BK Butler Tube Amps? CLOSE PLEASE

Jerry Overstreet · From: Louisville Ky

I have this TubeWorks 50/50 valve rack amp. I would say it's a dual mono amp v. stereo. I want to replace the 2 output tubes in one side to match the same type of original tubes in the other side.

They just have 6L6GC and the Tube Works name printed on them along with made in China.

The only tube I can find that look like those are Tung Sol STR "Clear Top". Does anyone know what type and mfg. of tubes BK Butler installed in these amps?

I'm looking for the most headroom, cleanest, loudest Fender type tube tone vs. metal or rock.

I'd really like to find the same type tube since it was what was installed at the factory.

Dave Meis · From: Olympic Peninsula, Washington, USA

While I can't answer your primary question (who made the originals), I can say that I've had good luck with the Tung-Sol STRs in all of my Fenders that use 6L6s...

Larry Dering · From: Missouri, USA

With the current tube manufacturing situation you may have trouble finding tube period. And the price has skyrocket since the war in Ukraine. I don't know what brand he used. Good luck.

Jerry Overstreet · From: Louisville Ky

I don't know about the big tube scare. Although they are made elsewhere, power tubes are available for sale in just about all types here in the US. They are likely more costly however.

I've seen Apex matched pairs of new 6L6GC priced anywhere from around $80 to $150 depending on the brand, type and seller. I suspect some of these are reissues of former types so I'm not sure about quality etc.

This amp has one cracked lost vacuum tube and the other one in the same side is different. Both of those are 5881 type of some mfg.

I guess it's not all that important, though these are separate pairs in a dual mono config, I just like to keep continuity. My only real experience with tubes is my old Silvertone 1482 6V6 powered amp so I'm pretty green about all the numbers and characteristics and wouldn't mind learning a little something more about them as I go.

Thanks for that helpful info too Dave.

Norman Evans · From: Tennessee

This might be helpful.
https://www.kcanostubes.com/content/fender-amp-preamp-tube-layout-and-recommendations

Jerry Overstreet · From: Louisville Ky

Thanks for that link Norman. Those are preamp tubes though and food for later thought. Right now, I'm interested in Power Tubes.

FWIW, at one seller I find the Tung Sol STR matched pair for about $85. They also have JJs for less than $60 a matched pair.

Are the TS that much better or will the JJs do an equal job at less cost?

Repeating, we're looking for the cleanest sound with the most headroom likely used for pedal steel and sometimes reg. guitar. Thanks for any other tube education anyone can offer.

Bill A. Moore · From: Silver City, New Mexico, USA

I can't say I have a discerning ear,(the VA has me wearing hearing aids), but I use JJ's. I have a matched set of Sventlana in my "Twin" clone, but my other amps sound fine with JJ's!

Jim Kennedy · From: Brentwood California, USA

I have no idea what brand of tubes are "best." What I do suggest is that you get a matched quad set of tubes and replace them all. Then, both sections of the amp will have balanced output.
_________________
ShoBud Pro 1, 75 Tele, 85 Yamaha SA 2000, Fender Cybertwin,

Bob Sigafoos · From: San Clemente, Calif. , U.S.

If the one tube needs replacing get two new tubes for that channel. Which manufacturer? Pull the tube and look for markings to I.D. it. Still not sure? my thinking is who cares. You at worst will have a slightly different sound/texture for each channel now if you have two pairs of different manufactures. Might sound better. If you bridge the two mono sounds into one it might sound great. If this was a HiFi amp I would want all four output tubes to match tho.
Now then, you're going to have to bias the new tube(s) you bought for your amp. This will probably be needed. Time to get your screwdriver out and pop the covering and find an adjusting pot and get your multimeter out. This could be a fun adventure! Does this amp have preamp tubes too? Might want to peek at those if the cover is off also. Preamp tubes usually last way longer than power tubes so I would'nt be too concerned about those if they are part if the circut. Might want to look at the power capacitors too. Yes a can of worms can be had.

Bob Sigafoos · From: San Clemente, Calif. , U.S.

Jerry, there are quite a few dealers that sell tubes. Take a photo and show the dealer what you have. Changing all four sound prudent tho. Your looking at 4 X $45 or more now! Check to see their refund policy. Why? Because there is a infant mortality rate for new tubes even under the best circumstances.

Jerry Overstreet · From: Louisville Ky

Thanks for your input Bob. Yes, I will be replacing both tubes on one section. I haven't decided whether to replace them all....costly as it is.

I'm not the original owner so I don't know the history of the tubes. I just thought I'd like to keep the 2 original tubes, but maybe it would be better to replace them as well since I don't know their age.

This amp doesn't have a bridging switch. Butler's skimpy manual says it requires Y cabling into both inputs and having both speakers connected to the amp.

Neither does the amp have preamp tubes. They use his proprietary driver transformers.

As near as I can find, the amp is self biasing. I haven't pulled the case, but from the photos I found online, I'm not able to locate a bias pot.

Butler had some different ideas with these ProValve tube amps it seems, I've been a big user of Tube Works products for years so I thought I'd give this thing a try too.

I have found some good info on tubes from tubesandmore but still would like to know more about the difference between the STRs that are listed as tetrode tube and the JJs listed as pentode and why the big difference in cost.

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

"Looks" means nothing as far as tubes go. You want tubes to be electrically matched for the best performance, and that can only be determined with test equipment.

What test equipment do you have?

Bob Sigafoos · From: San Clemente, Calif. , U.S.

Perhaps Ken Fox might have some insights on these amps. I've looked on a google search and there is not much info on these. I looked for "Tubeworks owners manual" for a search. I did and am still confused. To further muddy the water sometimes a tube dies because of a component failure upstream of a tube not the tube itself. I'm pretty familiar with Fender amps and HiFi amps and your amp is a different beast.
Self biasing is done with a fixed resistor rather than a vairiable resistance pot think Fender Champ type of design. Hows does this affect you and this amp? I'm shrugging my shoulders right now! How much did you pay for this amp vs how much to repair it might be in your future thoughts. I'd say don't buy any tubes yet get more info from some amp techs.

Jerry Overstreet · From: Louisville Ky

Thanks again Bob. Yeah, I'm still fishing for info. The amp plays fine as is. I don't expect to send it to a tech at this point. I'm not into it for a lot of money. I knew about the blown tube but everything I gathered seemed fine otherwise so I took a small chance.

BK Butler's stuff was really popular in the late 80s and 90s before being sold to Genz Benz. I realize that's not so now, particularly in this community as the products are kind of long in the tooth and getting some information on them can be frustrating.

Before I buy tubes, I am going to swap out the good one into the blown one's socket and see what happens there.

One never knows what to expect from any electronics down the road. The manual is pretty much useless except for the information I posted. There is some spec info disclosed concerning basic stuff and the only tube info just reads 6L6GC X4.

If you are interested, I can PM you an online link to this dinky 3 pg. manual ....provided I can find it again.

Butler had some different ideas with both SS and Tube style amps.

His propaganda states he decided to eliminate the preamp tubes and what he calls a phase splitter [inverter] via the method mentioned earlier.

I can see that the amp is geared for saturation to please tube junkie guitar players but what I can see so far, it's clean sound is going to be sufficient for steel...especially if I join the 2 channels by the method descrbed earlier. Even if not, I'm happy using it for lap, slide and reg guitar.

My reason for wanting to the match replacement tubes toward the existing good ones has nothing to do with aesthetics, rather attempting to match operation....similar electrical values and equalize the 2 channels......especially if combining the 2.

Bob Sigafoos · From: San Clemente, Calif. , U.S.

Jerry, Good idea to swap the good tube into the bad actors socket. Sometimes you can fix stuff by process of elimination. Maybe a dirty tube socket. Don't run the amp too long like that as the lone tube will be getting more voltage and current. Watch for red plating! You'll know that when you see it.

I've already looked at the manuals and brochures online and agree they are useless from a servicing perspective. If you by new tubes don;t pay more for matched tubes. This is a big deal in the HiFi world and not much in the guitar amp world as far as I care. What did we do in 1965 when you blew a tube in your twin reverb? You went to the drug store and tested your tube on the big assed tube tester machine and failed and then pulled a new one out from the cabinet below with no thought of manufacturer or performance rating. I've built a few amps with mis matched tubes and noticed no differance. Maybe my hearing is deficient from working in refineries for years but the mis match could add tonal charactor to the amp. Keep asking questions!

Jerry Overstreet · From: Louisville Ky

Bob, thanks so much for the valuable infromation and presenting it in a kind and calm manner that is understandable to the barely informed. You've been most helpful with me trying to separate the hype from the practical reality.
Been poking around the net too for some info.

I did swap out the tubes temporarily and the bad tube's socket works fine with the other tube, so I'll be looking to buy a tube or 2. I figured as much going in.

Re: matched pairs, every site I've been to only lists them as a single or matched set, or a burned in matched set for which I don't really see a reason.

One reason I was asking about the short bottles, is because of the depth of the case. Since the 5881 is shorter and stamped either/or on the glass as interchangeable that may very well be what's in there. I was just looking for the cleanest type with the most output.

Yeah Buddy, I remember well the old tube testers and servce centers...even the convenience stores had them. Transistors were not around when I was coming up. We had an old battery console radio cabinet that was big as a refrigerator to listen to the Grand Ole Opry. Tubes, guitar strings etc. at the drug store. We might buy just one string and it was marked 1st, 6th etc. We didn't even know the gauge and it just wasn't important to us at the time. My have things how changed.

Jim Kennedy · From: Brentwood California, USA

Go here to read about the difference between 6l6 and 5881 tubes:

https://www.ampvalves.co.uk/5881-6l6gc-valve-differences/
_________________
ShoBud Pro 1, 75 Tele, 85 Yamaha SA 2000, Fender Cybertwin,

Jerry Overstreet · From: Louisville Ky

Thanks Jim. Yes, I saw that. Here's my concern...the 6l6 is rated for 30W dissipation vs. the lower 23W of the 5881, thus the consideration for the more headroom Tung Sol 6L6CG STR clear top which is a shorter bottle like the 5881 and gives me more clearance from the open back rack mount case.

Jim Kennedy · From: Brentwood California, USA

From 23 to 30 watts is not much difference, and I doubt you, or anyone else, will hear it. The big difference comes in how you bias your tubes. The more heavily built 5881 can handle more voltage and current, and can be "under biased," allowing more voltage to flow through the tube, causing the tube to saturate quickly. This is great if you're a hard rocker and want to push your power section hard and reach saturation, and tube type distortion, quickly. If not, find a reliable set, either type, that fits your amp and your needs.
_________________
ShoBud Pro 1, 75 Tele, 85 Yamaha SA 2000, Fender Cybertwin,

Bob Sigafoos · From: San Clemente, Calif. , U.S.

Ok now that I have your attention… all three tubes are 6L6’s

So consider how far a new tube will stick out. Can’t say much about 5881’s as I haven’t us d them. Now to further confuse you I bought some Soviet Cold War era 6l6 variants for $15 or so a tube for my Tweed era Bassman clone. Loud and clear and impossible to kill.

Jerry Overstreet · From: Louisville Ky

OK, I have determined these original tubes are 6L6GCR side getter beam tetrode from Shuguang as specified by Mesa Boogie. I found a link that matches them up exactly. I can PM a link to anyone who is interested.

The electrical values seem quite different from other ones I've been looking at. Says they can reach 19W dissipation. They may be a lesser tube but if they are good enough for Mesa?

I found an offshore source by the name of Analog Metric which lists these cheap. I'm really cautious about buying anything offshore right now, particularly China and everything else I find stateside is sold out/unavailable.

I guess I'd really like to find those or a compatible replacement.

I'd also be interested in those Soviet tubes you mention Bob if there is still a source.

I know this thread is taking up a lot of space for just a few of us but I really appreciate the education I'm gettng with it. Thanks.

Bob Sigafoos · From: San Clemente, Calif. , U.S.

Jerry, I did a quick search for vendors of the soviet tubes:

Vendor:
https://www.tubeman.com/index.php?l=product_detail&p=948
Info:
https://www.thegearpage.net/board/index.php?threads/nos-6p3s-russian-6l6-question.796577/

I have no connection to this vendor but it appears he is located in Florida. Looking at his web page there is a mention of matching. Sounds OK to me. My thinking is fagetaboutit. I've tortured a pair of these tubes in my Bassman clone for 15 years and they are still going strong. $50 a pair seems reasonable. I also have a quad of EL84 type soviet tubes in my Trainwreck Liverpool. They sound rich with a tangy hint of chocolate and citrus highlights! Sorry..... I was talking to a wine snob yesterday.

Ken Morgan · From: Midland, Texas, USA

FWIW the last couple times I replaced power tubes, they came from Mesa, STR 441.
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67 Shobud Blue Darling III, scads of pedals and such, more 6 strings than I got room for

Ken Morgan
Midland, TX

Jerry Overstreet · From: Louisville Ky

Thanks Ken. Those are out of stock a lot of places, but I did find a pair at one source. Something to consider as they do seem to have some of the characteristics I think I would like.

What amp are you using them in?

Bob, thanks for the links. I notice those are a small base...this amp does have the clips and will be rack mounted with the tubes hanging upside down. Dunno if that would be an issue.

Nick Levine · From: Los Angeles, CA

Jerry, these Ruby tubes seem to be the same as yours just stamped with a different logo. You can buy a matched pair or quad here: https://dougstubes.com/collections/6l6-5881-kt66/products/ruby-6l6gcmstr?variant=40669518757949

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