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Old 2nd September 2012, 11:46 AM   #1
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Default Percentage input rail sag allowable...D amp

Hello,

We are designing a 320W SMPS, (80V, 4A) and are then going to find the cheapest class d amplifier that we can power with it.
(its for electric guitar amplifier)


So we want a Class D amplifier without feedback....as this will make it more complicated and expensive...so it will have a poor PSRR.

So, what percentage input rail sag is acceptable for the class D amplifier in this case?
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Old 2nd September 2012, 01:54 PM   #2
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This is directly depending on the deafness of your intended customers.

If you want to make it cheap - just build the cheapest class d you are able to get running and power it with the cheapest smps you can get running.
Undersize all power components.
Ingore thermal necessities, they are costly and need time to design.
Sell it to poor people and make them even more poor, because it will be such a dirty build that it offers no value for the money.
One can even improve the profit margin of this business model by paying a teacher to send children to the factory instead instead of teaching them...
I hope all this is not part of your business model.
..but I had to say this, because I am completely fed up by the cheapmania.

What happened to the mind setting of offering good value for the money??!!!
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Old 2nd September 2012, 03:51 PM   #3
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Its worth going for a class d amp with feedback.
In my design its two resistors and a capacitor!!! which equals about 20p in money terms.
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Old 2nd September 2012, 03:57 PM   #4
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Quote:
Originally Posted by nigelwright7557 View Post
Its worth going for a class d amp with feedback.
In my design its two resistors and a capacitor!!! which equals about 20p in money terms.
And if it's post filter feedback those 20p is easily regained in relaxed specifications for the filter inductor.
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Old 2nd September 2012, 04:17 PM   #5
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Guitar amplifiers are very different than hi-fi. Actually a huge sag is often considered desirable for dynamics compression. Why else on earth would guitar amps use vacuum diodes in a rectifier?
Neither PSRR or THD is any problem to guitar amp, huge distortion is hi-fi terms, like 0.5% is still a 'clean' guitar sound.
Thread starter, you and your guitar amp are responsible for ~50% new nonsense threads in power supply and class d sections during last months, go build the goddamn stuff and stop trolling.

Last edited by darkfenriz; 2nd September 2012 at 04:20 PM.
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Old 2nd September 2012, 05:03 PM   #6
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Quote:
Originally Posted by darkfenriz View Post
Thread starter, you and your guitar amp are responsible for ~50% new nonsense threads in power supply and class d sections during last months, go build the goddamn stuff and stop trolling.
... was just thinking about starting a thread on that. Good to see that I am not the only one who feels that way.

As long as the thread starter ignores any useful advice given in the "Class D supply dimensioning" thread, no one can really help him.

Stop spamming this beautiful forum, eem2am.

Andreas
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Old 2nd September 2012, 05:56 PM   #7
AndrewT is offline AndrewT  Scotland
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send all the musical instruments questions to the musical instruments section.
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Old 2nd September 2012, 09:29 PM   #8
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send all the musical instruments questions to the musical instruments section.
this
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Old 3rd September 2012, 12:28 AM   #9
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Does your guitar amp outfit have another engineer responsible for determining the sound of the amp? Surely you're not building a PA amp, you want the thing able to be driven into distortion and have it sound half decent when that's happening - whoever's doing the circuitry that affects the sound has to have an ear for what sounds good and what doesn't, and have them evaluate what you come up with.

You're undertaking a big project if you're rolling a guitar amp and you want it to be successful in the market. There's endless chinese amps you'll never compete with on price so forget that idea altogether, and on the high end you're up against either established amp companies that have been around for decades (marshall/fender/traynor/etc) or amp companies with a story about where they came from (whatever one you keep bringing up). You need your niche, and you're going to need to spend a lot of money fighting for it.
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Old 4th September 2012, 06:55 PM   #10
gmarsh is online now gmarsh  Canada
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Hate to bump this thread to say it, but I'd like to thank the moderators for banning eem2am.

Looking at the list of threads that they started is an ugly sight... you'd think after starting *100* threads basically asking how, they'd be able to build a SMPS that could power a class D amp. Hell, if their time spent on this forum was instead spent flipping burgers at McDonalds, they would have probably bought a half dozen different class D amplifiers to reverse engineer, and got quite a few prototypes built.

And in almost every thread, they asked for advice and then argued with those who actually put in some effort to help.

Good riddance!
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