[johnmatrix]

I am currently looking into building a KGSS for my SR-X phones and in the future a SR-007. This requires building a KGSS with normal and pro outputs. I was thinking about doing this by wiring the bias supply directly to the pro jack and having the supply connected to a voltage divider before it goes to a normal jack. One of the resistors would be a pot to adjust the ratio to get the proper voltage. I just had a few questions.

1. Will this give me both bias voltages?

2. Will I have to account for the resistance of the circuit behind the divider or can I ignore when choosing my two resistors?

Below is the link to the Hybrid PS design which is what I will use.

http://headwize.com/projects/showfil...lmore4_prj.htm

 

[spritzer]

I would just let the stock Bias supply be the Pro supply and add something like this here:

It's a very simple schematic for voltage doubler that Stax used for it's OEM stats

 

[kevin gilmore]

And it is referenced to the AC line.

DON'T do this.

Make an extra voltage divider across the .1uf cap and
use that for low bias.

 

[johnmatrix]

Quote:

Originally Posted by kevin gilmore /img/forum/go_quote.gif And it is referenced to the AC line. DON'T do this. Make an extra voltage divider across the .1uf cap and use that for low bias.

If I make the extra voltage divider across the .1 uF cap, I need a ratio that will give me 40% of the original voltage (250/580). So I will use a 400 and 600K as R1 and R2 respectively to make my divider and the 400K will be a pot to make the fine adjustments.

 

[kevin gilmore]

Yes that will work, don't forget the 10m series resistor.

 

[johnmatrix]

I am posting a quick drawing to make sure I get this right. I am using a 3.3 Mohm resistor to ground because with a 500 Kohm pot and the 4.7 Mohm resistor will give roughly the right voltage. The 10 Mohm resistor only drops the voltage by 66% and I need the voltage to drop 40% from 580V. The pot can be trimmed to achieve the proper voltage.

 

[kevin gilmore]

Nope that is not going to work.

You won't have enough voltage for the high bias that way.

You would not be able to plug in both headphones at the
same time that way and the capacitance of the high bias
headphones may damage the low bias ones.

You would not be able to adjust the bias anyway as the
impedance would be too high.

3 extra resistors off of the .1uf cap!

 

[johnmatrix]

Alright let's try this again. I simply added three resistor off of the .1 cap before the 4.7M resistor. The first is the 10M then the voltage divider formed by the next two with the 500K pot there for Voltage adjustments. Thanks for all your help.

 

[kevin gilmore]

Nope.

Go back to the original schematic.

Add a resistor say 600k to the point between the top
of the .1uf cap and the 4.7 meg resistor.

To the other end of that resistor add a 600k resistor
to ground and a 4.7 meg resistor to the low bias point.

 

[johnmatrix]

I am uncertain where you tap the circuit for the high bias input. Are there supposed to be two 4.7M resistors in series with one another?

 

[kevin gilmore]

The top picture is correct.