Audio Gestión is a young Spanish company just over a year old, and an importer of classic audio brands such as Altec Lansing and Cerwin-Vega, as well as lesser-known ones such as Digisintetic, Caw Boy and Q4 Audio, a manufacturer of signal processing and amplification gear, among other things. The latter is the subject of this article, with its DPI amplifier range, made up of the DPI10, DPI20, 30, 40 and 50 models with power ratings ranging from 300 to 1500 watts at 4 Ohms, and more specifically the DPI15 model. A range of power amps whose design is geared toward fixed installations for general sound reinforcement or large public address systems, theaters, nightclubs, etc.

Front view
The DPI15's front panel is fairly spartan, like the rest of the unit, although one shouldn't expect much from the look of a power amp; its job is simple, though it is the toughest in the audio chain, along with the speakers. Despite its simplicity, the front panel can't be faulted. Besides the power switch, it houses two generously sized fans that vertically take up almost the entire two rack units of this unit. Their speed depends on the temperature inside, mainly at the heat sinks of the output transistors. They run extremely quietly, being practically inaudible at a distance of more than one meter.

To cover them and house the air filters, there is a front cover that is simply fastened with a screw, which makes cleaning easier, something extremely important for the ventilation system to work properly.

In the center of the front panel are the potentiometers, of the stepped type, in 1 dB increments, and below them a switch and an indicator labeled "Remote," which activates the "Sense" amplified-signal feedback system (more on this later). Next to them are all the status indicators, which report a power supply overload, bridge mode operation (Bridge), fault protection (Ready / Protec), brief overloads (clip) and a limiter for overheating. A good array of indicators to give you, from the outside, a fairly accurate idea of what is going on inside it.

Rear panel
The rear panel is perhaps where the best features of this power amp are found, with a large number of connectivity options for outputs and inputs.

The signal input connections can be chosen among four different formats: stereo jack, male XLR (both on Neutrik Combo-type connectors), and Phoenix-type push-in connectors for bare wire. Also for the input signals, the rear panel has a block of switches to configure the signal inputs as stereo or parallel mono, plus two high-pass filter modes at 30 or 50 Hertz, to avoid amplifying frequencies below those, which demand a lot of effort from the power amp and may not be within the needs of the installation.

As for the amplified signal outputs, there are three four-pin Speakon connectors, for the right channel, the left channel and Bridge. In parallel for the left and right channels, it also has Phoenix connectors, which are common on gear for fixed installations. Next to the latter there are some connectors, also in this format though smaller, marked "SENSE," which, although we did not have the power amp's documentation for this test, we can assume by analogy with other amps that do have this system, are an input for the amplified signal coming back from the speakers themselves, so that the power amp has information about what is really happening with the electrical signal it is sending to the speakers, and can thus apply corrections to fix the usual aberrations in passive crossover systems. This control system can be turned on or off at will by means of a button on the front of the unit marked "Remote," which, when off (indicator unlit), makes the amp work as a conventional amplifier.

There is also another block of switches for the signal output. With them you can enable stereo or bridge (Bridge) operation, a mode in which the power amp becomes mono, with both channels working in opposite phase, thus achieving more power than the sum of both separately.

Also in this block of switches, you can choose how the "CLIP" light on the front panel warns of short-duration signal overloads, also known as "clipping." Depending on the setting, these overloads are shown instantly or only when distortion levels last longer.

Could I get 19 kilos of power amp, please?
The role of the power supply, and more specifically of the main transformer in any power amplifier, is fundamental to achieving the best sound, generally speaking even more important than the number or quality of the output transistors. To use a colloquial example, it is like a vehicle's engine, where all the energy needed to move it resides.

If the transformer does not have enough energy reserves, and by direct relation a large enough size and weight, it becomes a bottleneck in the amplification process. A sufficiently energetic input signal coming from a kick drum or a bass, for example, could be clipped if the transformer were unable to sustain that amount of electrical current for as long as the note lasts, and it would collapse, like cyclists who run out of steam halfway up a mountain pass and hit the wall.

In the case of the DPI15, the power supply is of a classic design, with a generously sized toroidal transformer, enough for this amp's specifications: 500 watts into 4 Ohms.

With this brief look at the transformer's role in power amps, it is safe to say that amplifiers can almost be bought by weight, knowing that a transformer is mostly copper, one of the heaviest metals in nature, although from this simple theory we have to exclude all those amplifiers that use switching power supplies, similar to those in computers, whose virtues have not yet won over all technicians, since many think there's nothing like a good transformer…

Also part of that weight, but with a much smaller role, is the unit's metal chassis, simple in its construction since it is self-supporting, that is, it has no internal frame to which the parts are attached, apart from the outer top, bottom, rear and front covers.

A look inside the power amp
Removing the top cover and taking a peek inside the amp, you can sense a great effort to shield it against external radio interference, whether electromagnetic or radio frequency, as shown by the generous choke filters made of ferrite rings wound with heavy-gauge copper wire, intended to act as radio-frequency firewalls. However, the placement of the signal input boards right below the power supply filters clashes and contrasts with this philosophy, because of the possibility that some of the junk signals dumped to ground by these filters could be radiated outward and contaminate these audio inputs due to their proximity, together with the proximity of the transformer. This input layout is, however, changed in other higher-end models, which move them a prudent distance away.

Standing out at a glance because of their size and silver color are the four heat sinks to which the four output transistors are attached. They are oriented lengthwise, from the back of the amp to the front, aligned with the airflow generated by the fans. Along this path, acting as a bottleneck, the air is forced through them, picking up their heat and expelling it outside.

The mechanical construction of the chassis is simple, overly so in some respects, as it does without an internal subchassis to hold all the components and allow access to the underside of the motherboard by removing the metal bottom cover for any repairs, so the maintenance technician is forced to remove the whole board to inspect it, with the risks any such disassembly involves, despite all the conveniences the manufacturer has come up with to simplify it.

The motherboard makes extensive use of very small SMD components, common in sound processors and other low-power devices, but not very suitable, in the opinion of the author of this article, for working with high power and temperatures; but time, better than I, will have the last word on whether these amps are prone to failure, or whether they prove ready for hard work without incident, which would avoid major repairs.

Conclusion
The sound of this power amp during the test was correct, with a small boost in level in the midrange. That gain, although outside what the purest theory says it should be, produces a voice presence that is very pleasant to listen to, appropriate if the intended purpose is public address systems in venues or large installations with 100-volt lines.
The sound of the fans was never even noticeable, and the indicator lights proved effective, even in extreme situations such as input signal overloads or short circuits at the speaker outputs, at which point the output protections kicked in quickly.

Judging from the data gathered in the test, and in the absence of written material from the manufacturer due to the product's newness, the designer's goal in building this amp seems to have been to keep manufacturing costs as tight as possible in some areas (chassis construction and finishes) in order to invest in others, such as firewall systems, operating status display through its external indicators and external signal control (Sense), and its connection versatility to adapt to a multitude of environments.

Technical specifications
- Maximum power at 1 kHz with less than 1% THD
8 Ohms 330 watts
4 Ohms 500 watts
2 Ohms 800 watts
Bridged at 8 Ohms 1,000 watts
Bridged at 4 Ohms 1,500 watts
- Intermodulation distortion: 0.05%
- Frequency range at ±0.5 dB: 20 Hz to 20,000 Hz
- Input impedance:
Balanced 20 kOhms
Unbalanced 10 kOhms
- Weight: 16 kilos
- Dimensions: height 88.9 mm, width 482 mm, depth 350 mm