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Chip Amps Amplifiers based on integrated circuits

right components to use for gainclone LM3875
right components to use for gainclone LM3875
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Old 8th February 2018, 01:57 AM   #1
cwteoh is offline cwteoh  Malaysia
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Default right components to use for gainclone LM3875

Hi all chip amp expert... recently I just digged out a old gainclone LM3875 bare PCB board (AudioSector - Peter Daniel) from a box after moving to a new place. So I decided to put everything together and see if I can build a nice gainclone amp for my Mordaunt-Short MS-15 speaker.

Here is my problem... I only have the PCB board and I need to source those parts like resistor and capasitor, but I do not know what brand or type of parts I should go for it... I need advise and my source mostly from Element14 previously called Farnell.

Can someone out there give me some guidance about my concern?

The attached file is the original recipe and circuit design for my PCB. You can get the full instruction PDF file from AudioSector website. By the way... this post is not discuss about how good this the design... but I just need to get advise from all experts to buy those parts.

Thanks in advance

Michael
Attached Images
File Type: png Components and Information..png (2.6 KB, 229 views)
File Type: png PowerSupply.png (929.3 KB, 235 views)
File Type: png MinimizedGCCircuit.png (321.1 KB, 224 views)
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Last edited by cwteoh; 8th February 2018 at 02:01 AM.
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Old 8th February 2018, 09:35 AM   #2
AndrewT is offline AndrewT  Scotland
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Remove C1 & C2 from the PSU.
Move the snubbers R1, R2, C3 & C4 to the transformer secondaries. They do not do any good on the output of the PSU.

Do not use the "minimised GC" circuit.
It gives more problems than it claims to solve.
I do not recommend the audiosector implementation.
Go to the chipamp datasheet and install ALL the optional components that National list.
Use the Farnell component filters to give you all the options they hold in stock for the VALUE and VOLTAGE you require.
You will see a long list. Some will only be available in reel (3000 or 5000) quantities. Select those available in 1, or 5, or 10 minimum quantity and find the cheapest. Look at the manufacturer are they a reputable commercial manufacturer?
Download the datasheet. Check the parameters are what you need.
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Last edited by AndrewT; 8th February 2018 at 09:42 AM.
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Old 9th February 2018, 12:35 AM   #3
cwteoh is offline cwteoh  Malaysia
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are you refer to this diagram? I still able to use my existing PCB for those component?
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File Type: png LM3875TF_Datasheets.png (12.7 KB, 183 views)
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Old 9th February 2018, 12:37 AM   #4
cwteoh is offline cwteoh  Malaysia
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Quote:
Originally Posted by AndrewT View Post
Remove C1 & C2 from the PSU.
Move the snubbers R1, R2, C3 & C4 to the transformer secondaries. They do not do any good on the output of the PSU.
What do you mean by MOVE the snubbers comps to the transformer secondaries? apply only R1, R2, C3 & C4 but remove C1 and C2?
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Last edited by cwteoh; 9th February 2018 at 12:44 AM.
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Old 9th February 2018, 01:59 AM   #5
nigelwright7557 is offline nigelwright7557  United Kingdom
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10uF seems very small for a smoothing capacitors C1 and C2.
I would be using at least 100uF.
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Old 9th February 2018, 02:44 AM   #6
cwteoh is offline cwteoh  Malaysia
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Quote:
Originally Posted by nigelwright7557 View Post
10uF seems very small for a smoothing capacitors C1 and C2.
I would be using at least 100uF.
previously, my friend told me to put 10000uf ->1000uf -> 100uf parallel. But I am not sure what is that about
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Old 9th February 2018, 03:04 AM   #7
indianajo is offline indianajo  United States
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The lowest noise resistors, particularly the 680k one, are metal film.
I have found the following brands metal film resistors from farnell US (newark) fine: vishay, welwyn, multicomp(farnell house brand).
Below 100k resistor noise is not very audible. Carbon film could work, although since the price differential is way below the shipping cost, I don't buy carbon film. Farnell hits you with a stocking charge if you don't buy a certain value of parts, maybe $50 although I've never been below that.
As I have frequently had to replace electrolytic caps in my electronic gear, I tend to buy the ones that have the longest listed service life. Farnell US allows you to see this specification, although the selector tool gets the order wrong, ie 2000 hours is bigger than 10000 (not).
If I can get the 10000 hour service life rated variety, I buy that. I've had to replace e-caps every 6-8 years in one amp, when buying caps from local parts shops. Turns out I was getting 500 hour rated caps. Other distributors don't stock anything above 1000 in most cases.
Best of luck.
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Old 12th February 2018, 07:38 AM   #8
cwteoh is offline cwteoh  Malaysia
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Quote:
Originally Posted by AndrewT View Post
Remove C1 & C2 from the PSU.
Move the snubbers R1, R2, C3 & C4 to the transformer secondaries. They do not do any good on the output of the PSU.

Do not use the "minimised GC" circuit.
It gives more problems than it claims to solve.
I do not recommend the audiosector implementation.
Go to the chipamp datasheet and install ALL the optional components that National list.
Use the Farnell component filters to give you all the options they hold in stock for the VALUE and VOLTAGE you require.
You will see a long list. Some will only be available in reel (3000 or 5000) quantities. Select those available in 1, or 5, or 10 minimum quantity and find the cheapest. Look at the manufacturer are they a reputable commercial manufacturer?
Download the datasheet. Check the parameters are what you need.
AndrewT,
If u don't mind... can you guide on the component as what you advise?
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Old 24th March 2018, 07:03 PM   #9
asuslover is offline asuslover  Romania
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right components to use for gainclone LM3875
Unfortunately he can't . R.I.P mister AndrewT!!!

Last edited by asuslover; 24th March 2018 at 07:06 PM.
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Old 26th March 2018, 03:47 AM   #10
cwteoh is offline cwteoh  Malaysia
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Quote:
Originally Posted by asuslover View Post
Unfortunately he can't . R.I.P mister AndrewT!!!
WHAT????
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