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What is a non-active pre-amp stage?? Are their advantages to this design??

I am considering an  Conrad Johnson CA-150 integrated amp which offers a "non active pre-amp stage"

Need and explanation of this design.  What are its pros and cons??  Does it provide better sound quality or performance, than an "active pre-amp stage" ?

Any comments about the C.J, CA-150 integrated amp sound quality??


Thank you,

S.J.



sunnyjim
pragmasi
212 posts
 

I am considering an Conrad Johnson CA-150 integrated amp which offers a "non active pre-amp stage"

Need and explanation of this design. What are its pros and cons?? Does it provide better sound quality or performance, than an "active pre-amp stage" ?

From the look of the product page on their site this is an integrated amp by another name without input buffering before the attenuator... which is a pretty normal integrated amp design.

Personally I prefer to buffer the input to the attenuator (which makes it active), this allows the use of lower value resistors (800Ω instead of 10,000Ω) in the attenuator which means lower (johnson) noise levels.

I'm afraid I've not heard the amp in question so can't comment on that but it might be worth auditioning passive vs active if you can get a dealer to set that up for you.


georgehifi's avatar
georgehifi
10,312 posts
 
sunnyjim
What is a non-active pre-amp stage?? Are their advantages to this design??
jond
non active preamp stage means the preamp stage is passive

You heard of Nelson Pass no doubt (Pass Labs, Threshold ect ect)
This is what he said about passive volume controls, and yes he does make/ designs active preamps after all he is a business man.

Quote from Nelson Pass

We’ve got lots of gain in our electronics. More gain than some of us need or want. At least 10 db more.

Think of it this way: If you are running your volume control down around 9 o’clock, you are actually throwing away signal level so that a subsequent gain stage can make it back up.

Routinely DIYers opt to make themselves a “passive preamp” - just an input selector and a volume control.

What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.

And yet there are guys out there who don’t care for the result. “It sucks the life out of the music”, is a commonly heard refrain (really - I’m being serious here!). Maybe they are reacting psychologically to the need to turn the volume control up compared to an active preamp.


Cheers George
pragmasi
212 posts
 
Just to be clear, an active preamp doesn't have to add gain, there is benefit to be had in using the active component/s to present a high impedance to the source and low impedance to the load. DIYers are in a better place to decide which way to go as they are more likely to properly understand the impact of their choices and the electrical characteristics of the equipment connected. 
A passive device needs to be selected carefully because too low an input impedance may overload the source equipment... okay so lets choose a high resistance pot / attenuator. But in the absence of any active components the output impedance of the preamp is the one presented by the pot / attenuator. The output impedance of any preamp in conjunction with cable capacitance creates a low pass filter - with well matched equipment this will be at a higher frequency than we care about in the audio world. However with a passive preamp this may start to creep in to the top end of the audio range.
There are other advantages to active preamps that I could go into but I feel I may have been too technical already.
One architecture isn't necessarily better than the other, but if you don't fully understand the characteristics of your components then you're probably safest going active.
pragmasi
212 posts
 
I just re-read the original post and realised I'd forgotten we were talking about an integrated amp (not a passive preamp). You will be able to trust the engineers have taken into account the impedance internally (and so can disregard most of what I just said), the unit has 10k input impedance so that should be fine for most, if not all sources. 

I still think that sometimes it's worth using active components to overcome the limitations of passive ones e.g. if you want minimum noise levels 10k pot has minimum noise of -115dBV, a 500Ω attenuator has minimum noise of 127dBV but will require some active buffering. 

Apologies if I've added more confusion, I should have re-read the original post properly before responding. 
georgehifi's avatar
georgehifi
10,312 posts
 
I still think that sometimes it’s worth using active components to overcome the limitations of passive ones
If there are no impedance issues "limitation" as you say, then a passive will sound better, more transparent, better dynamics, and less coloration/distortions. (see Nelsons quote)
And aren’t we searching for the Holly Grail?
Why compromise plus the expense with an active, why not strive to get the passive right? Or better still going direct if it allows it.

Cheers George
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