Tube substitution question

[guitaraddict]

Hello all. I have a chance to get 4 5881 nos tubes and was wanting to use them in one of two amps. The amps are a Earth pa2000 and a Peavey vtm120. The plate voltages listed on the schematics are 410 for the Peavey and 460 for the Earth. Will these tubes hold up? I have doubts because of the rating for the tubes is 400 I believe, although it makes a difference with the rectifier. Tube rectifiers will handle the difference but solid state may burn them up prematurely? Anyone have experience with this? Going to get them regardless because I am trading some extra speakers for them but looking to find a use for them. Thanks in advance, David.

[Gtr_tech]

If the tubes you want to get are NOS Tung Sol (or similar) "real" 5881s, don't get them anywhere near those amps. They are not interchangable with a 6L6GC, and you'll roast them in short order.

Mike Matthews should be shot for calling those Sovtek 6L6 replacements a 5881. This causes more confusion than I can deal with sometimes. If I have another kid walk thru the door with a 5150 and Tung Sol reissue 5881s in his hand I'm gonna have to go postal at the EH offices.....

[guitaraddict]

Thanks

Thaks for the response. I will find a use eventually.

[MWJB]

NOS Tung Sols will take the voltages in your amps just fine. Virtually all popular guitar amps (if not ALL) run their tubes over the data sheet voltage specs. Even when the 5F6A and 6G12 were new, before wall voltages increased, these amps used Tung Sol 5881. Excess current wil kill them, but voltages found in 6L6 guitar amps will not.

Bias around 15W per tube and you'll be safe as houses (they have been run at 35mA per tube in bassmans for years, a little over 16W).

As with any old/NOS tubes be sure that they are not just unmatched, untested pulls from old amps, they should come in appropriate boxes...otherwise they are worthless, unless you enjoy the odd gamble.

[Gtr_tech]

I don't recommend this. The bias circuit in a PV VTM is not adjustable, and they run a plate supply of around 525 IIRC with 100 ohm screen Rs. No fricken way 5881s will hang in that.....

The Earth should have a bias adjust. I don't know the plate supply in that, but since they were Twin knockoffs I'd expect 460-480. Still not worth the risk of torching them....

NOS Tung Sol 5881s are worth some serious cash and are sought after by the tweed bassman and hifi crowds. I would just sell them and get them in the hands of someone who *needs* them. You'll make enough money to buy a few sets of current production 6L6s that your amps were designed to use. And....you won't potentially wreck old stock tubes that ain't gettin' any easier to find.....

[MWJB]

"460-480" & "NOS Tung Sol 5881s are worth some serious cash and are sought after by the tweed bassman and hifi crowds".

Hmmm...460-480 is what tweed bassmans run. They are only worth serious cash when literally new in box & matched...used pulls are worth nothing, like all old knackered tubes.

[guitaraddict]

Thanks Gtr_tech and MWJB. You are right about the Earth, it shows 460 on the schematic. I dont need to replace the tubes on either was just curious. These 5881s are old, but still new in the original boxes. I dont have them in hand but the guy I am getting them from is both honest and an electrical repair guy with many amp repairs under his belt....so no reason to doubt him. I just thought I would ask. He also said that he thought the voltages may be high. Just a friendly trade, some old alnico speakers for some nos tubes. I have a surplus of speakers, he of tubes. I will find a use for them that seems more comfortable. Maybe its time to do my first amp build......hmmmmmmmm. Thanks again for the replies. David. P.S. He also has some older matal 6l6s but thes appear to be at 400 volts when new.