# Ordering tubes, a question...



## sulphur (Jun 2, 2011)

I'm looking at a set of tube from the TubeStore.
They offer an option for most of the tubes, "Matched Triodes (balanced)",
for a $5 upcharge for each tube that it's available for.

What's that about and is it worth that bit extra?


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## sulphur (Jun 2, 2011)

Google is my friend, it's on the same site!

http://www.thetubestore.com/Resources/Matching-and-other-tube-info/Matched-Sections-Service

I still have to ask if it's worth it though.


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## vadsy (Dec 2, 2010)

I was taught it is important to have a balanced phase inverter tube for Class A-B push pull operating amps. I hope it's true because I've gone out of my way to make sure this is the case in my gear. Some of the more knowledgable guys on here would know more on this and hopefully chime in. The one thing I can say I've noticed from personal experience is when I've put in a balanced phase inverter the amp always sits quieter at idle.


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## dcole (Oct 8, 2008)

Things that are taught in school are different then practice for the guitar world. Your amp at idle would be quieter because any common mode noise in the phase inverter is better cancelled out the more balanced it is. The things that are taught in school are usually meant for high quality audio and instrumentation applications where high S/N is required and low distortion. We as guitar players like a good S/N ratio as well but generally crave distortion in our signal chain to add character to the guitar.

When it comes to getting balanced tubes or not, I say its your choice. With the power tubes its a better idea to have them matched for a dc bias current as you don't want the mismatched currents to saturate your transformer. True matching would also include the ac parameters but you may or may not like the tone difference between the two. 

Basically what I am saying is audio guys may think the balanced triode option brings them benefits but the guitar guys may not notice benefits.



vadsy said:


> I was taught it is important to have a balanced phase inverter tube for Class A-B push pull operating amps. I hope it's true because I've gone out of my way to make sure this is the case in my gear. Some of the more knowledgable guys on here would know more on this and hopefully chime in. The one thing I can say I've noticed from personal experience is when I've put in a balanced phase inverter the amp always sits quieter at idle.


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## sulphur (Jun 2, 2011)

I understand the matching of the power tubes, I just hadn't heard of the balancing of the others.

If it helps keep the amp quieter, I'm all for that.
It's not a tone thing I'm after here, I was just wondering.


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## nonreverb (Sep 19, 2006)

Don't get too worried about perfect balancing in the Phase inverter. The phase inverter biasing on your typical guitar amp is not perfect anyways. There are instances where a an imbalance can occur but it's usually due to a PI tube fault. As stated, the power tube balance is the more important consideration.


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## GTmaker (Apr 24, 2006)

I'm by no means an expert in this amp thing BUT this is my take.
If you have more them one power tube , and most likely ONE pot to adjust the bias, then I think its impostant for the pawer tubes to be
ballanced so that when you set the bias point, both tubes will be in the same bias ballpark.

That makes sense to me untill I'm convinced otherwise.

G.


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## sulphur (Jun 2, 2011)

It's a single ended, class A cathode bias amp, or fixed bias.
No adjustment needed, just change the tubes.

I ordered three packages from the TubeStore, yet all of the packages showed as zeros in the cash out area.
Weird. I wonder what that will do to the order, we'll see.


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## Church-Audio (Sep 27, 2014)

A balanced phase inverter is not that important. For reasons already stated by some and a few more I can think of. I can't remember when the last time I saw a balanced output transformer. Two all the parts like grid stoppers and screen resistors are not matched further throwing an amp out of balance. So if it does not cost extra sure get it but if it does don't bother. I do believe in matched power tubes only so bias draw is about the same and therefor you don't get premature failure of a single tube but that rarely happens the other reason is so that all tubes in the output section are sharing the work load. That being said it never happens that way for other reasons I have mentioned.


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## dtsaudio (Apr 15, 2009)

> It's a single ended, class A cathode bias amp, or fixed bias.


Single ended, you don't need matched triodes. There's also no phase inverter. So again you don't need matched triodes.
Cathode bias and fixed bias are two different things. Fixed bias is where you need to adjust bias when changing tubes. Cathode bias you have no adjustment necessary.


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## Church-Audio (Sep 27, 2014)

I should have read the first post  yes single ended does not have a phase inverter. Even cathode biased amps should be checked for excessive current draw case in point the fender champ cathode resistor on early blackface and silver face is way to hot for today's 6v6s.. This is what I use to check chathode bias circuits and to bias amps. Great little calculator. 
http://www.webervst.com/tubes1/calcbias.htm


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