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12AT7 in place of 12AX7 (Read 1009 times)
Geno
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12AT7 in place of 12AX7
03/27/19 at 02:28:20
 
I read that the 12AT7 has lower gain than a 12AX7, but that this can result in possibly better sound quality. Id like to try one, but can I use it in the first position on the ZP3?
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Lon
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Re: 12AT7 in place of 12AX7
Reply #1 - 03/27/19 at 02:36:19
 
No, I don't think you can. I believe I tried this and it was a no go. You need to use a 12AU7 type.
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Geno
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Re: 12AT7 in place of 12AX7
Reply #2 - 03/27/19 at 02:40:27
 
Lon,

I am using a 12AU7 where it belongs. Im talking about in place of the first 12AX7.
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Lon
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Re: 12AT7 in place of 12AX7
Reply #3 - 03/27/19 at 03:27:57
 
Sorry, I had that backwards. But I don't think a 12AT7 can be subbed in the ZP3.
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Ace-Tone
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Re: 12AT7 in place of 12AX7
Reply #4 - 03/28/19 at 01:35:05
 
I tried a 12AT7 in the 12AU7 position....
It took the volume level down and the fidelity as well....so much so that it was immediately removed.
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pursuitofnow
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Re: 12AT7 in place of 12AX7
Reply #5 - 03/28/19 at 05:38:37
 
Replacing a 12ax7 with 12at7 seems like it may be too much of a drop in gain.

12AX7/12AX7A/7025/ECC83/CV4004
Gain factor: 100

5751
Gain factor: 70

12AT7/ECC81/E81CC/CV4024
Gain factor: 60

12AU7A/5963
Gain factor: 20
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Re: 12AT7 in place of 12AX7
Reply #6 - 03/28/19 at 05:53:44
 

If experimenting with the 12AT7, the tube should replace the first 12AX7 at the front of the ZP3.  Yes, the gain drops, so if you have a lowish output cartridge this change is not likely to do you any favors.  However if you have gain to spare from either a higher output cartridge and or a gain stage after the ZP3, the 12AT7 can in some cases be the magic bullet.  

One of my favorite combinations with the ZP3 is the ZSTAGE on its outputs.  This adds about 6 dB or more of noiseless gain and puts the dynamics of your cartridge on steroids...  If you have gain to spare like this, and you are occasionally hearing the midrange and top end become forward, using a 12AT7 would lay it back and mellow it out by taking the sharpness out without effecting the speed, resolution or frequency balance.

Steve
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