TUBE CARE & MAINTENANCE
VACUUM TUBE WARRANTY
We guarantee our tubes for ninety (90) days, which is the same warranty the we receive from our supplier.
CARE, MAINTENANCE & REPLACEMENT
1. START UP: For the sake of simplicity, the Steel Guitar Black Box does not have a stand-by switch to allow the tube to warm up before the high voltage is applied to it. This should be considered with regards to tube life. The cold start-up of a Black Box is best kept to a minimum. That means if you are going to turn it on in a given day, you may want to just leave it on and warm until you pack it up for the evening. Frequent start-ups can contribute to premature aging of the tube. Fortunately replacement tubes are very inexpensive for the Black Box. You may want to purchase a back-up to keep on hand. This really goes for any tube gear.
Both the Revelation Tube Preamp and the Tonic Tube Preamp has a stand-by switch. You should leave this switch in the down position when you turn on the power switch. Once power is on, wait about 15 seconds, and then turn on the Stand-By switch. The tube will be warmed by then and will not be stressed by the high voltage being applied.
2. REPLACEMENT: When the tubes begin to exhibit symptoms that suggest the need for replacement, the procedure is simple for any qualified person who understands the nature of a high voltage tube device. ONLY qualified personnel should attempt replacing the tubes. It must be done with the unit unplugged from the AC power source. Leave the Stand-By switch "up" and wait at least one minute. Then the lid is carefully removed by the Phillips screws on the top of the lid as well as the one on the faceplate. The tubes are then easily accessed by hand. The location of the tube type is clearly marked on the circuit board near the tube socket. Feel free to experiment with other brands of tubes as long as they are the same type.
STEEL GUITAR BLACK BOX - 1 tube
(1) 12AX7 (ECC83, 7025, 5751, ECC803 or similar) Not all new 12AX7's will work properly in the Black Box. The output stage section of the tube requires a certain voltage specification that many new tubes don't adhere to. Currently (Jan 2011) these new tubes will work reliably in the SGBB:
TAD 12AX7A/ECC83 Premium Selected (7025, 12AX7WA)
Sovtek 12AX7WA, 12AX7WB
Groove Tubes GT-12AX7-C
Earlier versions of the Steel Guitar Black Box used a 12AU7 tube instead. Be sure you know which version your Black Box is before replacing the tube. 12AU7's are a bit harder to find in a low noise version, but currently we know that the EH 12AU7 and the Shuguang 12AU7 do work well in the Black Box. These Shuguang 12AU7's can also be found under the brand, Ruby, Penta, Groove Tubes, and TAD (Tube Amp Doctor).
REVELATION TUBE PREAMP - 3 tubes
(3) 12AX7 (ECC83, 7025, 5751, ECC803 or similar). Tube #1 (far left side nearest the input) requires a certain limited variant of the 12AX7 tube. See the above list for the Steel Guitar Black Box when choosing a replacement tube for the first tube in a Revelation. Tubes #2 and #3 in the Rev Pre can pretty much be any 12AX7 type tube of your choosing.
Keep in mind that early or non-updated Revelations will have a different tube in positions #1 and #3 and require a 12AU7 instead. Be sure to check your Rev if unsure. 12AU7's are a bit harder to find in a low noise version, but currently we know that the EH 12AU7 and the Shuguang 12AU7 do work well in the Black Box. These Shuguang 12AU7's can also be found under the brand, Ruby, Penta, Groove Tubes, and TAD (Tube Amp Doctor). The EH (Electro Harmonix) is widely available.
SMS CLASSIC TUBE PREAMP - 2 tubes
(2) 12AX7 (ECC83, 7025, 5751, ECC803 or similar). The SMS Classic uses 12AX7 type tubes. Many are available, vintage used, new-old-stock, and new. Feel free to try the many available options.
TONIC TUBE PREAMP - 2 tubes
(2) 12AX7 (ECC83, 7025, 5751, ECC803 or similar). Earlier or non-updated versions of the Tonic will have one 12AU7 in there. Please contact us if you aren't sure which version you have.
REPLACEMENT TUBE UPDATE & ORDERING
As a manufacturer we strive to find the most reliable source of quality, newly manufactured tubes that we can. However, from season to season various tube brands seem to come and go due to inconsistent quality and reliability issues, thus requiring us to use different brands of tubes in our gear over the past few years. Put simply, they don't make them like they used to.
Most recently, we were again finding quality issues with a good share of our JJ 12AU7's and 12AX7's batches. After extensive research and consultation with other amp manufacturers and audiophile nuts, the path has led us to a recent generation tube manufactured by Shuguang in China.
I must admit, that for years I avoided these tubes because of my general bias against goods manufactured there. But I've since learned that this factory has not only been making good, solid preamp tubes since the '80s, but is now on the 9th generation of refinements. High end amp makers such as VHT/Fryette, Fuchs, Boogie, and many others have found these to be the most consistently reliable preamp tubes available today, far surpassing European tubes in many respects. Much to my surprise, these are proving to not only sound excellent in the clean circuits we manufacture, but are also reliable, low-noise, low in microphonics, and happen to be about the only new tube that truly holds up to certain critical voltage spec's as defined decades ago for these dual-triode types.
To further insure quality control, I've found that I currently like the service and consistency of the TAD - Tube Amp Doctor versions. TAD is a German company that deals directly thru MOJO here in the US. TAD only sells the premium selected versions of this tube, pre-tested for low noise and low microphonics.
For those who need to replace the 12AU7's in their older Black Boxes and Revelations and Tonics, I'd recommend these HERE, their premium 12AU7. The price is good and Mojo gives a 30 day guarantee on it.
For 12AX7 replacement in the Revelations, Tonics, SMS Classic preamps, and newer Black Boxes, I'd recommend either of these:
TAD 12AX7A-C Vacuum Tube or TAD 7025 Highgrade Vacuum Tube
Since I have a limited ability to keep a large stock of replacement tubes, I'd encourage people to contact MOJO at www.mojotone.com for affordable replacement tubes in their SMS gear. But if someone wants to spend some extra money, I'd surely recommend that people explore some of the various tube dealers and consider some new-old-stock premium brands that are tested for low-microphonics. Some brands to consider are: Telefunken, Brimar, Mullard, Tung-Sol, GE, RCA, Sylvania, and more. And as always, should you have any questions or concerns at all, please do not hesitate to contact us directly.