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EQUIPMENT FORUMS >> ZP3 / ZMC1,2,3 >> 12AT7 in place of 12AX7
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Message started by Geno on 03/27/19 at 02:28:20

Title: 12AT7 in place of 12AX7
Post by Geno on 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. I’d like to try one, but can I use it in the first position on the ZP3?

Title: Re: 12AT7 in place of 12AX7
Post by Lon on 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.

Title: Re: 12AT7 in place of 12AX7
Post by Geno on 03/27/19 at 02:40:27

Lon,

I am using a 12AU7 where it belongs. I’m talking about in place of the first 12AX7.

Title: Re: 12AT7 in place of 12AX7
Post by Lon on 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.

Title: Re: 12AT7 in place of 12AX7
Post by Acetone on 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.

Title: Re: 12AT7 in place of 12AX7
Post by pursuitofnow on 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

Title: Re: 12AT7 in place of 12AX7
Post by Steve Deckert on 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

Title: Re: 12AT7 in place of 12AX7
Post by Dilbert99 on 05/05/23 at 01:45:28

I just swapped out the front 12AX7 with a 12AT7 with very good results. Running a ZP3 through an all Decware system to Zu Soul Supremes.

I kept the volume levels consistent before and after swapping the tube, practically no noticeable drop in the level from a Nagaoka MP-110 with 5mV of output, so with a lower output cartridge you mileage may vary.

The tube only has a couple hours on it, so it hasn't reached its full sound potential just yet.

Pretty pleased with the result, especially given the lower price for good NOS 12AT7 as opposed to the 12AX7.

I haven't tried another 12AT7 in place of the middle 12AX7, not sure if that would have any further impact, or if it even advisable.

I'm curious to know if others have seen the same result as I or if they've had success with the swap in the middle position.

Title: Re: 12AT7 in place of 12AX7
Post by Rivieraranch on 05/20/23 at 23:55:29

What about a 5751?

Title: Re: 12AT7 in place of 12AX7
Post by surfers5 on 08/09/23 at 19:34:49

As Steve said, if you have gain to spare the 12at7 can be the magic bullet for the V1 position in the ZP3.

I just posted my in-depth experience of trying different gain tubes in the V1 and V2 spots of the ZP3 in the - Tube Rolling 12au7, 12ax7 thread.