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Hello all, I have been experiencing occasional popping in my rear speakers when shutting down my 1206 amp. This had occured in the past when I was running a passive sub on the amp. I removed the sub from the amp and turned the gain all the way down on that channel and everything was fine. But now that other channels are doing the same thing, I am wondering if something is wrong with the amp or if I need to re-work all the interconnects and or speaker cables. Any help or ideas would be greatly appreciated. TIA, Brian
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can you just shut your processor off first? -
It may be old school but I have always powered the amp down first, allowing it to completely discharge, and then turn off the pre/pro. This may not be necessary with these newer processors.
I swithced the rear speakers with the fronts at the amp and the popping moved to the fronts, so I assume it is the amp. BrianComment
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No, no, no! Even old-school that's wrong! (In my opinion).
With my 1987 high-end Technics SU-A200/SE-A100 combo, I had to power down the PREAMP FIRST. When powering down the preamp, it would disable any signal to the power amp (looking at the schematics, I recall that the output was grounded/short-circuit with a relay when powering off the pre-amp) and the power amp could then safely be turned off. Trying to turn off the power amp first, always resulted in a loud pop that probably was not good for my SB-M1 speakers.
Always turn off the preamp first, then the power amp....
(FWIW: The preamp has a small transformer [if any - it might be using a switching PS] and it is unlikely to cause any sparks that would cause electrical noise. Power amps on the other hand [disregarding the digital ones], have a huge transformer and when disabling the power there will be noise. Ideally the input should be short-circuit/grounded when a beast like this is powered off).
Peter
P.S. This applies to amps with a traditional mechanical power switch. These issues are handled by electronics in modern amps like the Halo series that have a "digital" power switch. When you turn off a Halo with its power button, it will simply tell the computer to short-circuit the inputs and power down the amp. All done with no noise since a computer program is controlling the electronic to do everything in the right order.Comment
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My amp is 1st on - 1st off before pre/pro.Comment
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NO NOT ALWAYS!!!
it appears ymmv depending on your equipment.
I have a Transcendent Sound Grounded Grid (GG) preamp and turn it on first and off last. This is the only way I can safely use that particular pre.
If I do it any other way it sends a nasty transient through my Simaudio W5 amp/speakers and my amp goes into safety shutdown. Bruce has designed a delayed turn-on/off circuit for the GG that resolves this issue but until I decide to buy the circuit, I'll keep my practice of shutting down the amp first.Comment
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Yeah, I was refrerring to mainstream (non boutique) gear. The boutique gear can sometimes be very "special".... (My current gear TacT Audio is a good example where room temperature makes a difference in behavior).
PeterComment
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Thank you for the response. I will try turning off the processor first and see what happens. BrianComment
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My system start up has always been the same:
Source -> pre -> Amp
Off has always been:
Amp -> Pre -> Source.
I'm not sure what a 1206 is, but some amps can do this. I know a few older ones that I have ran are evil with their strange behavior such as popping when you shut them off. But, really the problem could be a rather wide range of things from a rouge component in the amplifier to weakening power supply or even a dirty power switch to a weak interconnection.-JoeComment
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Me, I've got my A21 and A51 connected via power trigger to the C1. Turn on the C1, it turns it all on. No pops.
CHRIS
Well, we're safe for now. Thank goodness we're in a bowling alley.
- PleasantvilleComment
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Oooops.........I meant to say.Originally posted by Ken49r
ON = Amp > SSP > Source
OFF = Source > SSP > Amp
Is this the correct way using Rotel RSP-1069 and RMB-1095?Comment
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Well, I powered down the processor before the amp and I still have the thump through the front L speaker. It must be something in the amp. By the way, thanks to all who replied, Brian.Comment
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Try to disconnect all inputs to the amp. If you still have a thump in the FL speaker, then it's the amp (or speaker). If this is the case, try to reverse L/R speakers. If the sound moves to the FR speaker, then it's the speaker otherwise it's the amp...Comment
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With Amp's it's always always always last on first off. I do live sound with huge amps that defy imagination
and you always turn the amps on last and off first to prevent potential damage to your speakers from sources popping just as you described. If you want to let your amp warm up, power everything on and don't press play till they're warm 
- JonComment
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Originally posted by JonInRIWith Amp's it's always always always last on first off. I do live sound with huge amps that defy imagination and you always turn the amps on last and off first to prevent potential damage to your speakers from sources popping just as you described. If you want to let your amp warm up, power everything on and don't press play till they're warm
- Jon
This is exactly what I learned from the same place I learned it, live sound.-JoeComment
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Amp last on, first off
I agree that the power amp should be turned on last, and turned off first. That's one reason why Parasound (and most other manufacturers) provides a delayed turn-on function for the 12v DC trigger on their power amps. It gives the transistorized preamps a few seconds to stabilize before providing AC to the power amplifier circuits. If you are using a tube preamp, you may need to wait considerably longer than a few seconds for the tubes to fully come up to a stabile state. Likewise, the power amp should be turned off first. Most (but not all) power amplifiers have their outputs automatically disconnected by a solenoid upon power off, but if yours does not, you should wait a few seconds for the output capacitors to begin to discharge, before turning off the preamp. I don’t know if the 1206 amp has solenoids, but if you are hearing a popping, perhaps that channel’s solenoid is stuck closed.Comment
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If the output has a relay (solenoid), then it's no longer a High-End amplifier IMHO. High end equipment does not contaminate the signal path with a relay. That's a definite no-no! (None of the Parasound Halos have speaker relays).Originally posted by RJKuzma
As for my old Technics that popped - it HAD relays on the output and they DID NOT HELP. The proper procedure was to turn off the preamp first, so that it could short circuit the inputs to the power amp. (The problem remained from the day the amp was new to 18 years later when I sold the amp. Inbetween, I had replaced the relays once [after ~10 years] due to intermittent contact problems). It was not only the SE-A100. The SE-A5 and SE-A3 also showed the same symptom with my highly efficient SB-M1 speakers (96dB/W).
A relay is a mechanical device and is not fast enough to disengage. (The disconnection time is usually in the range 10~20ms for a small relay if I recall correctly). The power switch noise will be heard before the relays get a chance to break the signal path.
Again, this does not apply with modern amps like the Halos that have a "soft power" switch (relay operated power switch). It only applies to older amps with a high-amp mechanical power switch.Comment
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Peter,
You are absolutely correct about solenoids or relays, in that they are slow, and contaminate the signal path. And yes, most modern amps use soft-start circuitry to better accomplish the same task. I don’t know what is in the Parasound 1206 that Tanker first talked about. I also don’t know about your old Technics. I was simply offering a generic possibility as to the cause for his issue. I used the terms, solenoid, relay, and soft-start circuitry interchangeably as the device within the amplifier which might need attention.
However, in the thirty-five years I have been in this hobby, I have never the heard the recommendation that amplifiers should be turned on first. I have consistently heard, read, and understood that everything else in the chain should be on and stable before engaging the last, most powerful link in the sound amplification stage. This protects the speakers from potentially damaging thumps and transients. If the amplifier is operating correctly, this recommendation usually works. If the amplifier (or the preamplifier) is not working correctly, it may not work as desired. And perhaps for some systems which have unusual configurations, general rules may not apply. But as a general recommendation for the vast majority of modern electronics, and in those cases where it matters, the power amplifier should be turned on last in the sequence. Many power sequencers and conditioners rely on this principle in their designs. The general principle is just as valid for high end components as it is for professional sound equipment.
As Chris has already indicated (with presumably properly functioning equipment), with modern components, you can usually just turn on the preamp and the trigger controlled signal will turn on the amps without any drama. Many preamps also contain soft-start circuitry which won’t allow output until the circuits are stable. I operated my Halo C1 and JC1s this way for years. However, when I inserted a high-end tube preamp into my system, I had to delay the turn-on of the JC1s, in order to allow the tubes to fully come up to stability. In my case, the general principle applied. It is neither old school nor new school—just a good general recommendation.Comment
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The way that I always learned it was some preamplifiers when you shut them off can momentarily become unstable sending a voltage spike or drop which causes the "pop". A lot of devices are capacitor coupled but even so the short spike of DC or signal acts as AC and will ride right across the capacitor as it recovers. (A total deviation from the proper terminology, but who's keeping track.) I learned this the hard way and had to replace 12" drivers in my dad's PA speakers. Meyer Sound MSL-3 drivers were neither cheap nor easy to change...-JoeComment
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I never said anyting about the ON sequence, but I agree that the power amp should be turned on last, and this is what I have always done.Originally posted by RJKuzma
I am only referring to the OFF sequence, where my old Technics amps required that the preamp first shorted its outputs (preamp off first) so that the power amplifier would not pop when it was shut off. If the power amp was turned off first, the noise from its power switch was picked up by the amp itself and it caused a loud pop. If the preamp was turned off first, it shorted its outputs (effectively shortening the inputs to the power amp) and now the power amp did not pick up the noise from its own power switch, and everything was quiet. Turning off the power amp first always made me worry that I damaged the speaker due to the sometimes very loud and scary pop.
On the other hand, if the preamp does not have any fancy muting circuitry (like shortening the outputs), then it's probably better to turn off the power amp first. In the PRO world, preamps don't do fancy things like this, so like the proamp users say, turning off the power amp first is what applies in the pro amp world...
PeterComment
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Yes, but that's probably not a quality audiophile preamp. A good preamp has good filtering with a lot of capacitors. It takes a good while before they have discharged enough to cause unstable things to happen. If it's a good preamp, it will also have disabled its ouputs way before this happens.Originally posted by joetama
OTOH, in the pro-world this does not apply. Professional sound does not care about the same things that the home consumer.
Anyway, in the end it comes down to knowing your amp and understanding its functionality (e.g. by reading the schematic diagrams)! If I have to power unknown power amps on/off, I would do it in the sequence ON:last OFF:first.
(How do you power off the power amp first in a system with multiple power amplifiers? Powering off the first power amp could send a huge disturbance through all the other power amps that are still on... Food for thought!)
PeterComment
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Originally posted by Peter Nielsen
Knowing your system is very very important. On mine I just turn down the attenuators before shutting everything off, amplifiers first.
Just out of curiosity we know the output impedance of a preamplifier is very high. But I was under the impression that a system turned off would have a higher impedance than a system turned on. So, by turning off the preamplifier you are not showing a short but an open circuit with a capacitor network on each end with high resistance to ground. Which could cause weird oscillation if anything fed back from the amplifier in the turn off process. So, having multiple amplifiers connected to the reflecting preamplifier while still energized would be much worse than a slight 'pop'. But again, this all depends on the amplifier and preamplifier specifics.
Then again maybe I'm totally off base here.-JoeComment
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Very true. It all comes down to knowing your equipment. If you have a preamplifier that grounds its outputs (for instance by grounding [shorting] the outputs with a relay like my Technics did), which makes the output impedance close to zero, it's most likely safe to turn it off first. However, if the preamp leaves its outputs "dangling", it's a bad idea to turn it off first...Originally posted by joetama
PeterComment
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Funny things happen. Today I just bought M-AUDIO AV 40 speakers.
When I power them off, by a switch an a back wall, I hear a POP even when a volume knob is set to 0. But when I simply unplug them from walls - no pop are heard. Everything powers down smoothly. ....
Can you explain me, why does it happen?Comment
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Contact bounce that creates interference. Install a 0.1uF/250V~ capacitor across the two poles of the switch and problem is solved! :TOriginally posted by DJ TramrunnerComment
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