2. tech-talk
  3. 999049858

Problems with Passive Preamp, please Help

I recently added a single input pre amp to my system and even with the volume turned all the way up the sound level is not what I would call loud, it sound like it is in the 11oclock position in most systems, I was wondering if this is a component matching issue or if it could have anything to do with my large room and small speakers, my system is a CAL CL10 (3v output) to an Anodyne passive (the only spec on the passive I could find was 5.50k writtn on the bottom), into a Marsh A400 (input impedance 56kohms for unbalanced, input sensitivity 1,4 Vrms), into Castle Severn 2s (single 5.5" mid/woofer, 1" tweeter)
mkaes
mejames
986 posts
 
what length Interconnects are you using? Passive dictate the use of short [2 meter] or less length interconnects.
Ag insider logo xs@2x
audiophobe
3 posts
 
The CAL is a tube DAC? If that is the case, then 5.5K is probably way too low. I have heard that tube output stages commonly require more like 50K or even 100K impedance on the passive. I have run into this myself when using a 25K passive with a CJ dac: the sound lacked bass, and generally sounded small and compressed. When I changed the (very expensive) passive to a cheap home made one that was 50K, there was a huge sound improvement.

Hope this helps. Passive preamps are a real bear to get working sometimes.
marakanetz's avatar
marakanetz
5,473 posts
 
I think that there is nothing wrong with impedance matching. the input sencitivity of the power amp has to be <=500mV@1Khz in order to be able to operate 3V output from DAC with passive preamp.
bob_bundus
1,834 posts
 
It definitely sounds like an impedance mismatch issue. A DAC outputting in the 3V range should easily be able to drive an amp with half the sensitivity (1.4V) well into clipping. If you do not hear major distortion when your volume is cranked wide open then the amp is apparently signal starved. Try another line source component, borrow one from a friend if possible (tuner, cassette, or another CD player) & test again. If that doesn't help then you need a better passive pre or maybe even an active one to get the required gain. I'll email you privately with details on a rare unit that is presently available.
More to discover