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Απάντηση: MUSIC FIRST AUDIO PASSIVE MAGNETIC PREAMPLIFIER
Για να δούμε τι λέει ο κατασκευαστής :
The transformer is housed in a Mu-metal shielding can that measures
60.25mm (23/8in) in diameter x 72mm (213/16in) in height, excluding the
connecting leads. No inbuilt mounting hardware or mounting provisions are
included, due the substantial size and weight of the transformer which
would make the conventional methode unreliable.
The input and output connections are made via silver coated 0.6mm dia.
(22gauge) copper wire. The transformer has the primary winding split into
two identical, separately accessible sections.
The secondary (output) winding offers a number of taps allowing the
following attenuation values:
0 db, 3 db, 6 db, 8 db, 10 db, 12 db, 14 db, 16 db, 18 db, 20 db, 22 db, 24
db, 26 db, 28 db, 30 db, 32 db, 34 db, 40 db, 46 db
With these values the steps by which the volume is changed over the
majority of the range is smaller than the commonly acknowledged limit of
audibility (3db), giving a sufficiently fine control over the volume, when
compared to continuous controls. Obviously, any attenuation is reliably
repeatable.
The full primary (split primaries in series) has around 200 Ohm DC Winding
resistance. The same applies for the secondary winding. The primary
inductive reactance at 20 Hz is in excess of 50 kOhm (400 H Primary
Inductance) and thus provides an input impedance of more than 50 kOhm
across the audio band if the secondary loading is infinite.
If the split primary sections are wired for 6db voltage step-up with both
sections in parallel, the input impedance is 12.5kOhm or higher across the
whole audio band. In the case of the split primaries in parallel a 6db voltage
step-up is obtained for the no attenuation output tap, at the cost of lower
input impedance. So to speak a passive Voltage gain of 6db is obtained.
This is especially useful with power amplifiers having a minimal number of
stages and thus lowers gain than common.
An example may be a 2-Stage Single Ended Valve Amplifier using Western
Electric 437A or Reflektor 6S45PE Valves in the input stage and 45/2A3 or
300B DHT as output valves. Such an Amplifier often has a gain of only 16 –
18db and requires around 1.5V RMS for full power. Depending upon the
source and recording the added 6db Voltage gain may make the difference
between subjectively satisfying volume levels in such a system or requiring
more gain.
Για να δούμε τι λέει ο κατασκευαστής :
The transformer is housed in a Mu-metal shielding can that measures
60.25mm (23/8in) in diameter x 72mm (213/16in) in height, excluding the
connecting leads. No inbuilt mounting hardware or mounting provisions are
included, due the substantial size and weight of the transformer which
would make the conventional methode unreliable.
The input and output connections are made via silver coated 0.6mm dia.
(22gauge) copper wire. The transformer has the primary winding split into
two identical, separately accessible sections.
The secondary (output) winding offers a number of taps allowing the
following attenuation values:
0 db, 3 db, 6 db, 8 db, 10 db, 12 db, 14 db, 16 db, 18 db, 20 db, 22 db, 24
db, 26 db, 28 db, 30 db, 32 db, 34 db, 40 db, 46 db
With these values the steps by which the volume is changed over the
majority of the range is smaller than the commonly acknowledged limit of
audibility (3db), giving a sufficiently fine control over the volume, when
compared to continuous controls. Obviously, any attenuation is reliably
repeatable.
The full primary (split primaries in series) has around 200 Ohm DC Winding
resistance. The same applies for the secondary winding. The primary
inductive reactance at 20 Hz is in excess of 50 kOhm (400 H Primary
Inductance) and thus provides an input impedance of more than 50 kOhm
across the audio band if the secondary loading is infinite.
If the split primary sections are wired for 6db voltage step-up with both
sections in parallel, the input impedance is 12.5kOhm or higher across the
whole audio band. In the case of the split primaries in parallel a 6db voltage
step-up is obtained for the no attenuation output tap, at the cost of lower
input impedance. So to speak a passive Voltage gain of 6db is obtained.
This is especially useful with power amplifiers having a minimal number of
stages and thus lowers gain than common.
An example may be a 2-Stage Single Ended Valve Amplifier using Western
Electric 437A or Reflektor 6S45PE Valves in the input stage and 45/2A3 or
300B DHT as output valves. Such an Amplifier often has a gain of only 16 –
18db and requires around 1.5V RMS for full power. Depending upon the
source and recording the added 6db Voltage gain may make the difference
between subjectively satisfying volume levels in such a system or requiring
more gain.