BZLS attenuation before output caps

Ignatz · 17th January 2003, 12:59 PM

My attenuator places one resistor at a time between the + and - signal of my BZLS or P1.7 via a 23 position Electroswitch.

This method seems to work best when placed after the output caps; however, my BZLS splits the output to a 120 Hz high pass and an all pass.
If I place the atennuator at the input I have to isolate it from my sources via 10K0. This causes odd attenuation at some listening levels.

Can I connect my attenuator ahead of the output caps, before the DC is blocked? The DC voltage seen by the attenuator should be very small. The 8R1 is the lowest resistor value which shorts beween + and -.
Will I have a problem if the drains are shorted?

The attached jpg is a very rough version of a modified BZLS; however, it sounds much much better than it looks.

Peter Daniel · 17th January 2003, 01:56 PM

If you look at the schematic of D1, you'll see that attenuator is located before the output caps http://www.passlabs.com/pdf/d1-srv-man.pdf

Ignatz · 17th January 2003, 03:00 PM

Peter:

Thanks for the link.
What is the purpose of the 4.7 uF cap for on PL55 Volume Control dwg?

It looks like the shoulder frequency ranges from 1.1 Hz to 1.5 Hz.
Does the cap basically short out the unselected resistors for some reason?

Peter Daniel · 18th January 2003, 05:01 AM

Maybe the cap is there to reduce "pops" when switching.

17th January 2003, 12:59 PM	#1
Ignatz diyAudio Member Join Date: Apr 2002 Location: Toronto	BZLS attenuation before output caps My attenuator places one resistor at a time between the + and - signal of my BZLS or P1.7 via a 23 position Electroswitch. This method seems to work best when placed after the output caps; however, my BZLS splits the output to a 120 Hz high pass and an all pass. If I place the atennuator at the input I have to isolate it from my sources via 10K0. This causes odd attenuation at some listening levels. Can I connect my attenuator ahead of the output caps, before the DC is blocked? The DC voltage seen by the attenuator should be very small. The 8R1 is the lowest resistor value which shorts beween + and -. Will I have a problem if the drains are shorted? The attached jpg is a very rough version of a modified BZLS; however, it sounds much much better than it looks.

17th January 2003, 01:56 PM	#2
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	If you look at the schematic of D1, you'll see that attenuator is located before the output caps http://www.passlabs.com/pdf/d1-srv-man.pdf __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

17th January 2003, 03:00 PM	#3
Ignatz diyAudio Member Join Date: Apr 2002 Location: Toronto	BZLS attenuation before output caps Peter: Thanks for the link. What is the purpose of the 4.7 uF cap for on PL55 Volume Control dwg? It looks like the shoulder frequency ranges from 1.1 Hz to 1.5 Hz. Does the cap basically short out the unselected resistors for some reason?

18th January 2003, 05:01 AM	#4
Peter Daniel diyAudio Member Join Date: Jul 2002 Location: Toronto, Canada	Maybe the cap is there to reduce "pops" when switching. __________________ www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

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