active crossover with UCD problem

ackcheng · 27th April 2007, 04:21 AM

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

Jan-Peter · 27th April 2007, 04:40 AM

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

fredos · 27th April 2007, 06:36 AM

That's what we call a beating, your frequency at 1 Hz...Not a probleme with syncronized amplifier!

Fredos

Jan-Peter · 27th April 2007, 12:04 PM

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

ackcheng · 27th April 2007, 09:07 PM

SHould I add a resistor e.g. 8ohms in series to solve the problem?

ackcheng · 27th April 2007, 09:13 PM

would using UCD400 or 700 help in this case? I just thought that it may allow more current

ghemink · 28th April 2007, 01:31 AM

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

Eva · 28th April 2007, 01:58 AM

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)

ackcheng · 28th April 2007, 02:00 PM

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.

banana · 1st May 2007, 05:44 PM

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.

27th April 2007, 04:21 AM	#1
ackcheng diyAudio Member Join Date: Dec 2003 Location: hong Kong	active crossover with UCD problem 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

28th April 2007, 01:58 AM	#8
Eva diyAudio Member Join Date: Oct 2003 Location: Near the sea	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) __________________ I use to feel like the small child in The Emperor's New Clothes tale

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27th April 2007, 06:36 AM	#3
fredos diyAudio Member Join Date: Mar 2005 Location: Quebec	That's what we call a beating, your frequency at 1 Hz...Not a probleme with syncronized amplifier! Fredos

27th April 2007, 09:07 PM	#5
ackcheng diyAudio Member Join Date: Dec 2003 Location: hong Kong	SHould I add a resistor e.g. 8ohms in series to solve the problem?

27th April 2007, 09:13 PM	#6
ackcheng diyAudio Member Join Date: Dec 2003 Location: hong Kong	would using UCD400 or 700 help in this case? I just thought that it may allow more current

28th April 2007, 02:00 PM	#9
ackcheng diyAudio Member Join Date: Dec 2003 Location: hong Kong	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.

1st May 2007, 05:44 PM	#10
banana diyAudio Member Join Date: Feb 2003 Location: Hong Kong	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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