The CDS-4700 Composite Amplifier Revision 2.0 delivers high-definition audio so it can be used in professional applications for recording or post-production studios as well as in home environments.
The construction of this amplifier is achieved by using electronic components fully available from the various semiconductor vendors. Generally speaking, it is possible to use almost any available low-noise, low-distortion dual operational amplifier, although to obtain a total harmonic distortion value in the output signal of 0.000049%, the LM4562 or LM49720 op amp has to be used. It is possible to get very good results of these parameters using the NE5532 op amp, ubiquitous in countless audio equipment applications for several decades. If desired and available, the RC/NJM4580 operational amplifier can also be used, which, in our experience, has shown a great performance for this application as well.
The CDS-4700 Composite Amplifier features a balanced input for voltage signals built from a buffer and a differential amplifier for both the negative and positive sections of the balanced signal. The topology used has a high input impedance and a high common mode rejection ratio (CMRR), in addition to low noise and low harmonic distortion in the signal that is to be amplified.
In addition, the CDS-4700 amplifier includes a servo mechanism that allows correction of the offset voltage at its output to levels very close to zero volts. For this task it relies on a high precision operational amplifier, which can be either an OP177, an OPA277 or even an OPA227. This system eliminates the use of high capacitive components at the output. However to avoid the speakers suffer any damage due to an offset or DC voltage present in the output signal for a long time, it is recommended to include Olas audio’s SP-DR1200 speaker protection system.
The CDS-4700 composite amplifier also has a regulated bipolar source with protection against disconnection or failure of either of the two power rails. This mechanism protects the operational amplifiers and the rest of the circuitry.
The following are the main features of the CDS-4700 amplifier:
- Total harmonic distortion less than or equal to 000049% (-126.19 dBV) measured in an 8.3Ω resistive load connected to its output port with a power consumption of 2.25 Watts
- Total harmonic distortion less than or equal to 000227% (-112.91 dBV) measured in an 8.3Ω resistive load connected to its output port with a power consumption of 46 Watts. These results are obtained by applying a 1 kHz sinusoidal signal with total harmonic distortion less than or equal to 0.000015% at the input port of the amplifier
- Frequency response from 20 Hz to 20 kHz equal to -0.08 dBV and -0.27 dBV, respectively
- Bandwidth equal to 100 kHz
- Common mode rejection measured at the input stage equal to 99 dB for direct current and equal to 89 dB at 1 and 10 kHz
- The board layout allows you to install the LM3886 and LM2876 chip amps, as well as LM1875, all from Texas instruments
The PCB material used is FR-4, double sided, 1 oz. copper and the thickness of the card is 1.6 mm. Its approximate dimensions are: width = 10 cm, length = 12.8 cm and has a lead-free HASL-type surface finish. It uses through hole technology for easier component assembly.
The published price is for the PCB only. Bill of materials and instructions are sent upon purchase.