Inv Gain Clone with on board PSU - diyAudio
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Old 5th April 2006, 05:43 PM   #1
anbello is offline anbello  Italy
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Default Inv Gain Clone with on board PSU

I would like to share with you my first attempt at designing a compact inverting gainclone with onboard PSU. I have read here and there on the forum and i have learned something from the more experienced of you (i hope so). So there is nothing new in my design, only i whish to learn something more and to have a compact PCB with IGC + PSU. I am open to all kind of suggestion and critcism.

Andrea
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Old 5th April 2006, 05:47 PM   #2
anbello is offline anbello  Italy
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Default IGC + PSU 3D view

Eagle3d, nice sw.

Andrea
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Old 7th April 2006, 02:57 AM   #3
Leolabs is offline Leolabs  Malaysia
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nice design But why not place the output terminal near the chip???
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Old 7th April 2006, 04:38 AM   #4
dfdye is offline dfdye  United States
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I like the idea! C3 threw me for a minute, but I'm OK with that now. I would, however, run the ground wire for the chip directly to the ground aread instead of running it through the R2 pad. Same with the signal from the output pin to R6 instead of running it through the feedback resistor pad. Also, a bunch of people have soldered the feedback resistor directly to the chip pins, so you could even take that resistor off the board entirely if you wanted, but having a place for them on the board is nice as a backup. I would also beef up the output traces.

Overall, I like the idea and would love to know how it works when you get it implemented.
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Old 7th April 2006, 09:12 AM   #5
anbello is offline anbello  Italy
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Loeolabs and dfdyde
thanks for your comments, i'am trying to follow your hints,
what do you think of this new release?
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Old 7th April 2006, 10:05 AM   #6
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Nice but if you are going to make a doublesided board I'd recommend you to have a signal groundplane and let it be connected only in the Speaker ground.

It might also be a good idea to have two holes for the transformer ground. If you have a dual secondary winding you will have 4 wires also. Now you have 3 holes.

I recommend you also to decouple to ground close the LM3886. Output currents are taken from one of the rails to ground so the decoupling should be there also. Change C3 to ground and add one more on the other side.

R4 can be placed in the middle to the left of C1. No problem since you have a doublesided board.

Why don't you add 100 or 220 uF as delay for the MUTE? Then you'll have a completely silent power up.

Make the speaker traces a bit wider, 100-150 mils. No harm in that.

Have you seen my inverting Gainclone ?
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Old 7th April 2006, 04:17 PM   #7
anbello is offline anbello  Italy
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P-A thanks for your hints,
for the signal groundplane see the attached image and let me know if is good,
for the docoupling i think is better to have C3 between V+ and V- to filter differential mode noise becouse of the really high PSRR of the 3886,
for the C for the MUTE i don't use it on empirical basis: i have other chipamps with 3886 with no CM and are completely silent on power up.

ciao
andrea
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Old 7th April 2006, 04:29 PM   #8
anbello is offline anbello  Italy
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P-A i forgot to say that i see your gainclone: really really good, i like the input buffer, for the inv GC i think it's better with it, i haven't put it on my design for the sake of semplicity and becouse i use it with a pre. The only thing i can say is that the opamp used for the DC servo is too much. I think a less performing (and less expensive) opamp could be used without audible degradation.

ciao
andrea
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Old 7th April 2006, 04:48 PM   #9
anbello is offline anbello  Italy
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some minor changes ...
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Old 7th April 2006, 06:39 PM   #10
dfdye is offline dfdye  United States
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Nice improvements. I was wondering, though, what the point of the ground wire on the bottom side of the board was now that you have a ground plane on the top side of the board? I think you can get rid of that and just have the top ground plane.

Also, be careful with your name placements to avoid getting silkscreen components over solder pads. Specifically, your output title is over your R6 pad.
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