Help Understanding Tube Types

CSS · September 4th, 2007, 10:46 PM

Help me understand something. If a set of tubes are sold as "matching", does this mean the bias would not have to be changed on the amp? Also, I read where Groove Tubes, as long as the color codes are the same, the bias would not have to be adjusted.

I saw where some Mfg's have matched sets of 4. Well, my amp has 6 12AX7WC's. I guess I would order two sets of 4 and have a couple spares. Also, 2 12AT7's and 2 6L6GC's.

Oh yeah, is a 12AX7WC the same as a 12AX7 ?

Sorry for the newbie tube questions but I gotta know!

Westerly Sunn · September 5th, 2007, 03:40 AM

Quote:

Originally Posted by CSS

Help me understand something. If a set of tubes are sold as "matching", does this mean the bias would not have to be changed on the amp? No.

Also, I read where Groove Tubes, as long as the color codes are the same, the bias would not have to be adjusted. You can get away without adjusting the bias when you change tubes if the bias was previously adjusted for a set of "groove tubes" of that same "code"

I saw where some Mfg's have matched sets of 4. Well, my amp has 6 12AX7WC's. I guess I would order two sets of 4 and have a couple spares. Also, 2 12AT7's and 2 6L6GC's. The 6L6's are your power tubes... If you get "Matched" tubes, it would be these you'd get as a matched pair... What is important is that you get the amp re-biased for these when you change them. All those 12AX7 and 12AT7 do not need to be matched nor do you need to re-bias when changing them.

Oh yeah, is a 12AX7WC the same as a 12AX7 ? They are the same basic tube type and are interchangeble.

Sorry for the newbie tube questions but I gotta know!

Get referrals for a good tech in your area to service your amp.

Jef · September 5th, 2007, 04:34 AM

Matched sets are important for the power tubes in push pull amps only (amps with two power tubes or two pairs of power tubes: 6V6, 6L6, EL84, EL34 etc... Those are sold in matched paires or quartets.
Whether your amp has to be biased or not doen't really depend of the tubes being matched or not. If the bias of the power tubes in your amp is adjustable, I'd have it biased.
Preamp tubes (usually the small 9-pin 12A_7 or ECC8_ types) are sometimes sold as "matched" too. Those preamp tubes have usually two triodes inside one envelope. In some tubes both triodes are specially matched. Some people think this is important for the phase inverter tube but IMHO it doesn(t matter for a guitar amp. Preamp tubes also don't need to be biased.

CSS · September 5th, 2007, 09:23 PM

Thank you guys. I think I have it now. Can ya tell this is my "first" tube amp?

-Craig

JohnnyCrash · September 5th, 2007, 10:28 PM

If you buy tubes from the same place, they can match them to your previous set (like the color coding you mentioned earlier). In this case you wouldn't need to rebias.

Otherwise, you'll have to have any new power tubes rebiased... if they are not marked or bought from a different vendor.

Preamp tubes don't need biasing at all (too technical to explain, but they are just plug-and-play). 12A*7 type tubes (12AT7, 12AX7, 12AY7, etc) are all plug-and-play.

September 4th, 2007, 10:46 PM	#1 (permalink)
CSS Tele-Holic Join Date: May 2003 Location: Myrtle Beach, SC and Augusta, GA Age: 49 Posts: 832 25 Photos	Help Understanding Tube Types Help me understand something. If a set of tubes are sold as "matching", does this mean the bias would not have to be changed on the amp? Also, I read where Groove Tubes, as long as the color codes are the same, the bias would not have to be adjusted. I saw where some Mfg's have matched sets of 4. Well, my amp has 6 12AX7WC's. I guess I would order two sets of 4 and have a couple spares. Also, 2 12AT7's and 2 6L6GC's. Oh yeah, is a 12AX7WC the same as a 12AX7 ? Sorry for the newbie tube questions but I gotta know! __________________ "The only difference between me and the audience is the microphone" -John Waite

September 5th, 2007, 04:34 AM	#3 (permalink)
Jef Tele-Holic Join Date: Mar 2003 Location: Antwerp, Belgium Posts: 673 1 Photos	Matched sets are important for the power tubes in push pull amps only (amps with two power tubes or two pairs of power tubes: 6V6, 6L6, EL84, EL34 etc... Those are sold in matched paires or quartets. Whether your amp has to be biased or not doen't really depend of the tubes being matched or not. If the bias of the power tubes in your amp is adjustable, I'd have it biased. Preamp tubes (usually the small 9-pin 12A_7 or ECC8_ types) are sometimes sold as "matched" too. Those preamp tubes have usually two triodes inside one envelope. In some tubes both triodes are specially matched. Some people think this is important for the phase inverter tube but IMHO it doesn(t matter for a guitar amp. Preamp tubes also don't need to be biased. __________________ Amplification is not a social dinner, a literary event, a drawing or an embroidery; It cannot be done with elegance and courtesy. Amplification is an act of violence... (Mao Tse-Tube)

September 5th, 2007, 09:23 PM	#4 (permalink)
CSS Tele-Holic Join Date: May 2003 Location: Myrtle Beach, SC and Augusta, GA Age: 49 Posts: 832 25 Photos	Thank you guys. I think I have it now. Can ya tell this is my "first" tube amp? -Craig __________________ "The only difference between me and the audience is the microphone" -John Waite

September 5th, 2007, 10:28 PM	#5 (permalink)
JohnnyCrash Poster Extraordinaire Join Date: Mar 2005 Location: Lost Angeles and Orange County Posts: 7,128	If you buy tubes from the same place, they can match them to your previous set (like the color coding you mentioned earlier). In this case you wouldn't need to rebias. Otherwise, you'll have to have any new power tubes rebiased... if they are not marked or bought from a different vendor. Preamp tubes don't need biasing at all (too technical to explain, but they are just plug-and-play). 12A*7 type tubes (12AT7, 12AX7, 12AY7, etc) are all plug-and-play.