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station5343's picture
May 2009
2 years ago

Hi everybody,

I need to change my power tubes and I have a quad of sovtek 6L6'S but they are unmatched can I still use them? Also when biasing them will I need to bias each one individually because they are unmatched. Any advice anyone can offer will be appretiated.

Supergrunged's picture
Saco, ME
Feb 2005
1 year ago

Question is, how unmatched are they??? Is it two sets, or just individuals? Most high wattage amps are push pull, so you can get away with mismatched, as long as they're in sets. Also, what amp? I don't see how you could bias each tube.....

Gibson Les Paul Standard that's been to hell and back with me, Charvel Model 6 modded to a 5FX, tortex wedge picks, Maxon OD-9, 80's Ibanez AD-9, Mesa Stuido .22 probably other stuff off my shelf
 

Quote:
Originally Posted by jonny-b-brown
strats. It's like their own form of puberty.

 

station5343's picture
May 2009
2 years ago

Hey Supergrunged,

They are actually 2 sets, sorry I should have said that. I will be using them in a bugera 333. Also am I to understand that once the bias is set for 1 tube that it's set for all 4?

Supergrunged's picture
Saco, ME
Feb 2005
1 year ago

There isn't a screen grid for each tube, they work in sets. Typically, it'll be the two outer tubes are one set, and the two center tubes. There is only one bias pot to my knowledge, some have two for the sets, I've never seen one for each on of them... You can test each set, and find the middle ground for both of them. I'm sorry, I'm not to familiar with that amp.

Just watch out, there's high voltages in the amp that can kill you if you're not careful

Gibson Les Paul Standard that's been to hell and back with me, Charvel Model 6 modded to a 5FX, tortex wedge picks, Maxon OD-9, 80's Ibanez AD-9, Mesa Stuido .22 probably other stuff off my shelf
 

Quote:
Originally Posted by jonny-b-brown
strats. It's like their own form of puberty.

 

olddawg's picture
Southern California & Hawaii usually, but I get around
Dec 2004
2 years ago

The amp will not be damaged unless the tubes are red plating. A lot of people like the sound of mid-matched tubes because of asymmetric clipping. However, the amp may sound different to you because of that or because the tubes are biased a little hot or colder compared to the previous set. If you post an the Ampage site you will probably get a more complete answer from a Bugera authorized tech.

Stage Guitars: '80s Thin line LP Custom, '70 LP Standard, '83 Squier Black Headstock Strat w/ Dan Torres pickups, '59 Black Danelectro DC, sometimes others.

Pedal Board: Nady UHF 10 -> TU2 -> Rocktron Big Crush -> 70s MXR Phase 100 -> Cry Baby -> Bad Monkey -> Early '80s Rat -> Early '80s Ibanez CS 9 -> Ibanez DE 7 -> Behringer Dr 100 Stereo Reverb

Stage amps: '63 Blonde Tremolux w/ two original 2X10 cabinets with a '60 Ampeg Rocket/18 watt VTB Marshall clone/ Epi VJ into a Mashall 1965A

trem's picture
USA CA Fairfield
Jul 2009
2 years ago

Are you still dealing with this.?
Have you ever biased an amp before.?

station5343's picture
May 2009
2 years ago

Hello again everyone,

In reference to my post on biasing an amp and using unmatched power tubes. Is it safe to do this? Say for example 2 sets of 6L6'S one set with a plate voltage reading of 23.0 and the other 36.0 would it be ok to set the bias the same for both sets? If anyone who reads this knows the answer please feel free to post a reply...thanks.

trem's picture
USA CA Fairfield
Jul 2009
2 years ago
Originally Posted by station5343

Hello again everyone,

In reference to my post on biasing an amp and using unmatched power tubes. Is it safe to do this? Say for example 2 sets of 6L6'S one set with a plate voltage reading of 23.0 and the other 36.0 would it be ok to set the bias the same for both sets? If anyone who reads this knows the answer please feel free to post a reply...thanks.

How are you going to do that.?
Does your amp have dual bias.?
If so.....
If one pair runs at 23mA and the other at 36mA (not Volts you say) then they ARE matched.
Run one set together and the other together. That is, put one pair in the Inside/Outside position, and the other pair in the opposite.
best

station5343's picture
May 2009
2 years ago

Thanks trem,

That makes sense, so my next question is what about using individuals that aren't in sets? Olddawg posted a reply saying that it can be done as long as the tubes dont red plate. How do I keep the tubes from red plating?
Thanks

Supergrunged's picture
Saco, ME
Feb 2005
1 year ago

Keep the voltage down.... You don't want to cook your tubes..... Basically it's ohms law, if you're not familiar with Ohms law, I don't recommend even attempting it. Yea, there's a knob on the outside of the chassis to adjust it, with a place to put your probes, just like a 5150 II.... I still don't trust these things. You need to know the power, which is measured in watts..... So you have a 100 watt rated amp, you want to bias the tubes for 70 watts, that would be 70 percent, and they should last you for a couple years. The equation is P=I R, so if you know the resistance of the tube, and you know the wattage you need, all you need to figure out is the amperage you need to set the tubes for.

It's a fun process, and if you're familiar with electronics, resisitive loads, the basics of all components, I say try it. If you're just trying to save a buck by buying a multimeter, and thinking the probes on the back do the work, look into sending the amp to a tech to get it biased properly

Gibson Les Paul Standard that's been to hell and back with me, Charvel Model 6 modded to a 5FX, tortex wedge picks, Maxon OD-9, 80's Ibanez AD-9, Mesa Stuido .22 probably other stuff off my shelf
 

Quote:
Originally Posted by jonny-b-brown
strats. It's like their own form of puberty.

 

trem's picture
USA CA Fairfield
Jul 2009
2 years ago
Originally Posted by station5343

Thanks trem,

That makes sense, so my next question is what about using individuals that aren't in sets? Olddawg posted a reply saying that it can be done as long as the tubes dont red plate. How do I keep the tubes from red plating?
Thanks

Seriously.?
At your level of understanding......
Just buy a quad of matched tubes. Why the question about 4 un-matched power tubes. I thought you had two matched pairs with a dual bias amp.?
Good Luck