CAR FAQ

  1. What is the "Big Idea"?
  2. What is the "Russell O. Hamm" white paper? Why is it important?
  3. What is "negative feedback"?
  4. Why don't you use XLR connectors any more?
  5. What type of connectors do you use on the amplifier?
  6. What type of connectors fit?
  7. What size (gauge) wire should I use?
  8. What brand interconnects/wire do you recommend?
  9. What does it mean to "bridge" an amplifier?
  10. Are the amplifiers bridgeable?
  11. How much power do the amplifiers produce in bridged mode?
  12. What is the TDB575 designed for?
  13. How can I use the TDB575?
  14. What type of tube is used in the amplifiers?
  15. Can I "tube roll"?
  16. What is "tube rolling"?
  17. Do the tubes break?
  18. Do the tubes wear out? How often will I need to change the tubes?
  19. Is there an electronic crossover built into the amplifiers? What about the LDX-23?
  20. Do you sell a line driver? What about the LD-2?
  21. What is the sensitivity range of the amplifiers?
  22. What is the "gain control" for?
  23. How do I properly set "gain"?
  24. What is "signal to noise (S/N) ratio"?
  25. How high of an input voltage can I drive the amplifier with?
  26. What is "damping"? Does it matter?
  27. What is the current draw of the amplifiers?
  28. Can I use Tube Driver BLUE amplifiers to drive a subwoofer?
  29. What speakers do you recommend?
  30. What are the amplifier's dimensions?
  31. What is the warranty?
  32. Do you repair the original TubeDriver product?
  33. What model/version of TubeDriver do I have?
  34. How should I mount the amplifiers?
  35. What is the difference between the original TubeDriver amplifiers
    and the new TubeDriver BLUE amplifiers?


Q: What is the "Big Idea"?  Top of Page
A: The "Big Idea" is a result of the model that BK Butler used to inspire him to invent the TubeDriver BLUE circuitry. For more than 25 years, BK Butler designed tube related audio equipment for various applications. After many innovative tube-driven products, including the original 1995 design of the TubeDriver 1500, BK set out to find a way to unlock the secrets of how to meet the criteria specified in the Russell O. Hamm white paper "Tubes vs. Transistors - Is There an Audible Difference?" That paper is the most definitive study ever undertaken to determine what makes up "tube sound" and why it is better.

After BK Butler's critical subjective and in-depth technical analysis of this brilliantly written research paper, the two essential areas defining vacuum tube sound were disclosed:

  1. "Our extensive checking indicated...a definite audible difference in the sound quality...where there is a mechanical-electrical interface." "...power amplifiers driving speakers..."
  2. "The basic cause of the difference in tube and transistor sound is the weighting of harmonic distortion components in the amplifier's overload region."

The now-patented TubeDriver BLUE circuit design accurately fulfills both of these essential requirements for tube sound:

  • By directly interfacing the mechanical-electrical speaker load with twin-triode vacuum tubes, TubeDriver BLUE produces the response and tonality of 'all tube' power amplifiers.
  • Utilizing the original pure Edison effect, the TubeDriver BLUE circuit design safely biases the twin-triode tubes to a constant, near plate-saturated or overload condition. The results are greatly expanded dynamics, punch and presence from naturally produced vacuum tube harmonics.

Q: What is the Russell O. Hamm white paper? Why is it important?  Top of Page
A: It is the most definitive study ever undertaken to determine what makes up "tube sound" and why it is better. It is important for two reasons:

  1. It clearly outlines two specific points that answer two key questions:
    a) if tubes sound different than transistors
    and more importantly
    b) why they sound different and what it takes to produce that "sound".
  2. It inspired BK Butler to develop the TubeDriver BLUE technology that specifically addresses the points outlined in the Russell O. Hamm study and that you enjoy today.

Q: What is "negative feedback"?  Top of Page
A: It is a design method used to reduce THD in the output signal in which a portion of the signal from a later amplifier stage is "fed back" to an earlier stage (or to the same stage) in such a manner as to subtract from the input signal and is usually measured in dB. Although it is advantageous in reducing distortion to lower levels, it degrades the overall sonic quality of the output. The more negative feedback is applied to the circuit, the more the overall sonic quality is degraded. Part of the sonic virtues of the TubeDriver BLUE amplifiers is that all BK Butler designs employ ZERO negative feedback.

Q: Why don't you use XLR inputs any more?  Top of Page
A: There were many reasons, including:

  1. Lack of compatible equipment
  2. Questionable advantages in performance gains
  3. The excessive cost of the cables and adapters necessary for their use.
The primary reason is that it adds a significant amount to the price of the amplifiers with very little real gains in performance.

Q: What type of connectors do you use on the amplifiers?  Top of Page
A: The power and speaker terminal blocks used on the TubeDriver BLUE amplifiers are high quality, hard gold plated barrier strips with screw down terminals. They accept bare wire or you can terminate the wire by using standard size ¼" spades. The original TubeDriver amplifiers use the same type of terminal blocks as the TubeDriver BLUE amplifiers and they also accept bare wire or standard ¼" spades. You will notice that the original TubeDriver amplifiers have two connections each for the plus and minus main power terminals. These terminals are connected together internally. The amplifier was intentionally designed this way so that a larger gauge wire could easily be connected. (i.e., you could use two 8AWG wires to make the equivalent of a single 4AWG wire).

The Phaze Audio/PPI amplifiers use an unusual molded nylon connector that is no longer in production and has become very difficult to find. No replacements have ever been available from Butler Audio because the amplifiers were never designed or built by BK Butler/Butler Audio.

Q: What type of connectors fit?  Top of Page
A: Standard ¼" spade terminals for both power and speaker connection.

Q: What size (gauge) wire should I use?  Top of Page
A: These are the minimum recommended specifications:

  • Main Power: 8AWG with a high temperature jacket (105°C minimum) per amplifier.
  • Speaker Wire: 16AWG or larger multi-strand for main (front, rear) speakers.
  • Subwoofer Wire: 14AWG or larger multi-strand.
  • 18AWG wire for remote turn-on.
Oxygen Free Copper (OFC), silver or gold wire is best for car audio applications due to its non- corrosive properties.

Q: What brand interconnects/wire do you recommend?  Top of Page
A: We believe that interconnect (RCA) cables and speaker wire selection have more to do with personal taste than with measurable differences in the various manufacturers products. For that reason, we do not recommend a specific brand of wire but rather suggest that within reason, it has been our experience that you get what you pay for in cables/wire. A good set of shielded or twisted-pair interconnects (RCAs) with quality strain relief will be sufficient. "Directionality" is unimportant. The cable "geometry" (design) is less important than the overall build quality. Oxygen Free Copper (OFC), silver or gold wire is best for car audio applications due to its lower susceptibility to corrosion.

Q: What does it mean to "bridge" an amplifier?  Top of Page
A: To "bridge" an amplifier is to use 2 output channels to drive a single load. The sources of power are one output from either channel of the amplifier. It is commonly used to increase the power output of an amplifier.

Q: Are the amplifiers bridgeable?  Top of Page
A: The TDB275, TDB2150 and TDB475 amplifiers are bridgeable.

  • To bridge the TDB275 and TDB2150, you connect the speaker plus (red) connector to the amplifier Right plus connector and connect the speaker minus (black) to the amplifier Left minus connector.
  • To bridge the TDB475, you connect one speaker plus (red) to the amplifier Right Front plus connector and connect the same speakers minus (black) connector to the amplifier Left Front minus connector. You then repeat for the second speaker, connecting it to the appropriate Right and Left Rear speaker connectors on the amplifier.

The TDB575 is NOT bridgeable. The TDB575 is designed to be the main amplifier in a mobile audio surround sound system. All five channels are discrete.

Q: How much power do the amplifiers produce in bridged mode?  Top of Page
A: You can find this on the amplifiers specs page. Click on the specific model number below...

TDB275    TDB2150    TDB475

Q: What is the TDB575 designed for?  Top of Page
A: The TDB575 is designed as a 5-channel amplifier for surround sound and audio/video applications (i.e. right and left fronts, right and left rears and a center channel). Of course, it can be used in any multi-channel configuration.

Q: How can I use the TDB575?  Top of Page
A: the TDB575 can be used in a variety of ways:

  1. It can be used as the main amplifier in a mobile 5.1 A/V system. In this application, you would use channels 1 and 2 for the Left Front and Right Front, channels 3 and 4 for the Left Rear and Right Rear and channel 5 for the Center and then connect a subwoofer to a separate amplifier like a bridged TDB2150.
  2. You can connect channels 1 and 2 to the right midrange and tweeter, channels 3 and 4 to the left midrange and tweeter and channel 5 to the center channel and then connect a subwoofer to a separate amplifier like a bridged TDB2150.

Q: What type of tube is used in the amplifiers?  Top of Page
A: All the TubeDriver BLUE car amplifiers use a 6SL7GT twin triode, one for each channel. This tube was specifically chosen for its thermionic output characteristics within the circuit.

Q: Can I "tube roll"?  Top of Page
A: If the question means "can you change the tubes that come with the amplifier to another type", the answer is yes, and no. Yes, if you are skilled in electronics, you could change the tube. And no, it is not easily performed nor desired:

  1. The tubes are soldered into place for reliability thus you would need to change not only the tube but also the mounting scheme in order to accommodate a different type of tube
  2. The circuit is not designed to accommodate any other tube and no other tube type will perform better.

Q: What is "tube rolling"?  Top of Page
A: "Tube rolling" is a term used to describe when a person decides to alter the sound of a tube amplifier by changing the output tube to a different type/version on the premise that various tube types "sound" different. The premise is based on the idea that each different tube type has a different electrical characteristic and that by testing various tube types, you will find the "magic one" that will make the amplifier sound the best. Unfortunately, this "idea" stems from experiences people have with "typical" tube amplifiers. Because the TubeDriver BLUE amplifiers employ the patented TubeDriver BLUE circuitry, tube rolling is neither necessary nor desired. The patented TubeDriver BLUE circuitry delivers the "live stage" and "recording studio" sound via the thermionic emissions of the tube rather than the overload characteristics of the tube, like typical tube amplifiers. The 6SL7GT twin-triode tube was specifically selected for it's thermionic/emissive qualities and is an integral component in the natural, transparent, clean sound TubeDrive BLUE amplifiers deliver.

Q: Do the tubes break?  Top of Page
A: The design of the amplifiers makes the tubes very shock resistant and they have proven extremely reliable over time. The only time you should experience a tube failure is if a tube is directly struck and the glass cracks, releasing the vacuum. A cracked tube voids the warranty.

Q: Do the tubes wear out? How often will I need to change the tubes?  Top of Page
A: The tubes are driven at less than 5% of their maximum rating and thus are not stressed like in a typical tube amplifier. Under normal use, they should not need replacement.

Q: Is there an electronic crossover built into the amplifiers? What about the LDX-23?  Top of Page
A: No, none of the TubeDriver BLUE amplifiers have built-in crossovers. This was a deliberate decision. Butler Audio's belief in ultimate sonic performance and bulletproof build quality meant that if a crossover of equal build quality and sonic performance to the amplifier was to be included, the overall cost of the amplifier would have to be significantly higher. Including a lower quality crossover would have degraded the extreme quality, both mechanically and sonically, that Butler Audio products are renowned for. Additionally, the audiophile-level systems that these amplifiers were intended for typically have either outboard processors or controllers that include crossovers of high quality.

The LDX-23 is a crossover that was designed by BK Butler and sold by Phaze Audio under the Phaze Audio/TubeDriver brand name. It has been out of production since 1998.

Butler Audio is considering adding an audiophile-grade dedicated crossover to the TubeDriver BLUE car audio line. Drop us a line at info@butleraudio.com and let us know if you would be interested in an audiophile-grade stand-alone crossover.

Q: Do you sell a line driver? What about the LD-2?  Top of Page
A: No, not currently.

The LD-2 is a line driver that was designed by BK Butler and sold by Phaze Audio under the Phaze Audio/TubeDriver brand name. It has been out of production since 1998.

Butler Audio is considering adding an audiophile-grade line driver to the TubeDriver BLUE car audio line. Drop us a line at info@butleraudio.com and let us know if you would be interested in an audiophile-grade line driver.

Q: What is the sensitivity range of the amplifiers?  Top of Page
A: .5v to 10.5volts
You can find this on the amplifiers specs page. Click on the specific model number below...

TDB275    TDB2150    TDB475    TDB575

Q: What is the "gain control" for?  Top of Page
A: The gain control is used to set the amplifiers input level to match the output level of the source unit (CD/DVD/Tape/Radio). This is NOT a volume control. Turning the control clockwise increases the input sensitivity and turning the control counter-clockwise decreases the input sensitivity. Always set the input sensitivity a low as possible.

Q: How do I properly set "gain"?  Top of Page
A: The following suggestion is the most basic method to give you a good starting point for your system:

  1. Set the amplifiers gain control to minimum (all the way counter-clockwise)
  2. Set the source unit's volume control approximately ¾ level or to the highest undistorted level.
  3. With dynamic (i.e. "lively", not "elevator") music playing, slowly turn the gain control clockwise until you hear distortion. Stop, and turn the gain control just slightly counter-clockwise until the distortion ceases.

This setting will provide you with the approximate proper "headroom" level and the widest S/N ratio. There are more sophisticated/accurate methods for setting system gain. If you have the equipment and time to more accurately set your system gain, contact us at tech@butleraudio.com

Q: What is "signal to noise (S/N) ratio"?  Top of Page
A: The ratio of the level of the maximum signal output to the level of the noise floor of a shorted input. The larger the number is, the better. Usually expressed in dB. The best S/N ratio is achieved by using the highest undistorted level from the source unit and the lowest undistorted input level setting on the amplifier.

Q: How high of an input voltage can I drive the amplifier with?  Top of Page
A: 16.5 volts. Be aware that the amplifier's power supply is a softly regulated design.

Q: What is "damping"? Does it matter?  Top of Page
A: Damping is defined as the ratio of the load impedance to the output impedance of the amplifier.
Click here to read more about damping and what the numbers really mean.

Q: What is the current draw of the amplifiers?  Top of Page
A: You can find this on the amplifiers specs page. Click on the specific model number below...

TDB275    TDB2150    TDB475    TDB575

Q: Can I use TubeDriver BLUE amplifiers to drive a subwoofer?  Top of Page
A: Yes. TubeDriver BLUE amplifiers can easily drive any typical subwoofer. For example, the TDB2150 is rated at over 500 watts @ 4 Ohms with a very high current capability; more than sufficient to drive the most demanding subs.

Q: What speakers do you recommend?  Top of Page
A: We believe that speaker selection has more to do with personal taste than with measurable differences in the various manufacturers products. For that reason, we do not recommend a specific brand of speakers but rather suggest that you audition as many different types of speakers within your budget as you can and narrow down your selections according to what YOU specifically enjoy. A good set of quality speakers should be a lifetime investment and you should always buy as much speaker as you can afford.

Q: What are the amplifier's dimensions?  Top of Page
A: You can find this on the amplifiers specs page. Click on the specific model number below...

TDB275    TDB2150    TDB475    TDB575

Q: What is the warranty?  Top of Page
A: TubeDriver BLUE car amplifiers are covered for a period of one year from date of purchase, if you return the included warranty registration card. Otherwise, the warranty is 90 days. Please go to our WARRANTY page for more information.

Q: Do you repair the original TubeDriver product?  Top of Page
A: Yes, in most cases we can repair your amplifier. Please go to our POLICIES page for more information.

Q: What model/version of TubeDriver amplifier do I have?  Top of Page
A: Please go to our POLICIES page for more information.

Q: How should I mount the amplifiers?  Top of Page
A: Due to the MASSIVE aluminum heatsink design (over 400% larger than the original TubeDriver amplifiers), which is an integral part of the chassis, TubeDriver BLUE amplifiers can be mounted in any position as long as you leave at least 1" of space around the chassis.

Q: What is the difference between the original TubeDriver amplifiers and the new TubeDriver BLUE amplifiers?  Top of Page
A: The original TubeDriver amplifiers were a hybrid design developed by BK Butler. They used pentode 6L6GC tubes driving MosFETs in a unique circuit topology. Although it was considered to be a hybrid tube design, it was actually very unique in its operation.

TubeDriver BLUE amplifiers are a revolutionary new design patented by BK Butler. They are the end result of 25 years of experience in designing tube driven products for some of the world's most demanding end-users; professional musicians. They employ 6SL7GT twin-triode tubes directly coupled to the speaker and mated to audiophile-grade bi-polar devices to produce an amplifier that combines all the highly-desired sonic characteristics of the best in tube amplification (punch, dynamics, liquidity, detail) without any of the limitations (heat, wear, low power, rolled-off frequencies) AND have all the advantages of the best solid state amplifiers (power, current delivery, transparency) without any of the limitations (harshness, edginess, even order harmonic distortion).

The ONLY car audio amplifier to provide the best of both worlds... and its here today... ENJOY! - BK Butler

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