After updating the uProcessor board in the Beomaster 8000 that I am working on right now, it was decided to also update the opamps while the unit was in service position. We recently noticed that the opamps in the signal path of the Beomaster 8000 can degrade resulting in increased distortions (THD), i.e. it is a good idea to also replace the opamps when the boards are out for restoration. Here we go:
This shows the control panel PCB before the upgrade:
Most of the 8-pin ICs on this board are signal path opamps. This shows the board with new socketed LF535 opamps installed:
On to the preamp/input board. I forgot to take a picture of the original condition of the board. Here are a couple shots of the board after replacing the opamps with socketed LF353 units (except the phono input, which was replaced with a low noise LM833 type):
A detail photo of the phono pre-amp section:
After implanting the boards I characterized the performance of the unit with my QA400 audio analyzer. The bandwidth curve yielded the spec -1 dBV drop between 100 and 20,000Hz, and the total harmonic distortion (THD) values at volume 5.0 (just below clipping) were 0.008% on both channels, which is consistent with other Beomaster 8000s we measured. See here for a detailed discussion of such measurements. So far so good...the unit went on into our living room to see if the performance of this Beomaster 8000 is consistent in day-to-day operation.
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