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
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
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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.
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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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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previously, my friend told me to put 10000uf ->1000uf -> 100uf parallel. But I am not sure what is that about
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.
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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