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Audio Sector LM4780 "Overture" power amp
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Author:  mwhouston [ 22 Mar 2019, 21:46 ]
Post subject:  Audio Sector LM4780 "Overture" power amp

http://retro-thermionic.blogspot.com/2019/03/overture-lm4780-chip-power-amp.html

Chip amp based on a single Audio Sector LM4780 module. See link above for more detail.
Attachment:
Overture Front.jpg
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Overture inside.jpg
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Overture rear.jpg
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Overture.jpg

Author:  mwhouston [ 30 Mar 2019, 17:42 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

The new owner is pleased initially but felt the bass a bit loose. The amps is new and may need another 20 hours before it fully settles. I thought the bass good in my system. Not in the league of my bigger class Ds but good.

Author:  ILoveHiFi [ 31 Mar 2019, 00:28 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

IC amps typically use too small feedback capacitor in amp.
Cut off directly at 20hz or about 10-15hz.

Should be able to measure voltage drop at 20hz due to the feedback capacitor startign to increase impedance

Author:  mwhouston [ 31 Mar 2019, 02:08 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

It works out the speakers only had to be pushed back to the wall a little closer and the bass lifted. He is now happy.

Author:  mwhouston [ 10 May 2019, 23:49 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

Finally used up the other Audio Sector Overture chip amp module. A repurposed 1U enclosure and PS with parts at hand. 4500uf filter caps and 470uf LESR caps on brd. Low 2.5mV RMS of noise on worse case. Should produce 60W to go in TV system with 4S preamp with three inputs and 175W 12” subwoofer and Beyma 12” concentrics (96db sensitive). An EXover rolls in the subby at 100hZ.
Attachment:
CCA4D5AD-2CC3-497A-9517-CE3DF2857B1C.jpeg
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33F513E8-109A-44F3-A0AB-7843BDE4BF3C.jpeg
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48B2A344-C0DE-4B2B-B6F5-0983AC1B1282.jpeg

Author:  Gio [ 12 May 2019, 11:14 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

Hi Mark - looks good. How are the transformers configured in the second amp?

I like how these chipamps sound but the last one I put together uses a module complete with output protection circuitry and turn on delay. Otherwise the DC coupled output makes me nervous with expensive speakers. It also adresses any thumps at power on or off.

Author:  mwhouston [ 12 May 2019, 18:18 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

Gio wrote:
Hi Mark - looks good. How are the transformers configured in the second amp?

I like how these chipamps sound but the last one I put together uses a module complete with output protection circuitry and turn on delay. Otherwise the DC coupled output makes me nervous with expensive speakers. It also adresses any thumps at power on or off.

The trannies are two low profile 24V 160VAC toroids. They are in series to produce 48V with centre tap.

Author:  Gio [ 12 May 2019, 20:56 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

So it is configued for one power transforer per channel - dual monobloc.

Author:  mwhouston [ 12 May 2019, 23:20 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

Gio wrote:
So it is configued for one power transforer per channel - dual monobloc.

No the secondaries are in series. One 48VAC.

Author:  ILoveHiFi [ 23 May 2019, 16:39 ]
Post subject:  Re: Audio Sector LM4780 "Overture" power amp

Thought you can get some on rs components at fair price 48v single output, they have allot of choices

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