JLH "Ripple Eater"
Eric
As requested.Please note that the Current Limiter section should not be bypassed unless the input is from a LM78xx/LM79XX or LM317T/LM337T regulator , due to the very high inrush current on switch on. In that case, the inbuilt current limiting of the voltage regulators limits the surge due to trying to charge the equivalent of a .5 Farad capacitor. The present schematic is based around a relatively unknown design by the late John Linsley Hood, which was originally published in Electronics Today International (date unknown) I saved the pages from the original magazine, but there is no date printed. The current version has the 4 x 1,000uF capacitors replaced by 2 x 2,200uF 10V low ESR electrolytics. also attached is a photo of an earlier version. The PCB is approximately 3" x 3"
SandyK
Eric
As requested.Please note that the Current Limiter section should not be bypassed unless the input is from a LM78xx/LM79XX or LM317T/LM337T regulator , due to the very high inrush current on switch on. In that case, the inbuilt current limiting of the voltage regulators limits the surge due to trying to charge the equivalent of a .5 Farad capacitor. The present schematic is based around a relatively unknown design by the late John Linsley Hood, which was originally published in Electronics Today International (date unknown) I saved the pages from the original magazine, but there is no date printed. The current version has the 4 x 1,000uF capacitors replaced by 2 x 2,200uF 10V low ESR electrolytics. also attached is a photo of an earlier version. The PCB is approximately 3" x 3"
SandyK
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
JLH "Ripple Eater"
Nordic
If the Current Limiter feature is used, it gives a slow start of several seconds, depending on the Current Limiter's setting, as well as the actual load. When used for the front end of my Class A amplifier, it eliminates switch on thump.
Current limit = 0.65V/R12
SandyK
Nordic
If the Current Limiter feature is used, it gives a slow start of several seconds, depending on the Current Limiter's setting, as well as the actual load. When used for the front end of my Class A amplifier, it eliminates switch on thump.
Current limit = 0.65V/R12
SandyK
Cool, I have been hard at work designing a regulator all week, but the thing will be as hot as a class A amp.... Dissipating between 15 and 100W at the two extremes of its settings.
It is fine I guess for large high current drops, simming shows no problems doing up to 10A depending on the load and sows only a few mV of change to output even when output load shifs drasticaly....
I was dissapointed in how misleading the datasheet schematic was for a high current adjustable reg...there is a minimum load resistance needed when you set it for matching at the highest V output you fall out of regulation as you reduce the voltage... setting it to the lowest means, at high output that load resistor is dissipating twice as much as the minimum (cooking at about 2.1W).. When they say adjustable, they mean over a very small range ... say 12V (+ the 2.5-3.5V dropout), in practice... and unreliable due to high component temperatures....
I made my design to use multiple resistors in parallel (up to 10) so the max dissipation seen on any resistor should be about 200mW.
So it is very nice for a high powered bench supply (in excess of 100W) on a 35V supply. But it is too bulky (big heatsink) for adding to an amp... consider you want two rails possibly and you have twice the problem... I calculated the price diffirence between the components and heatsink and just getting the right transformer, the transformer was only about $6 more expensive, but that excludes rail capacitors I would then need.
Not even realy sure how efficient it is... shows it will burn about 120 odd W for putting out about 100W.
I hope the ripple eater can do the job on minimum rail capacitance...
It is fine I guess for large high current drops, simming shows no problems doing up to 10A depending on the load and sows only a few mV of change to output even when output load shifs drasticaly....
I was dissapointed in how misleading the datasheet schematic was for a high current adjustable reg...there is a minimum load resistance needed when you set it for matching at the highest V output you fall out of regulation as you reduce the voltage... setting it to the lowest means, at high output that load resistor is dissipating twice as much as the minimum (cooking at about 2.1W).. When they say adjustable, they mean over a very small range ... say 12V (+ the 2.5-3.5V dropout), in practice... and unreliable due to high component temperatures....
I made my design to use multiple resistors in parallel (up to 10) so the max dissipation seen on any resistor should be about 200mW.
So it is very nice for a high powered bench supply (in excess of 100W) on a 35V supply. But it is too bulky (big heatsink) for adding to an amp... consider you want two rails possibly and you have twice the problem... I calculated the price diffirence between the components and heatsink and just getting the right transformer, the transformer was only about $6 more expensive, but that excludes rail capacitors I would then need.
Not even realy sure how efficient it is... shows it will burn about 120 odd W for putting out about 100W.
I hope the ripple eater can do the job on minimum rail capacitance...
JLH "Ripple Eater"
Nordic
JLH's original published article only showed values for working up to 100mA. The version supplying my Class A preamp is set to a current limit of just over 500mA , to reduce turn on delay. I have a non current limited version used in conjunction with a dual regulated +-15V supply (LM317/LM337) supplying a complete Musical Fidelity X-DAC V3 , in place of the original 24V CT 500mA AC wallwart.
SandyK
Nordic
JLH's original published article only showed values for working up to 100mA. The version supplying my Class A preamp is set to a current limit of just over 500mA , to reduce turn on delay. I have a non current limited version used in conjunction with a dual regulated +-15V supply (LM317/LM337) supplying a complete Musical Fidelity X-DAC V3 , in place of the original 24V CT 500mA AC wallwart.
SandyK
Hi,
I was deadly serious.
The circuit shorts out the ripple to ground but leaves the DC unaltered.
You have already confirmed that the circuit still works with the CCS disabled. I was surprised at that. but if it works with the CCS disabled then why should it not work with the CCS set to 5A?
I was deadly serious.
The circuit shorts out the ripple to ground but leaves the DC unaltered.
You have already confirmed that the circuit still works with the CCS disabled. I was surprised at that. but if it works with the CCS disabled then why should it not work with the CCS set to 5A?
Andrew
The emitter resistor of the CL would need to be a fraction of an ohm, the CL transistor would need to be a higher current type also, to avoid excessive voltage drop. Q4 may not be too happy either, at least in the long term. However, I am only guessing, as I have already pushed the circuit way past JLH's original design limits, and never really contemplated pushing much harder.
Bear in mind also, that Q4 and Q5 in the original design were only BC636/BC637
SandyK
The emitter resistor of the CL would need to be a fraction of an ohm, the CL transistor would need to be a higher current type also, to avoid excessive voltage drop. Q4 may not be too happy either, at least in the long term. However, I am only guessing, as I have already pushed the circuit way past JLH's original design limits, and never really contemplated pushing much harder.
Bear in mind also, that Q4 and Q5 in the original design were only BC636/BC637
SandyK
I appreciate the suggestion colin... I started to concider a zener referenced cap multiplier... similar to what is in DX amps to regulate the power to the front.... but that would mean I need to make a new PCB...
But now that you mention it, I do have a 2x24 PCB-mount trafo somewhere.
Won't have time today as I need to go help some people setting up a stage and wireing for a heavy metal band day...
But now that you mention it, I do have a 2x24 PCB-mount trafo somewhere.
Won't have time today as I need to go help some people setting up a stage and wireing for a heavy metal band day...
I returned SandyK's ripple eater to Sandy and built my own yesterday. It is working.
Apparently the ripple eater is still subject to the capacitor sound. I initially used 2x2,200uF Rubycon ZL and the sound was no better than what it was, actually more "closed" possibly due to one pair of the ZL being new without much run-in.
I then replaced them with a pair of Panasonic FC 4,700uF. Initially the sound only equalled the regulator without the JLH. After about 2 hours run-in, the sound opened up more and was better than without the JLH.
There was some small improvement on the mid and high frequencies but definitely cleaner in the lower frequencies.
The difference was not as dramatic as last time when I plugged in Sandy's.
I wondered why? I used the same PCB layout as Sandy's. It has got to do with the capacitors. Sandy uses the Jaycar 2,200uF/10v capacitors. I guess they happen to compensate the short coming of my system.
Perhaps I should ditch all those low impedance capacitors!
I will wait until the capacitors are further run in before making any conclusions.
Apparently the ripple eater is still subject to the capacitor sound. I initially used 2x2,200uF Rubycon ZL and the sound was no better than what it was, actually more "closed" possibly due to one pair of the ZL being new without much run-in.
I then replaced them with a pair of Panasonic FC 4,700uF. Initially the sound only equalled the regulator without the JLH. After about 2 hours run-in, the sound opened up more and was better than without the JLH.
There was some small improvement on the mid and high frequencies but definitely cleaner in the lower frequencies.
The difference was not as dramatic as last time when I plugged in Sandy's.
I wondered why? I used the same PCB layout as Sandy's. It has got to do with the capacitors. Sandy uses the Jaycar 2,200uF/10v capacitors. I guess they happen to compensate the short coming of my system.
Perhaps I should ditch all those low impedance capacitors!
I will wait until the capacitors are further run in before making any conclusions.
JLH Ripple Eater
"Perhaps I should ditch all those low impedance capacitors!"
Bill
Definitely !
These types of "Audio Grade" capacitors all have an impedance decreasing towards 100KHZ. I have consistenly found that 2 x 2,200uF generic low ESR capacitors in parallel give the best results, as well as needing very little time to fully stabilise.
I found this combination also works best, even when supplying my complete Musical Fidelity X-DAC V3, which already uses onboard voltage regulators for each section. (also noticeably better than a 2 x 1,000uF and 1 x2,200uF low ESR combination)To be honest, I am not a real fan of the usually more expensive Audio Grade capacitors ,due to them often resulting in increased sibilance in many applications. I note that Silicon Chip magazine states that these types of capacitors are of no added benefit in a well designed amplifier.
Yes, I realise that there will be many people who will vehemently disagree with that statement.
BTW, all of the Audio Grade electrolytic capacitors need substantial run in time, as I mentioned earlier in the thread, sometimes in the 100s of hours, before they fully stabilise. Seriously ! Another local DiyAudio member recently recapped his old Krell preamplifier, with from memory, Elna capacitors, and it took several months to reach optimum performance.
SandyK
"Perhaps I should ditch all those low impedance capacitors!"
Bill
Definitely !
These types of "Audio Grade" capacitors all have an impedance decreasing towards 100KHZ. I have consistenly found that 2 x 2,200uF generic low ESR capacitors in parallel give the best results, as well as needing very little time to fully stabilise.
I found this combination also works best, even when supplying my complete Musical Fidelity X-DAC V3, which already uses onboard voltage regulators for each section. (also noticeably better than a 2 x 1,000uF and 1 x2,200uF low ESR combination)To be honest, I am not a real fan of the usually more expensive Audio Grade capacitors ,due to them often resulting in increased sibilance in many applications. I note that Silicon Chip magazine states that these types of capacitors are of no added benefit in a well designed amplifier.
Yes, I realise that there will be many people who will vehemently disagree with that statement.
BTW, all of the Audio Grade electrolytic capacitors need substantial run in time, as I mentioned earlier in the thread, sometimes in the 100s of hours, before they fully stabilise. Seriously ! Another local DiyAudio member recently recapped his old Krell preamplifier, with from memory, Elna capacitors, and it took several months to reach optimum performance.
SandyK
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