Decco, internal shots



For our purposes Decco's DAC stage is of primary importance as we’re concentrating on use as a playback device for PC digital music files. As far as circuit topology, Scott Nixon designs more often include vacuum tube buffer. For Decco the DAC circuitry is deceptively solid state until you consider the vacuum tube driver stage on the pre-amplifier section. In this application all sources analog or "digital" benefit from tube Sonics. The difference insofar as Scott Nixon designs is the location of the tube on the pre-amp section rather then on the DAC PCB itself.



The PCB including the A/D and D/A stages pictured above uses not one, but two Phillips TDA1543 chips. The same chips found in some high cost, High End DACs i.e. Wavelength Audio DPU Silver edition retailing at around $10k. At the audio website HeadFi.org the forum member Infinitesymphony has generated a lengthy list including 148 external DACs and PC Soundcards by the D/A chips found within. The list entitled: All the DACs money can't buy, pt.2 arranges each product by cost and then the chipset used among other data. From this list I find two specific DAC chips tend to find their way into more successful designs then any other. These are; Burr Brown PCM1704 chipset and Phillips TDA1541 Double Crown chipset, the latter found in one of the most coveted DACs on the market, the $15k Zanden Model 5000 Signature. As for the Burr Brown (or Texas Instruments) PCM1704 this is found in the exceptionally value prices $400 Tecon Model 55 (integrated SET amp w/DAC) and on the other extreme the 63k USD / 44k EUR GTE Trinity DAC. This product is as controversial as it is costly and utilizes 16 Burr Brown PCM1704 as the analog filter stage (reviewed at TNT-Audio). I don't expect Decco nor the Tecon to stand up to any system in which Zanden's $15k DAC (and $34k transport) would occupy, and although I can imagine a system built around the GTE Trinity, I can also imagine owning a Buggati Veyron 16.4.



In the photo above looking down from the rear of the amplifier, placement of the DAC PCB was well thought out. Given the chassis dimensions the DAC is about as far from the torroidal transformer as possible. There are many ways to reduce such potential electrical noise, the simplest and most effective is to isolate or keep the components apart. Compared to alternatives such as the installation of noise reduction circuitry which must have some deterioration or outright distortion on the signal, this simple philosophy stands behind a "separate" concept dictating much of High End design.



Next we look to the volume or potentiometer which looked to be an Alps. I contacted Peachtree whom stated many units did in fact leave the factory with Alps motorized pots, but this is not guaranteed. The included motorized volume was clean throughout the spectrum without a hint of static or noise introduced into the signal. In the photo below the motorized "pot" is mounted on the amplification PCB with a small daughter-card atop (below far left).



Where manufacturing costs are concerned, the attenuator is one of the most critical parts in any integrated or pre-amplifier. The signal will eventually pass through therefore its quality or lack thereof will have an effect on sound. A valid design concept in 47-Labs literature was minimizing the number of devices and the length itself of the signal path. As we know any chip-amp success we spoke of is the reduction in the number of parts in the signal path (no pun intended). While they might seem equal in purpose they are nonetheless an equalizer when it comes to signal integrity.



There are more costly products out there which may use an inferior attenuator. Audiophile grade products at the Purist level will rely on stepped attenuators. Stepped attenuators (or volume potentiometers) may feature "...high-quality fixed resistors replacing the carbon track...and high quality switch contacts replace the metal scraper." The logarithmic taper is maintained with greater separation between increments hence signal loss or "bleeding" is kept to a minimum. Note the Steps each with a matching resistor in the Shallco Attenuator below.



Finally, our power source which is very healthy for what is essentially a chip-amp. The torroidal power supply looks be relatively robust and is part of the reason this amp has such high speed control over transients. The power source and capacitance go as long way in providing deep controlled base (below). The thumbnails below the main photo provide some more insights to the build quality and topology.





Onto the Era Design-4 Specs...