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Old 30th January 2013, 05:03 AM   #8311
dvv is offline dvv  Serbia
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Originally Posted by gootee View Post
Just a thought, and I realize it would double some "bad" things, too, but if we "stacked" the outputs of two such 20V/us chipamps, or arithmetically summed them, then the combination would achieve 40 V/us.
True, which is why I am not discarding them so easily.

I will not go below that figure, after all, I qualify for the title "gumpy old fart".
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Old 30th January 2013, 05:28 AM   #8312
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I've discarded the usual suspects (LM388x, TDA729x) for the better sounding climes of the old Philips car radio parts which come bridged as standard. Power output is more limited into higher impedance loads due to the restricted voltage (18V) so stacking might be the best way forward for me to increase the power
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Old 30th January 2013, 06:59 AM   #8313
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Bridge connection gives you the slew rate doubling across the load
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Old 30th January 2013, 07:00 AM   #8314
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Flights of fancy are almost always doable ... I once seriously conceived a 2.4kW amp, done totally using chip amps; current drive of at least 50amps. Of course, this way you may as well go discrete, by the time you work out the hardware that's needed ... but still, a fun thing to do -- blow up someone's pro speakers using clean power from chip amps, just to prove it can be done ...

Frank
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Old 30th January 2013, 07:52 AM   #8315
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My biggest chip amp to date was 16 TDA7294s, bridged parallel monoblock. With two paralleled 500VA toroids. Bass still wasn't as good as ML No.33 but that has much bigger trafos.
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Old 30th January 2013, 07:53 AM   #8316
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The new kid on the block (at least to me) is Nat Semi's TAS 5630 B. They say it can do 300W stereo or 400W mono, and THD at 1W ito 4 Ohms is less than 0.03%. Even 4 times 145W, which is handy for active speakers. Sadly, it uses MOSFETs for output devices, so it's of no interest to me.
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Old 30th January 2013, 08:03 AM   #8317
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My biggest chip amp to date was 16 TDA7294s, bridged parallel monoblock. With two paralleled 500VA toroids. Bass still wasn't as good as ML No.33 but that has much bigger trafos.
Surely the above comment is in some way related to the volume used. I mean, very high quality bass is available from others as well, but at higher power levels, this may (and most often does) change in favor of larger transformers.

However, for your "typical" room listening levels, there shouldn't be a problem caused by power supplies. I find that most amps start to have problems once you've come to about 1/3 of their nominal voltage output. In normal rooms, even a nominally 50 Wrms amp will start rattling window panes by then. Unless you have an uncommonly large room by Euro standards, in which case you purchased the wrong amp in the first place.

I think Thorsten is right when he says it all depends on whether the amp was designed for show (looks), a price level or a sound quality level. If you design it for sound quality, it should be all right under most conditions. Obviously, once you decide to design for sound quality, chances are it will have "worse" specs than if it's designed for a price level. But if you look deep down, it will invariably be better designed than the run-off-the-mill products from mass manufacturers.
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Old 30th January 2013, 08:12 AM   #8318
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Surely the above comment is in some way related to the volume used. I mean, very high quality bass is available from others as well, but at higher power levels, this may (and most often does) change in favor of larger transformers.
This was not in a domestic setting, so yes I am guessing the guy who gave me that feedback on my efforts was stressing it somewhat. As far as I can recall the bass unit being driven was a 15inch one, 4 inch long throw VC.
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Old 30th January 2013, 08:41 AM   #8319
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This was not in a domestic setting, so yes I am guessing the guy who gave me that feedback on my efforts was stressing it somewhat. As far as I can recall the bass unit being driven was a 15inch one, 4 inch long throw VC.
There you go.

It wasn't hard to guess, actually, my own HK integrated amps have been consistently praised for their bass and mid drive energy and enthusiasm in the UK, German and Italian mags.

Truly, their grip on the bass drivers is amazing, BUT, as you might suspect, even if they hold out longer than others, eventually their power supplies come out short in comparison with the likes of Levinson. Though not as dismally short as the Levinsons and such like come in comparison with them in terms of prices.

In my view, there are two steps to take in such occasions:

1. Separate the VAS and output stage supply voltages, use regulated for the VAS. This will not aid actual power output much, if at all, but it will keep the sonic balance way longer than single supply units, and

2. Beef up the whole power supply, not just size up the capacitors. That's a good move only if you are upgrading an existing unit, but if you're doing it from scratch, go bigger right from the start, i.e. the transformer capacity.

For example, the mechanical and physical construction of my HK 680 integrated amps inhinbits bigger transformers, simply no space. Unfortunately, the space allowed for the 8,200 uF caps makes it impossible to use anything bigger than 10,000 uF caps, so I'll have to live with just a +22% upgrade. I would have preferred 12,000, or even 15,000 uF caps, but there you go, no space.

Not that I actually NEED more than it was designed with, but hey, if I'm going to do it, I might as well add as much as I can.
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Old 30th January 2013, 09:40 AM   #8320
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The subjective impression of good bass actually depends on the amp working correctly at the top end as well as the bottom end. Very few systems do this well, only the top of the line Bryston at the recent audio show demonstrated proper control at high impact levels. Most only achieve a type of wallowing effect, to my ears.

I'm reminded of when I auditioned active studio monitors: tried the top of the line Mackie, supposedly capable of better than 120dB, with a Sydney Opera House organ piece. What a mess it made of it ... and sound engineers are supposed to use these devices to assess "accuracy" ...?

Frank

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