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kentdream 19th February 2013 07:06 AM

chip model recommendation
 
I had a old pair of speaker come with a amp many years ago. After years i am interest to assemble a kit amp for it, i am looking for some kits which is easier to build. which kits that will fit my speaker?

I've check out those LM3875/3886, they had a output of 56w/65w, on below the speaker said max input 70w, will a 3886 kit hurt the speaker if the output is too large? what shall i take consider about the 6ohm impedance? i saw most amp kits are quote in 4/8ohm load. Is 87db hard to drive?

Bookshelf 2way
low-pass: 12cm cone type / high regions: 2.5cm
frequency band: 55Hz-35000Hz
max input: 70w @ 6ohm impedance / 87db/W/m
Crossover: 3.3kHZ

Details:
ONKYO D-032AX

many thanks in advance.

Mooly 19th February 2013 07:33 AM

You won't harm the speaker with a higher powered amp, in fact it can be lower powered ones that "clip" the waveform (when they run out of available voltage swing) that do most damage.

The LM3886 is highly regarded and would probably be my choice.

87db/w is no indicator of how "difficult" a load it is. This refers to the efficiency of the speaker and how much power is needed for a given level. Difficult loads are where the impedance dips to low levels deviating from the nominal value. I'm sure there won't be a problem with yours.

kentdream 19th February 2013 06:31 PM

Thx Mooly for your reply, i did consider there is a "spike protection" may cut out in some high notes area, this is why i might prefer to pick 3875 instead of 3886.

Would you still suggest 3886 to be the first choice?
*I had already "smoke" 3 DAC kits in last year, makes me very desperate now.. :(

So, i want something easier to build with.

AudioLapDance 19th February 2013 07:01 PM

Well a gainclone should build your DIY confidence because if you do 'smoke' them, they are easy to diagnose and fix (unlike digital:()

All of National's Overture series of amp chips have the SPIKE protection (3886, 3875, 3976 ...). You're thinking of LM1875 but that is lower power ... maybe too low.

Here's some good info:

Gainclone Chip Amp FAQ

I'd go with a lm3886 gainclone board or kit from somewhere. They all sound close enough at this beginning level but the 3886 has the added power and mute circuit that can be used for safety.

Then play with the parts, 3875, 1875 ... and maybe try a 3-d dead bug style!

Remember you don't want to push your gainclone too hard:

http://www.diyaudio.com/forums/blogs...012-03-30.html

(Don't change gain resistors like in the article. The point is ... don't drive them so hard)

Cheers,
Jeff

Jay 19th February 2013 07:04 PM

Quote:

Originally Posted by kentdream (Post 3376826)
Would you still suggest 3886 to be the first choice?

3875 if you want crystal clear mids, 3886 if you want woofer control. Looking from your small woofer, does the woofer give sweet midrange? Does it have passive crossover on the woofer? If no crossover or only one coil (first order) my intuition is that you better go with 3875.

Mooly 19th February 2013 07:22 PM

Quote:

Originally Posted by kentdream (Post 3376826)
Thx Mooly for your reply, i did consider there is a "spike protection" may cut out in some high notes area, this is why i might prefer to pick 3875 instead of 3886.

Would you still suggest 3886 to be the first choice?
*I had already "smoke" 3 DAC kits in last year, makes me very desperate now.. :(

So, i want something easier to build with.

Opinions are divided so its up to you :D I've told you the one I would go for :)

kentdream 21st February 2013 05:08 PM

yes. without proper tools and equipment is very difficult to diagnose what had gone wrong. really desperate if u had smoke 3 DAC kit.

i smoke 2 sets of dac5 v1.3, and 1 set of v1.7 (white smoke and red hot pin 7 & 14 from wm8741 )
very much like the one below: (has been discussed here)
Assembled Board DAC WM8741 WM8805 Coaxial Optical Decoder 24bit Weiliang DAC5 | eBay
i will buy assembled board directly from weilang this time. btw, how to check my old op-amp (op2604 x2 & N5532s x2) is not busted? 3 dead kit is already very costy..

may i ask, the dac pre-amp on above don't have a volume control, and the my desired chipamp don't have a volue control, where can i put it?


I will gave up sk3875 & LM1875 now because as AudioLapDance said output power seems low for my speaker. I will take Jay's advice since i prefer a clear mid, 2.0 is enough for this setup. Let me open up the speaker cabinet and see if there is any crossover inside.

i think i will stick with 3875 or 3886 as a simple buildup. Maybe i will order the kit from china, and may custom order a toroidal transformer for 24-0-24, will you suggest to add a second rail supply voltage(adding 9v x 2) for future use? Do i need really need a speaker protection circuit? I have confidence to build the rectifier kit.

(i've another cheap cheap & old 5.1 av speaker has re-cap last year, lucky i didn't smoke them, this seems a capacitor like 2.2uf for cross over, when i re-cap it changed to 4.7uf and bass freq. seems changed.)

i'm sure i have a long way to go and learn all these audio stuff.:o

KatieandDad 21st February 2013 05:54 PM

The GainClones are only medeochre Med-Fi at best. If you are only after 50W try one of the Pass amps.

AudioLapDance 21st February 2013 06:24 PM

Quote:

Originally Posted by KatieandDad (Post 3379835)
The GainClones are only medeochre Med-Fi at best. If you are only after 50W try one of the Pass amps.

Dude, let's just get him up and running and happy with a diy amp and then we'll worry about "mid fi".

AudioLapDance 21st February 2013 06:30 PM

Kentdream,

I wish you would have started slower more simply with the DACs and got one working. That must have been frustrating. :mad:


I'm a teacher and building on small successes is ... what we do! :)



You can put a 10k pot between the dac and a simple LM3886 non-inverting chip amp. It works fairly well and then we can build from there!

Remember: small successful steps! Don't worry about the 'ultimate' this or the 'audiophile' that ... for now ...

So, start with a simple 3886 kit, get it working, then upgrade parts, change gain/configurations, then maybe try a discrete (no chip) amp Pass F5, then more complex discrete ....


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