a triode/pentode switch.
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