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Old 25th May 2008, 05:18 PM   #11
Minion is offline Minion  Canada
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Quote:
Originally posted by weatherlight
thank you, a pcb without mute standbye stuff will be very helpful

Here is the Version of the PCB that i did from the Layout in the datasheet..

Click the image to open in full size.

As you see I got rid of a couple features as i didn"t need them for my amp, mostly just the Bootstrap feature which i wasn"t going to use as my supply Voltages were +/- 42V DC, and the Mute/standby feature is disabled...I also increased the track thickness and the overall size of the Traces and planes....

I hope you can use it....

Cheers
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Old 25th May 2008, 06:01 PM   #12
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We could, perhaps, fool it a bit. Try Nichicon Muse 0.47uF for your input filter cap.

And, just leave the NFB cap at values between 22uF and 10uF (probably you already have one of those installed). However, make that one a Nichicon KZ or Elna's Cerafine.

Substitute: You can add (parallel) a 4.7nF or 10nF, polyester (bubble) or ceramic, to a rather ordinary (22uF or 10uF) electrolytic cap for nearly-similar results. When using an ordinary power electrolytic cap in that role, make it a high voltage capacity model.

Additional experiment: Get some very cheap polyester caps at 5x smaller and 50x smaller than estimated values for electrolytic. For instance, you parallel the "5x smaller" with the "50x smaller" cap.

Well, there's some stuff to try.

P.S. If none of this works, then we need to look at the whole circuit and see if there's an impedance mismatch.
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Old 26th May 2008, 07:06 PM   #13
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paralleling the 10-22uF electrolytic caps with a 100nF or so does something similar to supply bypassing with 2 caps (100nF and 100uF etc)?

Also i'm planning to built the modular application circuit in the datasheets (since one tda will probably burn at 40V suplly with maximum gain, (100w). Do i need like 10000uF caps at power suplly and another 1000uF at tda suplly bypass?
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Old 26th May 2008, 08:11 PM   #14
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Quote:
Originally posted by weatherlight
paralleling the 10-22uF electrolytic caps with a 100nF or so does something similar to supply bypassing with 2 caps (100nF and 100uF etc)?

Also i'm planning to built the modular application circuit in the datasheets (since one tda will probably burn at 40V suplly with maximum gain, (100w). Do i need like 10000uF caps at power suplly and another 1000uF at tda suplly bypass?
I've just got two thing to say.

If an electrolytic cap is "made for power" then its probable that you can get good results from bypassing it with 100nF or smaller (or much smaller).

When you have a big offboard power supply, then the onboard (at amplifier) caps are usually smaller, say in the range of 330uF, and this is especially true of monobloc/dualmono layouts.
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Old 31st May 2008, 01:07 PM   #15
eketehe is offline eketehe  Indonesia
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Quote:
Originally posted by weatherlight
paralleling the 10-22uF electrolytic caps with a 100nF or so does something similar to supply bypassing with 2 caps (100nF and 100uF etc)?

Also i'm planning to built the modular application circuit in the datasheets (since one tda will probably burn at 40V suplly with maximum gain, (100w). Do i need like 10000uF caps at power suplly and another 1000uF at tda suplly bypass?
Hi There,
I'm curious about what Mr Ionomolo was says here :

My version of GC, a LM3886 based

as you also mention, i think the 1000uF he mentioned is on PCB / before the 100/220/330/470uF. our local KIT suplier also 'always' add a pair of 1000uF on their chipamp PCB ( TDA7293, 7294, lm1875, 3875, 3886 etc ) but none 1000uf for their BJTs PCB.
i think its for a good technical reasons than just sale the 1000uFs. they're cheap anyway.

Mr Ionomolo,
need yor kindly explanation and advs...

Brgds
Eka
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Old 31st May 2008, 02:12 PM   #16
eketehe is offline eketehe  Indonesia
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Quote:
Originally posted by Nordic
The experiment is cheap, the lessons priceless.. give it a try.
I just runs test for having a suitable lowpass input caps by compares 4 caps.
2 kind of polarized Electrolit and 2 other non/bipolar film caps. all 4.7uF.
the result : unlike the films. the electrolitycs a bit keep the sounds ( bass, kick bass, lower sound ) longer. the extra resonance is not good for sub woofer, we need the beat/ the speaker's cone reverse ontime. and join the stereo's sound naturaly/harmonicly.

that's may offtopic, only report tht : vary caps, same value, brands, may vary the result. n this 2 vs 2 may not enough to judge. except my personal define
my best choise for guitar amp ( 83Hz-880Hz is 2.2uF filmcaps / MKP 10 without additional smaller for bypass. ) on C input, and 22uF nonpolar at Ci for 2 x LM3886 / 2 x 10' fullrange.

get your best
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Old 18th June 2008, 10:29 AM   #17
bedil is offline bedil  Indonesia
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our local KIT suplier also 'always' add a pair of 1000uF on their chipamp PCB ( TDA7293, 7294, lm1875, 3875, 3886 etc ) but none 1000uf for their BJTs PCB.


Hi eketehe

I was wondering can you give the your local kit suplier addres/phone, is it bandung or jakarta ? and how much it's cost for lm 1875, I've been searching lm1875 kit at glodok but no luck thank
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Old 18th June 2008, 10:41 AM   #18
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my local suppliers tell me lm3875 is obsolete and i cant even find the lm3876 around here. is there a way i can find them or is it really obsolete ?
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Old 20th June 2008, 01:45 PM   #19
eketehe is offline eketehe  Indonesia
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Quote:
Originally posted by bedil
our local KIT suplier also 'always' add a pair of 1000uF on their chipamp PCB ( TDA7293, 7294, lm1875, 3875, 3886 etc ) but none 1000uf for their BJTs PCB.


Hi eketehe

I was wondering can you give the your local kit suplier addres/phone, is it bandung or jakarta ? and how much it's cost for lm 1875, I've been searching lm1875 kit at glodok but no luck thank

Hi Bedil,
Ok i'll send you a PM.
Brgds.
Eka
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Old 20th June 2008, 01:55 PM   #20
Dxvideo is offline Dxvideo  Turkey
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Quote:
Originally posted by weatherlight
my local suppliers tell me lm3875 is obsolete and i cant even find the lm3876 around here. is there a way i can find them or is it really obsolete ?
Dear weatherlight,

1- Do I know you?
2- If I dont know then why dont you join us also?
Who we are; forum.diyaudiotr.com
3- LM3875 is not recommended for new designs. Thats true, but it is NOT OBSOLETE. I think its the best sounding chipmap. And I am currently worlking on a LM3875 project for over one month.
4- You can find LM3875 from Farnell, Digikey and the other suppliers, may be you can request samples from National Semiconductors.
__________________
Best regards,
Ozgur
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