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dm8
ELECTRONIC DESIGN
In keeping with my philosophy of design, my basic aim was to produce a
preamplifier with which I, personally, am quite satisfied. I sincerely hope that
others will share my satisfaction with these products.
As I saw it, the major issues were:
Zero compromise on Transparency.
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Flexibility.
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Ease of use.
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Progressive design concepts.
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In order to meet this challenge, the resulting circuits have particular
characteristics:
First, all circuits in the preamp have distortion so low that it is
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immeasurable, whether THD, IM etc.
Second, all circuits in the preamp exhibit exceptionally low noise (see
Ÿ
specifications).
Third, there is no compromise whatever with the choice of components
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(Vishay resistors, FKP1 capacitors etc).
Fourth, the circuits are highly immune to electromagnetic interference.
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Some inputs and outputs include both first order filters and common
mode chokes.
Fifth, the power supply and microprocessor circuits are designed for
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minimal electromagnetic emissions (extensive 2
Sixth, the power supply switching frequency was chosen to be much
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higher than the audio band (>200kHz).
Seventh, the power supply rails are exceptionally well regulated,
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double regulation in fact (switch-mode and linear servo loops).
Eighth, components and design are selected for high reliability.
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The volume control is implemented so as to include two identical stages in
series. This minimizes output noise.
The dm8 & dm10 preamplifiers feature balanced, unbalanced, current mode
and bridged current mode outputs. The latter consists of a non-inverted and
inverted current output. There is also an unbalanced output for tape and
headphones.
By Bruce Candy
to 6
order filters).
nd
th
Page 4 of 26
TM
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