gZip

The head I picked up still has the original pre amp tubes in it from 1997.
I'd like to put some new tubes in it.

If I understand correctly peramp tubes need no biasing, and it looks like there are 4 of them in there. Three exposed and one under a metal cap thingy.

Long story short, theyre going to end up being Groove Tubes because of store credit and that's the only brand they sell.

Marshall Amps

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redscott131

Hello. Since they are only preamp tubes (12AX7), simply pull them directly out of the amp, and replace them with the new ones you're about to receive from the store. They will have metal pins (on the bottom of the tubes) that will only go in one way, so putting them back in won't be a problem.

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ics1974

You should also clean the tube sockets with contact cleaner before replacing the tubes. Spray the pins of the old tubes then work them in and out of the sockets a few times. Then put in the new tubes.

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gZip

Thanks

Tbonerocks80s

Ask for a Balanced Tube for the Phase Inverter. Thats the tube closest to the Power tubes. Marshall says your supposed to use one in V4. I have heard others say its not needed. Anybody got info on that?

Ken

No, do NOT get a balanced tube. Unbalanced ones sound better.

Ken

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1999 Marshall DSL 50
Music Man 65 Reverb late 1970's (?)
Late 1970's (?) Fender Champ
Marshall battery amp
1980 Model 1982A 4x12 cabinet G12H-80's 444 cones
1983 Model 1982B 4x12 cabinet G12-80's 444 cones
PRO 4x12 from the 1970's
Woodson 2x12
1976 Les Paul Standard
Epiphone Les Paul knockoff
ESP Lawsuit Explorer
1979 Chiquita Travel Guitar
1995 Taylor 310

big dooley

yes, according to santiago, the designer of the JVM, 2203KK, AFD100, YJM100 and god knows what's coming out this year, marshall has NEVER used balanced triode tubes in the PI position...
it's straight up, purified bollocks, as the circuit itself is out of balance anyway... do not fall into this utter lie

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GIBSON67

Your preamp tubes are probably ok, power tubes will wear out a lot faster. I'd get a set of power tubes before I invested in preamp tubes, assuming there are no known issues with your preamp tubes.

Tbonerocks80s

So why does the Eurotubes guy say you have to get a balanced tube for PI??? I swapped my PI tube with a non balanced one and I really cant tell the difference.

Tbonerocks80s

https://ssl.eurotubes.com/cart/index...category_id=47

This is his explaination right from his website.


#6. What is a phase inverter ( splitter ) and why should I use a balanced one?
A phase inverter or splitter is the tube that keeps your power tubes ( in a push pull A/B type of amp ) running 180 degrees out of phase. This is necessary because in a push pull amp one tube creates the upper half of the sine wave while the other tube creates the lower half. One of the symptoms of an unbalanced phase inverter is that some notes will sustain very well where others will fall off or sound dead. In 99% of all guitar amps the PI tube is the closest preamp tube to the power tubes and 99% of all A/B style guitar amps use a circuit that splits the phase inverter duties utilizing both triodes in this tube. We get questioned quite a bit on the subject of balanced PI tubes so I’ll elaborate a little. I use to be a real skeptic on this one because most PI circuits are not designed to be perfectly balanced. Ah ha!!! Say what? So it’s snake oil then?
No, I’ll explain. Most all circuits using long tail phase inverters are designed with a slight amount of asymmetry. The reason for this is because when both sides are dead on, the amp will sound a bit sterile and be missing that bit of 3D swirl that makes a tube amp sound alive. This is also the case with a way out of balance circuit, it will sound sterile and certain frequencies will suffer from phase cancellation.
Logic says (I’m a big fan of logic and common sense) then why balance the current on an imperfect circuit? The short answer is, to get the result the designer wanted, but I’ll go further into this. When I acquired the test equipment to check for balanced triodes I started stuffing balanced tubes in everything I have to see if there was a real difference or if it was snake oil. The results? In some amps it was nothing short of amazing and in others it was noticeable but not jaw dropping.
A good friend of mine who has a Marshall 6100 30th anniversary, (one of those amps I just love to hate, I call it the little Blue bastard), had fought getting a good tone with it for years so he brought it back in a few months after we started using balanced PI tubes and when we changed the PI tube for a balanced tube we both were astounded at the change. The amp simply went from so-so at best to, holy crap, is that the same amp!!
So, morale of the story? It’s just like the old argument that a rectifier tube does not change the tone of an amp because it’s not directly in the tone circuit. This of course is completely false and anyone who has ever done an A/B and compared a chinese, a sovtek, a JJ and different NOS rectifier tubes will tell you there is an amazing difference in dynamics and tone. A good balanced PI tube does make a difference and it’s not snake oil. All you need is a pair of ears to hear the difference.
You will still find a lot of skepticism and bad press from the "nay Sayers" on the benefits of using balanced PI tubes. The only question I would ask them is "have you personally had experience in listening to the difference between balanced and unbalanced PI tubes in different amps?" Oh, and request an honest answer when posing the question.

diesel king

Cuz he wants your money and likes to talk shit

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Tbonerocks80s

Well the part about using a balanced tube to retain the natural unbalance of the circuit created by the designer kinda makes sense. But trying other tubes to see what sounds better is the thing to do.

Ken

You answered your own question: you heard no difference.

I've never had a balanced PI so I souldn't have posted the unbalanced sounds better although lots of people whom I respect have said that, and had pretty good data to back it up. Something about even and odd harmonics.

Eurotubes has a reputation of putting business ahead of sound advice. This is but one example.

Ken

__________________
1999 Marshall DSL 50
Music Man 65 Reverb late 1970's (?)
Late 1970's (?) Fender Champ
Marshall battery amp
1980 Model 1982A 4x12 cabinet G12H-80's 444 cones
1983 Model 1982B 4x12 cabinet G12-80's 444 cones
PRO 4x12 from the 1970's
Woodson 2x12
1976 Les Paul Standard
Epiphone Les Paul knockoff
ESP Lawsuit Explorer
1979 Chiquita Travel Guitar
1995 Taylor 310

GIBSON67

In most cases the PI tube will work the hardest, so if people didn't change it as often as their power tubes, then a change to a balanced NEW tube would make a huge difference.

I read where harp players prefer grossly unbalanced PI tubes for more power tube distortion, and that's why some use a 12DW7, which has one triode equal to a 12AX7 and one triode equal to a 12AU7. I think I read that from one of Marty's posts.

Try to read through the Preamp tube thread, there's some great insight in there.

Jason77

To be fair, its not just Eurotubes. almost every online dealer says it. But I completely agree... the pi tube does not need to be balanced.

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LBKENNEDY

just in case you done know i think marty posted a flow path and tube position
descriptor, and that knowledge is beneficial, personally i dont worry
about modifying my amp for tonal and most envelope issues. i use a very
few external devices. when i first started playing with a marshall, i had
a cat in a music store tell me that i should keep it as simple as possible
because if you center your personal tone through too many externals,
any single failure could ruin your evening. same thing with a modified
amp. having said that, just be careful and enjoy happy trails lbk