Guitars of Love
Waveforms of the preamp in action ...
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At right are screen grabs the of the new simpler GuitFET preamp captured on an GWInstek GDS1022 oscilloscope with a frequency close to an A440Hz sine wave. The signals greatly increase in complexity with complex harmonics. The top trace is the input signal; the bottom trace the preamp output. These were done with the volume out at maximum so there is a large overall gain. Note: Since doing these tests on my breadboard prototype I have limited the frequency response to be within 3dB from about 35Hz to 50KHz. This is pretty much the spec on a typical good sounding Hi Fi amp such as a NAD or Rega, and is more than adequate for it's purpose. Going up into RF frequencies is not desirable! Low drive with little change in the sound: |
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| Slight OD with rounding when the FETs kick in with rich even order harmonics: |
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| More signal combines the clipping of the buffer transistor driving the OD FET and the FET itself: |
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Winding up the drive resulting in a sharpened wave form, but still with slight rounding from the FETs: |
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Maximum drive with hi input giving sharp square clipping: |
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400 Hz square wave response with clean signal and tone controls at neutral position: |
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Frequency response measurements taken with clean signal and tone controls in the neutral position at 20Hz / 200Hz / 2KHz / 20KHz / 200KHz: |
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| kelvin@guitars-of-love.com |
