This is an early version of the Altec 9067b filter, and it uses a similar layout and construction. The most notable difference on the front panel is the greater spacing used between the filter frequency detents (this version has about 300 degrees of rotation) compared with the switches used on the later models.
Internally it has a model 68A Low Pass and 69A High Pass filters (one each).
This unit has 11 positions on both the Lo and high Frequency Cut Offs:
Low Frequency Cut Off:
CW rotation from Off, 70, 100, 150, 250, 500, 1K, 2K, 3K, 5K, 7.5K.
Hi Frequency Cut off detents are CW rotation from 250, 500, 1K, 2K, 3K, 4K, 5K, 6K, 8K, 10K, OFF.
These are 18 db/Octave filters, and the effects are remarkable on program material, especially when the upper an lower points are within one position of a center frequency.
The unit is entirely passive, with a terminal strip on the rear of the unit that has what might be interpreted as a balanced interface, but is really a pair of unbalanced floating circuits that use a common ground.
Condition: For a 60 year old piece pretty good. There is significant wear to the rack mounting holes (slots really), with a piece of the the top right slot having been broken off. The knobs and paint are in surprisingly good condition, with marks around the rack ears, but none around the front panel longframe jacks, most likely since this unit was wired to a patch panel.
- There is a scratch through the 'R' in Filter just under the ALTEC logo.
- A few dents to the metal cap on the 'Out In' switch
- Some light marks to the green enamel at various spots, but nothing down to the metal.
This is from some Altec Literature:
For professional use in disc, tape and film recording - broadcastand telecast studios - for ’sound effects"- motion picture sound stages, public address and sound reinforcement systems.
These Altec variable filters are ideal for all phases of broadcasting, recording and reproduction of sound. As 'sound effects' or 'special effects' components, they are unsurpassed. The wide variety of effects possible-coupled with the simplicity and ease of operation-make these filters a necessity for professional audio applications wherever accurate control of the audio spectrum is required.
Incorporating both the 9068A and the 9069A, the Altec 9067 A Variable low Pass and High Pass Filter affords complete flexibility in one compact unit. The entire filter may be switched in and out of the transmission line instantly, or-if desired-either or both sections may be switched individually.
The low frequency control provides 10 cut-off characteristics: at 70, 100, 150,250, 500, 1000, 2000, 3000, 5000 and 7500 cycles.
An equal number are available with the high frequency control at 250, 500, 1000, 2000, 3000,4000, 5000, 6000, 8000, and 10,000 cycles. Regardless of the selected cut-off frequency, the attenuation rate remains constant at 18 db per octave.
Both controls have an 'off' position which allows the full frequency range of the program material to be transmitted. The silent action of positive detents allows frequency cut-off changes to be made during actual sound processing.
All inductances employed are toroidally wound, permitting the unit to be used in extremely low-level circuitry without noise or hum pick-up. The zero insertion loss facilitates the connection of these units to any point in the transmission line (having a level from -70 to +28 dbm) without the need for external power supplies or additional amplification stages.
The Altec 9067 A is totally enclosed with rear-mounted input and output terminals normaled through front panel jacks. It measures only 3.5” highby 19" wide and is 8” deep, and weighs 15 pounds.
The Altec 9068A Variable low Pass Filter and the Altec 9069A Variable High Pass Filter are electrically identical to the filters incorporated within the Altec 9067 A, but are furnished as individual units for custom mounting.