An easy implementation is having a speaker playing back what is being recorded while recording. One must be extremely careful with the ugly sound that can destroy speakers and hearing if the system goes into self oscillation. Gain must be increased very gently. And a limiter somewhere in the chain is very useful.
(In fact a tube with a high grid leak has automatic gain control.
It can be observed on a Neumann U47. (If the capsule is removed firstly one can observe there is very low thermal noise, although one because the grid leak resistor is many megohms). If we connect a signal generator and start increasing the level after some point the level on the output of the VF14 amplifier is not further increased, but the shape of the output is still sinewave. If we reduce abruptly the input signal, the output of the signal starts increasing at a time constant. This limiting action apparently happens when the grid is getting towards being positive, it attracts electrons. It therefore becomes negative. Repels electrons decreasing anode current. So transconductance decreases and with it voltage to current gain.)
With the method of the first paragraph one can get an echo room, reverberation chamber sound.
Other example is the guitar string close to the amplifier speaker effect.
Other example, a Siemens Tekefunken V72, uses positive feedback from one cathode to the other.
But how would regeneration sound on a Pleiades V6 preamplifier?
It can be implemented easily ny taking a single wire, pass a few turns through the toroidal input transformer and and continue to wind the same wire a few turns on the output transformer at the core the correct direction and then joining the two ends together or through a variable resistor. The resistor with vary the cutoff frequency of the positive feedback.
An easier method may be by a resistor from the secondary of the output transformer to the primary of the input transformer.
Or arranging the input transformer to be a hybrid transformer.
If not using a hybrid transformer it would be funny but at oscillation the sound will come out of the microphone.
A hybrid transformer will make possible the addition of the two signals, mic and positive feedback without getting the feedback signal back to the mic.
On second thoughts the membrane of the microphone be aided in movement by the preamplifier to amplify the signal to be amplified sounds nice, one has to be careful.
Regeneration increases selectivity, reduces bandwidth in rf circuits. So distant stations can be heared.
Would a similar sensitivity happen at audio applications?
Bandwidth restriction is a good thing as it makes the frequency responce from vocal chords of singer to the brain of the listener flat, (see next post).
(In fact a tube with a high grid leak has automatic gain control.
It can be observed on a Neumann U47. (If the capsule is removed firstly one can observe there is very low thermal noise, although one because the grid leak resistor is many megohms). If we connect a signal generator and start increasing the level after some point the level on the output of the VF14 amplifier is not further increased, but the shape of the output is still sinewave. If we reduce abruptly the input signal, the output of the signal starts increasing at a time constant. This limiting action apparently happens when the grid is getting towards being positive, it attracts electrons. It therefore becomes negative. Repels electrons decreasing anode current. So transconductance decreases and with it voltage to current gain.)
With the method of the first paragraph one can get an echo room, reverberation chamber sound.
Other example is the guitar string close to the amplifier speaker effect.
Other example, a Siemens Tekefunken V72, uses positive feedback from one cathode to the other.
But how would regeneration sound on a Pleiades V6 preamplifier?
It can be implemented easily ny taking a single wire, pass a few turns through the toroidal input transformer and and continue to wind the same wire a few turns on the output transformer at the core the correct direction and then joining the two ends together or through a variable resistor. The resistor with vary the cutoff frequency of the positive feedback.
An easier method may be by a resistor from the secondary of the output transformer to the primary of the input transformer.
Or arranging the input transformer to be a hybrid transformer.
If not using a hybrid transformer it would be funny but at oscillation the sound will come out of the microphone.
A hybrid transformer will make possible the addition of the two signals, mic and positive feedback without getting the feedback signal back to the mic.
On second thoughts the membrane of the microphone be aided in movement by the preamplifier to amplify the signal to be amplified sounds nice, one has to be careful.
Regeneration increases selectivity, reduces bandwidth in rf circuits. So distant stations can be heared.
Would a similar sensitivity happen at audio applications?
Bandwidth restriction is a good thing as it makes the frequency responce from vocal chords of singer to the brain of the listener flat, (see next post).
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