How often to change tube in 'SGBB?

Phil Halton · From: Holyoke, Massachusetts, USA

I took the Steel Guitar Black Box out of the signal path tonight and was shocked at how much brighter, clearer and sharper the tone got. I spent some time A B'ing my setup with and without the Black Box and it definitely is muddying and darkening the tone considerably. I keep the variZ knob at around 1:30, so I don't think that's a factor. I've had it for about 16 months now and have never changed out the tube. Is it time? What's a good tube to use, and where can I get them? Also, does the tube nneed to be biased when changed? Any help appreciated.

Marty Holmes · From: Magnolia ,TX USA

Phil,
I had the same exact problem it seem's so i bought a RCA 12AU7 cleartop tube from tubedepot.com for $40.00.It seemed to resolve the problem,and have'nt had any problem's since.It's definately worth a shot.And no rebiasing is needed for what these are called preamp tubes.Just pull the old one out and put the new one in very gently just as simple as that.
Marty

Brad Sarno · From: St. Louis, MO USA

Phil,

that surely doesn't sound right. Warm and smooth is ok, but muddy does not sound right. It very well could be a bad tube as that's about the only thing that goes wrong with a Black Box. Some people's tubes are lasting nearly 5 years so far, and others have failed well before that time. Also, the more frequently the unit gets powered on can also affect tube life.

I'm curious, are you using an active volume pedal? Because if you are, part of the brightness you hear without the black box could be the high input impedance of the volume pedal. The similar setting on the black box would be with its vari-z knob cranked all the way up. But if what you hear sounds muddy to you, then we should think about getting you a fresh tube. You should have lots of clarity and liveliness in the tone of the Black Box.

Please email me. I am selecting non-microphonic tubes to run in the Black Box. You can purchase 12AU7's from tube dealers, but it's a good chance that the tube they sell you will be too microphonic. I get them in batches and sort out the good ones. My current 12AU7 is the JJ ECC82. I recently stopped using the JJ ECC802 because they were becoming very inconsistent and far too many were microphonic. The good ECC802's sound killer, but I just couldn't count on them after my last two batches this past year.

sarnomusic@charter.net

Brad

Brad Sarno · From: St. Louis, MO USA

Marty,

thanks for the good recommendation. You can contact these tube dealers and ask them to test tubes for microphonics. There's nothing like a good new old stock tube. RCA, Mullard, Brimar, Telefunken, Sylvania, GE, Tung-Sol, Phillips, Mazda, and the like. Obviously not being a tube dealer myself, I can't provide such a stock or service, but I think it's a great idea for anyone deeply serious about their tube gear to consider looking into a real high end tube like that. They will be pricey, but very likely worth it. Also an old stock tube is likely to last many, many years. Just make sure the person selling it to you can test and guarantee it for low microphonics and other good test factors.

Brad

Ken Fox · From: Nashville GA USA

Wow, $40.00 for an RCA 12AU7 tube!! I have 29 of them on eBay right now and up to 199.00 for the lot. These were used, all out of a home organ and tested great.

Maybe I am letting them go a bit on the low side!!

Mark MacKenzie · From: Franklin, Tennessee, USA

Brad, could you clarify that statement about the active volume pedal a little for me?

I use a Hilton and the Black Box. I play jazz guitar with Kent Armstrong pickups through them and lap steel with old blade and other pickup configurations and a ShoBud. I have wondered about the impedance and what is the best setup. I have always used the instrument into the BB first.

Thanks.

BTW I love the Black Box! Great product!

Mark

Len Amaral · From: Rehoboth,MA 02769

The BB is my favorite unit when I use a plug into a SS amp. I have experimented with all types of setups and going directly from the steel guitar to BB then to a VP to the amp as that seems to provide the best signal,IMO. I use the Vari-Z as a tone control. I also use a Freeloader as a tone control into a tube amp.

Also, I change the 12au7 preamp tube in the BB once in great while as part of normal maintenance.

Steve Feldman · From: Central MA USA

Brad Sarno · From: St. Louis, MO USA

Ken,

$40 for a NEW old stock tube is what I was talkin about, not used old stock. But really, your lot for 40 is quite the deal. I may have to hop on over to eBay. Were you ever able to test them for microphonics?

Brad

Ken Fox · From: Nashville GA USA

No, I did not. They all came out of the same home organ and likely saw little use. I tested all on the tube tester. I have one bid, a guy in Japan.

I still have several nice Conn tubes as well. Not a lot of call for 12AU7 with guitar amps!!

Len Amaral · From: Rehoboth,MA 02769

Steve:

I basically use the BB with a SS amp or PA system as it warms the signal with steel or six string guitar. Very satisfying and useful. When I jam or practice with a band and use someone elses amp, I just bring the BB and dial in a usable sound. It's difficult to explain but you can feel the sensitivity using this unit.

The Freeloader I use if I am using a tube amp or a tube preamp as an added tone feature and it also gives the signal a "zing", not a technical term for sure but I think you get the idea?

I don't use the Freeloader and BB together.

Phil Halton · From: Holyoke, Massachusetts, USA

In regards to changing a tube, is there any trick to it? I had the cover off the SGBB and saw the tube, but having never changed a tube before I didn't want to risk breaking anything. It didn't want to come out willingly, I'll say that. Also, being nearly totally blind didn't boost my confidence level any. I felt what I expect was the socket--kind of a narled collar that the glass tube fit into--or was that part of the tube? Do you just grip the glass bottle and pull straight out of the socket? Tell me like you'd tell a blind person how to change the tube--thanks.

Tim Walker · From: Marin County, CA (originally U.K)

Hi Phil,

Here is a link to the Eurotubes sight which has a lot of useful tips on changing tubes. I found it very helpful.

http://www.eurotubes.com/euro-i.htm

Good luck,

Tim

Phil Halton · From: Holyoke, Massachusetts, USA

I get the feeling that some sight is required to change out a preamp tube. I guess you have to "index" the tube--or line up the pins in a certain way--is that right? If so I probably won't be trying this myself. Ah, what the heck, I'll try it anyway.

Bert Berthold · From: Peralta, New Mexico, USA

Brad,love my BB had to change tube once.Just how is tube tested for microphonics and is there a scale or rateing number for the test results?

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