[bmwpowere36m3]

Looking towards another project this time a speaker amp (stereo), expanding my horizons. This will be my first speaker amp, however have already conquered a CMoY, "SS" Millet, SOHAII, and a ϒ1.

There is so much info out their on this chip-amp its hard to make choices out of all the info

, but also a majority of it is on the LM3875. So to start off, I want to know some basic info...

Looking at the spec-sheet (LM3886) a Vcc of 30V seems like a good compromise between running a 4 or 8 ohm load. At this point I'm not sure what speakers I want to run, but I want keep this as universal as possible and powerful enough (just in case

). At 30V, 4-ohms, the output is ~85W and at 8-ohms ~45W. I'm not looking for SPL > SQ, more interested in SQ > SPL.

However looking at some of the distortion figures, I guess what's the problems with running too high a Vcc, heat dissipation of the chip and distortion? What's a good compromise? Is it worthwhile to build a PSU, that can output 30-40V?

Next up the trafo, how big (VA)? The chip specs a max output of 135W, so a stereo setup (2x chips) would need a trafo to support a max of 270VA.... correct or too much? I see other builds specing anywhere from 160-300VA.

Finally looking at two PSU designs to choose from, the first part of chipamp.com kit (CarlosFM):

A regular "snubberized PSU", they mention with a 18V trafo the output is ~25V and with a 22V trafo is ~34V. Finally the VA rating should be 220-330VA.

Another is PSU is CarlosFM's Regulated Snubberized PSU:

Again the same basic principle, but I guess a better design as the output is now more "regulated" via the LM338. From what I read over on the site which hosts this PSU design, it did improve the sound quality of the gainclone.

So is it worth building, I'm kinda leaning towards it and it doesn't seem anymore difficult to build. Here he lists to use a 2x 28-30V 250VA trafo, so again is 250VA enough?

Are the secondary voltages & VA they list for both these designs the same specs as called out by manufacturers like Avel Lindberg? I remember when building my SOHAII there was talk about the listed specs were for unloaded trafo's vs. loaded.

Finally I was thinking of using a "SS" millet as my pre-amp for this amp... good, no good? My concern is that it might have to much gain for the LM3886. Why do I want to use it, I dunno maybe give the amp a little tube flavor.

 

[BlingBlingDr]

Great questions. I hope someone answers them cuz I am going down the same road. Want a gainclone to use with my recently built Millet MiniMAX. I'd like to run some bookshelf and maybe even tower speakers with this setup.

 

[qusp]

if you arent afraid of SMD soldering; I would check out the gainclone at sjostromaudio includes probably one of the most sophisticated onboard power supplies I have ever seen!! its all included on the PCB and there is a forum packed with info on all manner of things, but power supplies, SMD headamps, power amps and a super version of the RIAA phono amp. pretty good support on the forum too. I have built and use his power supplies on 2 of my DACs and am a big fan of his smd version of the diamond buffer. heaps of parts on his gainclone though, so you gotta be pretty organized.

 

[bmwpowere36m3]

Ha, this is an old thread and I've built my GC since then. After reading and reading and struggling with choices, I finally settled on building a "simple" GC... In the end, the consensus from many users is the "magic Gainclone" sound came with its simplest design.

I ultimately tried to emulate the GC designs of Peter Daniel's from AudioSector (and a member on DIYaudio). I built my GC around a LM3886 chip, 22+22V 300VA transformer, and a simple three-resistor design (it has other parts as well).

Paired with a set of Fonken Speakers is sounds great (for bookshelf-type speakers, lacks a little low-end).

*edit* Also pairing headphone amps with a gainclone, has been ill-advised by many (at least that's what they told me). Headphone amps are there to drive headphones, and not input stages of power amplifiers. Maybe some headphone amps work, but the Millet "SS" Hybrid isn't one of them. I've just been listening: ϒ1 > GC > Fonkens

Maybe my SOHAII would work well, but is sounds great, so I haven't been messing around with it yet and it still needs to be cased!

 

[Magsy]

The premium Peter Daniels GC is something to behold, I bloody love it and wouldn't give it up for the world!!

I have a full dual mono setup, with his DAC and a r/c passive attenuator, it may not be super resolving but you always leave with a smile, it is very relaxing and musical!

Don't bother with the pre, I've tried all of my Headphone amps there and it just makes the sound worse. Straight through, passive is the way.

 

[fishski13]

Quote:

Originally Posted by bmwpowere36m3 /img/forum/go_quote.gif Ha, this is an old thread and I've built my GC since then. After reading and reading and struggling with choices, I finally settled on building a "simple" GC... In the end, the consensus from many users is the "magic Gainclone" sound came with its simplest design. I ultimately tried to emulate the GC designs of Peter Daniel's from AudioSector (and a member on DIYaudio). I built my GC around a LM3886 chip, 22+22V 300VA transformer, and a simple three-resistor design (it has other parts as well). Paired with a set of Fonken Speakers is sounds great (for bookshelf-type speakers, lacks a little low-end). *edit* Also pairing headphone amps with a gainclone, has been ill-advised by many (at least that's what they told me). Headphone amps are there to drive headphones, and not input stages of power amplifiers. Maybe some headphone amps work, but the Millet "SS" Hybrid isn't one of them. I've just been listening: ϒ1 > GC > Fonkens Maybe my SOHAII would work well, but is sounds great, so I haven't been messing around with it yet and it still needs to be cased!

love the minimalist y-1/GC/Fonkens set up you have there. i bet it sounds fantasic.

i built a similar set up for friend: y-1/CK2III/LM3875 Gainclone/uFonkens. i thought it sounded fantastic in my small room.

i'm in the process of building a y-2/B1/F5/uFonkens for my man-cave in the basement. my wife wants a GC/uFonken set-up for the living room too.