|22nd May 2010, 06:40 AM||#1|
Join Date: Oct 2002
John Linsley Hood Ripple Eater
This is a GB for the JLH Ripple Eater. It's a small run of 200 boards and is non-commercial. All profits will be going to Cancer Research UK, and I will also make a small donation to this forum.
As this GB spans a couple of forums, I have put all details here:
JLH Ripple Eater
If you'd like to register interest, please use the linked email address on the site, and you will get a holding reply. I will update the interest totals (currently 88 boards) on a regular basis.
Cost will be 3GBP per board, plus packing + postage to wherever on the planet you are - at cost.
Thanks for looking, and hopefully for your support!
JLH Ripple Eater
This will be a high-quality, professionally produced, double-sided PCB measuring 103mm x 31mm (4.06 x 1.22 ins approx). It may be used to smooth positive or negative power supplies in high-quality audio equipment. My notes below are largely based on JLH’s 1994 article.
History behind JLH Ripple Eater – original article.
The original circuit was designed by John Linsley Hood MIEE (February 9, 1925 to March 11, 2004) and published in Electronics Today International in April 1994. Further development of the circuit and layout has taken place over recent years by members of Rock Grotto forums - Rock Grotto - where the circuit is used to clean up power supplies on DIY headphone amplifiers and DACs.
What is it?
The JLH Power Supply Ripple Eater is an add-on circuit that sits between a power supply and end user. The Ripple Eater measurably reduces power supply output noise and ripple. JLH demonstrated a reduction in noise and ripple on his own bench supply from a figure, measured over the range of 20Hz to 20KHz, of 300uV to 4uV. When he connected a good quality 470uF electrolytic capacitor across the same bench power supply, there was no measurable improvement in ripple. In a similar experiment, the output noise from a selected 7815 IC voltage regulator was reduced from 60uV, itself better than the maker’s specification, to 3.5uV, when measured over the same bandwidth.
Why would you need one?
Need a quieter power supply? Of course you do!! Although JLH was reluctant to claim that this add-on circuit would lead to an improvement in the sound of audio equipment operated from simple IC stabilised power supplies, because he could not know what other people would hear, he was satisfied that, according to his test instruments, it did a useful job. We think JLH was being modest. Many JLH Ripple Eater users report audible improvements when using this circuit in their power supply chain.
How does it work?
The circuit consists of two parts: a ‘ripple detector’ arrangement based on a long-tailed pair, and a constant current source. Any ripple voltage present across the supply line can modulate this current. The aim being that if the output voltage were to momentarily increase or decrease, the current drawn would automatically increase or decrease to oppose these output voltage fluctuations. The impedance of the circuit depends on the size of the capacitors used – particularly that of C4, which can be large since it only needs to be 1V working. With the values chosen in this iteration, the circuit generates the electronic equivalent of about half a Farad or more.
It’s also been observed that “In essence it is an AC feedback loop”.
Why the new edition?
We were considering a new iteration of this design. A double-sided version that was slightly more compact than the original. This would also be a single board that could be stacked for a smaller in-chassis footprint.
Board design is 99% finalised, but expect: Double-sided, through-hole plated, coloured solder mask, gold flashed pads, 1.6-2mm FR4 board material, electrically tested etc.
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