Welcome Guest! To enable all features please Login or Register.

Notification

Icon
Error

Login


Options
View
Go to last post Go to first unread
rampantandroid  
#1 Posted : Friday, September 6, 2013 1:16:21 AM(UTC)
rampantandroid

Rank: Member

Groups: Member
Joined: 9/27/2011(UTC)
Posts: 4
Location: Seattle, WA

It looks like the mute pin for the LM4780 is just tied to ground via a 10k ohm resistor, making the amp never mute. Is it possible to instead tie a switch off to the pads to add a mute switch? Or to add a soft start circuit (per the TI manual on the 4780) using a capacitor tied to ground?

Would using soft start eliminate any turn on thump (or is there no thump heard in the default configuration)?

Thanks!
Brian Donegan  
#2 Posted : Friday, September 6, 2013 2:55:32 AM(UTC)
Brian Donegan

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA

Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
You could certainly add a mute function, but there are no transients at turn-on or turn-off.
Russ White  
#3 Posted : Friday, September 6, 2013 7:04:49 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
The Lm47080 is just one part of the entire amp, and it's output is part of a larger feedback loop. You shouldn't mute the LM4780 on its own. In any case as Brian said, it is completely not necessary, there is no thump.
rampantandroid  
#4 Posted : Saturday, September 7, 2013 1:18:09 AM(UTC)
rampantandroid

Rank: Member

Groups: Member
Joined: 9/27/2011(UTC)
Posts: 4
Location: Seattle, WA

OK, good info - thanks!

On an unrelated topic, if I wanted to run 4 amps in total (2 per speaker for bi-amping) what transformers should I be using? Would two +/-25VAC 600VA transformers cover my needs?

What about a crossover - would I need a crossover if I was bi-amping? And would I want to put it in the input side, or the output side?

Thanks again!
Russ White  
#5 Posted : Sunday, September 8, 2013 2:25:11 PM(UTC)
Russ White

Rank: Administration

Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN

Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
I would try to use one transformer per amp, but it is ok to share.

600VA should be fine even for two amps so long as you keep the output expectations reasonable. :)

You could do the crossover either way. If you speakers have a split passive crossover for bi-amping then you need only use that.

Otherwise you may want an active (or passive) crossover at the input to the amps.

Cheers!
Russ
Rss Feed  Atom Feed
Users browsing this topic
GuestUser (2)
Forum Jump  
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.