Old salvaged chip amp

Geleia · 7th January 2011, 07:17 PM

Well, I'm not really good with audio electronics yet and I happened to come across an old chip amp from Sanyo: LA4705. http://www.datasheetcatalog.org/data...f_e/LA4705.pdf

I have two 4ohm 20W speakers, and wanted to make an amplifier for them (general use, mostly studying guitar) and wanted it as mono. I could reach a total of 40W with these, right?

It seems, from the datasheet, that each channel has an inverting and a non-inverting output. If I use the same input at both channels and the inverting output from one, and the non-inverting from the other to connect the speakers, will it work like bridged, with something around 30W at 13.2V?

Thanks, and sorry for all those questions.

benb · 7th January 2011, 08:55 PM

The "inverting and noninverting" outputs means that each channel is already bridged. You won't gain anything by using both channels "bridged," in fact you'd only have the power output of one channel.

For mono, your best bet is to connect the inverting and noninverting output of each amp to one of the speakers, just as you would for stereo and as shown on the third page of that datasheet, and drive both inputs with the same signal (keeping both of the capacitors shown at the inputs).

Geleia · 7th January 2011, 09:25 PM

Well, I don't really care about the wattage of the output and etc. Driving each speaker from each channel with the same input on both will deliver more dB, right?

diptangshu · 8th January 2011, 12:43 PM

You can go for LA4743. or LM series ICs.

7th January 2011, 07:17 PM	#1
Geleia diyAudio Member Join Date: Jan 2011	Old salvaged chip amp Well, I'm not really good with audio electronics yet and I happened to come across an old chip amp from Sanyo: LA4705. http://www.datasheetcatalog.org/data...f_e/LA4705.pdf I have two 4ohm 20W speakers, and wanted to make an amplifier for them (general use, mostly studying guitar) and wanted it as mono. I could reach a total of 40W with these, right? It seems, from the datasheet, that each channel has an inverting and a non-inverting output. If I use the same input at both channels and the inverting output from one, and the non-inverting from the other to connect the speakers, will it work like bridged, with something around 30W at 13.2V? Thanks, and sorry for all those questions.

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7th January 2011, 08:55 PM	#2
benb diyAudio Member Join Date: Apr 2010	The "inverting and noninverting" outputs means that each channel is already bridged. You won't gain anything by using both channels "bridged," in fact you'd only have the power output of one channel. For mono, your best bet is to connect the inverting and noninverting output of each amp to one of the speakers, just as you would for stereo and as shown on the third page of that datasheet, and drive both inputs with the same signal (keeping both of the capacitors shown at the inputs).

7th January 2011, 09:25 PM	#3
Geleia diyAudio Member Join Date: Jan 2011	Well, I don't really care about the wattage of the output and etc. Driving each speaker from each channel with the same input on both will deliver more dB, right?

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