Protection
To get ouput protection in the event of a DC offset on the output of the amp, couldn't you just pull /on high with a transistor switch instead of fiddling with relays in output/power lines or mosfets?
To get ouput protection in the event of a DC offset on the output of the amp, couldn't you just pull /on high with a transistor switch instead of fiddling with relays in output/power lines or mosfets?
No because the cause of a DC fault is usually an output device blowing short circuit, so it won't matter what you tell it to do, it will still conduct.
How much damage would the discharge of 10,000uf per rail into the speakers cause if one of the output devices did fail? This would allow protection to be put into the AC line before the transformer....
Uhhh never tried that (at least not on purpose!).Zodiac said:
Let's run through a few numbers. Suppose the power supply voltage is 60V. Then, suppose a DC protection that disconnects the speaker or the amplifier after the power supply. If the reaction time is 10ms, we have 10ms*60V*60V/4ohm=9J dumped into the speaker during the reaction time.
Now suppose the version with the relay before the PSU. The stored energy in the cap will come on top of the 9J above. 60V*60V*10000uF/2=18J. Total 27J. So, moving the relay to the AC input would triple the energy dumped into a 4ohm load.
For me, this difference is enough to make sure the relay disconnects the amplifier, not the mains, but I do expect that most woofers would survive a 27J DC pulse.
(FYI, what makes DC so dangerous to speakers is that normal power ratings presume the cone is constantly moving, producing air flow around the voice coil to cool it. The DC power handling capacity of a woofer is *much* lower than AC. Because of this, saying 27J is only 27W during one second does not reflect the extent of the problem)
Hello all,
what interesting thread! A bit long to read but very useful.
I have a question, I intend to buy UCD 180 in order to try this fabulous amp on my tri amplified speaker.
My concern is the volume control located between the active crossover and UCD180.
(I would like to manage each driver separately)
Do you mean possible to use an attenuator, ladder type or other type, to do that?
does 10kohm will work correctly with UCD?
Thank a lot for your help!
JP
what interesting thread! A bit long to read but very useful.
I have a question, I intend to buy UCD 180 in order to try this fabulous amp on my tri amplified speaker.
My concern is the volume control located between the active crossover and UCD180.
(I would like to manage each driver separately)
Do you mean possible to use an attenuator, ladder type or other type, to do that?
does 10kohm will work correctly with UCD?
Thank a lot for your help!
JP
Bruno Putzeys said:
Given the failure rate of the modules, I would only use protection to stop a fire hazard, not protect the speaker drivers. All the other solutions appear to have some negative sound quality side effects due to the insertion of resistive components into the ps/after the amp modules or require multiple large relays to switch DC into the ps/after the amp modules. Putting the relay in the AC line would mean I would only need one and it could be moderately sized.
Plus I am only using the UCDs on my woofers....
Bruno Putzeys said:
Hello Bruno and others,
A reaction time of 10ms, that is very fast, in 10ms you have to detect the DC and a relay has to brake the contact. A DC detection circuit that detects DC in 10ms will trigger on a 50Hz square wave. Although I don't want to listen to 50Hz square waves, such a circuit would probably also trigger on 20Hz sinewaves. So say we need 50ms to detect and react to the DC (I think you stated the 50ms sometime earlier in this or another thread), then we are talking about 45J energy for the case with relay in the DC rails and 18J more, so 63J in the case with the 10.000uF caps. So maybe for woofers you can get away with a relay in the AC line??? I have no experience with this, so don't trust me. In all those years I never had an amp that put DC on the outputs, never fried any woofers.
For amps that are serving midwoofers (without passive filter), it would be good to have a faster reacting DC detection and less caps or the relay in the DC rail, tweeters (again without passive filter) probably burn out in a short flash, probably too fast to cause a fire.
Best regards
Gertjan
Hi,
given that specific heat of copper is 0.389J/(g x K), 27J would heat a hypotetic 1g coil for 69 degrees, which is still acceptable. I of course have no idea how much actual woofer coil weights, but I would be interested in such data.
Best regards,
Jaka Racman
given that specific heat of copper is 0.389J/(g x K), 27J would heat a hypotetic 1g coil for 69 degrees, which is still acceptable. I of course have no idea how much actual woofer coil weights, but I would be interested in such data.
Best regards,
Jaka Racman
Jaka Racman said:
And if you have an Aluminum voice coil former, then that increases the heat capacity further. My woofers have capton voice coil formers, I think heat capacity and conductivity of capton is not that good.
Gertjan
jpagc said:
A 10k attenuator works perfectly well with the modules.
Personally I would put the attenuator before the active filter though, because of tracking issues.
Bruno Putzeys said:
thank you for your quick answer.
I agree with you about the general control volume but I would
like to master the treeble and bass threshold separately
Regards
JP
UCD180 hiss
Hi folks,
ive had a UCD-180 amp running happily for some time now, and one thing ive always noticed is that even with no inputs, the amp is far from quiet.
theres a 'hiss' that is always present. not terrible, and ive been lving with it happily for a long time, but ive finally got around to wondering if there is anything I can do about it, or whether it is just how the modules are.
when a source is connected, its a balanced line connection from a denon mixer, but the hiss is present regardless of what is plugged in.
any ideas?
cheers,
ben
ps: heres a pic of the amp. wiring is messy, but it was finished in a hurry. has worked flawlessly as a portable amp.
Hi folks,
ive had a UCD-180 amp running happily for some time now, and one thing ive always noticed is that even with no inputs, the amp is far from quiet.
theres a 'hiss' that is always present. not terrible, and ive been lving with it happily for a long time, but ive finally got around to wondering if there is anything I can do about it, or whether it is just how the modules are.
when a source is connected, its a balanced line connection from a denon mixer, but the hiss is present regardless of what is plugged in.
any ideas?
cheers,
ben
ps: heres a pic of the amp. wiring is messy, but it was finished in a hurry. has worked flawlessly as a portable amp.
Attachments
Re: UCD180 hiss
If you leave the inputs open, hiss is quite normal because the noise voltage of the 100k input resistors will be amplified. You get approximately 180uV worth of noise with the inputs open. On the other hand, I don't know how quiet your source is. Could you try shorting the input and report back on your findings?anomalous said:
OT in this thread but I assume that only a small part of the heat is conducted away by the aluminium former most of it is radiated by convection from the winding itself. Even if voice-coil cooling is a little worse than with an aluminium former there is even a thermal advantage to Kapton: There is less heat CONDUCTION to the cone, this can be specially advantageous if a Poly cone is used.
Regards
Charles
Re: Re: UCD180 hiss
Sorry, messed up my reply. here it is
My UcD180s are the earliest version having the 10k input resistance I believe. With shorted inputs they are dead silent, just amazing, far more silent than my tripath (big difference) and far more silent than ZAPpulse (2.2SE). In fact, in my case, the preamp determines the noise level, with shut-off preamp, no noise at all, really have to put my ears in the tweeters in a very silent room to be able to hear something.
Are you using very high efficient speakers (like horn tweeters?), no problem with other amps? I think they are among the most silent amps on this planet. So maybe, try shorting the inputs as Bruno suggested and see what you get.
Gertjan
ghemink said:
Sorry, messed up my reply. here it is
My UcD180s are the earliest version having the 10k input resistance I believe. With shorted inputs they are dead silent, just amazing, far more silent than my tripath (big difference) and far more silent than ZAPpulse (2.2SE). In fact, in my case, the preamp determines the noise level, with shut-off preamp, no noise at all, really have to put my ears in the tweeters in a very silent room to be able to hear something.
Are you using very high efficient speakers (like horn tweeters?), no problem with other amps? I think they are among the most silent amps on this planet. So maybe, try shorting the inputs as Bruno suggested and see what you get.
Gertjan
UCD 180 silence
time to own up to being a silly boy.
It was the mixer. I thought i'd tried unplugging it, but clearly i hadnt. ive used this mixer with other amps and never noticed the hiss, but then the speakers im using in combination are extremely sensitive.
sorry for wasting your time folks. 🙂
one of the things i love about the ucd180 is that you don't need large heatsinks! makes for a small and lightweight but still powerful amp. mine doesnt have any heatsinks at all, other than the thick aluminium baseplate and frontpanel. the only thing that really seems to get hot is the little transformer on the module itself. not a problem if the case has ventilation - but i'm wondering about using in a closed box - is it ok to attach the transformer to the baseplate/heatsink, or would this cause a short?
thanks for your help...
ben
time to own up to being a silly boy.
It was the mixer. I thought i'd tried unplugging it, but clearly i hadnt. ive used this mixer with other amps and never noticed the hiss, but then the speakers im using in combination are extremely sensitive.
sorry for wasting your time folks. 🙂
one of the things i love about the ucd180 is that you don't need large heatsinks! makes for a small and lightweight but still powerful amp. mine doesnt have any heatsinks at all, other than the thick aluminium baseplate and frontpanel. the only thing that really seems to get hot is the little transformer on the module itself. not a problem if the case has ventilation - but i'm wondering about using in a closed box - is it ok to attach the transformer to the baseplate/heatsink, or would this cause a short?
thanks for your help...
ben
Re: UCD 180 silence
I think the small "transformer" you are referring to is the output filter coil. I would never move that coil from the PCB to some other position to get better cooling. One side of that coil carries the 450kHz square waves with full rail-to-rail swing, so moving the coil and attach some wires will work like a nice antenna spreading a lot of high frequency noise.
How hot is hot?
Gertjan
anomalous said:
I think the small "transformer" you are referring to is the output filter coil. I would never move that coil from the PCB to some other position to get better cooling. One side of that coil carries the 450kHz square waves with full rail-to-rail swing, so moving the coil and attach some wires will work like a nice antenna spreading a lot of high frequency noise.
How hot is hot?
Gertjan
The coil becomes around 50ºC in free air. This corresponds with a power loss of a fat half watt. A peek at the specs of the magnetic material shows that the core losses are actually are at a minimum at 90ºC. Not something which is practically useful though.
