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Tube Alchemy


Patrick Deno

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I have SOOO many questions and don't really know who to ask.

I've done a lot of reading up on the 2112/20 over the last few days and have come across a consensus that the factory tubes these things ship with are **** straight out of the box (what else would you expect from Sovtek? :D) We have 3 different brands of tubes that I can replace them with at the shop, which would you think would be best for power metal/speed/metalli-chunk type music? B)

1) Mesa Boogie (I'm leaning towards these personally but they're expensive!)

2) Sovtek (Again? But maybe a better, matched set?)

3) Electro Harmonix.

What do you think?

Which type should I get?

12AX7

12AT7

12AX7 WA

12 AX 7 WXT-PS

12 AX7 WB

Other

I have NO clue since I've never owned anything with tubes in them before. What's the difference between these little magic mounds of glass and metal?

How do I go about changing them? Or should I just have my repair workshop buds do it? I've heard some say you MUST get them biased (????) or you'll screw up your amp/unit and others say you can do it yourself because it makes no difference whatsoever. :D

***?

Welcome to the land of tube alchemy and psuedo-science LJ, now you're really phukt! :D

:D LJ

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I have two tube amps with 12AX7's.

For a tube amp, yes, you will be better off to get a matched set. Tubes typically will work in a push-pull configuration. You can think of it as one tube sitting on either side of the amp speaker. One tube pushes the speaker while the other one pulls from the other side. They go back and forth like this and that's what makes the sound...

Now. If you didn't have a balanced set one tube would be a little weaker (like playing tug of war with a 5 year old). Or, the speaker wont rest in a neutral position. While it'll work, it won't be nearly as loud because the speaker wont be able to move through it's entire range.

I've used Sovtek's before. They were cheaper than most everywhere else. Really, there are very few American companies left that make tubes. Russia is still in the business though. They still have radios over there that use 'em and stuff.

I can remember back in the 80's even that every 5-and-dime had one of those huge tube testers. You don't see those around anymore.

*sigh* I'm getting old. I remember when tubes were mainstream the first time around.

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First and most important. There are four different functions that different tubes perform.

Preamp tube - Typically these are from the 12AX7 family, which includes the following:

ECC83- for the Marshall sort of sound

7025 - for the Fender 60’s and 70’s sound

5751 - for blues and less aggressive attack

Preamp tubes are the most critical, least expensive, most overlooked tubes in your amp. The preamp tube in the first gain stage (usually V1 and / or V2) sets the tone and initial gain structure of the amplifier

Each half of the preamp tube works separately in the circuit even though it the same tube. It is good to have both halfs matched.

Best buy is in this group (In decreasing order)

1) JJ/Tesla 12AX7S

2) GE 12AX7WA

3) Ei EC83/12AX7

http://www.guitaramplifierblueprinting.com/12ax7.html

Rectifier tube

The rectifier basically converts the AC line current coming into your amplifier to the DC voltages that are needed. The power limits of your amp's transformer limit the choices that can be made!

GZ34 = 5AR4 GZ32 = 5U4 = 5V4GA GZ31 = 5U4GB GZ30 = 5Y3GT

Driver tube

The driver tube can be consider the interface between the preamp section and the power amp section

Power tube

Power tubes drive the speaker transformer and must be impedence match to it and the speakers.

Biasing - These are the tubes that are biased. (Although several amp manufacturer preset the bias and market it as "Self biasing or Cathode Biased) all thee tubes can be self-baised, that is preset to run with a certain voltage.

Class A verses Class A/B1 - Again more marketing stuff, all these tubes can be setup to be Class A or Class A/B.

Several different styles and power outputs for each power tube grouping.

6V6 Group - Fender Princeton sound

EL-84 Group - Mesa Boogie Dual Caliper sound

6L6 Group - US Rock and Roll via Fender

5881 Group (Confused with a 6L6, because it was designed as a military replacement, but not as a copy)

GEC KT-66 - Beano sound, Marshall bluesbreaker sound, No longer made by GEC - currently cheap copies

EL-34 Group - Classic English Marshall sound

KT-88 Group - Big round sound

6550 Group - Thickest and most powerful tube currently being used for guitar amps - Classic US Marshall sound

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  • 4 weeks later...

Hi guys,

if you want superb valves(tubes), resonably priced and great service, visit Eurotubes and give Bob a call. He is as helpful as Brian at sorting people out with their needs. :D

Tell him your amp and the sound you looking for and he will suggest the proper combination for you.

Also, most stock amps are biased cold, he will provide hotter preamp valves to let your amp sound the way it really should. rock

Cheers,

Chris.

Ireland

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