Regarding this circuit again http://mitglied.lycos.de/Promitheus/delay_circuit_for_toroids.htm, I have taken a couple more measurements and from looking at the turn-on transient voltage and also referring back to the original article that talks about using a suppression relay for turn on/off, I was thinking of modifying the above mentioned circuit. Please advice if what I describe below would work or not.
* From the above delay circuit, I would remove R4 to R7 (& the parrallel jumper wire & K2) and install a double pole double throw relay at the output of each channel. Basically keeping the rest of the circuit as power supply for the two relays (connected in parrallel).
* The reason I say double pole double throw is because this pre-amp has balance output ... so that the -ve and +ve output of each channel will be off during the turn-on transient and after a couple of seconds, both will be on once the relay kicks in.
My goal is to suppress the turn-on transient and nothing else.
* From the above delay circuit, I would remove R4 to R7 (& the parrallel jumper wire & K2) and install a double pole double throw relay at the output of each channel. Basically keeping the rest of the circuit as power supply for the two relays (connected in parrallel).
* The reason I say double pole double throw is because this pre-amp has balance output ... so that the -ve and +ve output of each channel will be off during the turn-on transient and after a couple of seconds, both will be on once the relay kicks in.
My goal is to suppress the turn-on transient and nothing else.
Speaker protection
Speaker protection is essential for me, hence the Linsey-Hood regulated power supply with protection, no relays. Fuses on transformer primary only. ETI May '89.
If more recent info available, please advise.
PeterS
http://users.classicfm.net/williamshart/
Speaker protection is essential for me, hence the Linsey-Hood regulated power supply with protection, no relays. Fuses on transformer primary only. ETI May '89.
If more recent info available, please advise.
PeterS
http://users.classicfm.net/williamshart/
I think that protection circuit can be built using relay
to make short circuit on amplifier's output in case of emerbency.
In normal situation relay contacts are open and
have no negative effect for sound. When something
goes wrong some circuit will turn on relay and relay contacts will short amplifier's output protecting this way
speakers. This can be modified to switch another relay in
primary of the transformer to switch off the power.
Yes, this circuit can't be used for power-on delay but can protect expensive speakers and have no impact on sound quality using cheap relatys!
to make short circuit on amplifier's output in case of emerbency.
In normal situation relay contacts are open and
have no negative effect for sound. When something
goes wrong some circuit will turn on relay and relay contacts will short amplifier's output protecting this way
speakers. This can be modified to switch another relay in
primary of the transformer to switch off the power.
Yes, this circuit can't be used for power-on delay but can protect expensive speakers and have no impact on sound quality using cheap relatys!
Yes it can.
But in all cases some MOSFETS are cheaper than quality speakers. In most cases these MOSFETS already will be failed and this circuit will prevent blowing the speakers which can be pretty expensive.
Power fuse can be choosen to blow in case of shorting amplifier's output so nothing worse will happen.
Instead of relay could be used triac rated for enough current and this way we can short output very quickly giving more protection to speakers.
But in all cases some MOSFETS are cheaper than quality speakers. In most cases these MOSFETS already will be failed and this circuit will prevent blowing the speakers which can be pretty expensive.
Power fuse can be choosen to blow in case of shorting amplifier's output so nothing worse will happen.
Instead of relay could be used triac rated for enough current and this way we can short output very quickly giving more protection to speakers.
Soft Start Circuit
Below is a soft-start circuit lifted from a pro-amplifier.
The delay is about half a second or so, and this seems sufficient.
As for protection, crowbar shorting (scr) of the DC rails causing 240V input fuse or breaker to trip would be the sonically least damaging configuration possible.
Eric.
Below is a soft-start circuit lifted from a pro-amplifier.
The delay is about half a second or so, and this seems sufficient.
As for protection, crowbar shorting (scr) of the DC rails causing 240V input fuse or breaker to trip would be the sonically least damaging configuration possible.
Eric.
Attachments
This post is a follow up on my earlier post regarding adding a soft start circuit to prevent turn on/off thump for my BOSOZ pre-amp. Having tried this circuit http://mitglied.lycos.de/Promitheus/delay_circuit_for_toroids.htm I have indicated that the turn on/off thump is still there. To cut the story short, I have modified the circuit and I was able to get it to turn on without thump but when I turn OFF the pre-amp, I still hear a thump.
I have tried another circuit recently. This time it's a 2 channel loudspeaker protection kit (Model #K4700) from Velleman http://www.audioxpress.com/bksprods/kits/kv-k4700U.htm Since I only have one kit and BOSOZ is a balanced pre-amp, I have installed it on one channel only. With this circuit in the BOSOZ, there is NO longer any turn on or turn off thump BUT there is a buzzing noise BEFORE the relay kicks in ... meaning that when the relay is on and outputting signal, the buzzing noise is gone.
My questions:
1. Is this Vellerman Kit K4700 not suitable for pre-amp with balanced output? I would think otherwise because it actually works once the relay kicks in. Or is it that this kit is only suitable to be used in power amp? Keep in mind that I'm only interested in supressing the turn on/off thump and nothing else.
2. Would the buzzing noise go away if I have a Vellerman Kit installed on each channels of the pre-amp? ... due to (I'm guessing here) different grounding method between pre-amp and power amp? I'm using Pass A40 power amp. Before I order the 2nd kit, I'm hoping for some feedback.
And here is some additional information that I hope would be helpful. If I hook up the BOSOZ without using any soft start circuit or Vellerman Kit and using the balanced output and hook up to the power amp with balanced input, there isn't any turn on or turn off thump what so ever. The turn on/off thump happens only on unbalanced operation.
I would like to try one more time before I take out all this "extra' circuit and I just have to live with the turn on/off thump (or leave the pre-amp on all the time). I'm hoping that somebody has done this before and could provide some feedback. Thanks in advance.
I have tried another circuit recently. This time it's a 2 channel loudspeaker protection kit (Model #K4700) from Velleman http://www.audioxpress.com/bksprods/kits/kv-k4700U.htm Since I only have one kit and BOSOZ is a balanced pre-amp, I have installed it on one channel only. With this circuit in the BOSOZ, there is NO longer any turn on or turn off thump BUT there is a buzzing noise BEFORE the relay kicks in ... meaning that when the relay is on and outputting signal, the buzzing noise is gone.
My questions:
1. Is this Vellerman Kit K4700 not suitable for pre-amp with balanced output? I would think otherwise because it actually works once the relay kicks in. Or is it that this kit is only suitable to be used in power amp? Keep in mind that I'm only interested in supressing the turn on/off thump and nothing else.
2. Would the buzzing noise go away if I have a Vellerman Kit installed on each channels of the pre-amp? ... due to (I'm guessing here) different grounding method between pre-amp and power amp? I'm using Pass A40 power amp. Before I order the 2nd kit, I'm hoping for some feedback.
And here is some additional information that I hope would be helpful. If I hook up the BOSOZ without using any soft start circuit or Vellerman Kit and using the balanced output and hook up to the power amp with balanced input, there isn't any turn on or turn off thump what so ever. The turn on/off thump happens only on unbalanced operation.
I would like to try one more time before I take out all this "extra' circuit and I just have to live with the turn on/off thump (or leave the pre-amp on all the time). I'm hoping that somebody has done this before and could provide some feedback. Thanks in advance.
Hi Fcel,
Easier and (?) better IMHO to leave the preamp on all the time. The preamps I have experience of (Naim, Musical Fidelity) have all benefited from this approach. The small amount of consumed power will hardly be noticed on the electric bill. Have occasionally left power amps on too, with a notable improvement in perceived sound quality. I won't be doing that with an Aleph though!
Regards
Paul
Easier and (?) better IMHO to leave the preamp on all the time. The preamps I have experience of (Naim, Musical Fidelity) have all benefited from this approach. The small amount of consumed power will hardly be noticed on the electric bill. Have occasionally left power amps on too, with a notable improvement in perceived sound quality. I won't be doing that with an Aleph though!
Regards
Paul
Hi all,
i've written off the speaker protection cct for these reasons;
You are only likely to blow one speaker at a time, a fault on both channels is unlikely. The cost of a bass driver for me is £35 or £135, but i offset that against the cost of the components for the speaker protection cct. I have also ofset the cost saving of the increased sound quality, i.e. it would cost me more than a driver in components to upgrade the sound quality of the amp(s) to negate the effect of the speaker protection cct.
However i would not recomend this stratergy if you have mega expensive or unobtainable drivers, mine are common diy items.
Mark
i've written off the speaker protection cct for these reasons;
You are only likely to blow one speaker at a time, a fault on both channels is unlikely. The cost of a bass driver for me is £35 or £135, but i offset that against the cost of the components for the speaker protection cct. I have also ofset the cost saving of the increased sound quality, i.e. it would cost me more than a driver in components to upgrade the sound quality of the amp(s) to negate the effect of the speaker protection cct.
However i would not recomend this stratergy if you have mega expensive or unobtainable drivers, mine are common diy items.
Mark
Paul and Mark ... I understand your point of view. My main interest now is to get it to work.
I have played with the Vellerman Kit for some time now and I have figured out how to wire it so that there isn't any buzzing noise before the relay kicks in. Basically I have wired the relay so that the output is short to ground before the pre-amp is turn on.
Now, there isn't any buzzing noise or turn-on thump anymore but when I turn off the pre-amp, there is a loud "pop" instead of a loud thump. Can anybody help me out here? What else can I do? Wire up some kind of capacitors (& value?) to ground to filter out the turn-off suppression? There must be something very simple but I can't figure out.
I have played with the Vellerman Kit for some time now and I have figured out how to wire it so that there isn't any buzzing noise before the relay kicks in. Basically I have wired the relay so that the output is short to ground before the pre-amp is turn on.
Now, there isn't any buzzing noise or turn-on thump anymore but when I turn off the pre-amp, there is a loud "pop" instead of a loud thump. Can anybody help me out here? What else can I do? Wire up some kind of capacitors (& value?) to ground to filter out the turn-off suppression? There must be something very simple but I can't figure out.
I'm also building a BOSOZ preamp and thought to try a relay setup I had in an old one for grounding the outputs after the output resistor or between two resistors. This setup will not pass the signal through the ralay since is only used for grounding.
This is a small relay (double contacts) suitable for PCB mounting operating in a NC condition, the delay is provided by 555 opamp which can be adjusted for a long or short delay via a cap and a couple of resistors, all of these mounted on a small PCB away from the main board mounted on the back plate of the preamp near the output connectors.
I know, nobody wants an opamp and relays (two relays for the BOSOZ) inside their preamps. But in the other hand it work with no problems inside a 12ax7 line preamp.
To use this one will need a separate small 12V PSU.
Have someone tryed a simillar setup?
This is a small relay (double contacts) suitable for PCB mounting operating in a NC condition, the delay is provided by 555 opamp which can be adjusted for a long or short delay via a cap and a couple of resistors, all of these mounted on a small PCB away from the main board mounted on the back plate of the preamp near the output connectors.
I know, nobody wants an opamp and relays (two relays for the BOSOZ) inside their preamps. But in the other hand it work with no problems inside a 12ax7 line preamp.
To use this one will need a separate small 12V PSU.
Have someone tryed a simillar setup?
Tony,
I'm pretty sure what you just described will work for turn on but I'm not sure about turn off.
It is the turn-off pop/thump that is giving me grief now. I don't know about other pre-amps but for BOSOZ, apparantly there is a high transient voltage (measured on digital meter) at turn on AND turn off. So, really, what I need is some kind of a circuit that would short the output to ground JUST BEFORE I turn off the BOSOZ. The Vellerman Kit allows me to do just that - but only on turn on - the output relay is short to ground JUST BEFORE I turn on the BOSOZ and thus not allowing the high transient turn on voltage to get to the power amp. I'm still hoping that some member here could suggest some modification to the Vellerman Kit or some totally new circuit that I could try out.
I'm pretty sure what you just described will work for turn on but I'm not sure about turn off.
It is the turn-off pop/thump that is giving me grief now. I don't know about other pre-amps but for BOSOZ, apparantly there is a high transient voltage (measured on digital meter) at turn on AND turn off. So, really, what I need is some kind of a circuit that would short the output to ground JUST BEFORE I turn off the BOSOZ. The Vellerman Kit allows me to do just that - but only on turn on - the output relay is short to ground JUST BEFORE I turn on the BOSOZ and thus not allowing the high transient turn on voltage to get to the power amp. I'm still hoping that some member here could suggest some modification to the Vellerman Kit or some totally new circuit that I could try out.
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