So you think batteries are clean do you?
Been meaning to do this for a while, and the oppportunity arose recently whilst doing some other stuff.
The plot below is the noise of a sealed lead-acid gel-cell (Yuasa NP series) under no-load and resistive load conditions. For comparison there's a discrete regulated supply. The resistive load represent about a 35mA current drain - it gets worse with increasing load current. Even more inportant the noise doesn't stop when a heavy load is removed, it takes seconds to settle, presumably due to the chemical reaction going on inside the cell.
Bear in mind these are resistive load conditions i.e. easy, when placed under a dynamic load (plots to come at a later date) things look much worse.
Particularly bad is that the voltage output bears no relation to A.C. load, and produces other noise products that are not remotely related to the load it sees.
Adding a 22,000u cap (not shown) gets the noise above the audio band down to the regulator levels.
As you can see the battery is only quieter under no-load conditions - not a great deal of use!
I'll do plots to compare to 3-term reg's later, which at low currents look cleaner, but noisier, the noise is inocuous though as they display far better linearity.
Been meaning to do this for a while, and the oppportunity arose recently whilst doing some other stuff.
The plot below is the noise of a sealed lead-acid gel-cell (Yuasa NP series) under no-load and resistive load conditions. For comparison there's a discrete regulated supply. The resistive load represent about a 35mA current drain - it gets worse with increasing load current. Even more inportant the noise doesn't stop when a heavy load is removed, it takes seconds to settle, presumably due to the chemical reaction going on inside the cell.
Bear in mind these are resistive load conditions i.e. easy, when placed under a dynamic load (plots to come at a later date) things look much worse.
Particularly bad is that the voltage output bears no relation to A.C. load, and produces other noise products that are not remotely related to the load it sees.
Adding a 22,000u cap (not shown) gets the noise above the audio band down to the regulator levels.
As you can see the battery is only quieter under no-load conditions - not a great deal of use!
I'll do plots to compare to 3-term reg's later, which at low currents look cleaner, but noisier, the noise is inocuous though as they display far better linearity.
Attachments
Battery charging
Hi,
I am in the process of building a 36v (3x12V SLA) power supply bypassed by 68Kuf to 136Kuf of capacitance per channel.
Going to make a float / trickle charger at 40v that I just plug in and charge... the amp will then be running of the charger and batteries at 40v not 36v... which is NOT a problem.
Can I make a simple circuit with a tranny and bridge rectifier?? Or do I need a couple of voltage regulators in there?
If so, what voltage should my tranny be? What current rating should the recitifier be?
Thanks!!!
p.s. how long should I run my amp at 1A from 7Ah batteries before I recharge them?
Hi,
I am in the process of building a 36v (3x12V SLA) power supply bypassed by 68Kuf to 136Kuf of capacitance per channel.
Going to make a float / trickle charger at 40v that I just plug in and charge... the amp will then be running of the charger and batteries at 40v not 36v... which is NOT a problem.
Can I make a simple circuit with a tranny and bridge rectifier?? Or do I need a couple of voltage regulators in there?
If so, what voltage should my tranny be? What current rating should the recitifier be?
Thanks!!!
p.s. how long should I run my amp at 1A from 7Ah batteries before I recharge them?
Re: Battery charging
>I am in the process of building a 36v (3x12V SLA) power supply bypassed by 68Kuf to 136Kuf of capacitance per channel.
Well get ready for some major arcing & sparking when you connect the batteries to caps of that size...
my caps are 10,000uf and that is quite wild enough. unless you use a soft start resistor you might end up arc welding the wires to the battery or cap terminals ! The initial current surge could well be 100 amps
If you are not in balanced working how are you planning to organise your speaker return if you are using three batteries ?
For non balanced working 4 batteries would be simpler as it gives you a zero volts centre point. In this case I suspect that 2x good quality 1000uF caps will be more ideal than the bigger ones. Otherwise you will need to organise a low impedance earth return in which case the big caps may be necessary.
>Going to make a float / trickle charger at 40v that I just plug in and charge... the amp will then be running of the charger and batteries at 40v not 36v... which is NOT a problem.
ideally each 12V cell should float at about 13.5 or a little more so 40 is about right. obviously in theory the amp should sound better when the battery is off charge but to be honest I can hardly tell the difference.
>Can I make a simple circuit with a tranny and bridge rectifier?? Or do I need a couple of voltage regulators in there?
I am quite happy with tranny & bridge, seems to work well
>If so, what voltage should my tranny be?
9 volts AC per 12V battery. ( This multipies up by 1.414 to DC and another 10% for typical tranny regulation minus diode drops = about 13.5V )
>What current rating should the recitifier be?
15 amps should be OK
>p.s. how long should I run my amp at 1A from 7Ah batteries before I recharge them
Well 7 hours I guess... ...but for best battery life charge them all the time you are not listening.
hope some of this is useful
mike
>I am in the process of building a 36v (3x12V SLA) power supply bypassed by 68Kuf to 136Kuf of capacitance per channel.
Well get ready for some major arcing & sparking when you connect the batteries to caps of that size...
my caps are 10,000uf and that is quite wild enough. unless you use a soft start resistor you might end up arc welding the wires to the battery or cap terminals ! The initial current surge could well be 100 amps
If you are not in balanced working how are you planning to organise your speaker return if you are using three batteries ?
For non balanced working 4 batteries would be simpler as it gives you a zero volts centre point. In this case I suspect that 2x good quality 1000uF caps will be more ideal than the bigger ones. Otherwise you will need to organise a low impedance earth return in which case the big caps may be necessary.
>Going to make a float / trickle charger at 40v that I just plug in and charge... the amp will then be running of the charger and batteries at 40v not 36v... which is NOT a problem.
ideally each 12V cell should float at about 13.5 or a little more so 40 is about right. obviously in theory the amp should sound better when the battery is off charge but to be honest I can hardly tell the difference.
>Can I make a simple circuit with a tranny and bridge rectifier?? Or do I need a couple of voltage regulators in there?
I am quite happy with tranny & bridge, seems to work well
>If so, what voltage should my tranny be?
9 volts AC per 12V battery. ( This multipies up by 1.414 to DC and another 10% for typical tranny regulation minus diode drops = about 13.5V )
>What current rating should the recitifier be?
15 amps should be OK
>p.s. how long should I run my amp at 1A from 7Ah batteries before I recharge them
Well 7 hours I guess...
...but for best battery life charge them all the time you are not listening.hope some of this is useful
mike
Re: So you think batteries are clean do you?
ALW,
the plots don't look right... how come the 50Hz spikes on the battery plots are higher than the (regulated) AC supply? Are you sure the BUT (battery under test ) is not still connected to it's AC charger and that you were measuring the noise of the charger?
ALW,
the plots don't look right... how come the 50Hz spikes on the battery plots are higher than the (regulated) AC supply? Are you sure the BUT (battery under test
) is not still connected to it's AC charger and that you were measuring the noise of the charger?Re: Re: So you think batteries are clean do you?
In any case a battery won't produce a 50Hz hum...(nor all those harmonics)Alex S said:ALW,
the plots don't look right... how come the 50Hz spikes on the battery plots are higher than the (regulated) AC supply? Are you sure the BUT (battery under test
batt psu for my phono stage
Hi, i was wondering if anyone can help me. I want to build an 18v batt psu for my graham slee phonostage but don't know where to start. After reading a few posts i'm thinking 2 x 12v SLAs with a voltage regulator and some smoothing caps. Put then i'm stuck, what order what values, what else? all help would be greatly appreciated.
Cheers
carlos671
Hi, i was wondering if anyone can help me. I want to build an 18v batt psu for my graham slee phonostage but don't know where to start. After reading a few posts i'm thinking 2 x 12v SLAs with a voltage regulator and some smoothing caps. Put then i'm stuck, what order what values, what else? all help would be greatly appreciated.
Cheers
carlos671
Single rail = two wires from the PS, + and - but this requires a big capacitors in series with the speaker, not so good.
Duoble rial = three wires from the PS, +, 0 and - The normal thing.
I really recommend that you take a good look in the datasheet for the LM3886 and also check the application note AN-1192 because there you have all basic info about "Gainclones".
Duoble rial = three wires from the PS, +, 0 and - The normal thing.
I really recommend that you take a good look in the datasheet for the LM3886 and also check the application note AN-1192 because there you have all basic info about "Gainclones".
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