|IAG -50dB STEPPED ATTENUATOR
transformers used in conjunction with a multi position switch
provide a high performance volume control function. Sowter
proprietary winding technique ensures 100 kHz bandwidth at all
switch positions. The transformer action of these attenuators
ensures the loading circuit sees a low driving impedance
regardless of the switch position. This ensures the maximum
bandwidth potential of the whole circuit can be realized at all
gain settings. As the attenuation is related to the number of
turns at the winding tap, the attenuation is exactly matched
between stereo channels. The Mumetal core ensures very low Total
Harmonic Distortion. High input impedance to minimize loading on
the driving circuit. Mumetal can to ensure minimal hum pick-up.
The transformers provide good dc isolation and can be used in
balanced or unbalanced circuits.
These transformers should be driven from a source impedance as
low as possible but will work well with a source up to 10k ohms.
Where necessary a blocking capacitor should be used to ensure no
dc is applied to either winding. The secondary load can be any
value the higher the better. A Zoebel network is not required
to damp high frequency resonances which are non-existent. These
transformers provide isolation and may be used for balanced to
unbalanced conversion or vice versa. It is recommended to use a
separate transformer in a high noise environment or if long
cables are to be used. If a ratio change, high common mode
rejection is required or dc in either winding is required we
will be happy to recommend a suitable transformer to be used in
concert with 9335. Depending on the circuit configuration this
may be possible with minimal loss of performance
IAG stepped attenuator is designed using a
Sowter 9335 -50db attenuator transformer and a Shallco "C"
series 27 position switch in a mumetal shielded enclosure.
The transformer is prewired to the the switch inside the
enclosure with only the input and the output connections exiting
The Sowter 9335 attenuator transformer is
normally in a mumetal case but in this application it is used
without the case for reduced size. The whole assembly will be
shielded in a new mumetal case.
The Shallco switch used is a very high quality
switch with silver plated contacts which are gold plated only at
the solder lugs and has a very smooth feel. The switch is
modified for low rotational torque making it very easy to turn
even with small diameter knobs.
Fully encased attenuator assembly ready for
installation in chassis of your choice or in an existing power
amp or preamp (assuming there is space). The entire
package is 2"x2"x3.25" in depth and has a.375" threaded mount
with a .250" shaft.
SPECIFICATIONS for type 9335
|TOTAL HARMONIC DISTORTION
+20 dBu 50 Hz
|0.03 % typical
|PHASE SHIFT AT 20 kHz
||Less than 1.0 degree
(Secondary open circuit) 10Hz to 65 kHz
|Better than 30k ohms
|COMMON MODE REJECTION
||50 dB at 50 Hz
6 db at 10 KHz