[hertz]

Hi,
I am new here. Forgive me if this sounds stupid  
Do bent audio do active pre-amps ? Do they have kits for active pre-amps ?

Thanks.

[John Chapman]

Hello!


All the systems we make are passive signal paths. Most pre-amps we build employ TVC's - Transformer Volume Controls. These are different than resistor passives in that they actually model more like an active pre-amp - nice high input impedance and a nice low output impedance. They do this by turning the excess voltage at the source into current drive at the output of the pre-amp.  The same priciple is used to step down high voltage power lines to the 120V you use in your home. With a resistor attenuator this excess voltage is just thrown away accross the attenuator's resistance. The downside is they cost a LOT more to make than a resistive attenuator. TVC's can also provide a modest amount of gain - about 6db.


Thansk!

John

[hertz]

I am not much experienced in actual electronics. But I do understand a bit.
I have heard that passive pre-amps work well only with certain source/power amp combinations. Is this the case with bent audio pre-amps incorporating TVC’s ? Will they work with all source/power amp combos ? Any pros/cons compared to a regular active pre-amp ?
How much will pre-amp with TVC with 4 RCA inputs and two outputs cost ? My source is a Marantz cd17 and planning to go for something like the odyssey Stratos power amp. Right now using Nad separates.
Thanks,
Hertz.

[John Chapman]

Hello!

TVC's are more forgiving than traditional resistive based passive pre-amps due to the better output impedance you get with a TVC. Resistive passives really should be located right at the amp inputs or if not there with very short cables. TVC's behave more like actives from an impedance point of view so are best located like a traditional pre-amp. It is rare to find combo's that don't work out with TVC's but is can happen.  Two things to avoid are very high output impedance sources (say over 1K or so). These are really rare in commercial products - typical cd players have output impedances from 50 ohms to 500 ohms or so as an example. The other thing is sources with very low voltage outputs - say 1,5V or less. Not so much a 'need to avoid' but more a 'need to be aware of' situation since the input sensitivity of the amps and the speaker sensitivity play a roll as well. Amp input impedances are less of an issue - the TVC's can drive wuite low input impedances.

For pricing info just e-mail direct or call and we can discuss options.

Thansk!

John