balanced volume control

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#61
It changes, but 50-550 ohm range difference is negligible in my opinion. Volume control is for convenience, and I usually use 5 position in the last 3/4 of a range. So i can say that my output impedance is fixed and around 200 ohms. I'd say it's not too bad.😉

As to 5k to output, maybe it's worth a try.
 
#64
Peter Daniel said:
I tried to do it yesterday and couldn't figure out either. Last time I did it was 1996. BTW, the chart comes from David Broudhurst and is recommended for his DAC. I thought it was 20logR1/R1+R2 but somehow the numbers don't come up.😉
Click to expand...

That won't work if R1 is the series resistor and R2 is the shunt resistor. If it is, then it's 20 x log R2/(R1 + R2).

se
 
#67
blschuler said:
That exactly what I have been doing, still can't duplicate the attenuation values in the Broudhurst chart.
Click to expand...

It works for me.

You're aware by the way that the calculator keeps the series resistor value constant, right? In other words, R<sub>x</sub> stays the same and only R<sub>y</sub> changes for each step.

So let's run through a simple one.

Set the series resistance to 1,000 ohms.

Set the number of steps to 1.

Set the first step attenuation to 20dB.

The calculator returns 1,000 ohms for R<sub>x</sub> (natch) and 111 ohms for R<sub>y</sub>

Now let's check it against the calculation 20 x log R<sub>y</sub>/(R<sub>x</sub> + R<sub>y</sub>).

R<sub>x</sub> + R<sub>y</sub> = 1,000 + 111 = 1,111.

R<sub>y</sub> / 1,111 = 111 / 1,111 = 0.0999

Log 0.0999 = -1

20 x -1 = -20.

So, we get -20dB.

It checks.

se
 
#71
Where can one find a suitable 2-point volume pot as mentioned by Daniel at the beginning of this thread, to be located between positive and negative of the two channels of BoSoZ?

...at reasonable price. No freak gear needed in my first DIY project...
 
#72
Resurrecting an old thread, which was brought to my attention by a friend.

Clearly there are a number of options as to exactly where a single pot/switch may be placed.

Which of the following (A/B/C) do we think would be the best option?

Thanks,
mark
 

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#74
I built a test board with 6 relays using the ADC0804 like in the pass preamp. Should I use a linear or log pot? I tried a linear pot 100K because there is a 10K resistor across middle pin (moving pin) and earth. This makes it act logarythmic. Also the relays switch in this fashion for linear movement. But I think in the begining the volume doesn´t go up so fast as at the end. I have to say I used it at the output of the BLS with full volume. So it could be that the volume pot interacts with the relay volume control. Just wanted to know if you guys used linear or log pot.
 
#75
I use a ADC0804 volume controll with my BOZ. For me the range is not enough, and this volume control makes a lot of noise, clicks and pops when volume is tuned. Also its not absoltely stable, sometimes relays change without me moving the pot knob. I use a 100k lin pot.

The better way with more range and less noise, absolutely stable, is this very simple microcontroller relays volume controll i made for my BZLS :

http://home.arcor.de/dddddd-/relais/relais.html

Its easy to use for SE only, mount only half the number of relays. It needs less parts than the ADC0804 version. Its very cheap.
 
#79
mefinnis said:
Resurrecting an old thread, which was brought to my attention by a friend.

Clearly there are a number of options as to exactly where a single pot/switch may be placed.

Which of the following (A/B/C) do we think would be the best option?

Thanks,
mark
Click to expand...

Don't forget changing the value of R15, except it works in the opposite direction. Higher resistance is lower gain.

Petter
 
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