Nakamichi DAC-101 (Part 5) Op-amps & Capacitors Upgrade

The upgrade of this Nakamichi DAC-101 is continue. Previously, by using the external linear power supply to this DAC unit gives significant audio improvement.

The DAC IC alone is not the only factor that determined how good the DAC could perform, but what comes around to support the DAC really matters to reveal the true potential of the DAC itself.

I think the analog stages after the DAC contributing a lot for the better sound. This Nakamichi DAC-101 analog stages is divided by many section, but I will explain based on the schematic and where should I start to upgrade it.

Please continue reading.

I get the Nakamichi DAC-101 analog stages schematic as shown on the picture bellow.

I am amazed on how well the Nakamichi engineering combined the op-amps for I/V, LPF and buffer stages with discrete transistor for the pre-amplifier output. This complex analog stage like this will contributing a lot in the sound quality.

This Nakamichi DAC-101 using dual TDA1541A S1 in balanced mode. The I/V stage is to convert from current to voltage signal also in balanced configuration. Then the signal are combined together to become the un-balance output that will goes to the next stages.

The next stages are the LPF, buffer, and the pre-amplifier are all in the un-balanced configuration.

The good thing about this analog stages is only using one coupling capacitor per channel. It is at the pre-amplifier discrete transistor output, indicate by C127R and C127L. This is means the upgrading cost for the new capacitor would be so much affordable.

The original capacitor used here is the Nichicon Muse. It is very popular at that era and quite good in the sound quality. For this upgrade, I will change it to the Elna Silmic capacitor.

And here it goes, the new capacitor are in. Look how big those are.

The first upgrade is done.

The next upgrade is changing the op-amps to the better specification

The original Nakamichi DAC-101 using 4 pieces of JRC 5532D op-amps for all the analog stages. It is a good choice but not the best. As per schematic above, on the buffer stages, the op-amps require to able set in the unity-gain and not much op-amps can do this perfectly.

So because previously I got a good sound impression with the OP275 op-amp, then I will use it now as well. It is an affordable op-amp, yet one of the best op-amp for audio application like this.

I also install the high quality gold plated 8 pin socket for future op-amps swap.

The upgrade is now finished.

This simple upgrade only takes me about 30 minutes to completed. I put back to my home audio system and starting to audition the sound quality after this upgrade.

As usual, every capacitors need some time for breaking-in. I just took about 2 hours playing the music and the capacitor performance start to reveal it true performance. The sound is now more smoother, more emphasis on the mid-range without loosing any detail in overall sound presentation.

The op-amps upgrade really contributing to the overall sound improvement as well. Especially on the micro detail of the music and the imaging is now really improving a lot.

So, in my opinion this upgrade is easy to do and really rewarding.

There is another upgrade that I need to do and that would be cover on the next post.

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