Chris and others have put great effort into improving amplifiers based on the LM1875 chip. The results achieved are very promising but evidently limited by the moderate current capability of the LM1875 chip.
In order to overcome the limited current handling of the LM1875, it has been discussed to design a version with more LM1875 operating in parallel such that the current handling is increased. A parallel version may allow for a BTL configured version based on LM1875s with an output power well exceeding 100W. As a last feature, it has been envisaged to use an OP-AMP controlling loop for a composite amplifier design. Composite amplifier designs can achieve very low THD values.
For a start it is foreseen to progress as follows:
a) Discussion of principles and design details, initially of a parallel LM1875 amplifier.
b) Establishment of a design for a parallel LM1875 amplifier.
c) Construction and test of such a parallel LM1875 amplifier.
d) Design of an OP-AMP control loop for the parallel LM1875 amplifier in a composite amplifier configuration.
e) Construction, test and trimming of the composite amplifier.
f) Construction of a similar composite amplifier for a BTL configuration.
g) Test of the composite BTL configured LM1875 amplifier.
h) Eventual PCB layout for those interested.
Anybody is evidently invited to take part, actively or more passively, in this project. It is obviously an objective that the project will end up in a high performance amplifier. But beside that aim, it is hoped that the process will show to less experienced diy’ers what considerations and methods are part of an amplifier design. It should be kept at a level were most members can follow the discussions.

In order to overcome the limited current handling of the LM1875, it has been discussed to design a version with more LM1875 operating in parallel such that the current handling is increased. A parallel version may allow for a BTL configured version based on LM1875s with an output power well exceeding 100W. As a last feature, it has been envisaged to use an OP-AMP controlling loop for a composite amplifier design. Composite amplifier designs can achieve very low THD values.
For a start it is foreseen to progress as follows:
a) Discussion of principles and design details, initially of a parallel LM1875 amplifier.
b) Establishment of a design for a parallel LM1875 amplifier.
c) Construction and test of such a parallel LM1875 amplifier.
d) Design of an OP-AMP control loop for the parallel LM1875 amplifier in a composite amplifier configuration.
e) Construction, test and trimming of the composite amplifier.
f) Construction of a similar composite amplifier for a BTL configuration.
g) Test of the composite BTL configured LM1875 amplifier.
h) Eventual PCB layout for those interested.
Anybody is evidently invited to take part, actively or more passively, in this project. It is obviously an objective that the project will end up in a high performance amplifier. But beside that aim, it is hoped that the process will show to less experienced diy’ers what considerations and methods are part of an amplifier design. It should be kept at a level were most members can follow the discussions.

Last edited: