SMSL SP200 Components Analysis

My review yesterday about the sound quality of this SMSL SP200 headphones amplifier surprisingly got a really good result. This is the most affordable THX certificate headphones amplifier on the market right now. Comparing to others manufacture, I saw they also made similar amplifier with also THX certificate and the main components inside is also the same. But the selling price is way more higher than this SMSL SP200. SMSL official websites have published the picture about what components they are using inside it. But I guess, if you're me that so curious to see it directly, you will do the same as I do, digging deeper about components inside it and finding any potential components to upgrade.

Opening this case is quite easy. All you need is a set of hex keys. This SMSL SP200 using 3 kind of hex size and the number of screw using on it is quite a lot. Unscrew everything then this is the first look of the full amplifier board.

In my opinion, this board is tidy and neat. The double layer PCB makes the bottom layout can be this clean. Unless there are two jumper wire still hanging around on the bottom. Those wires function is a jumper from power amplifier ground to audio ground at the headphones jack. Replace it by using better cooper or silver wire will perhaps improve the sonic for a little bit.

This is my short analysis at the amplifier board. I put 6 section to inspect them one by one. So let's start from the section 1, the power supply.

The on-board power supply luckily using linear power supply. This is CT output transformer and the dual AC 18 volt power output go through the single diode on each rail, then pass through the solid capacitor. This is the first stage ripple rejection using C-L-C, as you can see the value of the coil is 100uH. Then the IC for regulated power supply is using IC NCE4614 act as the second stage ripple rejection. This is IC Mosfet package that capable up to 40 volt 8 ampere current.

On the section 2 is a module for trigger the headphones output relay. You notice when powering this amplifier ON, the sound will not comes until you heard clicks from the relays. This is a delay time for the relay during start up the unit. Main purpose for this delay is to avoid any pop noise during ON or OFF the unit.

On the third section is the amplifier module unit consist of one op-amp IC on each channel. The IC is single channel OPA564 from Texas Instruments act as power amplifier for the headphones. The input before going through this power amplifier IC is pre-amp module using op-amp IC OPA1812A. This pre-amp also do the job as the gain selection that you can choose by toggle the front Gain switch to Low or High. As per my sound preference, I prefer the low gain for better sound quality and lower noise.

You will also notice at this power amplifier section, there are several transistor near them. In total 4 transistor near the OPA564 and 2 transistor near the OPA1812A. The function for that transistors are voltage regulated for the IC. I guess the THX certificate really means very clean audio measurement comes from pure and ripple free voltage feed to the IC.

In the fourth section is for the single ended RCA line audio input. You will notice the DC blocking capacitor is using Nichicon green BP 220 uF. One capacitor for each channel. Upgrading this capacitor might be the major improvement in audio quality. After passing through this capacitors, then the audio signal go to the op-amp IC for the input buffer. This IC is OPA1612A, the dual channel op-amp. Only one IC needed for single ended line input.

The section 5 is another regulated power supply. I not sure where it goes, but my prediction is going to the input buffer op-amps for all OPA1612A in single ended or balanced input section.

The section 6 is for sure is input buffer same as the section 4, except it is for balanced input to single ended output converter. The reason for this is because the input at the amplifier on section 3 is all single ended, so even the audio line input is balanced, they need to convert it to the single ended by using the op-amps before go to the volume control and the amplifier section. The op-amp IC are OPA1612A.

The audio signal from the balanced input socket pass through to the DC blocking capacitor first before going to the buffer IC. The capacitor as you can see is the pink color Nichicon. 2 pcs per channel because it is balanced. Each capacitor value is 220 uF.

You will also notice there is 2 relay near the buffer op-amp. One at the section 4 and another one near the section 6. This relay is an input selector for XLR or RCA that you can choose by toggle the switch on the front panel.

I think that's all the section covering all components inside this SP200 amplifier. Further more, I also inspecting the supporting components, such as input capacitors, the headphones sockets and the volume potentiometer is the parts need to upgrade to better quality. The Neutrik brand for the XLR headphones output will be my choice. Then the ALPS green will be very suitable as the SP200 potentiometer replacement. Then for the input capacitors upgrade will become a problems since they are comes with the high value capacitors. Replace it to the better quality such as MKP or the Blackgate will be very difficult due to the big size and very costly.

I should mention for the XLR 4 pin balanced headphones output is not true balanced. Means the negative pin on each headphones channels are connect directly to ground. It makes this connection same function as the single ended headphones jack output. The OPA564 is single ended output, one IC for one channel only, so there is no way this amplifier could do dual amplification for the balanced output.

So, the analysis result is quite surprising don't you? Especially on the both balanced input and output circuit. But anyway, regardless on how the circuit beneath this amplifier are designed, I am now very satisfy for not only the sound quality this SMSL SP200 capable of, but I also have some to-do-list for future components upgrade.

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