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The TDA1541 DAC from Philips is regarded as one of the best, most natural sounding DACs ever designed and can be found in a number of high end players from Naim to Marantz to the Arcam Alpha 5. It is normally partnered with is its digital filter, the SAA7220P/B which converts by over sampling the 16bit 44.1kHz data to 16bit 176.4kHz data. This pushes unwanted sampling artifacts higher up and out of the audio band where they are easier to filter out before the audio only signal is fed to the CD players output socket. When a non over sampling DAC is used, these unwanted signals are just above the audio band and are therefore harder to remove. Most amplifiers are fairly immune and unaffected by these ultrasonic signals and have little effect on overall sound quality. What does improve is the sound of the CD player once the SAA7220 has been bypassed, due to lower jitter signals being fed to the DAC and the over sampling error are removed. Although these errors are small, High Fidelity is all about the small signals, the last few percent of information which can dramatically change the perceived sound from obviously reproduced to almost real. Removing the digital filter prevents the small amount of corruption of the original data, and therefore the 'reality factor' is not lost.

As in any CD player, most Hi Fi owners will be aware of the detrimental effects that jitter can have on a CD player. The SAA7220 digital filter also contains a clock on board which is used to clock the data to the DAC and to run the CD player other chips. This clock as it is inside the SAA7220 chip is easily corrupted by the chips other workings. Data is being over sampled and shifted around inside the chip producing a very electrically noisy environment. This noise is picked up by the clock which is no more than 1 mm away on the same silicon die and is therefore incapable of producing a clean signal. On the NET Audio NOS Converter, it has its own on board clock which is used to feed the CD player itself and the NOS converter board. The clock chip and crystal have their own decoupling capacitors and are physically separated from the other chips to minimize any interference of the clocks operation thereby producing a clean clock signal.

Word Clock being regenerated (lower trace) by the NET Audio NOS Board compared to the standard word clock (upper trace).

The clock is buffered and fed to the CD players circuitry and also to the NOS boards other chips. These are used to synchronously regenerate the incoming data, word clock and bit clock signals so as to remove the jitter present on them and feed the nearby DAC chip with clean jitter free signals for maximum performance. They are regenerated in a synchronous manner so as to prevent data errors and 'clock beat', again to preserve the integrity of the data from the CD and to maximize performance.

This converter board works equally well with the TDA1543.

Please note:- When the NET Audio NOS board is fitted to a player the digital output for an external DAC is disabled.

Fitting Instructions can be downloaded here.

If you require even higher performance and there is space in your player around the SAA7220 chip, the NET Audio Super NOS board can also be fitted in the same way. The Super NOS has a higher quality clock on board and improved circuitry over the NOS board but does take up more space in the player. It also requires separate 12 to 15V DC power which can be taken from inside the player of from a dedicated power supply. Details are available here.


NET Audio Non Over Sampling Converter Board

NET Audio Prototype Non Over Sampling Converter Board fitted inside an Arcam Alpha 5

Dimensions are 31.5mm (L) x 19mm (W). The mounting leads are 0.64mm square (0.8mm across) and fit straight into the Arcam SAA7220P/B PCB drill holes.

 


NET Audio NOS Reclocker Board

The NET Audio NOS Reclocker boards were designed for those customers who wanted to NOS their player and improve the sound over the standard NOS board by fitting an external clock. The NOS Reclocker can be configured to be simply plugged into a CD player to replace the 7220 chip with no other modifications by using the CD players on board crystal or to be used in its External Clock Reclocker mode where an external clock is used for increased performance.

Fitting instructions can be downloaded here.

Configuration Jumpers are here.

 


TDA1541/TDA1543 Clock and Non Oversampling Converter

TDA1541/TDA1543 NOS Converter includes:-

  • One NET Audio TDA Clock and NOS Converter PCB with on board clock.
  • Fitting instructions in Adobe PDF format
Total Price excluding P+P = £40


TDA1541/TDA1543 NOS Reclocker 

TDA1541/TDA1543 NOS Reclocker includes:-

  • One NET Audio TDA  NOS Reclocker PCB
  • Fitting instructions in Adobe PDF format
Total Price excluding P+P = £35 

For use with the CD players on board crystal.

 


TDA1541/TDA1543 NOS Reclocker 

TDA1541/TDA1543 NOS Reclocker includes:-

  • One NET Audio TDA  NOS Reclocker PCB
  • Fitting instructions in Adobe PDF format
Total Price excluding P+P = £35

For use with an external clock.


NOS and Reclocker PCB Sockets 

TDA1541/TDA1543 NOS and Reclocker includes:-

  • Two 12 way sockets to enable the NOS Boards to fit a standard 0.6MM drill hole such as the Philips PCBs. Arcam Alpha 5 Boards are the correct hole size. The NOS boards require 0.8MM drill holes to fit correctly.
Total Price excluding P+P = £4

 

Item shown is a 3 way, the items posted will be 12 way x 2 pieces.