Inv Gain Clone with on board PSU

anbello · 5th April 2006, 04:43 PM

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

anbello · 5th April 2006, 04:47 PM

Eagle3d, nice sw.

Andrea

Leolabs · 7th April 2006, 01:57 AM

nice design

But why not place the output terminal near the chip???

dfdye · 7th April 2006, 03:38 AM

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.

anbello · 7th April 2006, 08:12 AM

Loeolabs and dfdyde
thanks for your comments, i'am trying to follow your hints,
what do you think of this new release?

peranders · 7th April 2006, 09:05 AM

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 ?

anbello · 7th April 2006, 03:17 PM

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

anbello · 7th April 2006, 03:29 PM

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

anbello · 7th April 2006, 03:48 PM

some minor changes ...

dfdye · 7th April 2006, 05:39 PM

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.

7th April 2006, 09:05 AM	#6
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	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 ? __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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7th April 2006, 01:57 AM	#3
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	nice design But why not place the output terminal near the chip???

7th April 2006, 03:38 AM	#4
dfdye diyAudio Member Join Date: Dec 2005 Location: USA	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.

7th April 2006, 03:29 PM	#8
anbello diyAudio Member Join Date: Sep 2004 Location: Italy	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

7th April 2006, 05:39 PM	#10
dfdye diyAudio Member Join Date: Dec 2005 Location: USA	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.