Nakamichi DAC-101 (Part 2) The Internal Components

Continuing my previous post about initial review of the dual TDA1541 S1 DAC from Nakamichi DAC-101 is surprisingly over my expectation compares to the previous review is CD Player Sony CDP-750 using single TDA1541A.

No wonder the CDP-750 is for budget CD player while the Nakamichi DAC-101 is a hi-end car audio components will sound much better. This Nakamichi DAC-101 is install in my home audio system by using 12 volt 5 ampere low noise SMPS wall adapter as main power supply to the unit. The sound characteristic from this DAC is smooth yet detail with the strong point in the warm of the vocal presentation.

Unfortunately this unit cannot pass the first 3 hours playing in my home audio system. It burnt and break-down. So, with lots of optimism with this unit, I will continue to see what the components inside it.

Disassembly this DAC unit is straight forward. Few screws removed from the bottom chassis and the side steel plate then I can have all the access to the internal components.

The first things I notice is the copper plate covering important circuit underneath it. This kind method is easily find in the hi-end audio for better low noise.

The PCB is dual layer wood material board. This PCB is very common for 90's electronic product. No fiberglass PCB here.

Another thick copper on the top of the two bellow is a heat-sink for the voltage regulator.

These are the 4 pieces IC volt regulator for supply the dual TDA1541 S1 and the analog stages.

As you can see the analog stages after the DAC is very complicated. They are 4 op-amps and few transistor.

The engineering from Nakamichi has think it so hard to make this kind of circuit. Yet the result is astonishing sound quality.

I make some marks on the picture below to explain each components category in this DAC unit.

Deeper inspection to the problem in my previous post is for sure inside this power supply unit. This indicated by the copper cover in the power supply unit is very hot and radiated to the whole unit heatsink. The funny smell is also come from inside of it.

The copper case is installed back-to-back on the PCB, so with de-solder the pins, they can be remove easily.

I also notice this power supply unit has been repaired before. It is easy to notice by see few capacitors brands are not the same with others. The new capacitors are using lower quality which very common if you ask a television repairman to do this kind of hi-end equipment repaired.

The PCB trace on the bottom side are mostly broken. This kind PCB is could not withstand with many de-soldering process.

Then this is the main reason where the smelly things came from. The main power supply transistor is almost cut by half! It cannot handle the current very well yet the heatsink is just too small.

Looking to the power supply circuit, it is basically 2 different unit in one board. The broken one is the dual voltage for the DAC and analog circuit. Then the other power supply is DC 5 volt only handle for the digital receiver unit.

The dual voltage power supply require high current which this power supply cannot handle very well. Despite there is a problem previously in this repaired power supply unit, it is clearly indicate that the Nakamichi DAC-101 has bad performance power supply design from the beginning.

I will not doing another repair on the bad design power supply like this. It is just wasting my time and yet there will be no improvement on the sound quality after all. Because the main reason I am using this DAC is for home audio system, then the next upgrade will be modify this power supply unit using external linear power supply for better linearity. This new power supply will deliver higher current for the DAC circuit. I will cover this upgrade on the next post.

Meanwhile, I still not finish open up all the copper cover.

The next one is the digital receiver unit, let's continue.

This digital receiver circuit in my opinion is clean and neat in the components arrangement.

The digital receiver is using PD0037 and the oversampling is using YM3414.

On the bottom of this unit lying few IC's that glue-logic IC for separate the digital signal to the dual TDA1541A S1 DAC.

The next things is finding the dual TDA1541 S1 DAC underneath the copper plate. This is the main reason for this Nakamichi DAC-101 is become a hi-end status.

Think that this DAC is came from the bubble economic era and the growing market of the first digital audio, so every manufacturer push their limit to create a hi-end product like this.

So I guess I had covered up all the internal components in this DAC.

There are a lot rooms to upgrade in this unit that I will be cover it up on the next post.

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