Amp protection cct problem or problem owner?
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From: N_Cook on 6 Feb 2010 03:28 Audiolab 8000A trips out on a bass note using the amp at about 60 percent volume. Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - wrt ground either channel, is that the expected sort of 8R speaker protection level? A function of the inductance of the speakers, generating back emf or something ? I asked the owner if he played weird stuff and he made no comment.
From: Dave Plowman (News) on 6 Feb 2010 03:55 In article <hkj94n$e8b$1(a)news.eternal-september.org>, N_Cook <diverse(a)tcp.co.uk> wrote: > Audiolab 8000A trips out on a bass note using the amp at about 60 percent > volume. > Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - wrt > ground either channel, is that the expected sort of 8R speaker protection > level? > A function of the inductance of the speakers, generating back emf or > something ? > I asked the owner if he played weird stuff and he made no comment. Can any reproduction equipment produce DC unless faulty? Can't see why it would need to, since it's not an audio signal. I'd also be surprised if a faulty electronic instrument producing DC would get through the recording chain too. -- *If they arrest the Energizer Bunny, would they charge it with battery? * Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: N_Cook on 6 Feb 2010 04:30 Dave Plowman (News) <dave(a)davenoise.co.uk> wrote in message news:50e53f920ddave(a)davenoise.co.uk... > In article <hkj94n$e8b$1(a)news.eternal-september.org>, > N_Cook <diverse(a)tcp.co.uk> wrote: > > Audiolab 8000A trips out on a bass note using the amp at about 60 percent > > volume. > > > Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - wrt > > ground either channel, is that the expected sort of 8R speaker protection > > level? > > A function of the inductance of the speakers, generating back emf or > > something ? > > I asked the owner if he played weird stuff and he made no comment. > > Can any reproduction equipment produce DC unless faulty? Can't see why it > would need to, since it's not an audio signal. I'd also be surprised if a > faulty electronic instrument producing DC would get through the recording > chain too. > > -- > *If they arrest the Energizer Bunny, would they charge it with battery? * > > Dave Plowman dave(a)davenoise.co.uk London SW > To e-mail, change noise into sound. A bit of clarification perhaps. Not a matter of trying to hear DC sound. The DC monitoring is to protect speakers from being damaged should there be a fault in the pa then the output line instread of being nominal DC 0V it should jump to 40V or more DC rail voltage. Is 4V trigger level too low for some sorts of music and or speaker inductance effects. ?There is some integration/standoff time , maybe shortens with higher detected voltage. At 4.5V it is about 1/2 second before relay clicks over, but 4V corresponds to only 2Watt of DC power
From: N_Cook on 6 Feb 2010 04:42 N_Cook <diverse(a)tcp.co.uk> wrote in message news:hkjcnf$og6$1(a)news.eternal-september.org... > Dave Plowman (News) <dave(a)davenoise.co.uk> wrote in message > news:50e53f920ddave(a)davenoise.co.uk... > > In article <hkj94n$e8b$1(a)news.eternal-september.org>, > > N_Cook <diverse(a)tcp.co.uk> wrote: > > > Audiolab 8000A trips out on a bass note using the amp at about 60 > percent > > > volume. > > > > > Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - wrt > > > ground either channel, is that the expected sort of 8R speaker > protection > > > level? > > > A function of the inductance of the speakers, generating back emf or > > > something ? > > > I asked the owner if he played weird stuff and he made no comment. > > > > Can any reproduction equipment produce DC unless faulty? Can't see why it > > would need to, since it's not an audio signal. I'd also be surprised if a > > faulty electronic instrument producing DC would get through the recording > > chain too. > > > > -- > > *If they arrest the Energizer Bunny, would they charge it with battery? * > > > > Dave Plowman dave(a)davenoise.co.uk London SW > > To e-mail, change noise into sound. > > A bit of clarification perhaps. > Not a matter of trying to hear DC sound. The DC monitoring is to protect > speakers from being damaged should there be a fault in the pa then the > output line instread of being nominal DC 0V it should jump to 40V or more DC > rail voltage. > > Is 4V trigger level too low for some sorts of music and or speaker > inductance effects. ?There is some integration/standoff time , maybe > shortens with higher detected voltage. At 4.5V it is about 1/2 second before > relay clicks over, but 4V corresponds to only 2Watt of DC power > > http://sound.westhost.com/project33.htm mentions "The detector circuit shown in Figure 1 (1) is simple and works well, and as shown will not trigger with a 30V RMS signal at 5Hz, but operates in 60ms with 30V DC applied, and in 50mS with a 45V DC supply. This should be sufficient for most applications, and allows the use of a non-polarised electrolytic capacitor in the filter. " well above 3.5 to 4.5 V dc fault trigger levels
From: Dave Plowman (News) on 6 Feb 2010 05:28 In article <hkjcnf$og6$1(a)news.eternal-september.org>, N_Cook <diverse(a)tcp.co.uk> wrote: > Dave Plowman (News) <dave(a)davenoise.co.uk> wrote in message > news:50e53f920ddave(a)davenoise.co.uk... > > In article <hkj94n$e8b$1(a)news.eternal-september.org>, > > N_Cook <diverse(a)tcp.co.uk> wrote: > > > Audiolab 8000A trips out on a bass note using the amp at about 60 > percent > > > volume. > > > > > Trigger voltage tested at somewhere between 3.5V and 4.5V DC + or - > > > wrt ground either channel, is that the expected sort of 8R speaker > protection > > > level? A function of the inductance of the speakers, generating back > > > emf or something ? I asked the owner if he played weird stuff and he > > > made no comment. > > > > Can any reproduction equipment produce DC unless faulty? Can't see why > > it would need to, since it's not an audio signal. I'd also be > > surprised if a faulty electronic instrument producing DC would get > > through the recording chain too. > A bit of clarification perhaps. Not a matter of trying to hear DC > sound. The DC monitoring is to protect speakers from being damaged > should there be a fault in the pa then the output line instread of being > nominal DC 0V it should jump to 40V or more DC rail voltage. Yes - I know what it does. But you suggested this DC offset could be caused by the type of music? I was merely querying this. > Is 4V trigger level too low for some sorts of music and or speaker > inductance effects. ?There is some integration/standoff time , maybe > shortens with higher detected voltage. At 4.5V it is about 1/2 second > before relay clicks over, but 4V corresponds to only 2Watt of DC power I have a kit DC offset protection unit from Vellerman sitting across the also home built amps in the workshop. That triggers at +/- 3 volts. Many older amp designs had preset DC offset, and this you set to zero, with a tolerance of only a few millivolts. I dunno how many watts of DC a say 100 watt speaker could handle for long. I'd guess at it being quite small. Most books say when checking the polarity of a speaker with DC to only use a 1.5v battery. -- *A bartender is just a pharmacist with a limited inventory * Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
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