LM3886 Plans, any mistakes?

[jkostans]

Hey everyone,

I am planning on using a dual mono LM3886 amp kit from www.chipamp.com with an AVEL 330VA 25V + 25V transformer from partsexpress. I'm new to this so I was hoping people could give me some advice, or point out any mistakes I've made so far.

I will most likely be driving a pair of Axiom M22 speakers which are 8 ohm, so I'm guessing the +/-35V rails will be ok. Each chip will have a 3.2" X 2.4" X 1.8" (L X W X H) aluminum heatsink.

I'm still not sure what kind of pot I want to use. Can anyone recommend one that's easily available in the US, has decent tracking between channels, and sounds good? (up to $30). Also, is 25k a decent value, or should I go lower/higher?

Also, should I keep the speaker and input grounds isolated from the chassis ground and each other like in the picture?

[ianpengelly]

Hi there!

Your layout is identical to mine, so it should work fine, though as others will tell you there is sometimes an issue with hum due to the ground loop between the two amp boards.

I would go for a 50k pot, try an ALPS Blue, that should fit in your budget.

Hope this helps.

[jkostans]

Thanks for the quick reply. I've been searching for the alps blue (RK27112), and no place seems to have this particular pot. You would think this would be more attainable in the US with the popularity among the DIY community. Is tangentsoft.net reliable to order from?

[mr.duck]

Originally posted by jkostans
Thanks for the quick reply. I've been searching for the alps blue (RK27112), and no place seems to have this particular pot. You would think this would be more attainable in the US with the popularity among the DIY community. Is tangentsoft.net reliable to order from?

Yea they are a pain to track down. tangentsoft.net is reliable. Also try ebay.

[seftali]

Only 3 left in mouser... click here

I remember a topic about the fake alps pots on ebay, beware!

[ianpengelly]

Don't know what they are like in the US, but I have just ordered a Alps Blue from RS Components and they had plenty in stock.

Good luck getting hold of one!

[jkostans]

Is there a big difference in sound quality between the 50k and 100k?

[lineup]

Originally posted by ianpengelly

Your layout is identical to mine, so it should work fine,
though as others will tell you there is sometimes an issue with hum
due to the ground loop between the two amp boards.

the good thing is you have drawn a nice overview
instead of simply connect anything just as it come

this will make it more easy for someone to give advice
if you get any 'hum' or 'ground loop' effects later

Better to have a plan before wiring
Wiring, as well as how PCB rails are designed,
are important things in amplifiers!
for correct working


Of course you will use isolated RCA, Left-right output jacks
this will make sure Chassis is only connected to Ground, 0V
at one single point
this is a way to avoid so called 'ground looping'

like you have done should work good


lineup