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In Reply to: RE: 80 Hz amp posted by RayP on November 24, 2015 at 06:47:51
Jack at Electra Print has this circuit on the front to do just that.
Follow Ups:
I am unclear on two things about this input.
The input is listed as a 1:2 step up loaded with a 10K pot. This puts the input impedance at 2500 ohms. What does the 10K and 100R values refer to? (10K suggests a 1:1 and 100R suggests a 1:10 ratio
The source impedance feeding the bass attenuator will change with the master volume control causing a slight shift in bass attenuation as you adjust volume. (worst case about 1.5dB) I presume the 4.7K resistor is added to temper this variability a bit but it doesn't do much.
dave
This type of circuit does work to provide a simple single volume control subwoofer option, provided the sub amp has a decent (24db) crossover. I use a very complex 24db electronic crossover that I have put in a lot of time and money into. It sounds great, but this little circuit probably can get you 90% of the way there with compromises.
In terms of the input transformer, you will have to ask Jack, it would seem the 10K and the 100R are the reflected impedance. I assume the 100R is a tap, not certain how it is calculated/implemented here.
I must not have been clear. I was thinking more about the design of an amp that would only go as low as 80 hz. Let me ask more specific questions.
Output transformer (SE)
Could the inductance requirements be reduced?
What core materials could be used that would work better than M6?
Could the gap be optimized for 80 hz
Coupling caps
Could these be reduced in value?
parafeed cap
could the value be reduced?
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Any other changes?
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Power supply?
ray
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