How clean could be a power supply with ICL7660A?
I intend to use it for a RIAA preamp which runs on batteries,
The ammount of noise is also of interest for me, thanks in advance for the one who measured the s/n ratio and will share for us!
I want to make it for +/-8v starting from 9v.
I intend to use it for a RIAA preamp which runs on batteries,
The ammount of noise is also of interest for me, thanks in advance for the one who measured the s/n ratio and will share for us!
I want to make it for +/-8v starting from 9v.
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I have seen ICL7660 used in several external DACs that are claimed to be "audiophile" so the practical results are better than what could be feared.
The ripple depends on the size of the storage capacitor (output) compared to the "flying" capacitor. I would at least use a solid sized storage capacitor (1000uF / low ESR) and their recommended 10uF "flying" capacitor.
You do not have decent voltage margins for including regulators to stabilize the voltages which would else have been preferable. The battery use has to foresee some lowering of the voltage.
With up to 10mA consumption of your RIAA preamp, you should be OK.
The ripple depends on the size of the storage capacitor (output) compared to the "flying" capacitor. I would at least use a solid sized storage capacitor (1000uF / low ESR) and their recommended 10uF "flying" capacitor.
You do not have decent voltage margins for including regulators to stabilize the voltages which would else have been preferable. The battery use has to foresee some lowering of the voltage.
With up to 10mA consumption of your RIAA preamp, you should be OK.
Just use two batteries.
A phono preamp is no place for a "buzzer". True, the '7660 buzzes above the audio band, but just barely, and with very large voltage swings and current spikes.
Two 9V batteries are VERY clean and will run a preamp a very long time. Assuming:
$2, 250mAH, 10mA, 2 batteries == $4 runs 25 hours at $0.16 per hour.
Going to the movies, the tavern, a concert, etc is likely to cost $5-$50 per hour. Buying and reading books (does anybody do that?) costs over $1/hour, or $0.50/hr for dusty ragged books from yard sales. $0.16/hour is very cheap entertainment.
Your phono needle also runs down. Say cartridges run $25 to $2,500 and you get a $250 model. Say it lasts 1,000 hours. This is $0.25/hour. You do not think of this the same as battery replacement, but it is. Unless you buy at the low end of the market, the needle costs more than the batteries.
FWIW: the 9V battery is the worst deal of all the common batts. AA size tends to be 4X the energy per buck. A dozen AA cells, non-fancy, name-brand, gives +/-8V, costs about $6, and will run a 10mA preamp about 100 hours, $0.06/hour.
The hard part is remembering to shut-down the battery when done. Your batt+7660 plan has the same issue. The simple/sure plan may be a small relay powered from the main system to break the battery leads when the main amp is turned off.
Yes, you are right, but I still want to give a try to the 7660A solution...I have a bunch of AA Ni-Mh rechargeable batteries NOS, of small capacity and intended to use them here.
The money in this case are not an issue, I have enough batteries to put them in both rails, but I assumed that the voltage could slightly become different, so the idea of having a regulated "supply doubler" sounds interesting. And it could be a waste of batteries if this works. If it's not proper, I will find an use for it for sure...
I took this as a technical possibility when I found one of this circuit in a portable osciloscope, and there was using for powering the op-amps, also in the input stages, so I think there also the power must be well regulated and clean.
***
For the others interesting in this experiment: keep in mind that the 7660 version without the A suffix dies above 10.5V, only the 7660A supports a maximum 13V supply.
EDIT: Also I want to say I use this preamp for digitising my old records and I still use desktop computer. There is a serious issue with the ground loop, even with the computer case grounded properly, so that's why I prefer to run on battery power.
The money in this case are not an issue, I have enough batteries to put them in both rails, but I assumed that the voltage could slightly become different, so the idea of having a regulated "supply doubler" sounds interesting. And it could be a waste of batteries if this works. If it's not proper, I will find an use for it for sure...
I took this as a technical possibility when I found one of this circuit in a portable osciloscope, and there was using for powering the op-amps, also in the input stages, so I think there also the power must be well regulated and clean.
***
For the others interesting in this experiment: keep in mind that the 7660 version without the A suffix dies above 10.5V, only the 7660A supports a maximum 13V supply.
EDIT: Also I want to say I use this preamp for digitising my old records and I still use desktop computer. There is a serious issue with the ground loop, even with the computer case grounded properly, so that's why I prefer to run on battery power.
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Batteries are a surefire solution, if you don't want to invest in a full galvanic/transformer signal isolation.
But I see a certain flaw in your reasoning to use a chargepump in a "recording" preamp: the more fool-proof and by all means eaiser way to handle the voltage (im)balance would be to use two or more batteries in series, and use a rail-splitter if you want symmetric +/0/- supply. Could be easily adorned with capacitance multipliers on each "rail" for some extra-clean-polish ...
ymmv
But I see a certain flaw in your reasoning to use a chargepump in a "recording" preamp: the more fool-proof and by all means eaiser way to handle the voltage (im)balance would be to use two or more batteries in series, and use a rail-splitter if you want symmetric +/0/- supply. Could be easily adorned with capacitance multipliers on each "rail" for some extra-clean-polish ...
ymmv
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