Power amp under development

[bigpanda]

Hi davorinjo,

Nive that you brought that up. I have never seen anyone putting scales on their pcb's except me. It makes other users easier to see if they have the iright size for the boards after the board images are transform, convert...., whatever many times. Bad habit or tradition maybe?

[quasi]

Originally posted by TomWaits


Very interesting. What is the impedance of the 340/350 stage? BTW R21 confuses me?

Shawn.

The impedance of the 3rd stage is limited only by the 3 resistors.

R21 is there to force a degree of symmetry at clipping. It only offers a partial solution to cater for varying gate drive requirements (i.e. driving into different speaker loads). As mentioned earlier in this thread avoiding the assymetric clipping problem with this circuit is not possible without significant changes. In practical terms this "problem" is irrelevant.

Cheers
Q

[quasi]

here is the 6 FET board.

[quasi]

here is the 10 FET board

[davorinjo]

Originally posted by bigpanda
Hi davorinjo,

Nive that you brought that up. I have never seen anyone putting scales on their pcb's except me. It makes other users easier to see if they have the iright size for the boards after the board images are transform, convert...., whatever many times. Bad habit or tradition maybe?

Yes, I saw it on Albert Kreuzer site and I think it is usefull even for printing from different machines.
I think mine will turn out fine, it measures right on my printer anyway.

[hoangduongo]

Hi quasi, I have another questions:
1. In your softstart circuit, if I want to use 12V relay, what do I have to change?
2. Must I use a seperate xformer for the softstart circuit, or can I use the 0-15VAC line from main xformer?
3. the main line in my country is 220V, what else would be change? i read in ESP that the value of the 5W resistors depends on ac the main line and power rate of main xformer.
Thanks, quasi.

[quasi]

You can use a relay rated to the voltage you are going to run the soft-start board at. Ie; you can run the board at 12 volts and use a 12 volt relay. Your timing will change though and with a 12 volt supply it will be longer. You can fix this by changing the charging resistor.

Or you can run the board off 24v DC and put a resistor in series with the relay coil. To halve the available voltage the resistor value should be about the same as the relay coil resistance.

You cannot use the secondary of the same transformer for this circuit because the transformer voltage will rise slowly and may never get to the voltage required by the slow start circuit before the resistors burn out (a few seconds). There are other ways of using the transformer secondary and I'll send something tonight (I'm at work now).

The values in the posted circuit will work fine for a 220v AC supply.

Cheers
Q

Umm ...why am I doing all the work here ? ...feel free to contribute anyone .....anyone??? hello...hello...... is this thing on? hello ?

[AndrewT]

Hi Quasi,
some prefer to defer to the expert.

Since you invited, I may jump in ocassionally when the information is available.

[hoangduongo]

Quasi, thanks for your help!
Now I'm looking for a small transformer for the softstart circuit, I use 12V relay, so the the transformer should be 12VAC, right? Is it better if I use a bit higher Dc voltage for that circuit, such as 15VDC?
I found that your DC detector is quite identical to the one from Silicon Chip, except some small change, I think it's because SC use 12V relay, I'll post that schematic later.

There are other ways of using the transformer secondary and I'll send something tonight (I'm at work now).

I'm waiting for your work, Quasi

[quasi]

Originally posted by quasi
There are other ways of using the transformer secondary and I'll send something tonight (I'm at work now).

The days a very long this side of the world....here it is finally.

This circuit can be adapted to run of the 15v windings.

Cheers
Q