Do tubes always need to be matched?

[playas]

...or just for push-pull?

Eg. The laney lionhearts have the tubes wired in parallel as against push-pull - not that I am very au fait with amp innards you understand - but in any case, can they be unmatched without any problems in that case, or do all need to be matched?

Purely curiosity...for now.

 

[GuitarStv]

They don't need to be matched for push-pull . . . only if they use the same resistor to set bias (then you want tubes that can be biased by the same value). And even then, perfectly matched tubes drift once you start using them so amps tend to be pretty forgiving of mismatches.

I don't think tube matching is really a big deal for most people.

 

[playas]

So buying matched pairs, cuads...it's really all a load of b***ocks?

Didn't realize that.

 

[formula73]

So buying matched pairs, cuads...it's really all a load of b***ocks?

Didn't realize that.

Yep

 

[dave74]

Well if they start way off and drift even more then it's even less ideal. I'd buy matched if possible.

 

[JMP/HBE]

mismatched tubes are NOISEY. So if you like amps that hum loud buy mismatched POS tubes.
Kinda like balancing your tires you don't have to balance your tires but its soo much nicer.
For the record nothing has to be "always" anything.

 

[GuitarStv]

mismatched tubes are NOISEY.

This is true if the mismatch is extreme. In my experience it's not usually true if the tubes aren't way off spec from each other. And the matched tubes tend to drift under use anyway, so once your amp heats up for a bit you're probably running a mismatch regardless of what you bought.

Although, I don't usually play with massive amounts of power tube distortion . . . so maybe it makes more difference for those who do.

 

[idsnowdog]

The idea that all need to be replaced at the same time is bogus. However, a tech should test the tubes to see if they fall within specifications to get the best performance. If they are out of spec replace some or all.

 

[hamerfan]

I think it's much more a hi-fi thing. If you buy a 10,000 bucks valve amp you might have some cash for selected and matched tubes.
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[Hank-]

If it's adjustable bias for each tube then it's not big deal, buy any and set the bias per tube. If it like 4 power tubes sharing one bias adjustment then best to buy matched sets because when I bought power tubes for my fixed adjustable bias amp, the rating affected the plate voltage which then changed the bias current, so one tube would run much hotter than the other and burn out quicker if extremely unmatched pair.

 

[JMP/HBE]

Those who bias their own and have ever had power tubes NOT bias in the proper range because the tube Z is all over the map know the benefit of a good matched pair or quad and why wouldn't anyone NOT want good matched tubes especially the crap they make theses days.

 

[idsnowdog]

Those who bias their own and have ever had power tubes NOT bias in the proper range because the tube Z is all over the map know the benefit of a good matched pair or quad and why wouldn't anyone NOT want good matched tubes especially the crap they make theses days.

Every tube should be tested whether new or old. I wouldn't count on a "matched set" from anyone being perfect.

 

[JMP/HBE]

Every tube should be tested whether new or old. I wouldn't count on a "matched set" from anyone being perfect.

Thats why its important to have a tube vendor you trust.

 

[El Dunco]

My adjustable amps have 2 bias controls, one per pair.

 

[playas]

The amp in question that piqued my curiosity is cathode biased - not that that means anything to me I'm afraid.

Laney Lionheart L20H, it has 4 el-84s in parallel and they are cathode biased apparently.

 

[Ascension]

Thats why its important to have a tube vendor you trust.

Bingo! For power tubes i always buy at least a matched pair if not a quad for an amp that runs a pair so I have spares. Key to not seeing bias drift is to buy from a reputable vendor who not only matches but also burns in tubes. Unless a amp has individual bias pots for each tube it's the only way to get a proper bias. It's much more critical in particular if you have an amp with a fixed bias like many Boogies and Carvins for examples.
Tube amp audiophiles in particular are really picky on this because of crossover distortion. It's not expensive to buy matched sets of power tubes only a couple bucks more most of the time so just makes sense.