6L6 vs 5881 Tubes?

Len Amaral · From: Rehoboth,MA 02769

I may replace the power tubes in my Fender PA 100 head.
Currently, this amp has four 6L6 power tubes. The 5881 power tube is an exact replacement for the 6L6 tubes. Is there a difference in tone with the 5881 tubes or should I go with the standard 6L6?
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I survived the sixties!

Carl Gallagher · From: New York, USA

Fist, a 5881 is not necessarily a direct replacement.The 6L6 has a number of variants,6L6, 6L6G, 6L6GB all of which are 19 watt tubes.Most modern amps are designed to use a 6L6GC, another variant that is a 30 watt tube.I assume your PA head uses the 6L6GC.If you use a "standard 6L6" as you called it or any of the earlier variants I mentioned they will not last and may blow on the first chord.Now a 5881 was an industrial version that is a 23 watt tube.It can be used as a sub for any of the 19 watt 6L6's but not the 6L6GC.To further confuse things, modern, current production 5881's like the Sovtek 5881 are 30 watt tubes,IMO just a 6L6GC labeled 5881.Bottom line is you should use a 6L6GC or a current production 5881 but DO NOT use any old stock 5881's or any of the 19 watt 6L6 variants.Another issue is bias,whenever you change power tubes the bias should be checked and adjusted if necessary to make sure they are in the right range.

Fred · From: Amesbury, MA

Another consideration is a 6L6GC has higher max plate voltage rating than a real 5881 and those 100 watt heads run at a really high voltage. If I remember remember right they exceed the max rating of the 6L6GC.

I wouldnâ€™t run a real 5881 in that amp. A modern one thatâ€™s probably a 6L6 in a different shaped bottle may survive.

Fred

Carl Gallagher · From: New York, USA

While it is a consideration,voltage is not a deal breaker.Most guitar amps run the power tubes well over the max ratings as far as voltage goes.For example, the Fender BF Deluxe runs the 6V6's at over 400 vdc on the plate with no problems.The max rating is 350 vdc for the 6V6.It will be a bigger problem if you run the plate current too high.There are problems with voltage with some current production tubes but old stock tubes are much hardier and can take the abuse.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

The 5881 will likely distort faster than a 6L6GC, so if you want a grittier or dirtier sound you can give them a try. But I'd rather get those sounds from a smaller amp that I could overdrive, or a stomp-box. That PA-design head just doesn't have the right tone network to be a versatile guitar amp, IMHO.

Tone controls are everything in a guitar or steel amp.

Carl Gallagher · From: New York, USA

A 100 watt PA isnt going to give up very much in the way of distortion.Like a hi-fi it is designed to give the cleanest lo distortion sound reproduction.Guitar amps are a different animal.Tone controls? They load down the signal by attenuating certain frequencies.If you want grit and distortion its better to do away with the tone controls,ala the Tweed Champ,compare one to a BF or SF Champ and you'll see what I mean.I have done a mod on Champs that is a switch that lifts the ground on the tone stack and basically eliminates the tone circuit.Players I've done it for tell me they no longer use the switch to re-connect the tone circuit.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Microphones have a far lower output than guitar pickups, so getting some decent guitar distortion with a PA won't be a problem if you keep the channel volume at max and the master low. I know some lead players like distortion or crunch sounds with no (or minimal) tone circuitry, but I have several amps in the 5 to15 watt category, and the all have bass-mid-treble controls. I can't stand being stuck with only one amp tone, no matter how creamy or smooth the distortion is.

Different strokes, et cÃ©tera. Cool

Carl Gallagher · From: New York, USA

Different strokes for sure.Tone is totally subjective.

Len Amaral · From: Rehoboth,MA 02769

Thanks all for the input. Iâ€™ll pick up a matched quad of 6L6 tubes. This amp actually sounds very nice as a guitar head. The are 2 tone controls in each of the 4 channels. Bass and treble with a +/- with dials at noon. Great Reverb also. I have one power tube that started glowing red/orange so I will replace them and bias the amp.
_________________
I survived the sixties!

Carl Gallagher · From: New York, USA

6L6GC.I wouldnt use the amp with that tube red plating.That tube is drawing way too much current and will blow and possibly take other components with it.

Len Amaral · From: Rehoboth,MA 02769

Thank Carl, When I noticed the tube glowing I shut the amp down and have not used it. Amps have come and gone but this one is a keeper.
_________________
I survived the sixties!

Donny Hinson · From: Glen Burnie, Md. U.S.A.

This amp has a power section like a Twin, and if you're at a gig and one of the tubes starts to "red plate" (bias problem caused by a bad tube or component), remember that the amp will still work (albeit at reduced power) if you pull either the two outside 6L6's, or the two inside ones. This also changes the output impedance, but it's nothing the OT can't handle.

This little trick got me through a couple of gigs when one tube had shorted. Wink

Mike Scaggs · From: Nashville, TN

Len Amaral · From: Rehoboth,MA 02769

I replaced the 6L6 tubes in the Fender PA 100 with a matched quad and biased the amp. All is well and and it sounds wonderful. About 6 years ago I had the filter caps replaced and serviced. This amp will outlive me Smile

_________________
I survived the sixties!

Tom Gorr · From: Three Hills, Alberta

I run Tungsol RI's 5881s in my main guitar amp. My favorite guitar tones but expect they'd be too mushy on the bottom end for steel.

JJ has some 5881s I played through a SF Twin once - also stellar tone for a Tele. Don't think they'd be as mushy as the Tungsols.

As above - research plate voltages - 5881's are rated at 400V afaik. JJ's might be rated higher.

Carl Gallagher · From: New York, USA

Those are not true 5881's.The "tung sol RI's" are made by Sovetek not really reissues at all.Should call them relabels not reissues since they are just relabeled Sovetek 6L6GC's.JJ's are also just relabeled Czech 6L6's.Both are spec'd as 6L6Gc's

Tom Gorr · From: Three Hills, Alberta

Carl Gallagher · From: New York, USA

"moreso than any other manufacturer including TAD."Just an fyi, TAD is a distributor, not a manufacturer.There are only 3 factories that make tubes,one in Russia, one in Czech, and one in China.All current production tubes come out of these factories.Tubes made today are made to much looser tolerances and do not last nearly as long as the old ones.They have to have a built in obsolescence in order to be profitable, there just isnt a big enough market today and environmental concerns makes it a very expensive process.Back in the day manufacturers would often run production of a particular tube for other manufacturers so they could fill an order without retooling in the middle of a run, tolerances were that tight.You could replace any brand with any other brand and the current draw would be the same.Today you see a lot of marketing schemes.Take GT for instance.They rated and marked tubes for current draw and "break up", soft, hard etc.This is merely to allow them to sell tubes that in the old days would have been rejected for being "out of spec".I have been involved in tube gear since the 60's when I worked in a TV repair shop in order to learn about guitar amps.I have been amassing old stock tubes since thew mid 80's and currently have a couple hundred various brands on hand.I can tell you none of the "re-issues" come anywhere near the real ones.I wont use any current production tubes, I would use a used old stock over a current production every time, and it will far outlast the new one and sound much better.Before production was stopped in the USA and most of Europe power tubes didnt really need to be biased as they came out of the box with a specific current draw and you could rely on them to perform to spec.Not with todays tubes, tolerances are all over the place.

Tom Gorr · From: Three Hills, Alberta

Carl Gallagher · From: New York, USA

First it is/was not my intention to lecture anybody,sorry if you took it that way,just stating facts.If TAD says TAD has many proprietary designs and contracts out manufacture of their designs to which they retain exclusive rights due to design propriety.
Its my opinion that this is pure marketing hype.They're saying they have improved tube production over what RCA, Mullard, etc did in the golden age?I hardly think so.Then why dont today's tubes outlast NOS or even used old stock.Look, tone is a totally subjective matter.If you think a certain tube sound good,that is all that matters.

Tom Gorr · From: Three Hills, Alberta

You might be stating facts but they are being applied in a manner that is far over-generalized.

Yes, there are rebranders and there are manufacturer's "stock" designs and then there are proprietary designs
with specific tonal signatures. Whether or not they are all manufactured in the same plant or not - they are made to sound different for all the reasons tubes can be made to sound different.

And opinions on the inferiority of modern tubes might speak to their useful life - but not to the quality of tone. There are some fabulous "flavours" of tubes being made today.

As a branded group, my personal favorite "flavours" come from the Tungsol RI line - 6v6's, EL34B and 5881 - all fantastic and the Tungsol RI is not rebranded by Mesa Ruby or Fender/ Groovetubes.

I think the general consensus in the guitarist cork sniffer world is that TAD has the best sounding 6L6 tubes. Their 6L6WGB and 6L6GC. Those are not rebranded by anyone else that I can determine. Whereas a Sovtek 6L6WXT is.

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