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Phonoclone 4.4s (and 4.5b)

Posted 16th February 2017 at 12:11 AM by rjm
Updated 16th May 2017 at 12:57 AM by rjm (added 4.5b BOM)

The Phonoclone 4 applies a major revision to the board layout, making it more logical with grouped, standardized I/O connections. The X-Reg has been replaced with the S-Reg shunt regulator circuit. Overall the BOM has been considerably simplified and the parts cost reduced.

Rev. 4.4s boards are back-compatible with earlier Phonoclone revisions, with the anachronistic 2.5"x3.5" mounting holes, so I can drop it into my existing chassis. 4.5b moves to 70x90mm mounting holes to be compatible with the Sapphire, VSPS200, and CrystalFET boards.


Build Notes

4.0b had some low level residual ripple on the output as a result of capacitive coupling or ground loop error. The boards were respun as 4.4s (special test run, limited, unsexy green color) which work as designed. The next wide release is 4.5b.

The BOM and board connectivity checks, no issues.

The Bourns trimmer, R21, comes from the factory set to the middle of the range so it can be used as-is and the S-Reg will work out to be almost perfectly balanced.

I reduced R17,18 to 6.8k (and R9,10 to match because it makes little difference). This lowers the V+, V- regulated output to about 8.5 V instead of about 12.5 V with 10k. I did this because I'm running 12 VAC secondaries on 100 V Japan line rather than 115 V AC, and my V++ is correspondingly low.

Included the 0.1 ceramic bypass caps, just because.

C3 is Multicap 3 uF. It doesn't need to be such a large value unless you are driving input impedances below 25 kohms. 1 uF is fine.


White dot of Q1 and Q3 incorrectly placed next to pin 3 instead of pin 1. BOM and board images edited to show the error and correct position.
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