Re: Re: 5 channel amp-supply
Why is the power factor that low for this type of supply? What is the effect of less VA and cap sizing?
Frans
Golgoth said:
Why is the power factor that low for this type of supply? What is the effect of less VA and cap sizing?
Frans
Re: Re: Re: 5 channel amp-supply
PF is low because current is very far from a sine wave proportional to voltage: it's in the shape of short current bursts at the peaks of the mains sine waveform.
Less VA and caps: you can't expect full power to be Hi Fi, but you probably don't need full power, especially if some of your speakers are high efficiency ones! You can actually work out your actual power needs from the max SPL in dB you want from each speaker at listening distance (no more than pain level 120dB in any case 🙂 and its efficiency in dB/W@1m (allow for -6dB per doubling of the distance). For a typical home installation you'll be surprised at how little power you actually need!
FransDHT said:
PF is low because current is very far from a sine wave proportional to voltage: it's in the shape of short current bursts at the peaks of the mains sine waveform.
Less VA and caps: you can't expect full power to be Hi Fi, but you probably don't need full power, especially if some of your speakers are high efficiency ones! You can actually work out your actual power needs from the max SPL in dB you want from each speaker at listening distance (no more than pain level 120dB in any case 🙂 and its efficiency in dB/W@1m (allow for -6dB per doubling of the distance). For a typical home installation you'll be surprised at how little power you actually need!
Re: Re: Re: Re: 5 channel amp-supply
Thanks Golgoth,
My front speakers hav a sensitivity of 88 dB/2,83V@1m. How do I get from there to Watts?
Frans
Golgoth said:
Thanks Golgoth,
My front speakers hav a sensitivity of 88 dB/2,83V@1m. How do I get from there to Watts?
Frans
Re: Re: Re: Re: 5 channel amp-supply
I got the idea the requirements rise very fast when you got speakers with low efficiency.
So in my case I found that 550VA simply was not enough for Hifi with my Apogee speakers and Zap mopdules. Especially treble was horrible ( 2* 1000 VA was sufficient and everything very good)
However: I'm also running a test with B&O ice modules,. They are actually running fine with the same 550VA transformer and even smaller capacitor banks. Does anyone have an idea why??
Golgoth said:
I got the idea the requirements rise very fast when you got speakers with low efficiency.
So in my case I found that 550VA simply was not enough for Hifi with my Apogee speakers and Zap mopdules. Especially treble was horrible ( 2* 1000 VA was sufficient and everything very good)
However: I'm also running a test with B&O ice modules,. They are actually running fine with the same 550VA transformer and even smaller capacitor banks. Does anyone have an idea why??
Hi,
You said smaller cap banks... =better power factor, maybe that's why?
__________________________________________________
I'd like to know how to calculate that as well Golgoth sensitivity on mine are 102dB @1W/1m, I'd like to see the equations, though, I doubt I'd actually use that method to design the supply, some sources just require turning up more before they come to life even with speakers like mine.
This is turning out to be a killer thread.
You said smaller cap banks... =better power factor, maybe that's why?
__________________________________________________
I'd like to know how to calculate that as well Golgoth sensitivity on mine are 102dB @1W/1m, I'd like to see the equations, though, I doubt I'd actually use that method to design the supply, some sources just require turning up more before they come to life even with speakers like mine.
This is turning out to be a killer thread.
Re: Re: Re: Re: Re: 5 channel amp-supply
Easy:
2.83V => 1W on 8 ohms (P=Vrms^2/R=2.83^2/8=1)
Suppose you want to be able to generate a maximum of 118 dB SPL (ouch) at 4m distance. 4m is two doublings of distance wrt 1m (1*2*2=4) so you need your speaker to produce 118+6*2=130dB SPL at 1m.
Now 130 - 88 = 42dB = 7 * 6dB -> 7 doublings of the 1W power necessary to produce 88dB (twice the watts = +6dB). So you need a maximum of 2^7=128 * 1 Watt = 128W from your amplifier, correct me someone if I am wrong.
FransDHT said:
Easy:
2.83V => 1W on 8 ohms (P=Vrms^2/R=2.83^2/8=1)
Suppose you want to be able to generate a maximum of 118 dB SPL (ouch) at 4m distance. 4m is two doublings of distance wrt 1m (1*2*2=4) so you need your speaker to produce 118+6*2=130dB SPL at 1m.
Now 130 - 88 = 42dB = 7 * 6dB -> 7 doublings of the 1W power necessary to produce 88dB (twice the watts = +6dB). So you need a maximum of 2^7=128 * 1 Watt = 128W from your amplifier, correct me someone if I am wrong.
Please check out my thread in Group Buys for nice toroid for UcD and ZAPpulse 🙂
http://www.diyaudio.com/forums/showthread.php?postid=518565#post518565
http://www.diyaudio.com/forums/showthread.php?postid=518565#post518565
Doubling the voltage is (approximately) 6dB. Doubling the power is (approximately) 3dB.
dB = 10*log(P1/P2)
dB = 20*log(V1/V2)
Power rating for a 42dB boost (130-88) = 1 * 10^(42/10) = 15849 watts. Time for a more efficient speaker if you want to play it that loud. 😉
catapult said:
Oops thanks catapult for correcting, silly me yes it's only +3dB SPL per doubling of the power, quite another game! You have it all here Frans:
http://dju.prodj.com/courses/soundreinforcement/c4a.html :
"EFFICIENCY
The ratio, usually expressed as a percentage, of the useful power output to the power input of a device. EFFICIENCY RATING OF A TRANSDUCER/ENCLOSURE...is the SPL the unit produces at a 1 W RMS input power level measured 1 meter from the unit. Doubling the input power raises the SPL 3 dB. Doubling the number of enclosures raises the SPL 3 dB. Doubling the input power and the number of enclosures raises the SPL 6 dB. Doubling the distance (near field) lowers the SPL 6 dB. "
Does anybody have experiance from, or info on these caps....
I'm planning to use 1 or 2 / rail in a UcD180 stereo amp.
Regards Stefan
An externally hosted image should be here but it was not working when we last tested it.
I'm planning to use 1 or 2 / rail in a UcD180 stereo amp.
Regards Stefan
Stefan:
http://www.bhc.co.uk/pdf/5444-fourth.pdf
http://www.bhc.co.uk/apt20_tc.htm
I can't seem to find any ESR spec's on the site, not even for the slit foil range....why would that be?
http://www.bhc.co.uk/pdf/5444-fourth.pdf
http://www.bhc.co.uk/apt20_tc.htm
I can't seem to find any ESR spec's on the site, not even for the slit foil range....why would that be?
They seem to be manufactured 1997...
But they are not used and have been stored i original box etc.
This is not a problem, right?
/Stefan
But they are not used and have been stored i original box etc.
This is not a problem, right?
/Stefan
Golgoth said:
Well, that means that there is no way I (or anyone else) will get 118dB at 4 meters (in hifi) with the class D's there are right now, I guess.
What would be a 'normal' loud sound level we would be able to achieve?? With UcD400, that is?
Frans
Doubling the enclosures and power, that is two frontspeakers driven by two UcD400's at 1 W will get me 94dB at 1m?
ericpeters said:
I noticed on page 5 of the first link
"For technical data covering
case size, ESR, impedance
and ripple current rating, on
any of the above designs,
contact BHC Components
technical sales."
That's... just stupid. It's hard enough to buy the suckers, they should at least provide the basics one requires, bad business
My view: If the specs can't speak for themselves, I sure don't want to talk to a salesman.
All I could find was one or two sights claiming they were low ESR, and had good high frequency characteristics..... but that's it, guess you have to take their word on it.
OA51 said:
Ummmmmm...... they've been sitting for seven years.. It could be a problem.
These kind of caps have a "shelf life".
Have a read:
http://www.acomstock.com/uploads/eccat2003.pdf
and I quote:
"Storage times in ambient temperatures of 40¡ÆC
or less can be four years or more before
leakage current should be checked for
conformance to the specified limit.
Longer storage times may require reforming of
the capacitor to reduce leakage current below
the specified limit. This can be accomplished by
applying rated voltage in series with a 1000§Ù
resistor for a time period of 30 ~ 60 minutes.
Under normal conditions, shelf life can exceed
10 years, providing that leakage current is
checked before use.
Long term storage in high humidity conditions
could cause oxidation of the terminal plating
which could adversely affect solderability."
I've seen some recommend 125% of rated voltage for the reforming process, and others recommending other methods, like sloowwwwwwwly bringing up the voltage to 125%, over a period of a day even, and leaving it over night. They all had one thing in common, limit the current! It's possibly best to go with the method the manufacturer in question recommends.
Looks like you have to call them to find out what the ESR is anyway.
If they were stored at room temp and not the trunk of a car the shelf life will be longer, these are long life caps, my guess is you'd be fine, but that's just a guess.
Know what I'd do? Put a 100W light bulb in series with each secondary to limit the current, turn it on and leave it for an hour or two, that'll reform them at the working voltage.
FransDHT said:
FransDHT said:
I'll try to do it right this time 🙂
Better to compute for one enclosure first (besides you can't be at 1m from both enclosures 😉
- UcD400 can output 210W into 8 ohms, let's round this to 256W so it's an integer number of doublings (we'll be wrong by less than 3dB anyway), namely 8 doublings wrt 1W (256=2^8):
-> 8 times +3dB = +24dB -> 88+24=112 dB SPL @1m
- two doublings of distance for 4m (1*2*2=4):
-> 2 times -6dB -> -12dB -> 112dB -12dB = 100dB SPL @4m
-two enclosures:
-> +3dB -> 100dB +3dB = 103dB SPL @4m for 2 enclosures
Now if your 8 ohms speaker is n dB more efficient at 1m (88+n) you'll get 103+n dB SPL at 4m.
(again correct me someone if I am wrong)
Now of course you must also take into account the max power that your particular speaker can take before blowing up!
Golgoth said:
But doesn't that mean you drive the two with one UcD400? And if you would drive each of them with one UcD ttaht you would have a 6dB+?
Frans
...and hence we can also see the argument for high efficiency speakers...
1) There was some quip from Jan-Peter that distortion on the UCD is somewhat lower at lower output levels (which is intuitive)
2) Power compression on the speakers rises rapidly with input power
3) Sticking 300W+ through a long piece of wire is never going to be ideal
The pro crowd are all into compression drivers with 100dB/watt sensitivity. Makes it quite easy to play something with 110dB peak levels (and lower average levels) without breaking a sweat. One enthusiast suggested to me that I benchmark any fancy "hifi" driver that I was thinking of building against a JPL pro driver first. These sorts of things do indeed set a high baseline standard...
1) There was some quip from Jan-Peter that distortion on the UCD is somewhat lower at lower output levels (which is intuitive)
2) Power compression on the speakers rises rapidly with input power
3) Sticking 300W+ through a long piece of wire is never going to be ideal
The pro crowd are all into compression drivers with 100dB/watt sensitivity. Makes it quite easy to play something with 110dB peak levels (and lower average levels) without breaking a sweat. One enthusiast suggested to me that I benchmark any fancy "hifi" driver that I was thinking of building against a JPL pro driver first. These sorts of things do indeed set a high baseline standard...
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