12axa-12at7 champ ??
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Carlin Mitchell
- Posts: 35
- Joined: Mon Oct 06, 2008 10:41 pm
- Location: Minneapolis, Minnesota
12axa-12at7 champ ??
Can either the 12AXA or 12AT7 be used in a CHAMP type amp and could someone briefly explain the difference between the champ 5C and 5F models ? Sorry..... I'm still so new.
Re: 12axa-12at7 champ ??
The mu or gain factor of a 12AX7 is 100 and a 12AT7 is about 60, but that is only one difference. The internal components are different and one notable difference is that the plate resistance on the 12AT7 is much lower. The difference in plate resistance means that a circuit designed for a 12AX7 isn't necessarily appropriate for a 12AT7 and vice versa. These tubes have identical pin out, and can generally be exchanged without harm to the amp, but that begs the question of whether such a substitution is appropriate or whether it will sound good.
Since I'm not ancient enough to have heard or played a 5C1 or 5F1, I'll just venture a guess on them.
The 5C1 Champ uses a pentode in the preamp and has only a volume knob. Pentodes tend to be noisy as preamp tubes and good luck finding a 6SJ7 that you think sounds good.
The 5F1 makes a big improvement by using a 12AX7 for the preamp, giving it two gain stages before the power tube. Again, this is a one knob amp. I am going to guess the 12AX7 provides more drive and less noise.
I imagine both of these amps are fairly gritty in tone.
The later blackface AA764 has a tonestack in it. If I were building, that's the one I'd choose. There are just a few more parts and it offers just a wee bit more flexibility in tone. It's still a gritty sounding amp.
I would say that you can't go wrong with a 5F1 (elegant simplicity) or a AA764. I never read about anyone building the 5C1.
Since I'm not ancient enough to have heard or played a 5C1 or 5F1, I'll just venture a guess on them.
The 5C1 Champ uses a pentode in the preamp and has only a volume knob. Pentodes tend to be noisy as preamp tubes and good luck finding a 6SJ7 that you think sounds good.
The 5F1 makes a big improvement by using a 12AX7 for the preamp, giving it two gain stages before the power tube. Again, this is a one knob amp. I am going to guess the 12AX7 provides more drive and less noise.
I imagine both of these amps are fairly gritty in tone.
The later blackface AA764 has a tonestack in it. If I were building, that's the one I'd choose. There are just a few more parts and it offers just a wee bit more flexibility in tone. It's still a gritty sounding amp.
I would say that you can't go wrong with a 5F1 (elegant simplicity) or a AA764. I never read about anyone building the 5C1.