7 - 1 TUBE MAINTENANCE: (Continued)
When the time comes to replace tubes, make a note of the color code on your power tubes before you call us with your order. At the bottom of the tubes, you will find a label listing a three letter abbreviation such as GRY, WHT, YEL, GRN...this is our in-house system of separating our computer- tested tubes into different Bias categories. Tubes with the same color coding draw identical current and thus insure perfectly matched behavior. This is important when you only replace isolated tubes and don’t retube the entire amp. Being a push-pull design, the two rows of three tubes per channel need to be perfectly matched to each other, and left to right channel. Even a single mismatched tube will throw off the balance, resulting in performance degradation and potential premature tube failure. It also prevents the auto-bias system from working properly.
7 - 2 TUBE ROLLING:
This term refers to experimenting with brands of tubes other than those supplied by the manufacturer. You have good reason to assume that we equip our amplifiers with the best tubes available for the purpose. After all, we select particular tubes to be part of the individual models from the very beginning of the design stage. Any and all modifications we incorporate during the design process are in response to these tubes chosen and account for a finished product that was optimized and voiced to work perfectly with the type and origin tubes that the amp is shipped with.
However, some listeners may wish to experiment and have access to tubes of the same type, but by a different manufacturer that could result in a change of the amp’s sonic signature. You are welcome to experiment along those lines, but please remember to only substitute tubes of the same type and pin configuration!
Any damages caused by shorting out Internal Circuitry due to a tube mismatch are NOT covered by the warranty.
The term NOS stands for New Old Stock and is applied to never-used surplus tubes that are no longer manufactured. You may find 12AX7s by Mullard, Telefunken or Tesla, or EL 84s from Sylvania or other old manufacturers. Inserting any of these tubes will result in a definite overall sonic change of character - whether for better or worse will be for you to decide. If you find NOS tubes that you prefer over our stock tubes, remember to purchase excess amounts for continuous maintenance - you might otherwise find that the limited supplies of your NOS have sold out by the time you need to retube your amplifier.
Chapter 8 - EVOLUTION OF THE TIGRIS:
For those curious about the design process, from idea to prototype to final product, we like to give you some background on the evolution of the TIGRIS: from the original prototype through generation II and III to the final production version. This will help you understand the passion for refinement and the concern for your satisfaction that went into it.
Beginning with our Mesa BARON as an engineering platform, we originally conceived of the TIGRIS as a dual-mono design taken to the equivalent extreme. The BARON’S dual-mono nature duplicates On/Off, Standby, Meter and Ground switches, even the power cords, and the circuit board layout is fully mirror-imaged and features separate power- and output transformers for each channel.
In the TIGRIS, this concept manifested externally as dual Volume controls, dual Input selectors and a single row of mirror-imaged RCA input terminals on the Rear Panel, while internally duplicating the BARON’S parameters of mirror-image layout and dual power- and output transformers: dual-mono taken to its logical conclusion. However, potential customers and retailers alike felt that taken this far, dual-mono would be more inconvenient to use than offer a real performance advantage. This would be of interest only to a small group of dedicated audiophiles willing to trade basic convenience for the theoretical purity of the design’s uncompromising execution. We quickly returned to the drawing room.
Without altering the design’s internal dual-mono construction, we redesigned the Rear-Panel for the more conventional dual rows of closely-spaced RCA jacks and simplified operations and the appearance of the Front Panel by substituting stereo controls for the formerly duplicated Input selector and attenuator. We also added the Headphone Output and buffered Preamp Output. To investigate
