Fredenstein HD Reference Preamplifier
Figure 4
Figures
5, 6, 7 show the harmonic levels at various output levels with the 40 dB gain setting and a
250 Hz input (chosen for a centered graph). Figure 4 at 0 dBu output, Figure 5 at +10 dBu output,
Figure 6 at +20 dBu output which is near where many A to D converters overload. Notice 2
nd
harmonic at 500 Hz and 3
rd
at 750 Hz and nothing above 7
th
. Tube circuits often display similar
harmonic signatures. The idea that tubes only generate even harmonics and solid state generates odd
harmonics is just a myth. It all depends on how they are biased. Most properly designed tube
circuits show similar amounts of 2
nd
and 3
rd
below clipping, often somewhat more 3
rd
. Similarly,
transformers usually display mostly 3
rd
and 5
th
harmonics at low frequencies and high levels, but are
sometimes biased them to bring in some 2
nd
. These graphs show a nice onset and harmonic balance.
Figure 8 shows two tones, 200 and 2 kHz, at 0 dBu input (each at -6 dB), to illustrate the virtually
invisible IM distortion at that level.
Figure 5
Figure 6
Figure 7
Figure 8
OK, that is enough of geeky graphs, but sometimes a picture is worth a thousand words. Even
though the frequency response goes amazingly high, don't expect that the HD Reference will be
“bright” because the frequency response is also very flat, but it may be brighter than a preamp with
a rolled off top end. Also, while you can get some pleasant color and character from this pre, it
depends on how hot the output is driven, and it may be subtle, depending on the source or
instrument. It wasn't designed to have a dramatic heavy signature sound and it certainly isn't a fuzz-
box. You can also see how at lower levels it becomes super clean.
Fredenstein HD Reference Manual V1.0 Feb 5, 2016 Page 7
Содержание HD Reference
Страница 1: ...HD REFERENCE Operating Manual...
