What Gainclone Amplifier's IC should I choose?

When you plan to build this Gainclone amplifier on your own, especially if this is the first-time build, you might asking the question, about of what kind IC's for this Gainclone amplifier should I use? This is a normal question and I will try to help you by describing the sound quality from each IC.

The original 47 Labs Gaincard amplifier only use the IC from the National Semiconductor. The older model use LM1875, a 20-watt maximum power output @ 8 ohm impedance. It is works on lower voltage, from dual differential 12 volt up to 30 volts.

The newer model Gaincard using LM3875, a 56-watt maximum power output @ 8 ohm impedance. It works from dual differential 12 volt up to 35 volts.

Let's talk about the LM1875 first. This LM1875 sound is very musical. I've ever read on the internet about this LM1875 is vacuum tube alike amplifier, but I am not argue about that since it is very subjective feeling. But for sure, this LM1875 still presenting very good detail of the music with more forward and warmer vocal than the LM3875.

Note should be taken that this LM1875 is the older IC amplifier compared to the LM3875. The internal circuit of LM1875 not a complex as the LM3875. It doesn't have the protection circuit to internally cut the noise from turn ON - OFF sequence. Means that this LM1875 will having a pop noise during turning the amplifier ON or OFF.

This pop noise can be eliminated by adding auto delay relay circuit to the speakers output. At least it needs 2 second delay during power ON before the relay contacting to the speakers. It also requires immediate cut off the relay upon powering OFF the system to prevent another pop noise cause from drain of the capacitors. This pop noise is a DC output to the speakers that potentially damaging your speakers.

Then I will talk about the LM3875. You can read my review This LM3875 here, the sound of this LM3875 is very dynamic, very open and details compare to the LM1875. But the vocal is not as sweet as LM1875.

The LM3875 has more advanced technology inside it. The pop noise output protector has included in this IC. This mean the LM3875 will not have the pop noise during ON-OFF like the LM1875.

The size of LM3875 is larger than LM1875, but I think this will not become a problem since they are both still consider a small IC's.

The only concern when build between those ICs, if based on the datasheet, is the input coupling capacitor is required for the LM1875. That is mean you should take care the quality of this input capacitors which mostly cost more expensive. Compares to the LM3875 which doesn't need any input coupling capacitors. The absent of the input coupling capacitors might reduce the cost of building LM3875 amplifier, but you should make sure that your music source, the CD player of anything are DC output free to prevent it damaging your speakers.

The others IC that including in this Gainclone amplifier is LM3886. The original Gaincard amplifier never use this LM3886 in their product line up. This LM3886 have the same size with LM3875 but the key different is this LM3886 has the Mute function. Although when building this LM3886 amplifier, we will always disabling this Mute function.

Basically, this LM3886 have the same sound characteristic of LM3875 but offer more watt to drive at 4-ohm impedance speakers. The power output is 68 watts at 4-ohm. For 8-ohm impedance, this LM3886 only produce maximum 36 watts which smaller compares to the LM3875.

This LM3886 become so much popular because it is using inside the Yamaha monitoring studio speaker type HS80M. The Jeff Rowland amplifier also using this LM3886 IC in parallel configuration.

Recently, if we are talking about Gainclone amplifier, the terminology has shift not only based on LM1875 or LM3875 IC only. This Gainclone amplifier terminology is now cover to all IC based amplifier that can sound good. This also including the TDA IC series from Philips, but I found this TDA is more economical solution than the LM series.

Let's take the example the TDA2020 which totally the same pinout and specification to the LM1875. The sound quality from TDA2020 is acceptable for less critical listener because it hardly better than the LM1875.

The STK IC's can be also include in this Gainclone amplifier because it is using IC as the main amplifier components. You might find this STK IC are very popular among Japanese brand amplifier before 90's such as Sansui, Akai, Sony, Pioneer and many other amplifier brands at that time. I am remembering the popular STK016, STK4132II, or STK050, but this STK series will not become my recommendation for this Gainclone amplifier project. The first reason is because original STK are very old in technology, it requires lots components outside the IC, and the second is the sound quality is not as refined as the LM series.

The class D amplifier also can be incuded in this game. It is now become the new player in this amplifier world. Could this class D amplifier become the next Gainclone amplifier? Or it is apart from what we are now?

This class D amplifier is not like the early class D introduction that having poor sound quality, but instead the specialist class D amplifier IC manufacture such as the Tripath from Korea is now become new kids on the block who shocking the hi-fidelity audio world. Other than the Tripath, we know that Philips NXP TDA and Texas Instruments has the same high quality class D amplifier IC as well.

The class D amplifier is very efficient, have bigger power output from the less power input because of its efficiency and can be supply by single power supply. The class D IC are in SOIC package and mostly comes in a complete board, so you only attach the input and output cables to make it work. I have heard the Tripath TA2024 is the best class D amplifier for sound quality. Personally, I think this might be the next Gainclone amplifier contender for this audio world.

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