attenuation using I/V - Page 2

David Davenport · 15th October 2008, 05:30 PM

Interesting looking attenuator – thanks for posting it. I see from the connectors that it is an RF attenuator. Is it stepped or continuous? Is it a linear taper? What is it and where can I get one?

Dave

ailouros6 · 15th October 2008, 05:34 PM

David
you are right about the resistor quality.I have tried several,from top series caddocks to some cheap nonames,and i found the best sounding resistor to be some B.I thick film.Day and night diffirences.

Also,i was thinking the same thing you did,variable shunt resistor after the first tube stage,right before the second stage.
That is,redusing the load resistance of the first stage from 100K to about 1K.Have you ever tried it?

David Davenport · 15th October 2008, 05:53 PM

My DAC active stage is a single-stage tube with a transformer coupled output. The output impedance is less than 1K. The schematic can be seen in this article, which also shows the attenuator on the input.

http://www.raleighaudio.com/active_output.htm

Dave

ailouros6 · 15th October 2008, 05:58 PM

I see...
I am sure if you use a parallel resistor to the stepper you won't get any pops.The pops are made because the dacs is loaded with a very large resistance for a very short period of time.It is a known problem to me.If you have a parallel resistor of the same value you won't get these pops.Yet,i will try soon and give you the results.

Stavros

David Davenport · 15th October 2008, 06:20 PM

Thanks Stavros,

I am looking forward to hearing about the results of your experiment.

Dave

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15th October 2008, 05:30 PM	#11
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	Interesting looking attenuator – thanks for posting it. I see from the connectors that it is an RF attenuator. Is it stepped or continuous? Is it a linear taper? What is it and where can I get one? Dave

15th October 2008, 05:34 PM	#12
ailouros6 diyAudio Member Join Date: May 2008	David you are right about the resistor quality.I have tried several,from top series caddocks to some cheap nonames,and i found the best sounding resistor to be some B.I thick film.Day and night diffirences. Also,i was thinking the same thing you did,variable shunt resistor after the first tube stage,right before the second stage. That is,redusing the load resistance of the first stage from 100K to about 1K.Have you ever tried it?

15th October 2008, 05:53 PM	#13
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	My DAC active stage is a single-stage tube with a transformer coupled output. The output impedance is less than 1K. The schematic can be seen in this article, which also shows the attenuator on the input. http://www.raleighaudio.com/active_output.htm Dave

15th October 2008, 05:58 PM	#14
ailouros6 diyAudio Member Join Date: May 2008	I see... I am sure if you use a parallel resistor to the stepper you won't get any pops.The pops are made because the dacs is loaded with a very large resistance for a very short period of time.It is a known problem to me.If you have a parallel resistor of the same value you won't get these pops.Yet,i will try soon and give you the results. Stavros

15th October 2008, 06:20 PM	#15
David Davenport diyAudio Member Join Date: Jun 2004 Location: Raleigh North Carolina	Thanks Stavros, I am looking forward to hearing about the results of your experiment. Dave