Quote:
Originally Posted by RiverRatt
Marty, while you're answering questions, I have a couple that I've been wondering about.
First, what effect does V2 have on the green channel on my DSL? I really like the 12BZ7 in V2, but it seems that the green channel has a little more of an edge than normal with this setup. Am I imagining this, or is the BZ7 coloring it a little? If so, do you have a recommendation that would work well in this setup?
Second, and this is probably the really stupid one, does the PI affect the bias of the power tubes, especially using a lower gain tube like a 12AT7?
I'll have to catch the reply tomorrow at work. My PC at home has been zapped by W32.Virut.CF for like the third time this year. Time for another re-install, as that thing corrupts so many system files that it's virtually impossible to recover from. Damned kids visiting porn sites, probably.
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Well Ratt, I'm the perfect candidate for looking at porn, 54 and single. However, I stay away from that shit, it will eat your brains up. I hope your kids respect you and will not go to virus prone sites. Okay enough about that.
First off, the way a Marshall works is that from the input it goes into the first preamp circuit and uses "one half" of the triode (12AX7). It then goes into the second preamp stage through "one half" of the next triode. A lot of people are under the impression that the signal goes through both sides of the tube. This is untrue, as it uses one half of V1 and V2 for the Green Channel. The other half is for your Crunch Channel.
A 12BZ7 will always provide more gain than a 12AX7. This has been discussed many times in this forum. A 12BZ7 has half the plate resistance of a 12AX7. However, some guitar amp circuits do not like a 12BZ7. Excessive gain sometimes isn't a good thing. I sent Josh a 35-35 tube and he sent it back. He went with a 7025 in V1 and an Amperex 12AX7 in V2. So far, based on my experiments and those by Joe and Josh, the 7025 is the key to having great overall Marshall sound. Pairing a 7025 up with a high gain (30-30) tube is what everyone is settling on, so there must be something to it.
I think the 12BZ7 may meet the expectations of a certain number of players who focus on a narrow band of tone requirements. The 12AX7 is to me a more musical sounding tube. The 12BZ7 I feel is going to make your clean channel a little gritty sounding. How do you rectify this? The only way would be to put a lesser gain tube in V1. This will clean up your Green Channel. However, you will have to make some adjustments to get your Crunch Channel sounding the way you like it, but it can be done.
The PI does not affect the bias of the power tubes. If it did, we all would be catching hell for tube rolling. Do you remember the guy I talked about recently? He had a Marshall and someone played a good one on him. It had two 12AU7's in it. One in V1 and the other in the PI. It was like putting a kink in a garden hose, the signal was choked off. I always wonder why some people will put a 12AU7 in a Marshall amp? I can handle a 12AT7 or a 5751, but not a tube with a gain of 17 to 19. What's that going to get you?
Well I hope I answered your questions. If not post them and I will try to get to them.
Marty