Good evening all,
Just out of a matter of interest, how many of you people have had speaker damage due to an amp malfunctioning ( Short circuit driver components) or whatever can really go wrong on a amp ? Is protection on the speaker output really necessary ?Maybe it depends on the monetary value for replacement of the speakers ? Some people say bypass the output relay, how long should a relay's contacts really last.? I know it is dependent on the load, but in normal circumstances, should you take a chance to bypass a output relay ?
Regards all
Jan
Just out of a matter of interest, how many of you people have had speaker damage due to an amp malfunctioning ( Short circuit driver components) or whatever can really go wrong on a amp ? Is protection on the speaker output really necessary ?Maybe it depends on the monetary value for replacement of the speakers ? Some people say bypass the output relay, how long should a relay's contacts really last.? I know it is dependent on the load, but in normal circumstances, should you take a chance to bypass a output relay ?
Regards all
Jan
Well I have have never had a an amp going bad on me to destroy speakers. Amps that channels go bad yes, but never any damage to speakers. That is 30 years. Amps from those years that you bought over a counter did not have any speaker protection. If you do, shoud'nt you leave out the relay and rather use electronic protection like a crowbar.Mechanical connections leads to bad electrical connections, or is it not so critical with good relay's ? ( Finder )
Regards
Jan
Regards
Jan
These days I use all tube amps and the transformers usually prevent damage to speakers in the event of a component failure, my experience with solid state amplifiers without protection relays is not nearly so good. I have lost a couple of speakers to output stage failures in commercial amps, not to mention protos and homebrews. Good relays should not cause a significant degradation of signal quality, and I certainly wouldn't defeat the relay.
If you are planning on using SCRs for crowbar protection you'll need a pair in anti-parallel with the appropriate offset detection and trigger circuitry.
There are other things you could consider like crow-barring the supplies simultaneously with SCRs - just make sure there are fuses on the supplies being crow-barred. You could also use a dpst relay to remove power to the output stage in the event of dc offset at the output - this is probably a bit kinder to other components in the system.
I also designed several SS amps without any output protection and had cause to regret that decision, accidents happen.
If you are planning on using SCRs for crowbar protection you'll need a pair in anti-parallel with the appropriate offset detection and trigger circuitry.
There are other things you could consider like crow-barring the supplies simultaneously with SCRs - just make sure there are fuses on the supplies being crow-barred. You could also use a dpst relay to remove power to the output stage in the event of dc offset at the output - this is probably a bit kinder to other components in the system.
I also designed several SS amps without any output protection and had cause to regret that decision, accidents happen.
Not sure where you got these amplifiers, but just about every amp/receiver sold here for domestic use from the early 1970's onwards that had a DC coupled output stage (bipolar supplies) has a speaker protection relay in it. This would include a plethora of Japanese and American made amps and receivers. My first receiver, a Kenwood KR-5200 bought used in 1976 was probably 3yrs old when I got it and had a speaker protection relay.
Well, whatever you feel comfortable with.
Personally, I prefer dc-protection with high quality relays (Omron has some very nice ones) as blown voice coils and/or burning speakers are too much of a concern to me compared to a minimal potential gain in sound quality.
I think there is so much else to improve before something like that really makes a difference - room acoustics anyone?
Hannes
Personally, I prefer dc-protection with high quality relays (Omron has some very nice ones) as blown voice coils and/or burning speakers are too much of a concern to me compared to a minimal potential gain in sound quality.
I think there is so much else to improve before something like that really makes a difference - room acoustics anyone?
Hannes
Speaker damage does occur (as witnessed by the many threads on here of failed amps and speakers)
Most relays (and circuitry) provide a delay on power on to prevent thumps etc as the amp power up.
Relay distortion particularly at lowish levels is a real effect... and it's happened to me. I now use solid state relays. It's all here, and this started out as a diy member having a blown speaker. It's a long thread but worth reading all of it,
http://www.diyaudio.com/forums/solid-state/191449-output-relays.html
Most relays (and circuitry) provide a delay on power on to prevent thumps etc as the amp power up.
Relay distortion particularly at lowish levels is a real effect... and it's happened to me. I now use solid state relays. It's all here, and this started out as a diy member having a blown speaker. It's a long thread but worth reading all of it,
http://www.diyaudio.com/forums/solid-state/191449-output-relays.html
relay protection can be placed also in main supply instead of output signal.
also soft-start relay prevent thumps and protects mains supply from electrical charging of capacitors
also soft-start relay prevent thumps and protects mains supply from electrical charging of capacitors
Vrystaat, ek is ook 'ou vrystaater. Ek sien baie drivers en tweeters wat blaas agv die amplifier self wat "gaan".
Nie 'n goeie idee om die relay te oorbrug nie!!! Baie keer is daar 'n protection circuit wat gekoppel is aan daai relay. MAW, daar is gewoonlik 'n rede hoekom die relay nie click nie. 😀
Nie 'n goeie idee om die relay te oorbrug nie!!! Baie keer is daar 'n protection circuit wat gekoppel is aan daai relay. MAW, daar is gewoonlik 'n rede hoekom die relay nie click nie. 😀
The Pass amps are virtually Bomb Proof, Its so unlikely thet output device failure will occur that you can dispence with relays in the output circuit.
Crap amps will fail. These amps will benefit from some sort of protection, but that wll cost in the fidelity stakes.
Crap amps will fail. These amps will benefit from some sort of protection, but that wll cost in the fidelity stakes.
I've lost two unmatchable tweeters from speakers with a tube amp with output transformers. That trashes the whole speaker pair if you have good ears. (I'm an amateur musician of some skill). It is not the cost of the speaker, it is the testing required to get good sound with the cheapo replacement speakers in stock at the distributor. The music instrument resale shop near me is full of speakers with new (cheap) woofers, and old amplifiers with shiny new output transistors. Make your own conclusions about the frequency of output transistor shortouts.
The first transistor amp I bought had a speaker protection capacitors between the output transistors and the speakers, so the 2 output transistor shortouts that occurred didn't hurt anything. Quite a fireball the last time it happened. (Now I have heatsink fans). But it will be a cold day in **** before I connect this split supply direct coupled transistor amp I'm working on now to an actual speaker. It came with the crowbar SCR traces completely burned off the PCB, and after I patched the PCB, burned the PCB again when I had bargain output transistors short out in it. The second blow up, the circuit breaker did not trip. It is an economy line PA amp, which means the only speaker protection is the SCR crowbar, and that is just to prevent speaker fires. I will change it to use the DC detection circuit that formerly tripped the SCR to open a power supply disconnect relay I install myself before I allow that $55 amp to be connected to my $1200 a pair (new) speakers. As Vibroking$ said, I'll use 2 pole relays on the power supplies. That means, I think, that significant voltage on the PS rails should allow the use of cheap copper contact relays instead of using the gold required for reliability after the Output Transistor's if you were running the output at 1 VAC. Also the relay contact is in the feedback loop if it is installed between power supply caps and the output transistors.
The first transistor amp I bought had a speaker protection capacitors between the output transistors and the speakers, so the 2 output transistor shortouts that occurred didn't hurt anything. Quite a fireball the last time it happened. (Now I have heatsink fans). But it will be a cold day in **** before I connect this split supply direct coupled transistor amp I'm working on now to an actual speaker. It came with the crowbar SCR traces completely burned off the PCB, and after I patched the PCB, burned the PCB again when I had bargain output transistors short out in it. The second blow up, the circuit breaker did not trip. It is an economy line PA amp, which means the only speaker protection is the SCR crowbar, and that is just to prevent speaker fires. I will change it to use the DC detection circuit that formerly tripped the SCR to open a power supply disconnect relay I install myself before I allow that $55 amp to be connected to my $1200 a pair (new) speakers. As Vibroking$ said, I'll use 2 pole relays on the power supplies. That means, I think, that significant voltage on the PS rails should allow the use of cheap copper contact relays instead of using the gold required for reliability after the Output Transistor's if you were running the output at 1 VAC. Also the relay contact is in the feedback loop if it is installed between power supply caps and the output transistors.
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When I built my test speaker, I was unaware that an L-Pad on the tweeter could leave it vulnerable. After replacing the tweeter and scorched cables, I added a 4.7uF Nichicon ES series to the tweeter, right at the tweeter and for additional protection. The replacement tweeter is now many years old and has not failed.
Due to the qualities of today's dome tweeters, most of which will waste your time, may I suggest that you duke it out with an electrostatic instead. If one requires a deep voiced treble section, well that is a bit harder, but a midrange plus an electrostatic tweeter could be appreciable and not waste your time.
There's not really a substitute for a small collection of reasonable value inductor coils; however, Nichicon ES and ordinary Polyester caps can put in good service as tweeter caps, and those smaller 5w (and 3w) resistors are less inductive. So, the prospect of crossover adaption does cost something but not a terrible amount. The thing is, you will need options so as to choose the most favorable. And, price does not equate to performance.
I said all this hoping it wasn't a series crossover in your speaker. Although no doubt a finer quality, those are more reliant on driver matching. You'd end up running a parallel crossover atop that series crossover (makes DeVore crossover). But, if you've got a regular parallel crossover, well, get busy and fix your speaker already. 🙂 This is not difficult, but it is slow--extremely slow with dome, so get some electrostatic types so you can have a good time. 🙂
I had a chipamp fail on me (possibly my own fault, I designed the PCB) and put 40Vdc on a 120W, 4ohm speaker. It didn't survive 😀 and now acts as a passive membrane covering its brother from cat-paws. (Isobaric looking config)
The same cat-paws that hacked into the surround of my HPM-60 speakers
after I had the whole drivers replaced 😱. I re-foamed the old drivers, but the glue used wasn't up to the task 🙁 hence buying new drivers.
The same cat-paws that hacked into the surround of my HPM-60 speakers
after I had the whole drivers replaced 😱. I re-foamed the old drivers, but the glue used wasn't up to the task 🙁 hence buying new drivers.I just made a similar comment on another topic here on output relays.
Solid-state relays and SCR protection have been reported by many as affecting the quality of the audio. I don't see how a common relay can add distortion, except if the circuit controlling it is not doing its job.
We are talking metal to metal contact here, and I think that is as less prone to distortion as it can get. We may argue on the metal quality or the plate quality, or how good that contact strength is, but I don't think that can be improved by any solid state relay where the interface is "sand" that does add distortion to the signal.
Am I wrong?
Solid-state relays and SCR protection have been reported by many as affecting the quality of the audio. I don't see how a common relay can add distortion, except if the circuit controlling it is not doing its job.
We are talking metal to metal contact here, and I think that is as less prone to distortion as it can get. We may argue on the metal quality or the plate quality, or how good that contact strength is, but I don't think that can be improved by any solid state relay where the interface is "sand" that does add distortion to the signal.
Am I wrong?
Happened to me once upon a time. One channel of a Lecson AP1 went bad and took out a very good speaker!
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