audio amp and power supply filter capacitors
ad...@my-dejanews.com
system. The amp is kinda cheap and I think the transformer dosen't supply
enough power for the output stage. The Filter caps in the power supply are
10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
would help with the sound quality, and decrease the strain on the
transformer. If I remember right caps are like batteries: two 10,000 uf
50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
in parallel will yield a 10,000 uf 100V cap. Is this right? Aaron Doss
Computer Programmer/Musician
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Tom MacIntyre
If I remember right caps are like batteries: two 10,000 uf
>50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
>in parallel will yield a 10,000 uf 100V cap. Is this right?
No...the value of caps in parallel add while their combined voltage
rating is equal to the lesser/least of the individual caps...the
voltage ratings add for caps in series, while the values combine like
parallel resistors, yeilding a lower overall value...If I'm not
mistaken, series caps should each have a resistor across it to assist
in proportioning the voltage drops across each one. You won't need to
worry about that if you are trying to increase your capacitance,
however. Good luck.
Tom
Aaron Doss
>Computer Programmer/Musician
da...@ensigma.com
ad...@my-dejanews.com wrote:
> I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
> system. The amp is kinda cheap and I think the transformer dosen't supply
> enough power for the output stage. The Filter caps in the power supply are
> 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
> would help with the sound quality, and decrease the strain on the
> transformer.
transformer is getting hot then you need a bigger transformer, more capacitors
won't help on their own. You probably need at least a 1500VA transformer
which wont be very cheap and quite large (go for a toroidial).
A 1000W is a lot for one sub-woofer, what's it rated at?
Is the amp actually 1000Wrms or 1000W peak all channels added up + tax
and service charge etc. = 10Wrms?
> If I remember right caps are like batteries: two 10,000 uf
> 50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
> in parallel will yield a 10,000 uf 100V cap. Is this right?
No.
Two 10,000uF 50v in series = 5,000uF 100v (best to put parellel resistors in
there as well).
Two 10,000uf 50v im parallel = 20,000uF 50v.
Bill Sloman
ad...@my-dejanews.com wrote:
> I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
> system. The amp is kinda cheap and I think the transformer dosen't supply
> enough power for the output stage. The Filter caps in the power supply are
> 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
> would help with the sound quality, and decrease the strain on the
> transformer.
>
> If I remember right caps are like batteries: two 10,000 uf
> 50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
> in parallel will yield a 10,000 uf 100V cap. Is this right?
This should have gone to sci.electronics.basics.
The answer to your first question is slightly paradoxical, since adding
extra reservoir capacitance may make your amplifier sound better,
because the supply voltage will sink less rapidly between mains peaks.
If your amplifier isn't clipping (and I imagine you would notice that),
reducing the ripple on the power supply helps by reducing the 100/120Hz
low level modulation this can put on the output.
Adding the extra capacitance will not decrease the stain on the
transformer - if anything it will increase it, because the bulk of
the current flows when the diodes start recharging the capacitors
as the main voltage approaches its peak, and more capacitance
means a higher peak current, and more dissipation in the transformer.
The answer to your second question is - "Wrong - capacitors are
rather different from batteries".
Capacitors in parallel aren't too different - two 10,000uF 50V
capacitors in parallel are equivalent to one 20,000uF 50V part.
Capacitors in series give less capacitance - two 10,000uF 50V
parts are equivalent to a 5,000uF 100V part, as you will
understand if you think about the charges flowing into each
capacitor as it sees half of the voltage swing across both
capacitors.
With real electrolytic capacitors, you don't actually get a 100V
working voltage out of two 50V parts in series, because the
large tolerances on the capacitance - +/-20% is typical and
-20%, +80% is not unknown - can give very unequal voltage
division across the two parts. A worst case +/-20% pair
would divide 100V as 40V and 60V, so you would
be wise to limit two such 50V parts in series at 83V
rather than 100V.
Bill Sloman, Nijmegen
ad...@ior.com
da...@ensigma.com wrote:
> In article <6qnj4h$gff$1...@nnrp1.dejanews.com>,
> ad...@my-dejanews.com wrote:
> > I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
> > system. The amp is kinda cheap and I think the transformer dosen't supply
> > enough power for the output stage. The Filter caps in the power supply are
> > 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
> > would help with the sound quality, and decrease the strain on the
> > transformer.
> transformer is getting hot then you need a bigger transformer, more capacitors
> won't help on their own. You probably need at least a 1500VA transformer
> which wont be very cheap and quite large (go for a toroidial).
> A 1000W is a lot for one sub-woofer, what's it rated at?
> Is the amp actually 1000Wrms or 1000W peak all channels added up + tax
> and service charge etc. = 10Wrms?
I use the amp in bridge mode into an 8 ohm 18" Eminence subwoofer, It
actually puts out 1k watts RMS, though I am not sure how long it will do it.
The transformer is quite big allready, though I dont know its spec's, It's
not a toroid though. As for the sub, it is rated at 800 w rms 1000 peak,
98db1watt/1meter, it has a huge magnet structure and huge vented voice coil.
It just seems kinda funny to put 10,000uF filter caps on the power supply for
an amp that big.
I will probably replace the transformer if it gives me more problems, where
can I get a 1kVA toroidal transformer? The largest that I have seen are
330VA toroid for $70.
Kendall Castor-Perry
<slo...@sci.kun.nl> writes
>
>
>ad...@my-dejanews.com wrote:
>
>> I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
>> system. The amp is kinda cheap and I think the transformer dosen't supply
>> enough power for the output stage. The Filter caps in the power supply are
>> 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
>> would help with the sound quality, and decrease the strain on the
>> transformer.
>>
>
>The answer to your first question is slightly paradoxical, since adding
>extra reservoir capacitance may make your amplifier sound better,
>because the supply voltage will sink less rapidly between mains peaks.
>
>If your amplifier isn't clipping (and I imagine you would notice that),
>reducing the ripple on the power supply helps by reducing the 100/120Hz
>low level modulation this can put on the output.
>
>Adding the extra capacitance will not decrease the stain on the
>transformer - if anything it will increase it, because the bulk of
>the current flows when the diodes start recharging the capacitors
>as the main voltage approaches its peak, and more capacitance
>means a higher peak current, and more dissipation in the transformer.
And therein lies one reason why increasing the capacitance value might
make the amplifier sound *worse* - if it is bad to start with! I've
seen significant amounts of the charging spikes of the storage caps get
coupled onto the output of an amplifier, and these can be clearly
audible under some conditions even to leaden ears like ours (-8
I'm probably more sympathetic than most (engineers...) in this group to
the idea that you *can* get subtle sound quality effects from a lot of
amplifier design details, but these are generally to do with reproducing
intricate and meaningful broad-band whole music signals. In my limited
experience the actual quality of a subwoofer amplifier is relatively
unimportant - with perhaps freedom from supply-related interference once
of the most important issues.
At this power level for subwoofer work most serious amps use switching
supplies anyway, pretty much as good as regulating the supplies and a
Good Thing for reducing low frequency modulation effects.
>
[snip rest]
Kendall Castor-Perry
"What problem could there be so hard as not to dissolve
in a sufficiently strong solution of nonsense?" - Stove
For email, use my *real* email address:
kendallcp at compuserve dot com
John Woodgate
>In article <6qp7pr$ngu$1...@nnrp1.dejanews.com>,
> da...@ensigma.com wrote:
>> In article <6qnj4h$gff$1...@nnrp1.dejanews.com>,
>> > I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
>> > system. The amp is kinda cheap and I think the transformer dosen't supply
>> > enough power for the output stage. The Filter caps in the power supply are
>> > 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
>> > would help with the sound quality, and decrease the strain on the
>> > transformer.
>> transformer is getting hot then you need a bigger transformer, more capacitors
>> won't help on their own. You probably need at least a 1500VA transformer
>> which wont be very cheap and quite large (go for a toroidial).
>> A 1000W is a lot for one sub-woofer, what's it rated at?
>> Is the amp actually 1000Wrms or 1000W peak all channels added up + tax
>> and service charge etc. = 10Wrms?
>> [some deleted]
>
>I use the amp in bridge mode into an 8 ohm 18" Eminence subwoofer, It
>actually puts out 1k watts RMS, though I am not sure how long it will do it.
>The transformer is quite big allready, though I dont know its spec's, It's
>not a toroid though. As for the sub, it is rated at 800 w rms 1000 peak,
>98db1watt/1meter, it has a huge magnet structure and huge vented voice coil.
>It just seems kinda funny to put 10,000uF filter caps on the power supply for
>an amp that big.
>
>I will probably replace the transformer if it gives me more problems, where
>can I get a 1kVA toroidal transformer? The largest that I have seen are
>330VA toroid for $70.
>
> Aaron Doss Computer Programmer/Musician
>
>
>
>-----== Posted via Deja News, The Leader in Internet Discussion ==-----
>http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
--
Regards, John Woodgate, Phone +44 (0)1268 747839 Fax +44 (0)1268 777124.
OOO - Own Opinions Only. You can fool all of the people some of the time, but
you can't please some of the people any of the time.
John Woodgate
>actually puts out 1k watts RMS, though I am not sure how long it will do it.
>The transformer is quite big allready, though I dont know its spec's, It's
>not a toroid though. As for the sub, it is rated at 800 w rms 1000 peak,
>98db1watt/1meter, it has a huge magnet structure and huge vented voice coil.
>It just seems kinda funny to put 10,000uF filter caps on the power supply for
>an amp that big.
>
>I will probably replace the transformer if it gives me more problems, where
>can I get a 1kVA toroidal transformer? The largest that I have seen are
>330VA toroid for $70.
You should leave things alone. With respect, you clearly do not have
enough technical insight to contemplate redesigning an amplifier power
supply. You will probably wreck it, and, considering the amount of
stored energy involved (even more than on a bit of Greek magnetic tape),
you might wreck yourself or someone else as well.
Dave Moore
consider looking for a pair of more efficient 18's
or 15's. The efficiency of the speakers can make
a big difference in some cases. However be prepared
to pay considerably more for the real deal.
=^^=DM
Stephen Walsh
>
<snip of other interesting stuff>
>
> With real electrolytic capacitors, you don't actually get a 100V
> working voltage out of two 50V parts in series, because the
> large tolerances on the capacitance - +/-20% is typical and
> -20%, +80% is not unknown - can give very unequal voltage
> division across the two parts. A worst case +/-20% pair
> would divide 100V as 40V and 60V, so you would
> be wise to limit two such 50V parts in series at 83V
> rather than 100V.
> Bill Sloman, Nijmegen
Of course you will also need biasing resistors across the series
combination of capacitors to reduce the effects of leakage
differences between the two series connected caps. In fact, if
you use a large enough bias current and the ripple current in
the capacitors is not large enough to cause significant voltage
movements in capacitor voltage, then you can sneak back to a full
100V rating for the series combination.
Even easier if you take into account the voltage surge rating
of the caps as well.
--
Power Converter Technologies Pty. Ltd.
Specialists in all types of Switched Mode Power Supply Design.
Email: wals...@zeta.org.au
Web: http://www.zeta.org.au/~walshsmr/
Ph: +61 2 9713 7711 Fx: +61 2 9713 8377 Mo: 0412 113 122
bta...@mostynent.com
> I have a 1000 watt amp which I use to drive a subwoofer for my band's sound
> system. The amp is kinda cheap and I think the transformer dosen't supply
> enough power for the output stage. The Filter caps in the power supply are
> 10,000 uf I was wondering if increasing the value to 20,000 or 30,000 uf
> would help with the sound quality, and decrease the strain on the
> transformer.
> 50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
> in parallel will yield a 10,000 uf 100V cap. Is this right?
> Computer Programmer/Musician
>
> -----== Posted via Deja News, The Leader in Internet Discussion ==-----
> http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum
Tim Wescott
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I'm looking for work -- see my website!
Don Y
>> If I remember right caps are like batteries: two 10,000 uf
>> 50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000 uf 50V caps
>> in parallel will yield a 10,000 uf 100V cap. Is this right?
upsid...@downunder.com
is relevant now due to technical advances.
If the band is doing gigs, it is preferable to have as light equipment
as possible.
For that reason, a Class-D amplifier would be simplest.
If analog amplifiers are preferred, e.g. due to some overload
distortion behaviors, at least use a switching mode power supply
(SMPS) which are much lighter. With proper power factor compensation
this will reduce the current harmonics on the mains. These harmonics
could cause problems to other equipment on the stage by getting into
microphone lines etc.
The OP was talking about 50 V capacitors, which would suggest a
+/-50Vdc amplifier feed. To get 1 kW continuous power, this would
require a 1 ohm load or 4 ohm load, if a bridged configuration is
used. The continues power rating is relevant for subwoofers, not some
pink noise signals.
rickman
Caps in series add voltage, but reduce capacitance. In parallel caps
add capacitance and voltage is the same.
--
Rick C
Dave M
Two 10000uF/50V capacitors in series will yield a 5000uF/100V capacitor.
Two 10000uF/50V capacitors in parallel will yield a 20000uF/50V capacitor
Dave M
amdx
power up, he might add a high wattage low ohm resistor before the caps,
or a soft start circuit.
But hopefully he has made it as a musician, has bought better
equipment and has roadies to move it around.
Mikek
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bill....@ieee.org
> Don Y wrote:
> >> On Monday, August 10, 1998 at 5:00:00 PM UTC+10,
> >> ad...@my-dejanews.com wrote:
> >
> >>> If I remember right caps are like batteries: two 10,000 uf
> >>> 50V caps in series will yield a 20,000 uf 50Vcap. And two 10,000
> >>> uf 50V caps in parallel will yield a 10,000 uf 100V cap. Is this
> >>> right?
> >
> > No, exactly reversed.
>
>
> Still no cigar.
> Two 10000uF/50V capacitors in series will yield a 5000uF/100V capacitor.
> Two 10000uF/50V capacitors in parallel will yield a 20000uF/50V capacitor
--
Bill Sloman, Sydney
legg
<seemyw...@myfooter.really> wrote:
>Hmm. 18 & some-odd years. Is that a record?
I'm lucky to get 60 days.
RL
bill....@ieee.org
--
Bill Sloman, Sydney