First Watt B4.....buffer, gain and impedance...

[superlian]

I have a First Watt B4 active crossover and conscider to skip the preamp.

Today i have:
Sonos - dac - Pass Labs XP10 - First Watt B4 crossover - biamp

When i remove the preamp, reduce signal level in B4 with dip switches and potmeter and finally use digital volume on Sonos within a range of 70-100% it sounds as good as with a preamp (maybe even a little bit more open).

I have heard that amps need a buffer in front and that only a passive pot could kill dynamics. Is it buffer in B4? And is it OK to place a passive ALPS potmeter before B4?

 

[Zen Mod]

B4 is acting buffer-like on outputs and it have buffer on input

so - pretty safe to put any kind of attenuator on input side

 

[superlian]

Great 🙂

 

[superlian]

Another Q:

Is the gain reduction via the potmeters for low and dipswitches for high reducing the sound quality in any way?

 

[Zen Mod]

every unnecessary attenuation is waste

if you need to do it , do it in one place - on one attenuator

those implemented in B4 itself are for level matching purposes

 

[superlian]

So, a remote controlled blue ALPS 50K before B4 would do the job?

Glasshouse Remote Control kit for Motorised Alps Hifi Collective



From the manual:

The B4 has a high input impedance of 100 Kohms and low output impedance of 150 ohms.
The bandwidth of the low pass is DC to the value of the filter frequency, and the bandwidth of
the high pass is about 0.5 dB down at 100 Khz.
Although DC coupled, each circuit has been trimmed for the very minimum of DC offset, and
so you should expect to see about 1 mV of DC through the system. very low noise and
distortion and wide bandwidth. It is important to note that any DC offset present at the input
from source components will be passed through the B4 Low Pass circuit.

 

[Zen Mod]

#2

 

[superlian]

Ok 🙂