Preamplifier / Power Amplifier Matching
Probably the second most critical interface connection in the audio chain is the interface between the preamplifier and the power amplifier. The interconnecting cable can also have an impact in this interface, especially if the cable is very long or is highly capacitive.
For the best and most predictable results it is often best to use pre- and power amplifiers from the same manufacturer, as it stands to reason that these components would form the most synergistic combination together, allowing the design engineer to make the best decisions for each component.
If different makes of pre- and power amplifier are being considered it may become necessary to compare the output impedance of the preamplifier and the input impedance of the power amplifier. Generally for full frequency response it is advisable to match component impedances with a look-up factor of at least 200.
This is not to say that the components would not work together. The audio industry does have open architecture and a common interface between components. However what can happen with disparate impedances is that there could be substantial frequency response roll-off between the two components, particularly in the low frequency bass region. This is only potentially a problem when considering a tube preamplifier to drive a solid state amplifier, as many tube preamplifiers have very high output impedances, (designed to drive high input impedance tube power amplifiers) and most solid state amplifiers have low input impedances. Sometimes a high output impedance preamplifier can be very sensitive to the capacitance of the interconnect cable, which tends to roll off the high frequencies also.
The combination of tube front end for voltage amplification and a solid state power amplifier for current demands can work very well in delivering the best that both technologies have to offer. This is provided the preamplifier is designed to drive the lower input impedance that solid state amplifiers typically present to the preamplifier. The VTL TL2.5 and TL5.5 with their output impedance of approximately 200ohms are both designed to be able to drive solid state amplifiers down to 45k ohm and 20k ohm input impedance respectively, with little or no noticeable roll-off in the bass.The TL7.5 will drive any power amplifier through any reasonable length of cable with predictable performance, with only slight bass loss into the punishing 600 ohm studio standard.top
Amplifier / Speaker Matching
Due primarily to their large power supplies and well-coupled output transformers, VTL power amplifiers are capable of delivering the power and performance to most loudspeakers available in the market today.
For best performance and proper use power amplifiers should ideally be matched to the chosen loudspeaker load, and we offer some general rules of thumb to follow when considering assembling a system.
In our experience the system begins with the loudspeaker that will work properly and sound good in the desired acoustic space. Matching the power amplifier to the loudspeaker is usually a function of driver size, efficiency and budget. Efficiency is not the only determinant – even though they may be very efficient, many speakers with large drivers need tremendous amounts of damping factor and current capability to control the driver properly.
To get everything out of the loudspeaker that it was designed to do we suggest that you use the highest power amplifier that you can. Then use the following general guideline to ensure that the amplifier can handle the load of the largest driver in the speaker:
| Model | Woofer Recommendation | |||
|---|---|---|---|---|
| IT-85 | 6″ and below, mini-monitor | |||
| ST-85 | 6″ and below, mini-monitor | |||
| MB-125 | 8″ (or 2x 6″) and below, floor standing | |||
| ST-150 | 8″ (or 2x 6″) and below, floor standing | |||
| S-200 | 10″ (or 2 x 8″) and below | |||
| MB-185 | 10″ (or 2 x 8″) and below | |||
| MB-450 | 12″ (or 2 x 10″) and below | |||
| S-400 | 15″ (or 2 x 12″) and below | |||
| Siegfried | 18″ (or 2 or more x 12″) and below | |||
As a cross-check, choose an amplifier in the VTL range that is approximately the same price bracket as the loudspeaker, and as a final check listen to the combination for yourself to determine whether or not it sounds right to you.
Be aware that these are only general guidelines. The recommendations may vary depending upon room size, volume level required and whether or not in your opinion the amplifier sounds like it has sufficient power for your loudspeaker.
Please note that these guidelines are provided as our recommendation for what VTL amplifiers are designed to drive. Exceeding these recommendation at high signal levels can cause premature failure of output tubes, which will not be covered under any warranty.top