| ackcheng |
Hi,
I am constructing my digital crossover with UCD180 as the amp pushing the tweeter, mid and woofer. Hwever, I have noticed that when I connect the UCD to the tweeter, there is a "blop" when I switch on the amp. I guess this could be due to some discharge when switching on.
However, after a silence of about 5 sec, I started to hear "tat" "tat" at the freuency of about 1 Hz. The strange thing is that this only happens to the tweeter but not with the mid and the woofer. It happens when I disconnect the preamp as well, so I am pretty sure it is the UCD amp causing the problem.
The tweeter I am using is Raven 2.0 with an input impedence of about 2.5ohms.
Any clue as to what has gone wrong?
Thanks in advance |
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| Jan-Peter |
| quote: | Originally posted by ackcheng
Hi,
I am constructing my digital crossover with UCD180 as the amp pushing the tweeter, mid and woofer. Hwever, I have noticed that when I connect the UCD to the tweeter, there is a "blop" when I switch on the amp. I guess this could be due to some discharge when switching on.
However, after a silence of about 5 sec, I started to hear "tat" "tat" at the freuency of about 1 Hz. The strange thing is that this only happens to the tweeter but not with the mid and the woofer. It happens when I disconnect the preamp as well, so I am pretty sure it is the UCD amp causing the problem.
The tweeter I am using is Raven 2.0 with an input impedence of about 2.5ohms.
Any clue as to what has gone wrong?
Thanks in advance |
Did you bypass the coupling capacitors?
Jan-Peter |
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| fredos |
That's what we call a beating, your frequency at 1 Hz...Not a probleme with syncronized amplifier!
Fredos |
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| Jan-Peter |
| quote: | Originally posted by fredos
That's what we call a beating, your frequency at 1 Hz...Not a probleme with syncronized amplifier!
Fredos |
Beating at 1Hz..... ;)
With a good design of Class-D amplfier you not have problems with heterodyne signals....
Ackcheng;
I did not know that the Raven tweeters use a transformer, basically the protection kicks in, it's or overvoltage protection in combination with a low impedance load (lower impedance makes is worse) and DC coupling. Or the short circuit protection is triggered because of the low impedance. Personally I guess there is an overvoltage protection going on...
Cheers,
Jan-Peter |
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| ackcheng |
| SHould I add a resistor e.g. 8ohms in series to solve the problem? |
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| ackcheng |
| would using UCD400 or 700 help in this case? I just thought that it may allow more current |
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| ghemink |
| quote: | Originally posted by ackcheng
SHould I add a resistor e.g. 8ohms in series to solve the problem? |
| quote: | Originally posted by ackcheng
would using UCD400 or 700 help in this case? I just thought that it may allow more current |
I would not add a resistor. If you have for some reason DC at the output (due to DC coupling), then even with a resistor you can get power supply issues (power supply pumping) that triggers the overvoltage protection. Safest would be to add a high quality capacitor in series with the tweeter. This will protect both amp and tweeter, although I guess the ravens are protected basically already by the transformer.
Best regards
Gertjan |
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| Eva |
| If there is a coupling transformer, then try a coupling capacitor of suitable size in series with the primary. If the transformer is only for the tweeter, you can try 10uF or so... (non-polar type) |
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| ackcheng |
| Thanks! I am planning to use the digital crossover at 2K Hz. I guess, I better place the caps to cut it at 1K Hz to give enough head room. Will try and report back. |
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| banana |
Hi ackcheng,
Which digital xover are u going to use?
I'm planning to use active crossover with the UCD too, but at a much lower frequency. |
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| ackcheng |
I am using my computer to do the digitalcrossover. With a program called acourate
www.acourate.com |
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| mbon |
| quote: | Originally posted by Jan-Peter
Beating at 1Hz..... ;)
With a good design of Class-D amplfier you not have problems with heterodyne signals....
Ackcheng;
I did not know that the Raven tweeters use a transformer, basically the protection kicks in, it's or overvoltage protection in combination with a low impedance load (lower impedance makes is worse) and DC coupling. Or the short circuit protection is triggered because of the low impedance. Personally I guess there is an overvoltage protection going on...
Cheers,
Jan-Peter |
Hi Jan-Peter !
how safe is a UCD module ? I mean when it come into protection, is there some dangerous signal in the output (big ploc/dirac, CC ?)
I am interrested by UCD design for my compression drivers wich are very fragile and of course I'm looking specialy to pop free modules (both start and stop) and very low noise. Wich kind of UCD has lowest noisefloor ? symetric ? asymetric, UCD180, UCD400 ?
Is there some news about the HG new modules ?
regards
Marc |
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| fumac |
| quote: | Originally posted by fredos
That's what we call a beating, your frequency at 1 Hz...Not a probleme with syncronized amplifier!
Fredos |
Mr ackcheng
i dont think this be beating
phps is from then gnd and power loop
the input gnds are connet together in the crossover ,
but the power is multi-channel monoblock,
and the GND of preamp in poweramp borad is separate,
so they will be a loop there,
u must try how to connet the GNDs in ur amp,
if u can post a pic that about the power loop ?
best rg
fumac |
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| ackcheng |
Thanks Guys,
I am happy to report back the after I put in a 27uF cap in series, the problem is solved. Good to know that digital crossover can compensate for phase shifts |
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| Jan-Peter |
| quote: | Originally posted by mbon
Hi Jan-Peter !
how safe is a UCD module ? I mean when it come into protection, is there some dangerous signal in the output (big ploc/dirac, CC ?)
I am interrested by UCD design for my compression drivers wich are very fragile and of course I'm looking specialy to pop free modules (both start and stop) and very low noise. Wich kind of UCD has lowest noisefloor ? symetric ? asymetric, UCD180, UCD400 ?
Is there some news about the HG new modules ?
regards
Marc |
The UcD modules are safe, but only in combination with our power supplies. However if you use very expensive HF compression drivers I would personally mount a high quality capacitor in series.
All UcD modules will have the same noise level. The noise level will be same between asymmetric or symmetric, however for the best performance we recommend to use a symmetrical connection.
All UcD modules works pop free, switch ON or OFF.
Cheers,
Jan-Peter |
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| peufeu |
Crossover at 2kHz is a bit low for Raven 2 (you'll get distortion).
I don't think you need UCD400 with a tweeter having this high efficiency. You don't even need a watt... |
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| ackcheng |
| What frequency you would recommend I should cross at? |
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| ackcheng |
| Thanks! I am using digital crossover with 96dB. Will try to use it at a higher crossover point |
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| patriz |
| quote: | Originally posted by Jan-Peter
The UcD modules are safe, but only in combination with our power supplies. However if you use very expensive HF compression drivers I would personally mount a high quality capacitor in series.
All UcD modules will have the same noise level. The noise level will be same between asymmetric or symmetric, however for the best performance we recommend to use a symmetrical connection.
All UcD modules works pop free, switch ON or OFF.
Cheers,
Jan-Peter |
I use ucd 180 and 400 for my multiamped high sensitivity compression drivers system and with hypex power supply you can hear just a very very low bump when turning on and absolute nothing when turning off. Once I tried high quality capacitors betwen ucd and the drivers and my legs are still trembling for what I heard when I switched on the amp. The same happened to a friend of mine so I never would do that again. |
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| banana |
| quote: | Originally posted by ackcheng
I am using my computer to do the digitalcrossover. With a program called acourate
www.acourate.com |
Thanks Ackcheng.
Are u going to use FIR filter? I'm very interested to heard the result.
Though ZaphK didn't tested the Raven R2, I suppose it'll behave very much like Aurum Cantus G3. Distortion is likely to rise gradually below 4KHz. How low it could be crossed really depends how loud u'd like to play.
2KHz might be ok only for Tsai Chin or Lily Chan. For big orchestra I suggest 3.5 or 4KHz, even with steep FIR filter. |
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| ghemink |
| quote: | Originally posted by patriz
I use ucd 180 and 400 for my multiamped high sensitivity compression drivers system and with hypex power supply you can hear just a very very low bump when turning on and absolute nothing when turning off. Once I tried high quality capacitors betwen ucd and the drivers and my legs are still trembling for what I heard when I switched on the amp. The same happened to a friend of mine so I never would do that again. |
What happened with the cap between UcD and driver? Maybe the UcD needs to see some resistive output load?
Hopefully Jan-Peter can comment? I use the UcD180 to drive tweeters directly (conventional voice coil type, not ribbons with transformers) , so no caps in series. Had no issues for more than 2 years or so.
It seems Arthur had no issues with the cap, however, if some form of resistive load is needed, maybe he should add a power resistor (how many Ohm should do (100 too high?) directly at the UcD output to prevent potential issues as you experienced.
The larger the better (you don't want to burn a lot of power in that resistor))
Thanks and best regards
Gertjan |
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| patriz |
| quote: | Originally posted by ghemink
What happened with the cap between UcD and driver? Maybe the UcD needs to see some resistive output load?
Hopefully Jan-Peter can comment? I use the UcD180 to drive tweeters directly (conventional voice coil type, not ribbons with transformers) , so no caps in series. Had no issues for more than 2 years or so.
It seems Arthur had no issues with the cap, however, if some form of resistive load is needed, maybe he should add a power resistor (how many Ohm should do (100 too high?) directly at the UcD output to prevent potential issues as you experienced.
The larger the better (you don't want to burn a lot of power in that resistor))
Thanks and best regards
Gertjan |
actually I don't remember if it was switching on or off.
Giorgio |
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| Jan-Peter |
| quote: | Originally posted by patriz
I use ucd 180 and 400 for my multiamped high sensitivity compression drivers system and with hypex power supply you can hear just a very very low bump when turning on and absolute nothing when turning off. Once I tried high quality capacitors betwen ucd and the drivers and my legs are still trembling for what I heard when I switched on the amp. The same happened to a friend of mine so I never would do that again. |
Strange....this can only happening if the capacitors are charged by with DC. The very first batches of the UcD modules did had a small DC voltage at the output when there was NO load. Perhaps you have one of the first modules? Anyway this particuler DC output voltage charges the coupling capacitor. When you switch the amp on, the capacitor will be discharge again and this creates the thump.
Jan-Peter |
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| patriz |
| quote: | Originally posted by Jan-Peter
Strange....this can only happening if the capacitors are charged by with DC. The very first batches of the UcD modules did had a small DC voltage at the output when there was NO load. Perhaps you have one of the first modules? Anyway this particuler DC output voltage charges the coupling capacitor. When you switch the amp on, the capacitor will be discharge again and this creates the thump.
Jan-Peter |
They are early boards but obviously they were connected to the load |
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| Jan-Peter |
| quote: | Originally posted by patriz
They are early boards but obviously they were connected to the load |
When you mount a resistor of 1K at the output of the amp to ground you will not have this problem anymore.
Jan-Peter |
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| ackcheng |
While I can now play with the tweeter, I am still gettng the "pop" when turning on.
I have connected a 27uF cap in series with the tweeter and i guess, this is what's happening! In stead of puting 1K resistor across the + and -, can I just put the 27uF on the over terminal of the tweeter? I just thought that the -ve terminal is grounded and my be it will discharge itself? |
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| ackcheng |
Just tried. Putting the cap on -ve terminal of the tweeter does not work. puting 1k resistor at the output of the UCD module to ground does not work either.
Any further hint of what i can do? |
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| fredos |
Basic Relay and delay circuit?
Fredos |
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| ackcheng |
| yes. basic relay and delay circuit with 555 |
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| djk |
Raven tweeters are a dead short at DC.
With only a few millivolts of DC off-set several amps will flow and the overcurrent protection will trip.
Always use a protection cap.
If the amplifier needs some DC resistance at its output, hang it directly on the amplifier output (before the cap). |
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