Passive pre with class ''D'' power amps, issues ??


Just wondering if there would be any issues using a passive preamp with powerfull digital amps like Bel Canto REF-1000 monoblocks and the like...

Many thanks if you can help !
If I read the specs on it correctly the input impedance is high enough to work with most passives, but I'd be a little concerned about the gain (27db) and sensitivity (3V rms to full output). Typically something in the area of 1V would be ideal. However, this also depends on the source driving the passive. Most digital sources are 2V but some are higher. You could try a couple and see what happens.
You'll improve your odds of success with something like the Sonic Euphoria, which controls attenuation via multiple transformer taps rather than resistors. With no AC input it can provide (depending on the configuration you specify) anything from 2 to 10dB gain IIRC. As these things go it's pretty reasonably priced as well.
I would join Jonnyb53 with his recommendation. If to use passive preamp then transformer based. I have had good experience with Promethius (spelling...) Ref 3. It was much better (and cheaper) then famed Placette

Still, I wish to point out that not a singke passive preamp was as good as high quality active preamps (I use tubed ones only) not inresoultion and detail - despite many testimonials and never ever dynamic range and bass extension.

Good Luck
Channel Island makes two versions of the same D100 or D200 class D amps: version to work with active preamp (26dB) and version for passive one (32dB).
I don't think a transformer based passive is going to make that much difference here given the gain and input sensitivity of the Bel Canto amp.

The high gain CIA D-200 or D-500 would be a much better candidate to match with a passive preamp. While I have experienced the benefits of transformer based passive designs, one non-transformer design recently caught my attention that I subsequently purchased and that is the Lightspeed attenuator. You can read up more on this uuit at You can buy one pre-built by the original designer for about $350.
I'm using a Bent NOH with Kharma MP-350 monoblocks; flawless performance.
I use a Creek passive attenuator between my RWA modded SB2 that has about 1.25 v output at best and my Cayin TA30 with about 26-28 db gain and it works very well.
Seems that one would have a leg up on system matching to use a Channel
Islands passive pre plus their Class D amps with 32 dB gain.

Anybody have news from Jeff HAGLER who ran Sonic Euphoria ?
He maybe have encountered problems, does not respond to messages, is he definitely out of business ?

Best regards
I believe he closed up shop.