D4 Technical Details

Below are some test measurements of the D4 for your reference.  All tests were performed using AES standards where possible.

First is impulse-chirp based frequency response.  This was measured using a 48kHz sample rate, so the measurement cuts off at 24kHz.  The transformer frequency response extends further than that (about 60kHz) but response to 24kHz seemed sufficient.

Next is noise performance.  It’s a little unusual to do this, but since EF86 pentodes can be noisy we wanted to show how the design behaves.  We felt this was crucial because we’re demanding more gain out of the circuit than it was originally designed with.  This test was taken using the analyzer’s noise power setting, using a 50 ohm source with the preamp set to maximum gain (60dB).  You can see in the chart that self noise under these conditions is below -90dBA.

Finally here’s a THD test with a 1kHz tone.  We followed the AES standard of setting preamp for maximum gain and trimming the output down to +4dBU.  In this graph you can also note the excellent power supply noise behavior at 60Hz and 120Hz.

Of course, none of these tests will tell you how the D4 sounds, but we felt it was important to provide a technical reference.  Visit this page for audio samples of the Dizengoff D4 preamp in action.