Passive Pre - No Regrets?

Gmood, where did you put your buffer and what did you use?

What you have is basically an active preamp broken into several sections. An active preamp usually consists of some switching - maybe an active gain stage that also acts as a buffer - passive volume control - maybe another gain stage which also acts as a buffer.

Most go switching - volume control - active stage, but some, like at least some VAC preamps, go switching - active stage - volume control.

The beauty of the active is that the designer can optimize the interaction of the gain stages and the volume control. Much tougher to do out here in the real world. So people try a pasive and fail and dismiss them and blame it on the fact that it is passive. Kind of ironic really considering that at the heart of their active preamp is a passive volume control.

I went from Active to passive, It was very difficult to get the passive working properly. It is hard work but it will be rewarded.
As a rule the output impedance of the source should be 10 times lower than the input impedance. My DAC has an output impedance of 50 ohms, my passive has an impedance of 1k (20 times 50 ohms) and my amps have an input impedance of 1meg. So it works nice, I tired impedances with my passives from 100k, 10k, 5k, 2.5k and 1.2k, believe me the diference from 1.2k to 1k is very noticeable, I get much better bass and fuller sound with 1k.
This is a shunt type resistor based passive with caddock resistors, and a resistor ladder going to ground, a pot does not work as good to ground!

I had a PLC and hated it....
I sometimes miss my Metaxas active SS preamp.

Best.

Hello Herman,
I use the Burson buffer before the TVC and after my Dac. My Dac's output impedance is fairly high 2700 ohms. After talking with a few people, two being the owner of the Jensen transformer company and Jack of Eletraprint transformers. It was clear I needed a buffer in order to use the TVC without penalty. Now instead of the TVC seeing 2700 ohms, it sees 15 ohms input. The buffer from the specs is also capable of 12 volt output verses my Dac's 2 volts.When looked upon as a whole..from your description it is an active preamp in seperate sections.

I sent this unit to an audiophile that owned a similar Dac and used the Django TVC. Before the buffer was added to his system, he got rolled off or dull highs , a flat soundstage and a over all thin sound. The buffer brought the highs up, opened up the sound making it fuller and more dynamic..from his description.

So as you've said..the matching is critical. Guessing from some of the other posters description's..this may have been one reason the Passive or TVC didn't work in their systems either.

Thanks for all the answers. I did not even know what a TVC was before, so of course I had to do some reading. This issue of electrical compatiblity seems a bit difficiult to grasp. So I throw it out there. The output impedance of my Audio Logic DAC is 225 ohms, the input impedance of my CAT amp is 100 kohms. This is complicated by the fact that the DAC gets plugged into the Merlin BAM bass equalizer which has 40KOhm input and 100 ohm output to the preamplifier. Do these impedances bode well for the use of one of these passives to drive my amplifier? Ultimately, I want to knwo if this will sound better than my CAT SL1 Ultimate, but I guess I won't really know that till I try it.

Pubul57 If you want to get a feel of the passive you can get a Luminous Audio passive, they supposedly calculate the impedance and sell you the passive, it is a shunt passive with a pot to ground, A friend has one and it does let you get the feel of a passive...full resistor loaded is much better, I talked to Guy from Placcete and he told me all his passives come with a 10k impedance, this impedance can work for you, he also changes impedances according to the customers settings. You can buy a placette passive and see if it "fits" your system, Guy will help you out even if the preamp is used (very cool guy!) this way you can be sure you have the passive matcing properly.