Lurker/newb here, I just had an idea: a setup which would allow you to listen to the distortion characteristic of a particular transistor.
Recently I've been reading about basic source-follower setups (i.e. headphone buffers), and how you can use two out-of-phase followers to get rid of the output capacitor (directly couple to the speaker/headphone).
Of course, if you don't have balanced input, you can use the setup in "single-ended input mode", i.e. ground one of the inputs. One of your outputs carries the signal and the other is constant.
Well, taking this a step further, if you fed both followers the same in-phase input, your speaker/headphone sees the same signal on both ends, no current flows, and no sound is produced. You can adjust the input pot all you want, it won't make any difference.
But what if we adjusted the input pots unevenly? Both followers would produce an in-phase signal, but of different amplitudes, so the speaker/headphones would see a reduced volume output.
By carefully adjusting the pots, you could increase the output signal produced by each follower while maintaining a constant volume as seen by the speaker/headphone. In this way, you could "turn up the distortion" while keeping the output volume the same.
Using this technique, you could swap out several different transistors / fets and compare what their distortion characteristic sounds like. Or you could try different bias current settings and compare what the distortion sounds like.
Perhaps an old idea, but news to me!
I've never really had the opportunity to compare what different types of distortion sound like, so this idea is appealing.
Recently I've been reading about basic source-follower setups (i.e. headphone buffers), and how you can use two out-of-phase followers to get rid of the output capacitor (directly couple to the speaker/headphone).
Of course, if you don't have balanced input, you can use the setup in "single-ended input mode", i.e. ground one of the inputs. One of your outputs carries the signal and the other is constant.
Well, taking this a step further, if you fed both followers the same in-phase input, your speaker/headphone sees the same signal on both ends, no current flows, and no sound is produced. You can adjust the input pot all you want, it won't make any difference.
But what if we adjusted the input pots unevenly? Both followers would produce an in-phase signal, but of different amplitudes, so the speaker/headphones would see a reduced volume output.
By carefully adjusting the pots, you could increase the output signal produced by each follower while maintaining a constant volume as seen by the speaker/headphone. In this way, you could "turn up the distortion" while keeping the output volume the same.
Using this technique, you could swap out several different transistors / fets and compare what their distortion characteristic sounds like. Or you could try different bias current settings and compare what the distortion sounds like.
Perhaps an old idea, but news to me!
I've never really had the opportunity to compare what different types of distortion sound like, so this idea is appealing.You can take this a step further by using a high quality op amp
feed the direct signal to the non inverting op amp input and the output of the transistor gain stage to the inverting input by using attenuators you can null out any common mod signal and the listen to the transistor distortion
I did this some 40 years ago
it really works
Trev
feed the direct signal to the non inverting op amp input and the output of the transistor gain stage to the inverting input by using attenuators you can null out any common mod signal and the listen to the transistor distortion
I did this some 40 years ago
it really works
Trev
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