DrNewcenstein
He Did the Monster Mash
It was mentioned in a recent thread that 12BZ7s are higher-gain than 12AX7s, so I picked up a few and tested them in my ADA MP-1.
The MP-1 used for the tests came to me with Sovtek 12AX7s in V1 and V2. They look fairly new. There's what appears to be a date code of 05 12. Not sure if that's Dec 2005 or May 2012.
The 12BZ7s (RCA) are old and used, but the listing claimed "tested strong". I would have to dig out my Dad's old tube tester to find out for myself. Probably have better luck finding Bigfoot.
The guitar used for the tests was mahogany/mahogany neckthrough, maple top, with a TB 59 with an A2 in the bridge and a 59 with a regular ceramic (A5-sized) in the neck.
At any rate, the first thing I did was set up a patch with the EQ zeroed (no boost, no cut), Gain 1 and Gain 2 on 0 (dead quiet), and the Master Volume on 5 (goes up to 10, so halfway), and set for Distorted Tube voicing.
Monitored through the headphone jack in the back of it.
I used the stock Sovteks first, then repeated the same steps with the RCAs.
Test:
Gain 1 on 10
Gain 2 on 0
Sovteks: Though the signal was weak, it was audible. Didn't have to strain to hear it, but it wasn't going to peel any paint.
Would need EQ tweaks to be useable but not a bad sound to start with.
12BZ7s: Failed on the first try. Same setting had the same saturation, but the volume was about 50%-75% of what the Sovteks put out.
The volume setting could have easily been tweaked to match the Sovtek output levels, but that doesn't really strike me as definitive of "higher gain". I would have expected more saturation while keeping the current volume at least, or maybe a slight increase in volume along with more gain.
I did record the tests with both sets of tubes, and looking at the waveforms, they appear nearly identical in volume on the later tests, where Gain 2 was set between 7 and 10 and Gain 1 was set between 3 and 5.
In those, the saturation levels also sounded identical to me. Certainly not as drastic a difference as I was expecting. I'd have to scrutinize each waveform to see the exact differences.
Running through some of the patches in the unit, from glassy cleans to face-melt, I'm still not detecting any "wow, that's hot" with the BZs. I imagine compared to AXs of the same vintage, there'd be a noticeable difference.
Next, I put an AX in V1 and a BZ in V2 and repeated the test.
Again, the BZ held it back.
Next, I put the BZ in V1 and an AX in V2.
Again, the BZ is not showing any signs of having more gain, and Gain 1 on 10 was still rather weak.
In summary, if you've got an amp running vintage 12AX7s and you want more gain, and you want to keep it period-correct for some reason, you might want to look into some vintage 12BZ7s, as I hear they're higher gain.
If you've got an amp running more-recent 12AX7s and you want more gain, you might want to look into having it modded.
The MP-1 used for the tests came to me with Sovtek 12AX7s in V1 and V2. They look fairly new. There's what appears to be a date code of 05 12. Not sure if that's Dec 2005 or May 2012.
The 12BZ7s (RCA) are old and used, but the listing claimed "tested strong". I would have to dig out my Dad's old tube tester to find out for myself. Probably have better luck finding Bigfoot.
The guitar used for the tests was mahogany/mahogany neckthrough, maple top, with a TB 59 with an A2 in the bridge and a 59 with a regular ceramic (A5-sized) in the neck.
At any rate, the first thing I did was set up a patch with the EQ zeroed (no boost, no cut), Gain 1 and Gain 2 on 0 (dead quiet), and the Master Volume on 5 (goes up to 10, so halfway), and set for Distorted Tube voicing.
Monitored through the headphone jack in the back of it.
I used the stock Sovteks first, then repeated the same steps with the RCAs.
Test:
Gain 1 on 10
Gain 2 on 0
Sovteks: Though the signal was weak, it was audible. Didn't have to strain to hear it, but it wasn't going to peel any paint.
Would need EQ tweaks to be useable but not a bad sound to start with.
12BZ7s: Failed on the first try. Same setting had the same saturation, but the volume was about 50%-75% of what the Sovteks put out.
The volume setting could have easily been tweaked to match the Sovtek output levels, but that doesn't really strike me as definitive of "higher gain". I would have expected more saturation while keeping the current volume at least, or maybe a slight increase in volume along with more gain.
I did record the tests with both sets of tubes, and looking at the waveforms, they appear nearly identical in volume on the later tests, where Gain 2 was set between 7 and 10 and Gain 1 was set between 3 and 5.
In those, the saturation levels also sounded identical to me. Certainly not as drastic a difference as I was expecting. I'd have to scrutinize each waveform to see the exact differences.
Running through some of the patches in the unit, from glassy cleans to face-melt, I'm still not detecting any "wow, that's hot" with the BZs. I imagine compared to AXs of the same vintage, there'd be a noticeable difference.
Next, I put an AX in V1 and a BZ in V2 and repeated the test.
Again, the BZ held it back.
Next, I put the BZ in V1 and an AX in V2.
Again, the BZ is not showing any signs of having more gain, and Gain 1 on 10 was still rather weak.
In summary, if you've got an amp running vintage 12AX7s and you want more gain, and you want to keep it period-correct for some reason, you might want to look into some vintage 12BZ7s, as I hear they're higher gain.
If you've got an amp running more-recent 12AX7s and you want more gain, you might want to look into having it modded.
