30/12/07 - Managed to cram 4 channels of 3875 amps into this little box. It's a two-tier setup. The whole system now sounds really great but I'm having problems with hum on the second pair of amp (pulling hair...). Also I don't know why the new pair runs hotter even though they are exact same design.
28/12/07 - Completed active crossover setup. Now I need a second pair of gainclones to make sure all frequency matched!
The active crossover is based on Rod Elliot design 'P09' with cutover freq. of 3.5kHz. Calculated C=39nF, R=820R
Install Foobar ASIO plugin (http://www.foobar2000.org/components/index.html) by copying the. dll in foobar directory. Then from Foobar go to preferences > playback > output > asio virtual device .. create ASIO4ALL as new device.
Once the device is created go back to 'output' then select ASIO: ASIO4ALL as the output device.
ASIO4ALL does not resample (it is why we want to use it after all), so for playing 24bit recording on 16bit DAC go to Foobar2000's DSP and activate resampler (PPHS) with 16 bit target sampling rate.
Simply plug in the USB and go to System > Preferences > Sound. Select 'USB Audio' in 'Sound Events' and 'Music and Movies' and click 'Test'. A test tone should confirm that it's working.
There is a catch. Although tests are ok, Ubuntu players (VLC, Totem, etc.) keeps using the PC loudspeaker instead of USB Audio. To fix this the following steps can be performed to set the default sound device:
- Open Terminal from Applications > Accessories
- run the command 'sudo asoundconf list', you need to enter admin password. On my IBMT23 I got back:
Names of available sound cards:
- Then run 'sudo asoundconf set-default-card PCM2702' followed by a reboot to test.
The same procedures can be used for other Ubuntu/Linux compatible DAC such as SoundBlaster Live!
There is no 'box' feeling. Just instruments and air that "breathes". There is an inherent low-frequency tradeoff as it is not as loud, but when it does get there -- what a bass! I love it so much I don't know what's next for improvement.
Perhaps it is time to finally .... listen.
8/1/08 - Fixed crossover calculation:
cutover freq 2500Hz
woofer imp. 8 ohms, L stays 0.5mH,
tweeter imp. 4 ohms (2x parallel 8 ohms), C changed from 3.3uF, then 2x3.3uF, then to 15uF but later back to 10uF in parallel (sounds better)
Upon connecting the speakers to my gainclone amps, I found the sonics are nice. The crossovers are then upgraded using Mundorf M-Cap Audiophiler capacitors with similiar 3.3uF value.
The Mundorf capacitors contributes in very transparent mids and highs.