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In line Attenuators with Passive Preamps

Most digital sources output 2 volts or more. Most amplifiers come to full power at far less voltage. This scenario creates using much of the attenuation provided by a preamp.  One way around this is to use an in line attenuator between source and preamp.  

My questions are: 1) Should a in line attenuator be considered when using a passive pre?, 2) What in line attenuators might be useful? and, 3) What capacitive load do they add to the signal between source and amp? This would certainly be of importance when using a passive preamp.
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mesch OP
1,679 posts
 
Tooblue, yes, you may be right, at least in some circumstances. There are 10dB attenuators. If someone has a digital source outputting 3V, a 10dB attenuator would, if my thinking is correct, reduce the output to ~1V (Have not done the math). One volt may be enough to drive many amplifiers to the loudest desired level. There may be attenuators available that are of lower than 10dB attenuation. 

My primary concern is the capacitive issue when using a passive pre.
tooblue
787 posts
 
For what it is worth I had a set of adjustable attenuators made for me stepped in 2db steps so I could play around with things and also use as preamp per sey when driving a digital combo to my amp.
donvito
81 posts
 
This might be what you are looking for!
http://www.schiit.com/products/sys
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mesch OP
1,679 posts
 
Donvito, Yes, the SYS is worthy product at it's cost. I own one and am currently using it. Need not get beyond 10 o'clock position for loudness. Was thinking I might remove so much potenteometer from signal path.

I believe I have over thought this issue. My best approach might be to purchase a better passive with different volume control. Luminous Audio with step ladder or Lightspeed. Will be used with a Nuforce STA200 or a Dynaco ST70 (original).  
georgehifi's avatar
georgehifi
4,966 posts
 
My questions are: 1) Should a in line attenuator be considered when using a passive pre?
No not a great idea unless you know your I/O impedances are still good, as they will change depending (where you put them) the input or output impedance matching, always for the worse, than what you had without them when using your passive preamp..

The best resistance value for a passive preamp is series/shunt 10kohm.
This value is high enough input impedance to suit 99% of sources (except high impedance >2kohm tube output sources)
And low enough to suit most poweramps inputs that are 33k or higher.

Cheers George

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