duncan twin tube bites the dust

Ben Jones · From: Seattle, Washington, USA

I guess these little military spec tubes can fail after all, cause my seymour duncan twin tube has started hissing badly. Cables, guitar, power source all swapped out...its definetly the duncan.

Unfortunately Ive become dependent on this thing for getting a decent guitar sound thru a solid state amp, and I have an audition tommorrow and recording session on saturday. perfect timing.

just thought id mention a downside to this wonderful pedal to balance out the constant praise I lavish upon it.

I'll be calling every music store in town today to try and find a new one before friday, then going online if that fails. $220 +tax...ouch. email sent to duncan to see if they can repair the old one, but like I said...need replacement NOW. bummer

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Um - if a tube has fried, you may just need a new tube. They're available. The problem is that they have to be soldered in - you may want a tech to do that unless you're pretty good with a soldering iron. I don't think I'll be sending mine back to Duncan.

I haven't had any problems yet, but I do know that I need to get a supply of the tubes, I think there are two in the unit. Guess I better get on it, I use mine quite a bit too.

David Doggett · Posted 3 Sep 2009 9:21 am

Dave, if you find out what those tubes are, and where to get spares, let us know.

Ben Jones · From: Seattle, Washington, USA

Dave M, those little tubes are miltary spec and not availble for public consumption to the best of my knowledge. Otherwise , Im very handy with soldering iron and build and repair my own pedals. Be advised there some large caps in side these pedals and what appears to be a tiny transformer, so watch yourself if your going inside.

If you run across a source for these tubes, as David D said, let me know for sure, but one of the big beefs people have with this pedal is that the tubes are supposedly not available to the public. The counter to this beef is usually that since they are military spec tubes, they should last as long as your pedal does, but obvioulsy this isnt always the case (ive seen others report tube failure).

I should also mention I bought this pedal used, and the person i bought i from had said they had also bought it used.

I'll let you guys know what duncan says as far as repair costs, if they will even do it.

Okay, time to let my fingers do the walkin and find that replacement.Please... someone have one locally...fingers crossed.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

There is nothing proprietary to the military about mil-spec tubes. I use practically nothing other than mil spec JAN NOS tubes in any of my tube amps. Mil-spec means that they're mo' betta', at least to me.

I just called this guy - http://www.radiodaze.com/tubes-10.htm

and ordered 30 of these 6021 tubes, which I consider my lifetime supply and then some. I've never used him, but he has a lotta tubes and seemed pretty reasonable on the phone. We'll see. In any case, they are available and quite inexpensive. I've been pondering making some pedals, I think they're a good basis for that. I know there are lots of them out there.

Ben, this won't get you through your audition this week, but if you can find one at a big-box store, you can return it if you decide you don't need it.

Be advised that soldering these tubes is a bit tricky - you'll see what I mean when you open it up - but no problem if you're good with a soldering iron. But any good tech should be able to do this quickly and inexpensively.

BTW - there are at least a couple of other sources for these plus fleabay, but all the ones I've seen are more expensive.

Mo' BTW - the specs for this pedal, including tube info - are here: http://www.seymourduncan.com/products/stompboxes/sfx03_twin_tube/

Ben Jones · From: Seattle, Washington, USA

Dave thats fantastic! THANK YOU.

Oops I had the numbers mixed up. that does indeed look like the correct tube!

ordering some now.

no store in town has this pedal so I guess I'll hvae to figure out a way to make it work friday and saturday without the thing Crying or Very sad

steels not so bad without , i can get by, especiall y i the stuido where I have aklot of tones avaiable.
Guitar , i can get by fine without it if I use a tube amp..but Steel AND guitar live thru the same amp solid state portable amp rig as I have to do on friday...I really need that thing. oh well...either my guitar tone will be butt-tastic or maybe they'll have tube amp for me to play guitar thru. the duncan was also my distortion and boost pedal of choice tho. sigh.....

ah, could be far worse I guess.
Thanks agian for the help, I knew i was posting this for more than just venting my frustration. the forum rules.

KENNY KRUPNICK · From: Columbus, Ohio

@ $2.70 per tube, a half dozen should last a while at 3 tube changes. It would be nice if they were user changeable.

Jon Light (deceased) · From: Saugerties, NY

fwiw---at your initial posting I did some searching and found some of these tubes (the right ones with long leads, not the one in your picture, Ben) on ebay. One seller was selling a tube with a separate socket so that, space allowing, you could solder the socket in place and never have to mess around with solder after that. OTOH, I could envision them using a tube position in the SD that is not socket-friendly in order to fit into the case.
Good luck.

oh, and Dave M--

Ben Jones · From: Seattle, Washington, USA

I opened the thing up last night and had a look around. Its not like any other pedal Ive ever worked on thats for sure, that crazy little transformer in there...the tubes themselves do indeed look like they are going to be a pain to swap, based on the size and spacing of the components and their leads, the small amount of space in the enclosure and the weird silver tube guard thingy they got going, but I havent poked around enough to see how bad its gonna be. I feel confident I can work it out tho.

It has "Danger:High Voltage" printed all over the board. The caps are small, but I guess i will drain em anyway.

Im contemplating bringing my tweed deluxe clone on friday. On one hand, great guitar tone..on the other hand, hauling two amps to an audition is lame. Kind of a drag ive become more discriminating ..i used to juts roll with whatevr was on hand and not care. There were some horrible horrible tones..and the occasional good one. haha. its hard to go back to bad tone.

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

Uh, yeah - but I have seen people call a two-stage tube a "twin tube" - sometimes marketeers tout the number of tube stages, not the number of tubes. Makes it seem mo' bettah, right? They could have called this the "quad tube" by that reasoning. But I guess Seymour is more honest than that. Hardee har. Smile

I've also been inside, which is why I made the caveat about knowing what you're doing before you fire up the soldering iron. It does appear to be put together well, but modern electronics stuff is not especially robust to hack repair people since they cram quite a bit inside the boxes.

As far as getting a socketed version - I thought about it, but I wasn't too sure the sockets would fit. As I said, there was quite a bit crammed in there.

I measured voltages on the transformer - it appears to step up the 18VAC input supply to the high voltage needed to run the tube plates. We discussed this before - I think that is a very strange design. Why not directly step up 120VAC line voltage? I assume there is some advantage from a UL ratings point of view. But since it's ultimately stepped up higher than that, that seems more than a little Washington-bureaucratic perverse to me.

Ben Jones · From: Seattle, Washington, USA

maybe they thought a big ole ac power chord would scare people off and kill their sales?

Jon Light (deceased) · From: Saugerties, NY

Or maybe it's cheaper to populate the board with low voltage components and only step up voltage for the tubes?
(As if I've got a clue).

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

I can't imagine the lack of a wall-wart would hurt sales any. Quite the opposite, I think the wall-wart - especially the odd voltage AC one - is a big turnoff.

It could be that they're running other active elements at low voltages. But the other thing I hadn't thought of is that they may want to keep the AC voltage inside the box down to reduce stray electromagnetic radiation.

Ben Jones · From: Seattle, Washington, USA

My thinking was that modern effects users are accustomed to wallwarts whereas they are only accustomed to big ole ac chords on ancient mxr and EH effects they've seen on ebay and thus the big ole ac chord might be alien to them or at best seem like old tech and put people off the product at first glance.

But like Jon said , as if I had a clue...

personally I prefer a wallwart to an ac chord because I can take the skinny walwart wire and coil it up in little ball and shove it between pedals, whereas that big round ac chord, not so much. of course my absolute preference is a topside mounted daisy chainable 9volt jack..but that wont power a 70's mxr flanger or the duncan twin tube.

David Mason · From: Cambridge, MD, USA

Blake Hawkins · From: Florida

Dave, you are right on about the UL reason for the wall wart. If they run 120 volts directly to the pedal, they have to go through a long and expensive
UL Approval process.
The Wall Warts are made in the millions and they
have UL approval.
By running low voltage to the pedal, Duncan does not have to worry about the UL and can change the design
anytime they please.
Blake

Mark van Allen · From: Watkinsville, Ga. USA

Love mine too, but I'm now on my third power supply. Duncan's been great about sending replacements, but the last one only lasted a few gigs before it gave up the ghost. I checked as well as I can, seems like no shorts or anything in the power supply section, but the last supply was D.O.A. very quickly with no real mechanical stress to it. The new one looks a bit more robust, here's hoping.
I can't find anything else that sounds like these puppies.

Jim Strawser · From: Montana, USA

Ever given any thought to the H K Butler Tube Driver or Blues Tube. It comes a 12AX7, but I ordered a 12 AT7 and a 12 AU7(warmer tone) and they arent soldered in, just a suggestion in my humble opinion is all!!!
_________________
"Steel players are like fine wine, we get better with age"

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

I fairly extensively tested both the Butler Tube Driver and Blue Tube pedals back when (for guitar). They didn't have what I was looking for at the time, but I never did try lower-gain tubes like the 5751, 12AY7, or 12AU7 - I never bought them and I don't think the stores would have been thrilled with me futzing with the tubes. In general, virtually every "distortion" pedal I tried was too gritty for what I wanted, which was the sound of a mildly overdriven tube amp. Most of the "tube overdrive/distortion" pedals I've tried didn't run the tubes at high voltage like the Duncan. Run at typical pedal voltages, I think these tubes operate pretty much as a diode, which is exactly what I'm trying to avoid.

One of the advantages of these 6021 subminiature tubes is that there are a lot of them out there, and are therefore reasonably priced and not heavily picked over - which I suspect is why they were chosen for this design - and they are high-quality and sound good (to my tastes). There are lower-gain sub-miniatures, and in fact Duncan has made a unit with one of these tubes (SD Twin Tube Blue).

I don't think the need to solder these is that big a deal. But perhaps it would have made sense to implement with a sub-miniature tube socket to avoid this objection. It may also be possible to retrofit the sockets - at this point, I haven't tried to do that. The question is whether or not there's enough room in there - it may not be problem, I don't know.

My power supply is still OK, but they do get much too warm (IMO), which tells me that they're under-designed. I imagine that there is probably a more robust one out there in the aftermarket, but haven't looked.

Jon Light (deceased) · From: Saugerties, NY

Just out of curiosity---any observations re: the blown power supplies? I blew the wart on a Holy Grail while I was inserting the plug into the jack of the unit. It made me think that the act of plugging it in caused a momentary short. Is that a potential general weakness? Or am I trying to establish a cause/effect from a coincidence?

Scott Appleton · From: Ashland, Oregon

I have never shorted a P supply by just pluggin it in .. Most of the time they
fail cause the skinny wire lv side gets twisted too many times and fray's
causing the short .. also heat gets to the components and they fail.
but i would vote no on just pluggin it in hot .. the plugs are designed to prevent
that from happenin .. corse you could air on the side of safety and never plug
in the wall side until all efx are jacked in .. just never happened to me ..

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

The Holy Grail uses a 9V DC 500 ma power supply, so there must be some decent-sized filter caps in it. Large caps can draw a fair amount of current while charging, which could stress the transformer. I also suppose it's possible a cap could short. QC on these cheap consumer-grade generic power supply stuff? My guess - probably far from great.

Even though a low-voltage AC power supply for something like this - the SDTTC uses a 16 VAC 600ma supply - is generally just a step-down transformer, the filtering section inside the effect unit can draw current while charging. I sometimes see a flash - arc - at the plug as I plug in a high-current power supply to the wall.

I guess I'd be looking for a highly over-rated power supply. Why do people use these cheap power supplies? IMO, mainly convenience. If you buy a well-made, industrial-strength regulated power supply, you need to do the research on what you need, find a good source, and then make your own connections. I've been pondering doing just that, but it takes what I have the least of right at the moment - time for non-critical "projects".

Brad Sarno · From: St. Louis, MO USA

Hey,

can someone post a photo or 2 of the innerds of the Duncan Twin Tube pedal? I'd like to see the little step-up transformer they're using inside there. I've read that there's 245 volts in the B+ supply, so they're stepping up the 16v quite a bit, and then turning that into filtered DC. Also, any electronics junkies notice if the heater supply is regulated DC or just AC?

Brad

Jan Jonsson · From: Gothenburg, Sweden

Hi Brad,

Here are some pictures from inside my Twin Tube Classic.

-- Jan
_________________
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Gear: 10-string Desert Rose "Delta Blues", Fender Deluxe 8, Fender CS Nocaster
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Brad Sarno · From: St. Louis, MO USA

Thanks Jan!

Brad

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