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Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD

Hi Tom,
Because Modulus-686 is a bridged amp come to speculate if it can run from a single supply and virtual ground as Sansui used lot back in eighties, wearing my audiophile glasses :D (get your audio off the ground) have always thought about below single supply block diagram that it looks very clean and beautiful, no common modes and no cold dirty speaker returns anywhere, cost of higher voltage capacitors for linear supply will take a hit but if performance numbers also increase a little bit some will probably like that.

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The Intelligent Soft Start is now ready for prime time. Boards are in stock! Images attached. Description here: ISS: Intelligent Soft Start

I've learned quite a bit building that circuit and discovered some failings of the commonly used resistor-based soft starts. I'll need to gather my thoughts and start a separate thread on that topic.

Starting said thread was pushed firmly to the back burner a couple of hours ago when my mom let me know that my dad has had a major stroke. So I'm headed out of town ASAP to be with family. I'll fill orders until my flight leaves.

Tom
 

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The Intelligent Soft Start looks good. Tell us more about it vs other solutions when you get time.

Well, I seem to find myself with about three hours before my next flight boards...

You'll get the highlights of the ISS vs other solutions by following the link to its page on my website that I linked to in Post #505. Also note that the description page has a link to an old HP Journal, which details the HP 14570A power controller. The ISS can be viewed as one channel of a 14570A power controller and the HP Journal is a good read.

In addition, considerable effort went into the selection of the NTC resistor used in the soft start. I optimized the circuit to ensure a fast startup while also limiting the inrush current.
Part of my design process was to compare the NTC-based solution with the more common (in DIY circles anyway) power resistor-based solution. I found the solution based on power resistors to be inefficient at limiting the inrush current as the current limiting resistor is usually way too large. While this does limit the initial inrush, the second inrush, which occurs when the relay closes and shorts out the resistor, is almost as large as the inrush current without any limiter. Basically: The power resistor-based inrush limiters are inferior to the NTC-based limiters, even when optimized.
I'll post data to support this once my situation gets back to normal.

Sorry to hear about your Dad's stroke - wishing him recovery and wish you safe travels. Take care.

From the latest report it doesn't sound like there'll be any recovery. Thanks for your thoughts, though.

Tom
 
Does anyone have a good recommendation for a shielded cable for the XLR connectors?

Also, I'm contemplating if I can use the same cable that connects my speakers within the Amp. A Kimber 8TC, might be a pain though to get the 9AWG cable connected to the molex connectors.

Would anyone see advantages or disadvantages of using such cable within the Amp chassis?

And finally another question: would there be pro's or con's in using a filtered IEC inlet?
 
Another question is regarding the connection from the ISS to my 4 meanwell RPS-400-36 PSU's..

The ISS documentation states to either configure for 115v or 230v.

I am assuming this configuration has to do with connecting the ISS to transformers as they typically need the primary wired in series

If I omit the wire bridge for 230v, am I correct in assuming that the output of the ISS will have two 230 VAC outputs (J8 --> AC | 0 | 0 | AC)?

Or do I also need the bridge for 230VAC above J8 when using the Meanwell SMPS's?
 
I'm about to start populating the ISS board, but I cannot find the detailed component mapping in the ISS docs.

Argh!! It looks like I forgot to include the BOM in the design doc. I'll fix that when I get home. I travel on July 3rd, so expect the doc to have been fixed by July 4th or 5th. Sorry for the omission.

Am I missing something?

Yes. The BOM... :)

Another question is regarding the connection from the ISS to my 4 meanwell RPS-400-36 PSU's..

The ISS documentation states to either configure for 115v or 230v.

Configure the board for your local mains voltage. Then hook the Mean Well supplies to the two AC terminals (terminal 1 and 4). I forget which is the live and which is neutral. You can easily trace the neutral on the board. If I recall correctly, terminal 4 (oval pad) is the Neutral and terminal 1 (rectangular pad) is the Live.

I should add that to the doc as well.

Tom