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Old 15th September 2003, 12:42 PM   #1
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Join Date: May 2002
Location: oz
Default aleph p + attenuator

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.
george a
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Old 15th September 2003, 12:54 PM   #2
UrSv is offline UrSv  Sweden
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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.
Those who say it can't be done should not stop those who are doing it.
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Old 15th September 2003, 02:11 PM   #3
Join Date: Apr 2002
Location: Germany, Clausthal
There by avoidong the complexity and cost of relay based
16*2 Relays
3.90 PIC MC
< 10 for resistors, transistors, PS
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Old 15th September 2003, 10:14 PM   #4
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Location: oz
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 ).


Any other comments out there?
george a
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Old 16th September 2003, 03:02 AM   #5
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Join Date: Feb 2001
Location: Adelaide, Australia
Default 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:

Any comments from the learned ones .... !

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