Rens Heijnis                                      custom-built audio equipment

A few examples of  pre-amplifiers

Different pre-amplifiers, only drawing available:

3 Channel pre-amplifier, desktop enclosure  3 channels
4 Channel pre-amplifier, in 19"rack  4 channels 19"
4 Channel pre-amplifier, desktop enclosure  4 channels  
14 Channel pre-amplifier, 19"rack  14 channels19"  
4 Channel portable mixer with rechargeable batteries  4 channels portable
8 Channel remote controlled pre-amplifier (drawing is the remote control)   8 channels RC

Batteries and sound quality of components

It is a well known and documented fact, that battery powered audio equipment (separated from the main voltage) 
sounds substantially better. There are several plausible reasons for this. Apart from getting rid of the pollution
on the main power, also the absence of interfering ground currents adds to the improvement also. 
What we found in our testing period, which extended over half a year of recording with prototypes, is:

• a much more relaxed projection of the sound images
• less noise artifacts
• a complete ‘black’ around the phantom images in the stereo and surround images.
  

In the block diagrams you can clearly see the difference.

To improve the sound quality of all the amplifiers we did various listening tests on different wiring and passive and
active components. The results are:

• the best capacitor is the Mundorf silver/oil
• the best resistors are metalfilm resistors (with differences between brands)
• potentiometers and connectors sound different
• with respect to wiring, number one is the Siltech silver wire

Another development which drastically improves the sound quality of my equipment is the fact that part of the design
goes without printed circuit boards.

Special light weight (2,9kg) 3 channel pre-amplifier with Lithium ion batteries and the latest developments in improved
sound quality. With DPA MircoDot (4060serie) and active (6pin) microphone input. With battery power for the microphones.
Recording time 34 hours with active microphones, 43 hours with only DPA MicroDot.
Back view
 

4 Channel pre-amplifier, on batteries, with the latest developments in improved sound quality.
Phantom 48V and active power +60V on batteries. Weight 15kg, operating time 24: hours

10 Channel balanced pre-amplifier, on batteries, 19"enclosure, MS circuit
with the latest developments in improved sound quality,
Weight 15kg, operating time: 24 hours.
Back view

2 Channel pre-amplifier, on batteries, 48V phantom power (switch on the back) with the latest developments in
improved sound quality . (price: 1450 euro).

2 Channel pre-amplifier, on batteries, with the latest developments in improved sound quality
For technical specifications see:   balanced pre-amp
(price: 1900 euro).

4 Channel pre-amplifier, on batteries, with the latest developments in improved sound quality.
Uses a separate battery house
For technical specifications see:  unbalanced pre-amp  
(price: 2890 euro).

 See also the Sonodore battery powered pre-amplifier MPB-502

2 Channel pre-amplifier with phantom power, low pass filter and 19"enclosure (price: 1000 euro).

2 channel pre-amplifier for outdoor recording.
With power supply for the microphones. Can work 18 hours on a 9V battery.
Weight only 600gram, Size: 13*4,5*13,5cm