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Audio Amplifier Accessories

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#21
LED VU/clip meter based on LM3915

Hi Cristi,

To my knowledge, none of the ConnexElectronic amp modules have built in clip lights. They are not essential but are very useful. Can you make available a cheap module/accessory perhaps based on the LM3915 chip for this purpose? It doesn't need to be big and bright and could even use those multiple colour LEDs.

cheers,

col.
 
#22
Cristi said:
sorry for late reply, i just came back after Easter Holiday, i had no internet where i was....
to use the speaker protection circuit for a BTL connected amplifier, the reference voltage (the floating GND which can be disconnected from the backside of the board) must be biased with a DC voltage equal to the output voltage with no input signal. if the amplifier is supplied at 30V DC, the outputs will have about 15V at idle. the GND reference of the speaker protection must be connected with a resistor divider between 30V and GND, and the amplifier supply voltage must be isolated from the speaker protection module supply voltage, with a small transformer or a separate transformer winding. i can provide you the transformer as well.
Click to expand...

Cristi, I have your speaker protection modules with another vendors amp modules. Some modules for eg. are 2xBTL, TAS5630, with integrated SMPS on the module. I think supply voltage is 50vDC.

I think I understand your instructions that I have quoted. Is there a way to get the bias voltage without me having to intercept the supply voltage somewhere on the module's pcb?

Also, is it correct that the 'jumper' on back of board must be desoldered/disconnected to use with BTL amp?

Thanks
 
#23
fb,
you must supply the speaker protection board with 12V which has no common GND with the amplifier. then connect the GND reference to a voltage divider which will provide half of the supply voltage, 25V. you can get this with a resistor divider which has a 47uF capacitor in parallel with each resistor. the resistor can be 2.2-4.7K at least 0.5W
 
#29
If the speaker protection circuit is powered with AC voltage, it will disconnect in about 100-150ms after the AC voltage is lost. if the speaker protection module is powered from a DC voltage source such as SMPS, the AC detector should be connected at the 12V supply pin. then the relays will disconnect after the voltage will drop below threshold, about 8-9V. if need to disconnect faster, then a Zenner diode can be connected between the main voltage and speaker protection circuit, AC detect, for example +-50V supply. the diode should be connected with cathode at +50V and anode at AC detect. i used a 33 - 39V diode, so when the voltage will drop below 3x + threshold, will disconnect.
the TA3020v3c have this function, and the speaker protection disconnect the speaker relay imediatly after AC voltage is lost for the v3c AC power version or as soon as the voltage drop below 40-43V for the DC version. this might take 500ms to 1.5 seconds, depending on the capacitors size and supply voltage.
the TA3020v4 have the function as well, and disconnect the relay in about 300 - 500mS after power off.
 
#32
Power Soft Start

Hi Cristi,

I received the Soft Start module today and I'm impressed with the quality.

Just a question. I tried powering it up without a load and I noticed that without connecting pin 1 & 2 of J2 (ON/OFF switch), there is already 240V in pin 1 & 2 in J1 (LOAD connector). Is this normal?

Thanks,
 
#34
Hi Cristi,
I bought a SPC from you ages ago and have only now got round to using it .
I have a Helder Tripath TA2020 mk111 ( with a 14vdc PSU) I want to use it for.
Would a transformer with output of 11v 0.8amps be ok and how do I connect it
( just a beginner) AC1 and AC2 ? and what about GRD?
thanks
simon
 
#35
For a TA2020 based amplifier, must make a simple modification in order to use the speaker protection circuit. the TA2020 amplifiers have BTL output, so each output has about half the supply voltage at idle. the speaker protection circuit must be ground referenced to this half supply voltage instead GND. this can be done using a simple resistor divider, let's say 2 pcs 100R at 1W each connected in series from +12V supply to GND. then the GND reference of the speaker protection circuit must be connected to the middle point of the resistors. also, 2 pcs 100uF capacitors should be added in parallel with each resistors, and they will be in series from +12V to GND. one speaker protection module can be used to protect one amplifier channel, so for one amplifier should use 2 modules for complete protection. also, the supply voltage for the speaker protection module should be separate and referenced to the virtual GND, the 2 resistors middle point.
 
#37
Yes, the 11V AC transformer is fine, after rectification and filtering you will get about 14V DC with no load, and will drop to 12-13V when the relay is closed. the current draw is below 40mA, so is fine for both modules.
Make sure you understand what i mean with the virtual GND, otherwise will not work.
 
#39
The only components which have to be changed to allow higher voltage to be used are the electrolytic capacitors, from the current value, 4700uF at 70V to something similar, rated for 80V or 100V. with the actual capacitors the maximum voltage should not be over +-68V. higher voltage rating capacitors have lower capacitance for the same can size. for example at 80V can be 3300uF and at 100V, 2200uF or 2700uF. If you need them, contact me and i will search them and use for the boards which you want to order.

Also, the PSPC has a lot of features, described in manual which can be used for any class D amplifier, not only for L25. it has power soft-start, speaker protection circuit and peaking detection circuit. please read the manual for more details. http://www.connexelectronic.com/documents/PSPC.pdf
 
#40
Cristi said:
Also, the PSPC has a lot of features, described in manual which can be used for any class D amplifier, not only for L25. it has power soft-start, speaker protection circuit and peaking detection circuit. please read the manual for more details.
Click to expand...

I know, the PSPC is like seperate modules as mentioned above, but you get a peaking circuit for free. I will keep the cap voltage issue in mind.
 
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