DCP going south??

[laatsch55]

That's why you need to look at it with the scope....a clipped sine wave will appear to speakers and the DCP as DC.....it's merely speculation if you can't see what the conditions were at the time....

 

[roccus]

That's why you need to look at it with the scope....a clipped sine wave will appear to speakers and the DCP as DC.....it's merely speculation if you can't see what the conditions were at the time....

OK cool so am I looking for a smooth wave verses a spiked or square wave?

 

[laatsch55]

You're looking for a "clipped" sine wave...that's why it's called clipping an amplifier, it cuts the top and bottom portions of the sine wave so they appear flat at that point.....and yes, you can clip an unloaded amplifier....

 

[roccus]

You're looking for a "clipped" sine wave...that's why it's called clipping an amplifier, it cuts the top and bottom portions of the sine wave so they appear flat at that point.....and yes, you can clip an unloaded amplifier....

Lee you happen to have any screen captures of this?? Would be he;pful to me and maybe others trying to learn how this all works.. I do hope this thread will help others as well as me

 

[jbeckva]

Lee you happen to have any screen captures of this?? Would be he;pful to me and maybe others trying to learn how this all works.. I do hope this thread will help others as well as me

Go here.. pic right at the top..

https://en.wikipedia.org/wiki/Clipping_(signal_processing)

 

[Gepetto]

Lee you happen to have any screen captures of this?? Would be he;pful to me and maybe others trying to learn how this all works.. I do hope this thread will help others as well as me

If the 1.8V is an RMS AC input signal to the amp then the amp should be in solid flat top clipping at the peaks. It would not be unusual to trip the DCP under such conditions because the symmetry between the plus and minus rails is not that close. A small difference in the plus rail to minus rail value over time will integrate slowly or rapidly into a DC offset, depending on the magnitude of the rail plus to minus difference

Understand?

 

[roccus]

If the 1.8V is an RMS AC input signal to the amp then the amp should be in solid flat top clipping at the peaks. It would not be unusual to trip the DCP under such conditions because the symmetry between the plus and minus rails is not that close. A small difference in the plus rail to minus rail value over time will integrate slowly or rapidly into a DC offset, depending on the magnitude of the rail plus to minus difference

Understand?

I think so Joe like an unbalanced washing machine when it starts to spin it starts to shake the faster it spins the more it shakes and at full spin that shaking can get violent in this case the more the voltage the more the unbalance... right?

 

[Gepetto]

I think so Joe like an unbalanced washing machine when it starts to spin it starts to shake the faster it spins the more it shakes and at full spin that shaking can get violent in this case the more the voltage the more the unbalance... right?

Kind of. Let's extend your analogy. This is the washing machine is imbalanced so it starts walking across the floor (the integral function I referred to is the walking across the floor). Eventually it hits a wall and that is your DC trip.

 

[roccus]

One more question about preamps... can a preamp clip and if it can would the amp amply the clip out of the preamp?

 

[laatsch55]

Yep, but highly unlikely you'd get that far, check your pre-amp specs , it's usually wayyyyyy above 2 volts.....

 

[roccus]

Yep, but highly unlikely you'd get that far, check your pre-amp specs , it's usually wayyyyyy above 2 volts.....

I will.. my load resistors got here today but was so busy never got a chance to even open the box to take a look at them yet the 67 chevell is going back home tomorrow.. think I will be moving everything into the spare bedroom over the next couple days I have a lot to do other than just the wopl

According to PL 3000 manual 2.0 V RMS is output
and the C-1 manual says 3.0 V RMS output

 

[laatsch55]

Dos it give a clip spec??

 

[roccus]

Dos it give a clip spec??

Just took a look Lee not listed in the specs of either preamp may be somewhere in the service manual text though not sure I will get more into it after the move I also have all the parts here to recap my sx939 and tx9100

 

[Gepetto]

Just took a look Lee not listed in the specs of either preamp may be somewhere in the service manual text though not sure I will get more into it after the move I also have all the parts here to recap my sx939 and tx9100

Most preamps put out so much signal voltage it will easily put the amp into clip. Don't even think about that.

 

[laatsch55]

The Spec will go to 8 IIRC....

 

[roccus]

Most preamps put out so much signal voltage it will easily put the amp into clip. Don't even think about that.

Hi Joe yes I saw that the PL preamp I was checking out was pushing out over 5V peaks.... I learned a lot of cool things last week how things work but as Lee said I am not going to concern myself with the preamp going forward just the amp but I learned things a preamp does I never knew or thought of before now with your input I understand clipping and how sub frequencies can clip it turns a sine wave square and to me a square wave is DC

 

[Gepetto]

Hi Joe yes I saw that the PL preamp I was checking out was pushing out over 5V peaks.... I learned a lot of cool things last week how things work but as Lee said I am not going to concern myself with the preamp going forward just the amp but I learned things a preamp does I never knew or thought of before now with your input I understand clipping and how sub frequencies can clip it turns a sine wave square and to me a square wave is DC

Hi Ray
a square wave is not DC but an asymmetric square wave gets turned into DC after being integrated by the low pass filter on the DCP board. Understand?

 

[roccus]

Hi Ray
a square wave is not DC but an asymmetric square wave gets turned into DC after being integrated by the low pass filter on the DCP board. Understand?

Ahh so the square I am seeing is from the DCP output? I had my scope connected to the speaker terminals

 

[NavLinear]

Ahh so the square I am seeing is from the DCP output? I had my scope connected to the speaker terminals

Joe is not here so I'll give you my interpretation.

The DCP does not change the signal characteristics so it is not the cause of the square wave you're seeing. What happens is the output of the amplifier is routed through the DCP relay directly to the output jack posts. The DC protect circuit monitors the output and when it sees either a low frequency or a DC signal the IC triggers the relay and that opens up the signal path to the speakers. What Joe is saying is the DCP interprets an asymmetrical square wave as DC and will open the output signal relay.

 

[roccus]

OK, let's do it like this.......


Hook meter up to output of amp, get your load resistors on that too. Walk up input from zero to NO MORE THAN 40 volts on output. sTART WITH 100HZ, THEN 40, THEN 20 , AND LAST 10HZ.

Your pre amp is fine but we dont need it right now. What we are trying to establish right now is that the DCP is doing what it's supposed to. 40 volts out is 200 watts out.

Hello Lee finally got the bench in the spare bedroom set up hooked up wired and all connect and a bit of time this evening to get the test measurements you asked for.....

Right channel
100HZ cranked up to 40 VAC output - DCP did not trip no clipping seen on scope @ 40 VAC
40HZ " " just started to clip @ 40 VAC
20HZ " " just started to clip @ 39 VAC
10HZ " " just started to clip @ 39 VAC

Left channel
100HZ " " just started to clip @ 39 VAC
40HZ " " just started to clip @ 39 VAC
20HZ " " no clipping @ 40 VAC
10HZ " " no clipping @ 40 VAC

On the ones that did not clip @ 40 VAC ended up starting to clip around 41 or 42 VAC
The DCP never tripped in any of these tests but boy that 8 ohm load resistor sure did get some hot!