Looking for a DC Protection schematic...

msamkl · 7th April 2006, 04:26 PM

Does anybody have a DC Protection schematic for Power amps?
I've built Gregs GB150D amp and I'd like to add a circuit to provide Dc protection to the loudspeakers...

Thanks in advance.

Thanasis.

primare · 7th April 2006, 08:06 PM

Quote:

Originally posted by msamkl
Does anybody have a DC Protection schematic for Power amps?
I've built Gregs GB150D amp and I'd like to add a circuit to provide Dc protection to the loudspeakers...

Thanks in advance.

Thanasis.

The simplest way to do that is using a servo for which there are many circuits around. More complicated arrangements use a comparator that in the presence of dc offset, will shut down the power to the amp.

VEC7OR · 8th April 2006, 12:38 AM

I've tried Rods http://sound.westhost.com/project33.htm
and it worked out real nice.

fab · 8th April 2006, 12:51 AM

Hi

Here is a DC protection that latches when Vdc at power amp output. IN addition there is an "in-rush" circuit (in bonus). It is incorporated in my power amp (I have 2 x 500 VA transfo).

When DC voltage reaches the threshold (+/- 3 V) RL2 contact opens then power voltage for output section is disconnected. RL3 makes the circuit to latch. You need a separate power supply for the detection circuit (same as for the audio driver circuit of the power amp). You may have to adjust components values to suit your amp voltages

It has worked fine since it is installed.

Good luck

djk · 8th April 2006, 04:17 AM

I have always liked the Hafler DH500 circuit.

I used to buy the board and use them in many other amplifiers (Adcom GFA555, DIY, etc).

http://www.hafler.com/techsupport/pd...00_amp_man.pdf

PC-9C board on page 16.

An inexpensive LM339 is the heart of the circuit. A couple of resistors set the DC trip voltage, turn-on delay, and it has a quick drop-out on power off. One resistor sets the relay voltage, I've used both 24V and 48V relays with a wide range of B+ voltages. A seperate supply is not needed. I use with a three pole relay, the third contact is used to short out an inrush current limiter.

The foil layout for the PC-9C is on page 19, it could be made smaller too.

bigpanda · 8th April 2006, 11:57 AM

Like to look at this one ?

http://users.otenet.gr/~athsam/protection_2_EN.htm

I had some pcb for it (stereo)

fab · 8th April 2006, 01:49 PM

Small comment: if you want to preserve the maximum damping of your amp , if you pay attention, the circuit in post #4 has no relay contacts in series with the load as opposed to the the 2 previous posts circuit.

Gandalph · 8th April 2006, 04:47 PM

Greetings from Norfolk

I like the idea of the post #4 in this thread, but can you clarify the connectivity / operation of the circuit around Q1, Q2 & Q3. The connections are not clear to me

Richard

sagarverma · 8th April 2006, 05:08 PM

http://www.richie00boy.pwp.blueyonde...atic_small.png

SCHEMATIC COPYRIGHT VELLEMAN

good n simple one.giving active service.

djk · 8th April 2006, 09:42 PM

"Small comment: if you want to preserve the maximum damping of your amp"

Considering that this has no effect on how the bass sounds on an amplifier, I would rather have a relay (treated with de-oxit and a small bypass cap).

My McIntosh MC2120 has a DF of 14, and sounds tighter in the bass than direct-coupled high feedback designs that have DF in the hundreds, if not thousands.

DF is a huge red-herring.

7th April 2006, 04:26 PM	#1
msamkl diyAudio Member Join Date: Nov 2005 Location: Athens	Looking for a DC Protection schematic... Does anybody have a DC Protection schematic for Power amps? I've built Gregs GB150D amp and I'd like to add a circuit to provide Dc protection to the loudspeakers... Thanks in advance. Thanasis.

8th April 2006, 12:38 AM	#3
VEC7OR diyAudio Member Join Date: Jul 2003 Location: Vilnius	I've tried Rods http://sound.westhost.com/project33.htm and it worked out real nice. __________________ Profanity took a very interesting form in Russia where there exists a language of sorts, most of its words based on four basic profane roots - nouns p...is, wh.0.e, c..t and verb f..k. It is possible to sensibly communicate using just these four basic roots.

8th April 2006, 01:49 PM	#7
fab diyAudio Member Join Date: Mar 2004 Location: Canada	Output Relay in series with load... Small comment: if you want to preserve the maximum damping of your amp , if you pay attention, the circuit in post #4 has no relay contacts in series with the load as opposed to the the 2 previous posts circuit.

8th April 2006, 05:08 PM	#9
sagarverma diyAudio Member Join Date: Feb 2005 Location: NEW DELHI	http://www.richie00boy.pwp.blueyonde...atic_small.png SCHEMATIC COPYRIGHT VELLEMAN good n simple one.giving active service. __________________ Never Underestimate The Bandwidth of A Station Wagon Full Of Magnetic Tapes Hurtling Down The Highway...................Andrew S Tanenbaum

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8th April 2006, 04:17 AM	#5
djk diyAudio Member Join Date: Feb 2001 Location: USA	I have always liked the Hafler DH500 circuit. I used to buy the board and use them in many other amplifiers (Adcom GFA555, DIY, etc). http://www.hafler.com/techsupport/pd...00_amp_man.pdf PC-9C board on page 16. An inexpensive LM339 is the heart of the circuit. A couple of resistors set the DC trip voltage, turn-on delay, and it has a quick drop-out on power off. One resistor sets the relay voltage, I've used both 24V and 48V relays with a wide range of B+ voltages. A seperate supply is not needed. I use with a three pole relay, the third contact is used to short out an inrush current limiter. The foil layout for the PC-9C is on page 19, it could be made smaller too.

8th April 2006, 11:57 AM	#6
bigpanda diyAudio Member Join Date: Jun 2004 Location: HKSAR	Like to look at this one ? http://users.otenet.gr/~athsam/protection_2_EN.htm I had some pcb for it (stereo)

8th April 2006, 04:47 PM	#8
Gandalph diyAudio Member Join Date: Dec 2005 Location: Norfolk	Greetings from Norfolk I like the idea of the post #4 in this thread, but can you clarify the connectivity / operation of the circuit around Q1, Q2 & Q3. The connections are not clear to me Richard

8th April 2006, 09:42 PM	#10
djk diyAudio Member Join Date: Feb 2001 Location: USA	"Small comment: if you want to preserve the maximum damping of your amp" Considering that this has no effect on how the bass sounds on an amplifier, I would rather have a relay (treated with de-oxit and a small bypass cap). My McIntosh MC2120 has a DF of 14, and sounds tighter in the bass than direct-coupled high feedback designs that have DF in the hundreds, if not thousands. DF is a huge red-herring.

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