2. amps-preamps
  3. 1426779273

Is my preamp useless?

I enjoy my current system, which is built around a BAT VK-52SE preamp. I listen mostly to digital, via a Bryston BDP-2 player into a PS Audio DSD. I also enjoy vinyl on my VPI Classic/Dynavector/Sutherland 20-20 combo. Like most of us, I’m usually on the upgrade path. For me, the next component to upgrade would be the BAT preamp from a 52SE to a 53SE. But something occurred to me. I don’t listen loud. The gain on my PSA DSD is set to less than 100 and the BAT preamp is usually set between -20 and -10. So if my volume control is never set in the + range, is my preamp doing ANYTHING other than attenuating the volume and serving as a multi-input switch? Is all that Super Tube, single gain stage, zero feedback, high energy storage circuitry a waste of money?

Don’t get me wrong. I am very pleased with the sounds I hear. But if my pre isn’t doing anything, then I’d be better off to sell it and get a very simple passive attenuator, wouldn’t I? If that’s the case, what brands and models should I listen to?
Thanks for any advice.
slanski62
georgehifi's avatar
georgehifi
10,312 posts
 


Scare tactics of the capacitance of interconnects with passive preamps are off the mark. As most good interconnect cables are less than <100pf (picofarad) per foot. And at 1-2mts are fine.

Only when you get into cheap nasty cables do these scare tactics come into play, when they have >200pf per foot or higher, and those types of cables have no right in hi-end audio.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 

Just to add to the above, when these high capacitance interconnects (>200pf per foot) are used, they can cause a high frequency filter, not only with passives but also with the many tube preamps.
This is another reason they have no place in hi-end audio. Thank god there are not too many of them around.

Cheers George
zd542
5,339 posts
 
"Does it mean that all these highly regarded active preamps also have not been designed properly? So which one would you say is wrong: cables or active preamp?
Milpai (System | Reviews | Threads | Answers | This Thread)"

Neither is wrong. Audio components are usually designed with the understanding that they will be used in a wide variety of systems. Its impossible for any designer to make products that will be optimal in all systems. It just can't happen. That's why there's nothing wrong with the cables or the preamp. They just can't work for everyone in every situation.
georgehifi's avatar
georgehifi
10,312 posts
 

Just to give an example,
A 10kohm passive preamp which all solid state sources can drive, has a worst case 2.5kohm output impedance.

In the worst case of 2.5kohm, this passive preamp driving reasonable quality interconnects of 100pf per foot at 2mts long will give a high frequency roll off at -3db @ 106khz!!!

And with just one meter interconnects it is -3db @ 212khz!!!

And this is interconnects of 100pf, if you get good quality ones that are 50pf per foot, the HF roll off point off doubles again
To -3db @ 212khz for 2mts!!
And -3db @ 424khz for 1mt!!

As you can see only dogs and bats can hear this kind of HF filtering.

Cheers George
georgehifi's avatar
georgehifi
10,312 posts
 


Here is the graph of a 10kohm passive output impedance.
On the left (vertical axis) is it's output impedance, for the given volume resistance (horizontal axis).
As you can see at half volume rotation it is at the worst 2.5kohm output impedance, either side it's output impedance is lower.

http://i.stack.imgur.com/cVUCc.png

Cheers George
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