Gainclones

rpgc1
In this article Robert Powell takes us through some of the "Gainclone" amplifiers that he has built.   "Gainclones" if you haven't heard are clone copies of the Gaincard amplifier made by 47 Labs, though "Gainclone" these days is a label that is commonly used to describe any National Semiconductor LM Overture series chip based amplifier

Don't you get just a little bit tired of the normal HiFi speak you read in reviews? "the natural timbre of the instruments was........"

 

"it was like a veil had been lifted....."

 

"suddenly I was hearing detail that I had genuinely never heard before"

 

"my shoes started to catch fire when the scorching bass line burst

in"

 

Eh?... What the bloody hell are you on about.

 

I love the smell of solder as much as the next man, but burning rubber I can do without! Where is all this leading you may ask? Well, having written numerous reviews and read more HiFi mages than I could probably afford, I have got to the stage where I feel that a fresh approach is required.

 

I was once asked if I could liken my HiFi to a breakfast cereal.Sugar Puffs was my reply, because the enjoyment lingers even after the last mouthful has been consumed. Take a pee about 2 hours later and you'll see what I mean.

 

So, what's your poison, Weetabix, Muesli, Snap, Crackle and Pop? The last option will probably be your first taste of DIY audio if your experiences are anything like mine. I was a little bit slow in catching on to the Gainclone phenomenon, but once the bug bit, I was well and truly hooked.

 

I had messed around with simple electronics; you know upgrading op-amps in CD players and swapping capacitors. I also joined in the Sonic Impact crazies and modded quite a few of those. That was my first introduction to the joys of Surface Mount components. I made a Tripath 2020 kit and tweaked a Teac AL700P. Messed around with the Tripath based Kensington 2000 iPod dock and bought some of the Sure electronics Tripath TA2024 based boards. However I was more intrigued by the Gainclone phenomena, given the original exorbitant price of the 47Labs amps.

Pic 1
I thought I would start out by playing it safe and purchased a kit from www.chipamp.com a stereo LM3886 based amp. (See Pic1) The case is an inverted Homebase Bread Bin.

 

As the kit provided all the components and printed circuit boards, unless you were a complete numpty it couldn't really go wrong. In fact it was as easy as painting by numbers. Having finished the amp with no traumas, I felt I needed more of a challenge. A point to point Gainclone was what I needed.

 

This time I thought I would try not only the LM3886, but the LM3875 as well. For the LM3875 you needed to use fewer components and cut off most of the pins.

 

My first experiences were interesting to say the least. After soldering all the bits and pieces to what I assumed were the correct pins, all I got was.......nothing, no hiss, buzz, pop....just nothing.

 

rpgc1aGreat, I've bitten off more than I can chew and wasted my money.When these things happen it's best to give it a rest and go away and come back some hours later, or leave it till the next day. Trouble is I am a stubborn sort and if I take the trouble to start something, then I am bloody well going to finish it to my satisfaction!So I just stuck at it. I eventually got something......a buzz, What!! I nearly cried with joy. I got a buzz... the creature lived. If I got a buzz, then surely I could get music. After many hours I finally managed to get it make music, boy was I happy......hungry and thirsty, but happy. I then tidied it all up, stuck it all on some Vero board and sat down and listened to MY amplifier. (See Pic 2)

 

Pic 2I felt like I was a true pioneer, battling uncharted waters and untold dangers to reach my goal. Yea, bit over the top I admit, but have you seen Bear Grylls, what a hero? shame nobody thinks about the cameraman who has to be there as well!

 

Sound Quality, Yup it made sound.......Oh I see.... you want me to eulogise about the timbre of Cymbals, the lifelike vocals, the dry mouth, the expansive soundstage that extended way beyond the perimeter of the speakers, the inky black silences and the enjoyment of "being there"..... Nope it had none of that, it err, well....just made music. O.K it makes very good music in fact. The "boogie factor" being very evident indeed. To me it has a rightness that needs no other augmentation. I am sure we have all had amps that we would have liked to have tone controls that would make up for a lack of treble or to cut or boost the bass. National Semiconductor must have geeks with very good ears to have voiced these chips so well (IMO) This is all of course very subjective. I know what I like and what I don't like and I am sure you are the same.However it is interesting to read feedback of HiFi shows where a "bad" demo is comprehensively loathed by all. So having liked my own efforts and there are many satisfied others.....................

 

I then thought that having been so clever as to make my own amp; I would make something bigger and better. This time I opted for a bridged LM3886. This would give approx 100W per channel (depending on PS voltage). I used the same circuit as for the single chip amp, but then used the bridging circuit on the National Semiconductor application notes. This was more successful and worked first time. (See Pic 3)

 

Pic 3I would say here that I don't want anyone to get the impression that my handiwork is the epitome of the pristine wirework as is the norm for say Naim, but rather a spaghetti or rats nest of wires underneath the cloak that is Vero board!. However the test is of course whether it works, hums, pops, bangs or buzzes as to whether it actually matters a jot or not.

 

I then tried the LM3875 and travelled the same route of stereo amp and then bridged. This time the bridged amp was not so successful and any attempt to remove the "motor boating" failed. This was only a problem if the phono lead was pulled out whilst the amp was on. I would never do it, but somebody else might and I felt that it was not right as a result. The amp sits forlornly on a shelf at the moment waiting for the next tide.

 

So which of these chips do I prefer? The answer is.........the LM3875. The LM3886 is the more analytical of the two, the 3875 the more musical. Both of these are a steal at about £4.00 per chip. Factor in a few capacitors and resistors and a transformer and you can build a stereo amp for about £30. I have had many commercial amps over the years and these would embarrass many of those.

 

Let's use another analogy. If I was to compare my LM3875 amp to a fruit it would be a banana, easy to access, nutritious and satisfying. Go pick yourself one now.