Sony STR-DB2000 Review

The STR-DB2000 was a full-featured Audio/Video Receiver Amplifier manufactured by the Sony Corporation in 2003. It is a discrete 6-channel digital class-d amplifier with s-master pro chipset and features such as QS, digital theatre system (dts), Dolby Digital EX, Pro Logic II, and Digital Cinema Sound (DCS). This amplifier is very similar to the STR-DA2000ES, which had variations in the tuner and remote control. With 8 Ω load, you can expect 120-watts per channel, and 0.6 % THD. The STR-DB2000 came supplied with RM-PP412 remote control, whilst the STR-DA2000ES comes with RM-LG112.

The introduction of the s-master pro was first in 2003 making it Sony's third-generation digital amplifier product. The improvement was their use of discrete output transistors and an additional digital processing stage, DC Phase Linearizer (DCPL). This stage enables the adjustment of low-frequency phase shift that produces warmer bass.

The STR-DB2000 had many features and was for the professional who wanted the best in sound quality. The tuner has Radio Data System (RDS), which displays the name of the radio station. It has a huge plethora of inputs and outputs at the back. For the audiophile who still uses records, there is a phono input with RIAA preamplifier built-in. The digital connections consist of one coaxial input, and 3 optical inputs, with an additional optical output for Mini Discs. There is also a subwoofer output through an RCA socket for connecting an external amplified loudspeaker.

Anything with s-master pro tends to be expensive even in the pre-used market; however, I was lucky to find this amp that was broken and was able to repair it. The sound quality is remarkable, because it faithfully reproduces any levels of bass and treble introduced at the inputs.

Traditional analogue amplifiers usually require the conversion of digital input signals to analogue, however; in a digital amplifier, these types of conversion stages are not used, and the digital input signal remains intact throughout to the last stages. The final output stage usually consists of a variant of Pulse Width Modulation (PWM) circuitry, where a digital signal drives the speaker load. The S-Master Pro uses similar technology, which Sony calls Complementary Pulse Length Modulation (C-PLM). Their version is of course better because it controls and minimizes second-order harmonic distortion inherent in such circuits.

Digital amplifiers are easily susceptible to damage if you short their output terminals because the final output transistor drive is hard and fast and they do not take kindly to overloads. Consequently, many people sell them on eBay if they start showing Protector Code 11, because repairs are expensive.

In a typical channel, a digital power amplifier IC (HIP2101IB) generates a fast 1-bit pulse stream that switches a pair of MOSFET "booster" power transistors (SUP18N15-95). Their positive rail usually passes through a pair of 0.025 Ω resistors in series. For example, the positive rail for Q1653 and Q1663 is through the series pair R1633 and R1643. Similarly, Q1652 and Q1622 receive their positive rail through R1632 and 1642 series pairs. When a MOSFET transistor shorts, these resistors usually behave as fuses by going open thereby cutting power. Therefore, if you detect a short booster transistor, then also look for open resistors associated with its voltage rail.

The booster transistors are on the digital amplifier (D-AMP) board underneath all the other boards, which means that you have to take the whole amplifier apart just to get to them. With all the wire looms going from one board to the other, and the screws, it takes half a day of your time to take this amp apart -- assuming it is your first time and you are following the service manual. Once you have taken it apart, you cannot take any voltage readings, because the PSU board requires removal as well. Hence, one has to diagnose the fault simply by measuring component values and seeing if they are operating within normal parameters.

Digital amplifiers usually have extremely complex power supplies, and in this design, they are using a switched mode power supply. One of the problems with these is that very few people can actually understand their operation or repair them. If the chopper transformer were to fail, then very few people in the UK would be capable of diagnosing the fault.

Price/eBay

This digital amplifier is extremely desirable due to its high sound quality and equal power channels, making it a high-end of surround sound systems. The build quality is also extremely high of the type you would expect for a Nakamichi amp. For that reason, its value remains almost the same as when it was new. However, a broken one that is going into protect mode can be costly to repair due to the complex power supply and therefore broken ones might sell cheaply. Any repair of this amplifier will be expensive due to its complexity and engineers usually charge a premium.

Get a New Sony!

This amplifier is extremely complicated and requires a qualified, experienced, and talented engineer to repair it, and there are very few out there these days. At best, people check and replace the fuse on the PSU board and if it keeps blowing then it is best to sell it on eBay as spares, so that someone with the skills has a chance to fix it.

Once you know that this is a big job to repair, you can happily sell it as spares or repairs without feeling guilty. The good news is that you will have room to buy a new Sony amplifier, and their latest ones have more functions, more buttons, and more settings for you to fiddle with, and at half the price! So just think of all the fun you could have.

This is a multi-page article and in the following pages, you can see the inside of one of these amplifiers, including the MOSFET output transistor that I replaced during repair.

This Article Continues...