Balanced tubes

[Nelg]

What are "balanced" tubes? For Mesas, do all the tubes in all positions need to be balanced?

 

[stokes]

I assume you are refering to balanced triodes,such as a 12AX7 type.There is a school of thought that they perform better in the phase inverter position.They are selected by testing the two triodes and using tubes that both triodes have the same gm or transconductance.In a push-pull power output the idea is that they will drive both halves of the out put symetrically.If it is beneficial at all it would only be so in the phase inverter position.Dont want to open a can of worms here but I wouldnt pay extra for a "balanced triode" for a guitar amp,maybe for Hi-Fi but I dont think a guitar amp needs to be that precise.

 

[Dale B.]

Exactly! Most of the Class A/B guitar amplifiers on the market have a long-tail phase inverter design in their circuits. That means that both sides of the circuitry aren't matched to begin with.

 

[stokes]

Not to mention the fact that most PP OT's dont match exactly from center tap to either side.Simple check with an ohmmeter will show that.And just about all the components are +/- 5 to 20% in a tube amp,and may drift further apart when heat is applied.

 

[Nelg]

So what is all this about Mesa claiming that it's blasphemy and the earth's going to abruptly stop spinning and we'll all be flung into space to use other tubes besides their own because their tubes are specially biased or something like that?

 

[stokes]

They are refering to power tubes.They prematch and grade the tubes they sell so they fall into a certain bias range in their amps.You can use any tube in a Mesa if you can check the bias and adjust if it needs to be.

 

[fatboy135]

Dont want to open a can of worms here but I wouldnt pay extra for a "balanced triode" for a guitar amp,maybe for Hi-Fi but I dont think a guitar amp needs to be that precise.

You open pandora´s box :lol:
Ok being serious the balanced triodes is just a taste matter and your mind goals, for example if you want a better clean tone go for the balance tube, if you want a rude overdrive gets a non balanced tube, the non balanced tube causes an special kind of square saturation with an odd harmonic full richness. Tubes usually generates less odd harmonics, we know that odd harmonics is directly related with the psychoacoustic effect of rough, or rude tone, more distorted in electronics terms, so if you play jazzy tones go for a balanced tube, if you play pantera style go for a non balanced tube, and if you plays like santana, better switch off your amp and go to the cinema :lol:

 

[stokes]

Okay although I do somewhat agree with fatboys analogy to a point, I dont think simply a balanced PI tube is going to make that drastic a distortion difference by itself.You can get very nice clean tones with unbalanced tubes.In Fenders heyday the amps were considered the best clean tone out there and nobody even heard of balanced triodes.Just dont overdrive the rest of the circuit.Of course if all the components were 1% tolerance and the OT has a specially wound primary that is balanced then the balanced tube would make sense.But our amps are made with components that are 5-10% tolerance at best (they tend to drift when they get hot) and I have yet to measure an OT that matched from either side of the primary to the CT.But if the balanced triode does it for you then that is what counts,it is all subjective.

 

[fatboy135]

anyway a balanced tube is only 3 euros more, you will not enrich with that 3 euros I recommend like in other cases just to test by yourself, if we were talking about a bogner or a boogie well it is 3000 dollars but a balanced tube is only 3 euros more, don´t be afraid for the balanced triodes issue, just enjoy your guitar

 

[alejandro]

... and if you plays like santana, better switch off your amp and go to the cinema :lol:

I just opened up Pandora's Box in your general direction! Prepare for the doom of your crops! Your baby seals will be given Ecstasy and clubbed!

 

[fatboy135]

I never surrender to the dark force of santana :twisted: