pre amp tubes

[bluesfloyd]

hi guys,
my amp is fitted with three pre amp tubes 12Ax7/ ecc83
can I use 12AT7/ecc81 or 12AU7/ ecc82 if I wish ?????? and if so, what tone/sound difference will I hear ??????
all the best, bluesfloyd

 

[Gone_Shootin]

Re: pre amp tubes

Basically, you will expirence a drop in gain.

This page explains the differences quite well: http://billmaudio.com/wp/?page_id=131
He talks exclusevly about the Fender Blues Jr, but the info regarding the differences in tubes is the same, regardless of the amplifier.

 

[El Supremo]

Re: pre amp tubes

12at7 and 12au7 are generally better as drivers and phase inverters in the power amp section. If you want a decrease in gain, I'd suggest you try a 5751 in v1.

 

[bluesfloyd]

Re: pre amp tubes

hi guys,
thanks for your replies,
bluesfloyd,

 

[DrNewcenstein]

Re: pre amp tubes

Anything hotter than a 12ax7 yet?

 

[El Supremo]

Re: pre amp tubes

Anything hotter than a 12ax7 yet?

That would be the 12bz7 I believe.

 

[DrNewcenstein]

Re: pre amp tubes

Nice. How much do they differ? 12AX7 vs 12AT7 or more like 12AX7 vs 12AY7?

 

[El Supremo]

Re: pre amp tubes

They're supposed to have up to 30% more gain compared to a 12ax7. A bit taller than regular 12ax7's and as far as I know, they're only available as NOS.

 

[gordon_39422]

Re: pre amp tubes

12AX7 has a mu of 100
12AT7 has a mu of 70
12AU7 has a mu of 20

So, the T will have 70 of the gain of an x... This is good for clean headroom if you like to use pedals for your distortion and rely on the amp to produce sincerely pure tones... I have even placed U's in an amp and REALLY like the cleans it produced, but with a loss in overall gain...

 

[DrNewcenstein]

Re: pre amp tubes

Found some BZs on Ebay. Gonna see what they do for my Marshall head, and my spare MP-1 vs my stock MP-1. I had thought about retubing the spare MP-1 with Ts or Us and using that just for clean tube/dirty tube tones, and my main MP-1 for the "Metal" tones.

Wonder what a BZ would do for a Chandler TD pedal. I know those can kick a Marshall nicely already.

 

[El Supremo]

Re: pre amp tubes

Good find. I'm happy with the EI's in my Marshall, but have been wondering about the 12BZ7's Which brand did you get?

 

[Gone_Shootin]

Re: pre amp tubes

12BZ7, huh?

That number seems familiar.....gonna have to root around in those old TV tubes I have stashed.

 

[DrNewcenstein]

Re: pre amp tubes

Good find. I'm happy with the EI's in my Marshall, but have been wondering about the 12BZ7's Which brand did you get?

They appear to be RCAs. Not sure how old.