Jims Audio LM4780 Schematic or advice?

[borninthefifties]

In order to get the mute to work I would need a switch of some kind right? If I understand correctly, the data sheet has v- > resistor > switch > mute pins

In order to get the mute to work I would need a switch of some kind right? If I understand correctly, the data sheet has v- > resistor > switch > mute pins

Correct!
Been using these cases Audio power amplifier case chassis enclousure diy heat dissipation UK stock | eBay
UK Seller, so quick despatch, and cheap!(ish)

 

[dakku]

Correct!
Been using these cases Audio power amplifier case chassis enclousure diy heat dissipation UK stock | eBay
UK Seller, so quick despatch, and cheap!(ish)

thanks mate, thats just the case i need. will be keeping an eye to see when its back in stock.

 

[dakku]

guys, how would I go about mounting an LED on this pcb?

Reverse engineering the AudioSector Board it seems you need
V+ > 1k resistor > led anode
led cathode to PG+

So, given the above crude "reverse engineering", would this work??

An externally hosted image should be here but it was not working when we last tested it.

 

[abraxalito]

Any thoughts or opinions?

An observation - no separation of signal and power grounds, single ground fill used doing double duty.

 

[AndrewT]

.............they are very techy on here, and will shoot the newbies down if you post!............

The Members are not in general "very techy".

I am different from the general Membership and I am not afraid to forewarn overly ambitious juniors that real problems wait around the corner to bite back.

 

[dakku]

Andrew, in your opinion, would the above LED light up or is it a disaster?

 

[dakku]

An observation - no separation of signal and power grounds, single ground fill used doing double duty.

Thanks mate, i thought it was a little different from the audiosector boards. Is there a difference to the sound quality or safety due to single ground?

 

[abraxalito]

In my experience, boards which lack a distinction between the two grounds don't give nearly as much listening satisfaction as those that do. No difference in safety though, that's related to a protective earth (chassis) connection.

 

[dakku]

thanks again mate, I will try to hook these up soon and compare to my audiosector lm3875

 

[abraxalito]

I shall be interested in your listening experience comparing the two. Audiosector seem to understand pretty well how to do good layout, at least that's the impression I got from looking at one of their boards a few years back.

 

[dakku]

I was originally going to get the audiosector kits, the cost was a little higher. Then I came across a forum member selling these boards built with good quality parts. Will post pics of the assembled boards

 

[AndrewT]

Andrew, in your opinion, would the above LED light up or is it a disaster?

A LED indicator light will work with just a resistor to limit the current and set the brightness.

If I am using a LED indicator light for a PSU that supplies a single voltage, then I am interested in when the nearly correct voltage is present on the supply rails.

I do this by using a series combination of resistor, Zener and LED.
eg.
30Vdc supply: using 24V Zener + 1.9V green LED + 2k resistor
This passes [30V - 1.9V - 24V] / 2k ~ 2mA
At 33V it will pass ~ 3.5mA, noticeably brighter.
At 26V it will pass ~ 0.2mA, almost off.

This can be used across a dual DC supply to indicate when one supply is OFF or very low and can be doubled up to show LED for each half of the supply.

 

[dakku]

thanks Andrew, i hadnt thought about using it that way..

 

[danielwritesbac]

As for bridging LM4780, there's 2 of 65W cores.
2 * 65 = 130
So, I get the Overture Design Guide spreadsheet out to find out what transformer voltages to use for not exceeding 130W total.
For bridged LM4780, that's an 18+18vac transformer if 8 ohm speakers or a 13.5+13.5vac transformer if 4 ohm speakers.

Easy bridge or "simple bridge" is suitable for a subwoofer amplifier; however, you might want a better performing bridge adapter circuit (looks like a little preamp) if using it full bandwidth.
http://www.diyaudio.com/forums/chip-amps/49414-lm3886-gc-simplest-ever-amplifier-bridging.html

P.S.
An alternative option for approaching 130W is a parallel amplifier, with 25+25vac transformer, and 4 ohm speakers. Paralleling cuts the load (per core) in half, thereby improving linearity and preserving audio quality. So, that is something to consider whenever 4 ohm speakers are used.