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Chip Amps Amplifiers based on integrated circuits

Neurochrome LM3886DR Build
Neurochrome LM3886DR Build
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Old 11th July 2018, 06:51 AM   #401
rsqt is offline rsqt  Germany
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If I am using four 12V (fully load 13,3V) batteries in series as "power supply" will I have to switch all 3 wires with an SSR or only "+ and -"?
Found an SSR from Panasonic. May be better than no-name-Ebay.
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Old 11th July 2018, 05:28 PM   #402
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by 454Casull View Post
I see the cup is blue instead of red...
Yeah... It's my one personality flaw. I've always preferred blue & white. Much to the locals' dismay.

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Originally Posted by chrisb View Post
I happened to have heard both this little guy, and one of Tom’s personal Modulus86 (4 channel for his LX Mini, IIRC?) in my home system before the cited event.
Yep. That 4xMOD86 is still driving my LXmini speakers.

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Originally Posted by chrisb View Post
Tom please feel free to rebut, but as much as the DR was at least the equal to any number of similarly powered commercial products or DIY chippers I’ve heard in my sordid career, the Modulus was something pretty darned special.
That's what I remember as well. The LM3886DR is every bit as good as any good LM3886 implementation. The trick is to find a good implementation as there are many ways to muck it up.

The LM3886DR (and a few other amps) did get some playing time at the DIY meet, but folks quickly requested the MOD86 to be hooked back up.

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Originally Posted by chrisb View Post
I’d always been of the opinion that past a certain point “vanishing / immeasurably low” distortion was just an exercise in specmanship, but there is something going on with that piece that either is, or is not, directly related.
My suspicion is that people have been so focused on the THD at 1 kHz that they've lost track of everything else. The THD of the LM3886 does rise above audible both at the low end and the high end. Some may prefer the higher THD at LF as it creates a bit of a warmer sound due to harmonic extension. Others (including me) find it to be slightly muddy. In the high end, there's almost universal agreement that the chip amps, including the LM3886, sound a little strained, harsh, or "like a chipamp". That I think is because the rising THD vs frequency of the LM3886.
The Modulus-86 uses error correction to reduce the THD (and a wide array of other parameters) to levels well below audible at all frequencies.

That said, the LM3886DR wrings as much performance out of the LM3886 as possible. It actually beats the data sheet specs on a few parameters (THD, for example) thanks in part to the better components we have available now versus when the data for the data sheet curves were taken.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 11th July 2018, 05:33 PM   #403
tomchr is offline tomchr  Canada
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Originally Posted by rsqt View Post
If I am using four 12V (fully load 13,3V) batteries in series as "power supply" will I have to switch all 3 wires with an SSR or only "+ and -"?
Yep. There's no need to switch the ground. Just switch V+ and V-.

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Originally Posted by rsqt View Post
Found an SSR from Panasonic.
May be better than no-name-Ebay.
I'd say definitely better than a no-name from ePay.

Double-check with the data sheet that the SSR you've chosen is suitable for switching DC. Also note that some SSRs have zero-detection and require the switched voltage to be near zero before they'll switch. That'll work great for AC, which crosses 0 V twice every cycle, but not for DC.

You could also make your own SSR by using a pair of power MOSFETs and a floating photovoltaic gate driver.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 11th July 2018, 07:07 PM   #404
Mooly is offline Mooly  United Kingdom
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Neurochrome LM3886DR Build
Something like this could be workable. Switching R2 into circuit enables both FET's (together) and opening the connection turns them both off. The zeners ensure that Vgs is never exceeded.

The switch in series with R2 could even be replaced by an opto enabling remote control of the PSU.

(Its just a quick doodle and not intended as a fully worked optimised example).
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Old 11th July 2018, 07:22 PM   #405
tomchr is offline tomchr  Canada
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Yep. That'd work.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 12th July 2018, 03:25 AM   #406
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Tom, once again - sorry for how this season started out for you, but it’s great to have you back. I’m borrowing this from a source that doesn’t apply here, but - one day at a time.
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Old 12th July 2018, 05:55 AM   #407
tomchr is offline tomchr  Canada
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It's good to be back, actually.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 12th July 2018, 08:27 AM   #408
rsqt is offline rsqt  Germany
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Thank you.


So because of the rising THD vs. frequency of the LM3886 may be the best could be to use them for midrange in an active 2.1 or 3-way active system. (if someone wants to spare some $ not using the Mod86 for all ways)
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Old 12th July 2018, 08:38 AM   #409
rsqt is offline rsqt  Germany
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In case if the batteries/voltage go down ( not enough sun) I want to add a PSU/charger. Is it better to use one with about 52-56VDC or better two with about 26-28VDC in series or one with +/- 26-28V? May be I want to listen to music while loading.

Again thanks for your help.
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Old 13th July 2018, 01:46 AM   #410
tomchr is offline tomchr  Canada
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I'd probably aim for ±28 V. That said, battery management is not my area of expertise so to say anything more useful than that, I'd have to read up on it.

Tom
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Modulus-86, 186, 286, 286 Kit, & 686: 40-240W (8Ω) at <-120dB THD. HP-1: 3W/20Ω, -130dB THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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