My version of GC, a LM3886 based

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lanchile

lanchile

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Joined 2008
The "bleeder resistors" are optional.some people put them some people do not!.in my case I do not use them(maybe in the future),I know well not to touch those caps(big punch).and if I have to work inside my amp I discharge caps before touching them.Beside How often am I going to open and work inside my amp?.These amps are very reliable!.:yes:
 
lanchile

lanchile

Member
Joined 2008
No, the bleeder resistor will not "damage" the sound.their job is just to discharge caps faster. as I said before,there are people that put them and there are people that do not!.another example is with the caps in each diode rectifier (0.01uf 103) to reduce and clean some noise and Rf in the power supply. it is like the capacitance in the power supply,some people use small caps and some people use big caps.this is the fun part of DIY"it is your amp,it is your choice".:smash:
 
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samsagaz

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Joined 2004
OK, will use bleeder resistor, sounds safe for me.

i want that my PSU have Bleeders resistors + Led

will build 4 or 5 diferents PSU and will measure it and listen the same AMP using diferents PSU :)

About the 0.01uf caps to add to each diode i dont need to create the holes because can solder it in the bottom of the PCB.
Btw, wich is the best material for these Caps?
 
lanchile

lanchile

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Joined 2008
It is your choice!

I am using these caps .01 uF 400V 5% .4" LS Radial Film Capacitors http://cgi.ebay.com/01uF-01-uF-400V...oryZ4662QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

about the led...I did not want to "interrupt" the power supply so I used 120VAC lamp part # 272-712 (very nice and small) from Radio shack.These lamps come in many colors and the good part is you can even see it from wider angle than the LED (more than double).you just connect it after the power switch ,you do not need nothing else.
But again this is my way...maybe you or someone else like LED or different parts or configurations.as long as you are happy with your design and sound...that is what matters to you.Good luck!:cheers:
 
lanchile

lanchile

Member
Joined 2008
lol,I know what you mean Vecino! if I can help you with something let me know.some parts can be very expensive like Black Gates caps I spent almost $150 just for the caps( I use them in my amp ...What a difference!). But some people use Panasonic FC caps with some good result.Good luck with your amp.:cheers:
 
Dino-Indo

Dino-Indo

Member
Joined 2007
lanchile said:
No, the bleeder resistor will not "damage" the sound.their job is just to discharge caps faster. as I said before,there are people that put them and there are people that do not!.another example is with the caps in each diode rectifier (0.01uf 103) to reduce and clean some noise and Rf in the power supply. it is like the capacitance in the power supply,some people use small caps and some people use big caps.this is the fun part of DIY"it is your amp,it is your choice".:smash:
Click to expand...

Hi Lanchile! Hi Samsagaz,

Yes, I did not put the bleeder resistors on this amp .. but I did applied them on my other GC LM3876TF :D
And confirmed.. as Lanchile said.. doesn't degrade or affect the sound at all... :D
 
Dino-Indo

Dino-Indo

Member
Joined 2007
Hehehe.. Thanks Lanchile..

:) So far :smash: , I've built 3 amps based on LM3886 (one for myself and two for friend and relative) , 1 amp using LM1875 (for my computer) and the latest one is based on LM3876TF :smash: . Hehehe... :D

Oh ya, I would strongly suggest you (and everybody) to try Mr. Nelson Pass' Buffer Preamp circuit (using SK170BL FET) which I install it on my LM3876TF.... love the sound of these combo.... :D

Now, whenever I want to listen to pop and rock... I'm using the LM3886 coz its punchier
but when I want to listen to vocal or jazzy tunes... I'm switching to my LM3876TF...
Hahaha... troublesome? You betcha... but I do it for the 'sound...'
 
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samsagaz

Member
Joined 2004
Dino-Indo said:
PCB view...

Simple PCB layout, several Riken RM resistors , one 0.7uH inductor paralleled with 10R 1 Watt resistor (at bottom side of PCB), Nichicon Gold 47uF, Nippon Chemicon 100uF...

LM3886 supply pins (at the bottom side) decoupled to ground with 3300pF Wima FKS and ground pin connected to central grounding with 22K Resistor... reducing the DC offset from 30mV to approx. 4mV....
Click to expand...

Dear Dino, when you say that used the Ground Pin Connected to the Central GND with 22k Resistor, its used as you say to reduce the DC Offset? How you found that value? just start switching resistors and see wich is better?
 
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samsagaz

Member
Joined 2004
lanchile said:
lol,I know what you mean Vecino! if I can help you with something let me know.some parts can be very expensive like Black Gates caps I spent almost $150 just for the caps( I use them in my amp ...What a difference!). But some people use Panasonic FC caps with some good result.Good luck with your amp.:cheers:
Click to expand...


Where you purchase the BGs?

:)
 
Dino-Indo

Dino-Indo

Member
Joined 2007
samsagaz said:


Dear Dino, when you say that used the Ground Pin Connected to the Central GND with 22k Resistor, its used as you say to reduce the DC Offset? How you found that value? just start switching resistors and see wich is better?
Click to expand...


Hi Samsagaz,

Thanks for your e-mail...
Well, honestly, I was doing that approach as 'trial and error'... all because of the low level hum when I first completed the kit.. I didn't specifically calculated that measurement.... but somehow it had effect on reduced DC offset....
Frankly, I hope it wouldn't affect the performance of the whole system of the LM3886 circuitry..

But FYI, I did not install the same resistor on my LM3876TF as well as my LM1875 gainclones.. hehehe.. all relying on the DC grounding circuit as suggested in Rod Elliot's website.. using a bridged rectifiers/diodes, one resistor (sorry, forgot the measurement) and one 10uF MKP cap...
 
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