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Modulus-86  build thread
Modulus-86  build thread
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Old 16th April 2018, 07:01 PM   #4001
zgtc is online now zgtc  Europe
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Modulus-86  build thread
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Originally Posted by tomchr View Post
Thanks to everybody who have contributed so far, and especially thanks to Bill who started this thread. He has yet to finish his amp but has grown his family exponentially instead. Bill! This the year! No pressure...
hey that gives me 2.5 yrs of extra margin... got mine last summer
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Old 16th April 2018, 08:10 PM   #4002
tomchr is offline tomchr  Canada
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Nice...!

My website is now operational again. Back in business.

Tom
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Modulus-86, 186, 286, & 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 16th April 2018, 11:03 PM   #4003
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Modulus-86  build thread
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Originally Posted by tomchr View Post
So I thought I'd ask: Are there any other features that you'd like to see in this supply board?
I like the idea of support for a CRC snubber network. Even if the snubber doesn't benefit the Modulus amplifiers measurably, it would make the power supply have broader appeal for usage in other amplifiers that might not be so forgiving with their power supply.

I agree that a 12 V trigger input is a nice addition.

What about an option to use discrete diodes vs bridge rectifiers? Would that be getting to complicated?

Also, for the +5 V always on auxiliary output, would this be powered from a separate transformer?
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Old 16th April 2018, 11:12 PM   #4004
billshurv is online now billshurv  United Kingdom
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Modulus-86  build thread
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Originally Posted by tomchr View Post
, and especially thanks to Bill who started this thread. He has yet to finish his amp but has grown his family exponentially instead. Bill! This the year! No pressure...

Thanks all!

Tom
Every morning when I leave for work I see a board against the headsink and think I should start the swarf and sawdust making. Making progress with sleep training youngest one so I am hopeful of news soon...Honest
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Old 17th April 2018, 12:06 AM   #4005
BigE is offline BigE  Canada
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You need to match the snubber to the transformer. It does work to reduce ringing. The quasimodo no math jig works great to select resistor values.
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Old 17th April 2018, 12:09 AM   #4006
brian92fs is offline brian92fs  United States
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Modulus-86  build thread
That's my understanding. But it would be nice to see component provisions for this on the PCB so the buyer could implement if they desired. Knowing they'd need to determine the values specific to their transformer as you described.
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Old 17th April 2018, 03:43 AM   #4007
tomchr is offline tomchr  Canada
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Quote:
Originally Posted by brian92fs View Post
I like the idea of support for a CRC snubber network. Even if the snubber doesn't benefit the Modulus amplifiers measurably, it would make the power supply have broader appeal for usage in other amplifiers that might not be so forgiving with their power supply.
That's basically my thought.

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Originally Posted by brian92fs View Post
What about an option to use discrete diodes vs bridge rectifiers? Would that be getting to complicated?
To support a stereo Modulus-686, the diodes will very likely need to be discrete anyway. Discrete with heat sinks. So either a TO-220 or TO-247 package kind of deal.

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Originally Posted by brian92fs View Post
Also, for the +5 V always on auxiliary output, would this be powered from a separate transformer?
I'm thinking a Mean Well switcher. They cost about a quarter of what a transformer-based supply would cost, are dead quiet, and take international mains in.

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Originally Posted by BigE View Post
You need to match the snubber to the transformer. It does work to reduce ringing.
True. But so does the single cap across the transformer secondary - and that, in contrast to the RC snubber, does not need to be sized to the transformer. I can certainly include instructions for how to determine the RC snubber should anyone desire to pursue that angle, but optimizing the snubber to the transformer (and its wiring harness!) will be up to the end user.

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Originally Posted by billshurv View Post
Every morning when I leave for work I see a board against the headsink and think I should start the swarf and sawdust making.


Tom
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Modulus-86, 186, 286, & 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 17th April 2018, 04:21 AM   #4008
wcwc is offline wcwc  United States
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Any idea yet how big the board will be compared to the Power-86? Would anything change with regards to the required transformers?
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Old 17th April 2018, 06:22 AM   #4009
HarmonicTHD is offline HarmonicTHD  Switzerland
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My two cents to the Power 686.

I also like the CRC snubber option, the 12v trigger and of course the soft start.

To further increase flexibility and appeal to non Mod users I could imagine to leave some room for the capacitor diameter so people can use even larger caps than the two 22000uF per rail.
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Old 17th April 2018, 04:09 PM   #4010
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Originally Posted by wcwc View Post
Any idea yet how big the board will be compared to the Power-86? Would anything change with regards to the required transformers?
No changes to the transformer.

The board will probably be twice as long as the discrete diodes + heat sinks take up quite a bit of room and allowing for twice the capacitance will take up some space. Add 1.0-1.5" to the width to accommodate the Mean Well switcher and associated bits. Fitting the board within 5x6 to 5x7 inches would be pretty nice. The current Power-86 is 3.3x3.6 inches.
No promises on the board size. I'm familiar with the various constraints of shoehorning an amp into an enclosure and will keep those constraints in mind when deciding the board size. The board will be large enough to accommodate the features but no larger than that. Smaller is better when it comes to board size.

Quote:
Originally Posted by HarmonicTHD View Post
I also like the CRC snubber option, the 12v trigger and of course the soft start.

To further increase flexibility and appeal to non Mod users I could imagine to leave some room for the capacitor diameter so people can use even larger caps than the two 22000uF per rail.
I hear ya. The Power-86 supports two 40 mm diameter caps. The two caps I specify are actually 35 mm in diameter. So there's room to grow. 40 mm gets up to 27000 uF (27 mF) per cap for 50-63 V snap-in types. The next sizes up are 50 mm and 63 mm diameter. Mouser shows exactly one (1) non-stocked 33 mF 50 mm cap in the 50-63 V range. The two (2) 63 mm caps are both 22 mF (and non-stock as well). The difference between 27 mF and 33 mF is negligible in this context, honestly.
This is how I landed on the 40 mm footprint in the first place. There are quite a few options to choose from in the 35-40 mm range.

So I'll stick with the 40 mm footprint. I did take into account when designing that footprint that a "40 mm" specified cap may be a tad larger due to production tolerances and the footprint can accommodate that too. If the resulting 4x27 mF = 108 mF isn't enough capacitance for you, you'll probably want to go with the chassis-mounted screw terminal caps rather than board mounted caps.
I use 10 mm pin pitch on the caps, so you have tons of options to choose from.

Tom
__________________
Modulus-86, 186, 286, & 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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