Duncan Twin Tube Blue SFX-11 problem

[kilbey]

Hello all- My beloved Twin Tube Blue has recently begun to make some bad sounds. The clean channel (only) is making those crackling/pffft sounds when I am not playing. Drive channel is perfect, no problems.

Should I look into replacing a filter cap or two? This is the sound that my old tube amp was making until I replaced the filter caps. I thought those took a long time to go bad though.

Of course the tubes are supposed to be mil-spec, so one would hope they'd last longer than a few years.

Should I just order and replace the caps? Which cap would effect the clean channel only? I can't read a schematic, but I can safely replace caps and resistors etc.

Thanks in advance--

 

[Funkfingers]

Re: Duncan Twin Tube Blue SFX-11 problem

Welcome to the forum.

How old is your unit? When (if ever) did you last change the valves?

My inclination would be to remove both valves, clean the pins and bases thoroughly and try them again. If nothing improves, consider fresh valves.

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

Thanks FF. Welcome to the Twin Tube Blue- the tubes are soldered in! I can reason that one tube is bad if it is configured as 1 tube per channel. I think V1 is probably the clean channel.

Anyone know any more about this? Did the submini tubes live up to SD's st idea of longevity, or fail somewhat?

-B

Welcome to the forum.

How old is your unit? When (if ever) did you last change the valves?

My inclination would be to remove both valves, clean the pins and bases thoroughly and try them again. If nothing improves, consider fresh valves.

 

[Funkfingers]

Re: Duncan Twin Tube Blue SFX-11 problem

Each 12AX7/ECC83 valve is actually two gain stages in one envelope. Pre-amplifier stages are cascaded to achieve gain. There will, almost inevitably be integrated circuit op-amp chips involved somewhere in the signal chain. (The Marshall JMP-1 pre-amp operated on similar principles.)

If the valves - rather than just the valve mounting bases - are soldered to the PCB, you are going to have a fun time desoldering them, cleaning the old solder off then soldering in replacement valves.

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

Amigo, these are sub-minis. About the size of a cigarette butt:
http://images.search.yahoo.com/sear...x34Ap2Bx.9w4?p=submini 6111&fr=onesearch&fr2=

They have wires rather than pins.

-K

Each 12AX7/ECC83 valve is actually two gain stages in one envelope. Pre-amplifier stages are cascaded to achieve gain. There will, almost inevitably be integrated circuit op-amp chips involved somewhere in the signal chain. (The Marshall JMP-1 pre-amp operated on similar principles.)

If the valves - rather than just the valve mounting bases - are soldered to the PCB, you are going to have a fun time desoldering them, cleaning the old solder off then soldering in replacement valves.

 

[Funkfingers]

Re: Duncan Twin Tube Blue SFX-11 problem

That rules out dirty and/or corroded pin bases. Could still be dry/cold solder joints on the PCB.

 

[IM4Tone]

Re: Duncan Twin Tube Blue SFX-11 problem

Why not just contact SD and ask them to service it. I've read great reports on this forum of excellent customer service on these twins. I have the Twin Tube Classic and love it. Had it quite some time with no issues, but if one came up, that's what I'd do.

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

I can't afford to do that.

Why not just contact SD and ask them to service it. I've read great reports on this forum of excellent customer service on these twins. I have the Twin Tube Classic and love it. Had it quite some time with no issues, but if one came up, that's what I'd do.

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

I am probably going to do the pencil test on the tubes to check if they are microphonic.

 

[Funkfingers]

Re: Duncan Twin Tube Blue SFX-11 problem

I can't afford to do that.

Can you afford NOT to have the unit serviced by an approved technician?

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

Yes, I can definitely afford not to. I tend to do as much as possible for myself--

replace brake pads and calipers, tune-ups on cars,

plumbing, build walls, general carpentry, fix leaking roofs, cut and haul firewood, build a tile hearth pad,

replace filter caps, cobble together and refinish guitars, intonation/setup, install tremolos tuners and pickups, re-string,

cook, do dishes, laundry, self-medicate :O), make art, gardening...

Those are all things I can't afford to pay someone else to do. I make money when I do these things by virtue of saving money.

-K

 

[Diminished Triad]

Re: Duncan Twin Tube Blue SFX-11 problem

Yes, I can definitely afford not to. I tend to do as much as possible for myself--

replace brake pads and calipers, tune-ups on cars,

plumbing, build walls, general carpentry, fix leaking roofs, cut and haul firewood, build a tile hearth pad,

replace filter caps, cobble together and refinish guitars, intonation/setup, install tremolos tuners and pickups, re-string,

cook, do dishes, laundry, self-medicate :O), make art, gardening...

Those are all things I can't afford to pay someone else to do. I make money when I do these things by virtue of saving money.

-K

Kilbey, how is the twin tube preamp? Saw it on SD and it is not on musiciansfriend - found it available on amazon. The reviews are nice.........truly delivers on a bluezy tone on youtube............how does it do for you (this question is for everyone) in real life? Thanks!

 

[kilbey]

Re: Duncan Twin Tube Blue SFX-11 problem

Well, that's a pisser- I wrote several paragraphs singing the praises. Gone.

Anyways, yes, I do highly recommend it. For my purposes, I would prefer the clean channel of the BLue, but the drive channel of the Twin Tube Classic-- it's got a nice juicy sustain akin to a Rat pedal.

I am using the TTB as a sort of boost in to my late-model Peavey Bandit. It gives a lot of natural compression and richness to the clean. I had been using it straight in to the (tube) power amp in of a Peavey MX. Sounded great!

I have not used it for recording, but I believe it would work very well.

-K