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Old 30th June 2005, 02:52 AM   #1
shyfx is offline shyfx  Australia
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Default Gainclone Component Help

Hi guy, I am building a gainclone and I need some help with component selection.

http://www.decdun.fsnet.co.uk/gc/nixgccdl.gif

I am using that schematic, and I have selected so far:
http://www1.jaycar.com.au/productVie...Max=&SUBCATID=
this is an easy one

http://www1.jaycar.com.au/productVie...Max=&SUBCATID=
http://www1.jaycar.com.au/productVie...Max=&SUBCATID=
I have chosen for the 0.1 and 0.22 uF caps respectively.

http://www.decdun.fsnet.co.uk/gc/cloneamp1.jpg

From that picture, the two 0.1uF caps look more like crossover capacitors. I can't seem to find any polyproylene caps in a store close to me at 0.1 and 0.22 uF though. The lowest I have seen is 1uF.
Should those mains suppresion caps be right, or are they completely inappropriate?

Also, I am confused as to what shoudl be used for the 47uF.

http://www1.jaycar.com.au/productVie...Max=&SUBCATID=

Does that seem suitable at all?

I also want to ask about tolerances. Which components should be the highest tolerance? I suspend the feedback resistor? I have allocated on my PCB up to 5 resistors (since I won't have access to high quality components) so that I can get the closest I can to 216K. I have 5% 10K 1W carbon film, 1% 56K 1/2W metal film and 5% 100R 1W carbon film. Should they be fine in terms of tolerances and power handling?

Thanks for any help guys!!

-mikey
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Old 30th June 2005, 09:51 AM   #2
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hi shyfx,

I have used RE6236 and they are OK.

Next, don't use X2 caps. They usually are used across the incoming 240Vac near the switch. Use the MKT polyster instead.

Is 47uF the right value? I have used 4.7uF NP crossover caps - RY-6904 or RY-6954

Don't worry about R tolerances, it doesn't matter. All resistors are OK, 0.5 or 1 watt.

Better components are available on line from RSComponents.
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Old 30th June 2005, 10:59 AM   #3
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.1 uF is commonly found via a small high voltage box cap (polyprop)
http://www1.jaycar.com.au/productVie...Max=&SUBCATID=

Those big yellow caps in the pictures are film caps. They go directly in the signal path and should be of the highest quality possible to block DC, but not hurt your SQ. If you had a crossover with those caps then good for you, they're probaly good caps.

47uF for a DC blocking cap seems excessive. I use 4.7uF film caps in my amps and they do a fantastic job. People on a budget even use .1uF box polyprop caps, but at a reduced sound quality. My best recommendation is get a good film cap of the highest value possible.
http://www1.jaycar.com.au/productVie...Max=&SUBCATID=

For this amp I don't have any good advice as far as resistors go. All I can say is the feedback resistor should be as close to the pins as possible and it will dissipate almost no power (small resistor).

I think the 100 ohm near chassis ground should be a higher power (not sure)

I think standard tolerances throughout will work just fine. If you want the two channels of your amp equal volume you should probaly match up your feedback resistors closely.

Good luck, and will someone with more experience than I double check my recommendations.
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Old 30th June 2005, 11:42 AM   #4
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Default cheaper than jaycar

check out www.rockby.com.au especially their stuff on sale. You'll be able to get some of the stuff there cheaper, i got the .1uf mkt caps for 10c each today. They are in melbourne just near monash uni (clayton)
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Old 30th June 2005, 04:57 PM   #5
shyfx is offline shyfx  Australia
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Thanks guys for the help

re: rswww.com.au yes they are good, but my friend and i were getting together to make a few. I hope in the future to order some blackgate, rikken, plitron and other fancy components, but this is just going to be a Protel exercise in making some nice pcb's and getting some sound happening in my new room in the shed and for these small speakers now powering the bedtime music

If anyone want's my PCB's, just ask and I will gladly give them up
They are in PDF format and thus far have printed to scale perfectly. I use the laser-toner transfer method to make my PCB's at home. Although still trying to find the best paper, for wider traces its working just fine.

I never heard of Rockby, might have to go out that way to get components some time. Thanks for that.

asgorath: I think i am going to just use a 5W wirewound 10%, seems to be for filtering out noise from the earth, so it shouldn't hurt I hope

-Mikey

Toner transfer PCB
http://www.fullnet.com/u/tomg/gooteepc.htm
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Old 2nd July 2005, 08:38 AM   #6
shyfx is offline shyfx  Australia
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Location: Melbourne, Australia
I built my amp, DC offset is good, now to test audio!

Thanks for the help guys.

-Mikey
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