PA 2500 R Integrated Amplifier
The Integrated Amplifier
Twice as tall, higher output power and even more connection facilities – the PA 2500 R exceeds the specification of the PA 2000 R in many areas, but its character in terms of sound quality is in no way inferior to its smaller sibling. This by no means goes without saying, because very powerful amplifiers often forfeit the finer points of dynamics and detail tracery. Our PA 2500 R integrated amplifier circumvents this danger: its basic circuit is the same as that of the PA 2000 R, and even the circuit board layouts are identical. However, its heat-sinks are twice the size, and the case accommodates two of our new high-performance mains power supply units, with the result that it can deliver more than 280 Watts of continuous power per channel into 4 Ohms loudspeakers. The amplifier is therefore effortlessly capable of controlling speakers which are extremely critical in terms of phase and impedance. The PA 2500 is even more powerful than the smaller machine, but retains exactly the same dynamism and cultured sound.
Power supply
The quality of any output stage is determined to a very great extent by the mains power supply as well as the circuit topology. Mains power supply units must be as stable and resilient as possible, to ensure that the voltage they generate does not collapse even when very high peaks are encountered. In conventional equipment this requires very large transformers, but the limited space available in the low-profile R-series machines spurred on our engineers to develop an ingenious alternative solution: a regulated high-frequency sine-wave mains power supply with generous reservoir capacity, capable of delivering up to 1200 Watts without problem. The mains power supply can deliver very large quantities of current extremely quickly, even when the gradient of the peak signals is steep. Our experience in building amplifiers over a period of thirty years has taught us the importance of the quality of audiophile modules for the final outcome in terms of sound quality, and that is why we choose our components with great care and then select them according to strict criteria, to ensure optimum characteristics for each specific application.
Connections
We use low-loss mica capacitors with silver electrodes, zero-induction resistors, precision low-noise audio resistors, and nickel-free gold- or rhodium plated terminals specially manufactured for T+A. Many of these components were developed for military applications, and therefore fulfil exacting requirements in terms of quality and durability. Another in-house development for the latest R-series is a completely new and very fast data bus for data exchange between the devices, which makes it possible to control a whole system with a single remote control handset. Alternatively, if the system includes an MP 2000 R, the equipment can be controlled using the T+A App for iOS or Android. Both amplifiers are equipped with a sophisticated protective circuit which is situated outside the signal path, and therefore cannot possibly have any adverse effect on sound quality. The protective circuit constantly compares the input signal before the output stage with the output signal, and instantaneously switches off the output relays if it detects the slightest deviation (clipping, distortion, etc.). The protective circuit is also triggered if overheating occurs, or if a short-circuit is present at the outputs. All the electronic circuitry for controlling the machines is recessed into the solid aluminum front profile, where the shielding effect is outstanding. The front panel features a bright, dimmable screen (VFD) and control knobs with variable lighting.
Amplifier Technology
R-series pre-amplifiers and power amplifiers are constructed in accordance with the double-mono principle. This means that we completely isolate the left and right channels from each other – even in mechanical terms – and use identical circuit boards, so that the sound quality of both channels is identical. The two separate amplifier circuit boards – with input section, volume control, high-voltage amplifier and current amplifier stage – are housed in the right-hand half of the case, where they are shielded from the mains power supply and the output section by the massive heat-sink. As with our HV-series machines, the circuit topology of the input stage is based on a cascoded differential amplifier with hand-selected audio J-FET transistors and stages of completely discrete construction, without operational amplifiers (op-amps). This overall circuit design, combined with the high quality of the components employed, virtually eliminates the need for overall negative feedback. The result is that the amplifier boasts excellent linearity combined with an extremely wide dynamic range. Signals up to 60 Vss can be processed without any hint of distortion. The volume control takes the form of discrete precision resistors and bi-stable gold-contact relays, resulting in absolutely exact channel matching combined with the shortest possible signal paths; this in turn virtually eliminates noise and distortion. The following voltage amplifier stage and current amplifier are completely isolated from each other galvanically. This uncompromising design completely avoids the danger of feedback effects from the loudspeaker currents into the voltage amplifier stages, and also precludes adverse effects from the loudspeaker load.
The amplifiers are fitted with separate tone controls for each channel, and the function can be completely by-pased by means of gold-contact relays. A loundness circuit is present which can be adjusted to match the efficiency of the loudspeakers.
Specifications
Preamplifier stage
| Frequency response + 0 / − 3 dB | 0,5 Hz – 300 kHz |
| Signal / noise ratio, unweighted / A-weighted | 105 / 109 dB |
| Total harmonic distortion/Intermodulation | < 0,001 % / < 0,001 % |
| Channel separation | > 90 dB |
| Loudness | Switchable, variable to suit loudspeaker efficiency |
| Tone controls Bass Treble |
Switchable, channel-separate −6 … +8 dB −6 … +8 dB |
| Nominal input sensitivity | 4 × 250 mV … 4 Veff/20 kOhms |
| High level (RCA) | |
| Balanced (XLR) | 3 × 500 mV … 8 Veff/5 kOhms |
| Phono-MM (optional*) *Phono module replaces one high-level input | 1 – 5 mV, 16 Capacitances |
| Phono-MM (optional*) *Phono module replaces one high-level input | 60 – 1000 µV, 16 Impedances |
Outputs
| Headphone | 50 Ohms |
| PRE out RCA | Nom 1 Veff, Max 9,5 Veff, 75 Ohms |
| PRE out XLR |
Nom 1,45 Veff, Max 19,6 Veff, 75 Ohms
|
Output stage
| Nominal output per channel | into 8 Ohms 140 Watts into 4 Ohms 280 Watts into 2 Ohms 560 Watts |
| Frequency response + 0/– 3 dB | 1 Hz – 150 kHz |
| Slew rate | 60 V/µs |
| Damping factor | > 65 |
| Total harmonic distortion | < 0,02 % |
| Reservoir capacity | 120000 µF |
Mains / Accessories / Dimensions
| Control interface | R2-Link |
| Remote control | SRC 1 |
| Mains connection | 100 – 120 V or 200 – 240 V, 50 – 60 Hz Max. 2000 Watt |
| Standby | < 0,5 W |
| Additional features | Trigger input +5V … 20V via adapter plug for remote power-on Input 3 (symmetrical) or 5 (asymmetrical) can be configured as Surround Pass Through |
| Optional Accessories | PHE-P/PA R MM or MC phono content_default | Power Three HD (Carbon) | Power Bar | Audio Quad (Carbon) | Speaker Hex (Carbon) |
| Dimensions (H x W x D) | 16,5 × 46 × 40,5 cm |
| Weight | 14,5 kg |
| Finishes | Silver anodised aluminium (43), black anodised aluminium (42), brushed |
| Technical modifications reserved |
