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Chip Amp in Nabu chassis – 60 wpc

I built a “Chip Amp” a couple weeks ago.  Well, “finished” is always relative…

 

This is based on the National LM3886 chip which is basically an entire audio amp on a chip.  It is rated for approximately 68 watts into an 8 ohm load with the right supply voltages.  I initially ran a pair of Heyboer 12V trannys in series to emulate a 12VAC-0-12VAC tranny.  This is roughly half of what it was supposed to be.  I was only getting about 20 watts with that voltage setup.  I replaced those with a pair of 22-0-22 toroidal transformers which are nearly silent mechanically and provide the voltage that the chip expects to see..  It is now producing full power, somewhere around 50 or 60 watts.  Also, it is basically two mono-blocks in one chassis as it has two separate transformers and two separate power supplies for left and right.

 

Here are pictures in the Nebraska Surplus “Nabu” chassis before I switched to the toroids.

nabu-amp-001m.jpg  nabu-amp-004m.jpg  nabu-amp-005m.jpg

Total cost was: 

Chip amp dual mono kit $85  http://www.chipamp.com/

Nabu chassis (inc S&H) $29

Transformers $80

Misc jacks, wire etc $15

Total = $209 

It works great. It has more than enough clean headroom to play at loud volumes in my 26′ x 24′ living room with my TransLam Alpha speakers.  I hooked up my CD changer with my Harmon-Kardon receiver but pulled the jumpers between the pre out and power amp ins so I am using only the preamp portion of the H-K receiver.

Stereo imaging is fantastic. I’ve played a bunch of Stereophile and Carver test CDs as well as some selected CDs from my music collection that I knew had challenging or interesting passages. The stereo soundstaging is excellent. I often heard instruments coming from outside the two speakers. Granted, that is due primarily to good speakers and a decent listening environment, but the amp sure helps. I never heard that with my other amplifiers in this same listening environment with the same speakers.

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One comment

  1. You have updated your transformer from a smaller rating to higher rating and also higher voltages, I read your comparison at DIY audio, is there any other things you want to add, eg better bass, more powerful? mid range suffers or remains unchange? any change to the high freq.?

    any feedback is welcomed.

    thanks
    [GDS-thanks for your question. The only thing that really jumped out at me is that the bass seemed to be better with the smaller EI transformers. The toroids are certainly much louder due to the increased voltage most likely. Also, all of my observations are subjective. I didn’t put any instrumentation on it.]



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