Captain Aloia, regarding SRPP, said that there is an optimal load (in relation to the output impedance) which minimizes the distortion even if a little at the expense of the maximum output voltage excursion, which, sometimes, it might not even matter.
If I remember correctly, from some readings, this optimal load was equal to five times the circuit's own output impedance.
In addition to the source "Bart" ... it is something that we read very often around, this is the ideal impedance.
I don't know if he is the forerunner of this (applied) "theory".
Another example written by an environmental expert:
"The SRPP is often thought of as a circuit with a particularly low distortion, which is not entirely correct.
It is also said that the SRPP has the strange characteristic, compared to the normal gain stages, of having the distortion decreasing at the decrease of the impedance of the load, and this too is not entirely correct.
What occurs is that as the impedance of the load decreases, the distortion increases regularly, up to a certain impedance value. By further reducing the impedance of the load, the distortion instead begins a decrease and reaches a minimum, beyond which however there is a rather marked increase in the distortion.
This phenomenon has been (relatively) recently analyzed and exploited by Bartolomeo Aloia in his creations.
The knowledge of this phenomenon therefore allows to minimize the distortion of an SRPP stage simply by appropriately choosing the impedance of the load.
This becomes very interesting because the impedances we are talking about are generally quite low: for example, from the simulations I made it would appear that in a case very similar to that of "SIMPRE" (ecc88) the distortion grows inversely proportional to the load when this decreases above 50kohm, then it begins to decrease again up to a minimum placed around 15k ohm of load impedance and below 15kohm it begins to grow again very rapidly. In practice the distortion with an impedance of 50kohm is almost double that with a load of 15 kohm.
Aloia therefore in its creations adopts the technique of minimizing distortion precisely through the careful selection of the load. "
In my srpp that I have just built, I am undecided whether to put an input pot (100k) or a very low value output pot. I use a 6n6p srpp at 200vdc and 14mA.
Opinions?
Thanks 😀
If I remember correctly, from some readings, this optimal load was equal to five times the circuit's own output impedance.
In addition to the source "Bart" ... it is something that we read very often around, this is the ideal impedance.
I don't know if he is the forerunner of this (applied) "theory".
Another example written by an environmental expert:
"The SRPP is often thought of as a circuit with a particularly low distortion, which is not entirely correct.
It is also said that the SRPP has the strange characteristic, compared to the normal gain stages, of having the distortion decreasing at the decrease of the impedance of the load, and this too is not entirely correct.
What occurs is that as the impedance of the load decreases, the distortion increases regularly, up to a certain impedance value. By further reducing the impedance of the load, the distortion instead begins a decrease and reaches a minimum, beyond which however there is a rather marked increase in the distortion.
This phenomenon has been (relatively) recently analyzed and exploited by Bartolomeo Aloia in his creations.
The knowledge of this phenomenon therefore allows to minimize the distortion of an SRPP stage simply by appropriately choosing the impedance of the load.
This becomes very interesting because the impedances we are talking about are generally quite low: for example, from the simulations I made it would appear that in a case very similar to that of "SIMPRE" (ecc88) the distortion grows inversely proportional to the load when this decreases above 50kohm, then it begins to decrease again up to a minimum placed around 15k ohm of load impedance and below 15kohm it begins to grow again very rapidly. In practice the distortion with an impedance of 50kohm is almost double that with a load of 15 kohm.
Aloia therefore in its creations adopts the technique of minimizing distortion precisely through the careful selection of the load. "
In my srpp that I have just built, I am undecided whether to put an input pot (100k) or a very low value output pot. I use a 6n6p srpp at 200vdc and 14mA.
Opinions?
Thanks 😀
SRPP was often used in old valve TV's to drive a loudspeaker.
I have used them a few times as front ends for hybrid power amplifiers and they sound fine to me despite driving a high impedance.
I have used them a few times as front ends for hybrid power amplifiers and they sound fine to me despite driving a high impedance.
