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Neurochrome Modulus-286: 65W (8Ω); 125W (4Ω) @ <-120dB THD Composite Amplifier Module
Neurochrome Modulus-286: 65W (8Ω); 125W (4Ω) @ <-120dB THD Composite Amplifier Module
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Old 24th January 2021, 02:15 AM   #201
tomchr is offline tomchr  Canada
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I suggest reading about composite amplifiers. Walt Jung's book (free download) and Sergio Franco's book (not free by any stretch of imagination) are good places to start. I give the full references here: Become a Better Audio Circuit Designer: Recommended Texts – Neurochrome

Once you understand how composite amplifiers work, I think your remaining questions will fall into place.

The short answer is: Loop gain reduces errors. Lots of loop gain (or at least sufficient loop gain) makes the amplifier insensitive to the outside world. That's why the Modulus amps perform as well on a linear or switching supply as they do on a well-regulated lab power supply.

Tom
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Modulus-86, 186, 286, & 686: 40-240W (8Ω), <-120dB THD. HP-2 Headphone Amp: 660mW, <-130dB THD. Taming the LM3886.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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Old 24th January 2021, 05:20 AM   #202
Edgar77 is offline Edgar77  Thailand
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Neurochrome Modulus-286: 65W (8&#937;); 125W (4&#937;) @ &lt;-120dB THD Composite Amplifier Module
Thanks Tom

I will read and learn.

I looked at your amp specification on your website and this thread and I didn't find anywhere how steady (probably the wrong word) the power supply has to be.
What amount of ripple is acceptable for your amp?
Are there clear defined minimum and recommended specifications for the power supply to your amp(s)?

When I look at your Power-86 it supports capacitors up to 41.5mm. The biggest for that size which I found on Mouser has 22,000uF/40V. Would 10,000 or 2*22,000 make an audible difference?
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Old 24th January 2021, 06:34 AM   #203
BrianL is offline BrianL  United States
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Neurochrome Modulus-286: 65W (8&#937;); 125W (4&#937;) @ &lt;-120dB THD Composite Amplifier Module
Don't forget that the controlling op-amp also needs good Power Supply Rejection (PSRR)
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Old 24th January 2021, 09:11 PM   #204
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by BrianL View Post
Don't forget that the controlling op-amp also needs good Power Supply Rejection (PSRR)
True. That said, the controlling opamp is behind a local regulator, so its power supply is quite isolated from the supply connected to the board already.

Quote:
Originally Posted by Edgar77 View Post
What amount of ripple is acceptable for your amp?
Are there clear defined minimum and recommended specifications for the power supply to your amp(s)?
I can't give you a clear number because reality is fuzzy. I have measured the performance of the Modulus-86, -186, and -286 with a power supply that has 2x22000 uF total capacitance (so 22000 uF per rail). It measures line-on-line with the lab supply until the point of clipping.

Lower capacitance will give you higher ripple. Higher ripple results in lower supply voltage under load, which means an amp that runs with lower supply capacitance will clip a few watt earlier than an amp that runs with more supply capacitance.

Quote:
Originally Posted by Edgar77 View Post
When I look at your Power-86 it supports capacitors up to 41.5mm. The biggest for that size which I found on Mouser has 22,000uF/40V. Would 10,000 or 2*22,000 make an audible difference?
Probably not. 2x10000 uF total (10000 uF per rail) is the lowest I'd go. Going from 10000 uF to 22000 uF increases the cost of the cap by ~50%. Going to 33000 uF is roughly 3x the cost of the 10000 uF cap. Still, 2x33000 uF (CDE P/N: 380LX333M050A082 for example) would set you back about $20, so it shouldn't blow the budget completely.

Tom
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Modulus-86, 186, 286, & 686: 40-240W (8Ω), <-120dB THD. HP-2 Headphone Amp: 660mW, <-130dB THD. Taming the LM3886.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
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