aleph p + attenuator

[george a]

Hi All

There seems to have been some talk about an alternative methos of signal attenuation in the BOSOZ designs which relies on effectively placing a potentiometer between the +ve & -ve outputs. There by avoidong the complexity and cost of relay based or the precision 4 ganged stepped attenuators.

has anybody tried this on the Aleph P1.7 preamp design or have any comments suggestions.
What happens when the pot resistance drops to zero ( at minimum volume) ie effectivley shorting the +ve and -ve outputs together- is this a bad thing?

thanks and regards.

 

[UrSv]

That would be a bad thing for the attenuator itself. Fortunately there is a 100 Ohm resistor on the output for each output that makes it possible giving a minimum of 200 Ohm across the output.

 

[till]

There by avoidong the complexity and cost of relay based

16*2€ Relays
3.90€ PIC MC
< 10€ for resistors, transistors, PS

 

[george a]

Thank you Ursv & Till

I forgot about the 100ohm resistors, but still i wonder if thers might be a probklem as my understanding of the circuit implies there is usually a greater load on the outputs than i would be providing.

As for cost and complexity- I do not understand and therefore am uncomfortable with digital electronics.
Same problem trying to fix a car with electronic fuel injection compared to one with a carburettor (to me at least ).

Thanks

Any other comments out there?

 

[mefinnis]

Hi George

For once in my life there is someone on the list who lives in the same city

Thus we are collaborating somewhat on this project and while I am less worried about cost (I already have my relays), the single attenuator across the output would simplify things considerably.

I have a working BLS to "play" with but I was wondering the best approach in terms of pot placement.

Alas, I posted to another thread:

http://www.diyaudio.com/forums/showthread.php?postid=235994#post235994

Any comments from the learned ones .... !

regards
mark