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Chip Amps Amplifiers based on integrated circuits

6 mono channel LM3875
6 mono channel LM3875
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Old 10th September 2017, 07:24 PM   #1
fotsinijts is offline fotsinijts
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Default 6 mono channel LM3875

I've just build a dual mono chip amp (Audio Sector LM3875 Amplifier Kit). I use it for my active x-over speakers.

It powers my compression drivers in a synergy horn. I'm VERY pleased with the sound and I want to build the more of them, for the mids and lows.

The ones I've build now is dual mono and I thinking to proceed this way for the other 4 channels. I'm using Airlink Transformers so doubling the transformer number is price wise not an issue I think.

I thought it was a good idea to stick all the parts in one chassis, with the transformers in the middle (standing up tall, to minimize the space they take)

HIFI 2000 4U Heatsink Chassis 400mm - 10mm front Black - Audiophonics

I think this would be a good chassis.

Does anyone has some tips to build this? Should I go for a seperate powersupply chassis? Or maybe 3 stereo amps?
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Old 10th September 2017, 08:16 PM   #2
tomchr is offline tomchr  Canada
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The HiFi2000 aka Modushop enclosures are quite nice. I certainly recommend them. You might consider getting the version with aluminum panels as it's easier to work with than the rather hard steel panels that come with the enclosures by default.

I'm not a fan of a separate power supply chassis as it greatly increases the supply impedance. Also it greatly increases the odds of supply-induced distortion. Douglas Self writes about that in his Power Amp Design Handbook (and the Wireless World article series that led to the book).

To make the amp a bit easier to handle, three stereo amps is certainly a way to go. You can fit a stereo amp pretty easily in a 2U Modushop Dissipante chassis.
Another way to make the amp a bit easier to handle is to use multi-pole Neutrik SpeakON connectors. They're available at Mouser and are excellent connectors. They come with as many as eight poles (so enough connections for a 4-way speaker in one connector). My standard speaker connector is the 4-pole NL4MP.

Tom
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Old 10th September 2017, 08:44 PM   #3
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by tomchr View Post
I'm not a fan of a separate power supply chassis as it greatly increases the supply impedance. Also it greatly increases the odds of supply-induced distortion. Douglas Self writes about that in his Power Amp Design Handbook (and the Wireless World article series that led to the book).
Self suggests dividing the smoothing between the PSU chassis and amplifier chassis to mitigate this IIRC
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Old 10th September 2017, 11:07 PM   #4
ttan98 is offline ttan98  Australia
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Quote:
Originally Posted by fotsinijts View Post
I've just build a dual mono chip amp (Audio Sector LM3875 Amplifier Kit). I use it for my active x-over speakers.

It powers my compression drivers in a synergy horn. I'm VERY pleased with the sound and I want to build the more of them, for the mids and lows.

The ones I've build now is dual mono and I thinking to proceed this way for the other 4 channels. I'm using Airlink Transformers so doubling the transformer number is price wise not an issue I think.

I thought it was a good idea to stick all the parts in one chassis, with the transformers in the middle (standing up tall, to minimize the space they take)

HIFI 2000 4U Heatsink Chassis 400mm - 10mm front Black - Audiophonics

I think this would be a good chassis.

Does anyone has some tips to build this? Should I go for a seperate powersupply chassis? Or maybe 3 stereo amps?
The chassis is an overkill, I use a single CPU heatsink(with 1*LM3875 attached) with the fan removed and the amp is running for years, >5years. If you want to save money build a wooden chassis or buy a aluminium box.
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Old 12th September 2017, 08:36 PM   #5
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by scottjoplin View Post
Self suggests dividing the smoothing between the PSU chassis and amplifier chassis to mitigate this IIRC
That will certainly help on the supply-induced distortion but does very little to help lowering the supply impedance - and no help at all at DC. We need superconductors at room temperature!

Tom
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