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Old 15th August 2006, 07:49 PM   #21
mikeks is offline mikeks  United Kingdom
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Default Re: Muting/limiting

Quote:
Originally posted by Netlist
Like Peavey. Their DDT protection works flawless and at the output they use the famous Triac protection in many series. Drawback is often a broken Triac to be replaced.
In pro-series amps I consider this a good solution.

/Hugo
I suspect they use it just for DC offset protection...Didn't Self object to this on the grounds that the triac would have to be replaced, and that the output devices might well be destroyed as the rail fuse could not be relied upon to blow in time to save them when the triac shorts the output to ground?
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Old 15th August 2006, 07:52 PM   #22
mikeks is offline mikeks  United Kingdom
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Quote:
Originally posted by anatech
The triac pretty much guaranties blown outputs. In some cases huge expanses of copper trace as well.
-Chris
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Old 15th August 2006, 08:40 PM   #23
mikeks is offline mikeks  United Kingdom
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Quote:
Originally posted by anatech
I guess if you focus on the detection part, you are correct.

-Chris
See this patent for example.
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Old 15th August 2006, 08:48 PM   #24
Netlist is offline Netlist  Belgium
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Don't know about Self but indeed, this is speaker protection, not SOA protection.
Anyway, I've seen a lot of Peavey's with only a blown Triac, no notion from customers with blown speakers.
Some indeed with broken outputs.

/Hugo
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Old 15th August 2006, 09:19 PM   #25
mikeks is offline mikeks  United Kingdom
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Quote:
Originally posted by anatech
I still don't think they are concerned with SOA issues...
-Chris

see patent
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Old 15th August 2006, 09:22 PM   #26
anatech is offline anatech  Canada
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Hi Mike,
Yes, this is SOA limiting as we are familiar with. Each polarity having it's own limiting and detection device.

What I don't care for is one device to sense over current for both polarities. Either across one emitter resistor or both. This usually means that current limiting will not occur in the normal fashion, but rather more globally.

In my view, brief over current events should cause current starving or some kind of "clipping" rather than a global shut down. Opening a set of relay contacts pretty much ensures poor sound quality to follow. This is unnecessary and avoidable. Classic base clamping methods achieve this goal with no lasting sonic cost.

-Chris
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Old 16th August 2006, 07:21 PM   #27
AndrewT is offline AndrewT  Scotland
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Hi,
based on the dynamic headroom data posted by Mike, then Sony's best are pretty terrible.

A dynamic headroom of 1.8db for an 8ohm load is attrocious, when they should be striving for 0.5db or better in their best amps and possibly as bad as 1db in their good amps.

This appears to be a Japanese manufacturer using advertising script writers to make a bad feature/specification look as if it were attractive.
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Old 16th August 2006, 09:49 PM   #28
ilimzn is offline ilimzn  Croatia
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Quote:
Originally posted by AndrewT
A dynamic headroom of 1.8db for an 8ohm load is attrocious, when they should be striving for 0.5db or better in their best amps and possibly as bad as 1db in their good amps.
This appears to be a Japanese manufacturer using advertising script writers to make a bad feature/specification look as if it were attractive.
Um, why should anyone strive for LESS dynamic headroom? Last I looked, this was a figure determining how much short term power you can get from an amp OVER it's rated power output. The on;y problem I can find with this is that no-one tends to define the 'short' in 'short term'...
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Old 17th August 2006, 12:52 AM   #29
AndrewT is offline AndrewT  Scotland
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Hi,
although I have never had the oportunity to read the IHF standard, it defines how the test should be done.

A high dynamic headroom indicates a poor ability of the amplifier to supply sustained power. The higher the IHF headroom the worse the amplifier.

An ability to maintain output current at low frequency requires the opposite to dynamic headroom.
Have you been conned by the
Quote:
script writers to make a bad feature/specification look as if it were attractive
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Old 17th August 2006, 02:55 AM   #30
anatech is offline anatech  Canada
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Hi Andrew,
I believe the headroom spec on my Marantz 300DC was 3 dB, or close to it. It makes a more efficient amplifier as I don't play test tones. I don't think the Marantz is a terrible amplifier.

I get what you are saying, but I don't buy it. A Krell would do well in this test, but I don't want such a heavy, hot object in my living room. An amp that can deliver peaks of this magnitude is impressive given the 8 R RMS rating is 150W / ch. A 20W amp. that collapses down to a 10 W amp. on sustained notes would be pretty wimpy.

-Chris
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