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Chip Amps Amplifiers based on integrated circuits

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Old 25th June 2013, 02:00 AM   #11
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Ok, a lot of reading and solder fumes later I have successfully completed 2 power supplies for some pcb kit amps, said kit amps, three point to point/perforated board iterations of the np100v12 headphone amp, one of which heavily modified and sounding excellent both as headphone amp and as preamp, and now I have finally amassed most of the parts needed for a lm3886 build including the power supply.
At first I mostly followed what was used in Mick Feuerbacher's amp posted earlier in this thread as I scoured local electronic stores and this is what I sourced so far:
2x LM3886
2x transformers with 110v primary and 0-13-26 secondary at 4A
8x 4700uf 63v nichicon caps for PSU
I also have the required supplies and resistors to follow the advised PSU and most of the resistors for the P2P amp build, but being that i got most of it from local stores, i have no idea what family of resistors i have and what tolerances i will be working with... so these supplies are just sitting unused in my parts bin for now.

At this point I am getting ready to place an order with mouser, and I was wondering if I am following the right schematic. My friend from Italy swears that I should follow the original Nat Semicon schematic to the T, and most of what I read online is torn between 2 camps.
Is there something I am missing? Does anyone have a tried and tested schematic with BOM that I would be advised to follow? Is that power supply schematic entirely too complicated?
Please help shed light on the issues dear sirs, I am less green behind the ears now and subsequently I might actually be able to understand your suggestions.

I have an hungry pair of Beovox MS150 speakers that can't wait to meet a finished LM3886 amp as this far its seen nothing but the wimpy output of a TDA1554...
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Old 25th June 2013, 03:05 AM   #12
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TDA1554 is certainly short of watts when compared to an LM3886 but it more than makes up for that in SQ, in my experience.
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Old 25th June 2013, 03:37 AM   #13
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Quote:
Originally Posted by abraxalito View Post
TDA1554 is certainly short of watts when compared to an LM3886 but it more than makes up for that in SQ, in my experience.
What circuit do you use for yours? i am about to rebuild my TDA1554 amp as i want to take the pcb away and go point to point. With my current setup i get slightly weak bass, but that's taken care of by the pre-amp i feed it with, the NP100v12 amp.

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Old 25th June 2013, 03:45 AM   #14
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excuse the painfully bad pictures/messy desk.
Cellphone camera at the wee hours of the morning...
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Old 25th June 2013, 03:51 AM   #15
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Quote:
Originally Posted by nubskillz View Post
What circuit do you use for yours?
I have a couple of examples up on my blog (link on the number of entries to the left of this post). Don't be put off by the part numbers being somewhat different, from studying the DSs it seems the TDA8561 is pretty much the same internally. The TDA8566 is again very similar just with a beefier output stage (and balanced inputs), and that's the one I currently listen to in my system.

I've improved on the schematic shown in the blog by listening - in particular the PSU being regulated (LM350T) improves the bass, as does adding seemingly crazy numbers of reservoir caps - at present I have about 170,000uF per channel. Adding caps made me realize that for such a long time I lived with and accepted murky bass - its unbelievably tight and agile with massive decoupling

There's a pic of my amp up on this thread - Possibly the most frugal high-end sounding amp? - Page 4. There are so many caps, the chip itself is hidden It is laid out on a small PCB which a colleague did for me.

As for your desk, here's mine
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Last edited by abraxalito; 25th June 2013 at 04:01 AM.
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Old 25th June 2013, 04:14 AM   #16
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Originally Posted by abraxalito View Post
at present I have about 170,000uF per channel.
That is actually ridiculous. Until i saw the picture i could not actually understand what i was about to look at. I can't really get that extreme, Right now i have about 15k uF in the power supply and 3300uF on the board, but since it was a kit i don't even know what schematic they used.. i just replaced the largest cap that came witht he kit for a 3300uf nichicon. This is the kit: Philmore-Datak 80-050 44 Watt Mobile Stereo Amp Kit
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Old 25th June 2013, 04:16 AM   #17
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I hope that doesn't sit in your bedroom, mine sadly does.

Last edited by nubskillz; 25th June 2013 at 04:19 AM.
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Old 25th June 2013, 04:26 AM   #18
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Quote:
Originally Posted by nubskillz View Post
That is actually ridiculous.
Yeah I originally believed so too, but the SQ tells me I can't accept lower now. Interestingly Thorsten L who used to post a lot here came to a rather similar conclusion from his own listening - that an amp needs 5-10mF per watt of output power (mine's only 10W - so his estimate would say 100mF).. I reckon its about output current though, not output watts. This I think is a reason why valve amps score because they drive effectively much higher impedance loads..

Yes the pic of my desk I took sitting on my bed.
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Old 25th June 2013, 05:13 AM   #19
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Now I don't feel so bad. Ha.
So you're saying i should take the 8 caps i have set aside for my lm3886 and use them to rebuild my tda1554 amp?
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Old 25th June 2013, 05:22 AM   #20
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Well I don't like telling people what they 'should' do - it looks as though your space is bigger than mine so perhaps you're more in need of watts? But if you put SQ first then yes, the TDA is just a better designed chip I reckon than the LM. One objective reason for that is PSRR - chipamps are very sensitive to the quality of their power. My TDA only sounds good with a large number of ceramic caps across the supply to reduce the HF noise. I originally listened to it with 4 1uF X7R ceramics per channel and considered the top end poor and was tempted to dump it because I figured that should have been enough HF decoupling. But fortunately curiosity got the better of me and I began playing with upping the number......
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