But don't do the detecting off the main rails!
Fit your own, separate pair of rectifiers from any power transformer secondary; a small enough capacitor and shunt resistor, that it substantially discharges within 2 or 3 power-line cycles. Use that to turn-on the transistor that controls the relay; the power for the relay can come from anywhere that's convenient and sufficient -- main rail or other.
That technique is usually fast enough. Confirm with your own testing, however.
Cheers
Fit your own, separate pair of rectifiers from any power transformer secondary; a small enough capacitor and shunt resistor, that it substantially discharges within 2 or 3 power-line cycles. Use that to turn-on the transistor that controls the relay; the power for the relay can come from anywhere that's convenient and sufficient -- main rail or other.
That technique is usually fast enough. Confirm with your own testing, however.
Cheers
zeagan, Sorry to hear about your Bryston 4B thump. Neither of the ones I have, have ever had that problem, but they are pretty old - 1978-ish. After several years of 6-night, 50-weeks/year service, one of them does have a charming little chirp, just one, about 8 or 10 seconds after power-off. Sounds a little like an Original Star Trek sound effect. But no diaphragm shredding.
Regards
Regards
A couple of weeks ago I go a good deal on some 18Sound ND4015be 1.5" throat 4" Beryllium diaphragm compression drivers and now have them installed in some JBL 2384 horns driven by Aleph J in a Bi-Amp active setup. Beautiful sound! BUT, Aleph J has a noticeable switch off thump and although I have a mute switch on the amp when I power it down I am concerned that a power outage or an error could send this thump to my Be diaphragms
So I guess a protection capacitor is needed? Crossover is 630Hz so if I go an octave below that I'm going to need quite a large capacitor!
Any suggestions as to a good cap for this job? They sound so good I don't really want a capacitor in the signal path to affect anything
Very nice! I use a JBL 2453h-SL on my JBL 2384 waveguides driven by ACA's which also have the turn off thump. I also use steep slope digital XO's (software DSP) in a triamp scenario.
I used a chart like this: https://www.markertek.com/attachments/ATS004711.pdf to determine the value of the protection cap. Best practice is to select a capacitor that is active at approximately one octave below the crossover frequency, assuring minimal acoustic interference with crossover region performance while maintaining a good degree of protection.
In my case, the crossover frequency is 630 Hz so the cap would “kick in” at around 300 Hz and below. My JBL 2453H-SL large format compression drivers are 8Ω. So looking at the chart, we see a value of 66μF to 80μF for 300 Hz to 250 Hz range. Since I could not find a 66μF cap at the time, I went with these high speed, 82μF Solen caps: PB8200 - Solen Electronique Inc.
Very happy with the result with no impact on the SQ that I can hear. A quick listening test I used was to have one side using the protection cap and the other side not. I can't hear (or measure) a difference. So the protection caps stays in.
Good luck and would love to hear more about the sound of those 18Sound Beryllium CD's!
Then please explain the difference between a Voltage source driven speaker, a current source driven speaker with an impedance conjugate, and a current source driven speaker with line level EQ compensation..
I thought we used active filters because:
- they're more efficient - less amp power wasted
- higher order filters are practical
- you can change a crossover frequency at the gig(!), 5 minutes before the 1st tune if necessary - very flexible
- time alignment is practical (DSP crossover or digital amp) - can't with passive
Sorry seanny, but I've never given a moment's thought to 'maximum control of the transducers'.
Also eagerly awaiting the reports/impressions on the 18Sound Be CD's.
Cheers
- they're more efficient - less amp power wasted
- higher order filters are practical
- you can change a crossover frequency at the gig(!), 5 minutes before the 1st tune if necessary - very flexible
- time alignment is practical (DSP crossover or digital amp) - can't with passive
Sorry seanny, but I've never given a moment's thought to 'maximum control of the transducers'.
Also eagerly awaiting the reports/impressions on the 18Sound Be CD's.
Cheers
Thanks Mitchba, I was looking at caps around 80uF as the impedance is back to around 8Ohms by 250Hz but they get quite expensive! I think I'm going to revisit the amp/speaker protection as the source of the problem rather than trying to 'fix' it further down the line and find a solution that way. TBH I don't have a problem with using my mute button on the amp it's only that this doesn't prevent accidents or help in the event of a power failure.
As for the 18Sound comps, I should be sorting the amp issue or taking more measurements but I can't stop listening to them! Incredible amounts of resolving power, well recorded vocals sound uncannily real but with none of the harshness that I find uncomfortable with most of the Ti diaphragms I have heard. My room is quite small and I was afraid that these large horns would be too much but they work beautifully.
As for the 18Sound comps, I should be sorting the amp issue or taking more measurements but I can't stop listening to them! Incredible amounts of resolving power, well recorded vocals sound uncannily real but with none of the harshness that I find uncomfortable with most of the Ti diaphragms I have heard. My room is quite small and I was afraid that these large horns would be too much but they work beautifully.
I think adding more components in the audio path is a less-than-ideal solution to protecting an expensive driver. I prefer Rod Elliott's approach:
Loudspeaker Protection and Muting
Also gets rid of the thump at power on/off.
Loudspeaker Protection and Muting
Also gets rid of the thump at power on/off.
AllenB,
what is your listening experience about passive vs active please ? At iso correction, can ears make a difference ?
My opinion which is not related to experience-I don't know- is the active is more costly than good enough cheap mkp coils and resistors ? -cause good active devices with good noise floor level are a little more expensive than the cheapest-
The protection cap is arming not too much anyway because the electronic delay than DSP introduce for time correction is damping much more ? = don't be worry with a big caps it's arming less than we think vs the DSP circuitry?
Some says they don't hear the difference, some says they hear, some are did the exact response-matching, some are didn't.
Even if someone did the exact frequency/phase/timing response-matching, the impedance would not easy to match.
I did a fr/ph/ti response-matching before and heard a difference if a cap was in the signal path or not. That's my experience. The cap(s) didn't stayed, even an expensive one needed to leave.
Even if someone did the exact frequency/phase/timing response-matching, the impedance would not easy to match.
I did a fr/ph/ti response-matching before and heard a difference if a cap was in the signal path or not. That's my experience. The cap(s) didn't stayed, even an expensive one needed to leave.
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They both take about the same time. Active saves me a few minutes each time I make changes plus a few minutes more of simming. The rest of the work Is needed for either kind.
Usually I have a combination of line level passive/ analogue active built into the amps themselves, and some global EQ. The active filters I do with software.
Usually I have a combination of line level passive/ analogue active built into the amps themselves, and some global EQ. The active filters I do with software.
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