Tube ?

[ND13]

Someone tell me if I understand this correctly.

I can swap out 12AT7s and 12AU7s for 12AX7s, but can't sub 12AX7s for those, right??? Something to do with voltage being higher in the X variant, correct?? The Ts have the lowest of the three. so it can be used as a replacement for either the U or X, but those can't be put in where a T is called for, right??

12AT7= 12AU7 or 12AX7
12AU7= 12AX7
12AX7= 12AX7

Make sense???

[ND13]

Surely someone knows if this is right or wrong or close...

[beardog03]

I fear that`s a question for Russman, bro...

Sorry, I can`t help ya..

[BlueMDPicker]

Check the specs of the tubes in question on this (http://www.nj7p.org/Tube.php) data sheet lookup database. I've never subbed the tubes you listed. That is not to say they cannot be subbed, though.

[RuSsMaN]

He has a quad of something other than AX, that he wants permission to put in his MLP.

What he needs to do, is quit dicking around, and use what he has, or pony up for a quad of AX that he wants (or thinks he wants). Noel, using what the circuit was designed for is ALWAYS the best option.

Going DOWN in gain factor is usually ok, going up - proceed at your own risk.

[ND13]

No, I don't have a quad of something else. I have a quad of something else available to me on the cheap if I want them, though ;) And the question had arisin in a conversation with friend of mine who wanted to know the answer for himself.

[organ]

Noel,
I did a research on this at audioasylum after reading your post and it's not a good idea to sub U7 for an X7. The U7 only has 1/10 the gain of an X7. It will also change the voltage/current flow in the circuit. The only tube people sub for X7's are 5751.

[ND13]

Thanks, won't need these anyways, just ran across a quad of smooth plate, diamond bottom Teles :D

[BlueMDPicker]

Noel,

Since Gary Dodd is accessible, have you asked what tube(s) he used during his prototyping of the preamp? NOS tubes are a lot of fun to roll through a signal path. But, I've found, many "boutique" designers build their circuit on the characteristics of current production tubes.

The only Tele smooth plate I've had experience with (12AU7) was in my MiniMax pre. It was too "bright" for my tastes. Some have speculated this "brightness" in modern circuits can be attributed to a conscious design philosophy of the tube aimed at overcoming some of the "darker" tonal characteristics of contemporary circuitry of that era.

Mike

[ND13]

Mine aren't bright at all, so far. I would date them around the late 50s-early 60s era. alot of the lettering is worn off, but the important parts are still legible, like 12AX7, made in West Germany, and of course the diamond on the bottom of the tube is the dead giveaway of what you have. I have a much better looking matched pair of the same that I need to find another pair to go with. I have a feeling those might just get a little salty to acquire.