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Budget Amplifiers for Studio Monitors

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Re: Budget Amplifiers for Studio Monitors

Postby Hugh Robjohns » Fri Jan 25, 2019 2:24 pm

Wonks wrote:Maybe worth an SOS update article on this? The last one I could find was David Mellor's 2006 article which gives the impression that the damping factor is normally low on class D unless extra sophisticated circuitry is used to improve it.

The technology has come on in leaps and bounds over the last decade, and 'digital' class-D amps which tend to have a highish output impedance are now a rarity -- at least in quality audio applications.

But yes, maybe an article topic to refresh in the future.

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Re: Budget Amplifiers for Studio Monitors

Postby Hugh Robjohns » Fri Jan 25, 2019 2:42 pm

ef37a wrote:Self says output Z for class D is usually higher than a good class B amp.

Much as I rate Mr Self enormously highly, the world of Class-D amps is a very specialised one, and there are few designs that are actually designed properly for high-quality audio applications. Check out any of Bruno's AES presentations online and see if you don't develop a furrowed brow, and then a throbbing headache by slide 3! :lol:

Seriously, though, if Bruno says proper design provides 'vanishingly low output impedance' I ain't going to doubt it... But we do all know that 'proper design' is often elusive, especially in the cheapest products.

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Re: Budget Amplifiers for Studio Monitors

Postby Wonks » Fri Jan 25, 2019 2:58 pm

Hugh Robjohns wrote:* In the Hypex amps this feedback topology is referred to as PID or Proportional Integrating Derivative! :ugeek

Strictly speaking, this should be P+I+D; proportional plus integral plus derivitive. It's the standard control loop (for positioning valves and mixing dampers) in heating and cooling systems, and I've been using them since 1982. Most slow reacting HVAC applications only use the P+I part of the loop, with the D part only used on quick responding systems, so the full P+I+D mode is more likely to be used for valve positioning in process control applications.

Obviously electronics are very quick responding systems, so the full P+I+D mode will be used for speaker control.

It's important (if slightly pedantic) to use the + sign between the letters, as PI control (proportional integral - so integral only) is different from P+I (proportional plus integral) control. :ugeek: :ugeek:
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Re: Budget Amplifiers for Studio Monitors

Postby Hugh Robjohns » Fri Jan 25, 2019 3:07 pm

I'll gladly take your word for it! I was just quoting from one of Bruno's PowerPoint slides! :thumbup:
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Re: Budget Amplifiers for Studio Monitors

Postby pkalder » Sun Jan 27, 2019 12:49 am

Thanks all for the replies. The ideas were to save money and do my own hacks while also learning. Mike Senior on his Cambridge MT website suggested some of the NHTs, but I'm thinking these were an earlier models. His sealed enclosure explanations made sense, so I had been searching accordingly. It is very difficult to find entry level ($200-$300) sealed monitors. My goal would be a $30 amp and passive sealed monitors around $100 each. Of course, we can't always get what we want. But if you try sometime...
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Re: Budget Amplifiers for Studio Monitors

Postby James Perrett » Sun Jan 27, 2019 2:21 am

Hugh Robjohns wrote:Bruno Putzeys -- Chief Engineer at Phillips Class D Audio Systems Laboratory -- explains briefly in this Bryston article on the topic of Class-D amps:

http://www.bryston.com/PDF/newsletters/Bryston_Newsletter_V7_4.pdf

I wonder if Bruno is aware of that article? I very much doubt that he would agree with the last few paragraphs which Bryston seem to have added and which look more like audiophile marketing spin. It is very disappointing to see the hijacking of Bruno's article from a company that usually have such a good reputation.

I know that some people consider Bruno's designs to be better sounding that Bryston's and I certainly have no complaints with my self built Hypex based monitor amp.
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Re: Budget Amplifiers for Studio Monitors

Postby Hugh Robjohns » Sun Jan 27, 2019 2:32 am

Yes, it is quite an odd marketing piece, and I also wondered if that article from Bruno had been used with his knowledge. They seem to be promoting the benefits of well designed class-D amps, and then justify their reasons for not going down that route themselves! Weird!

I agree that the Hypex amps are exceptionally good, and they continue to be developed... But still like beefy Class-AB and between the plasma telly and Bryston 4B SST2, I rarely need to turn the radiators up, let alone light the fire in the lounge! :lol:
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