I have a transformer with 3 secondaries 24vac 30vac and 34vac and i would like to use it for a 200 watt amplifier. I don't understand how to get a centre tap from this transformer or if i can parell the secondary's up to get it or what the best option is to use is it has a configuration like this
____ 0 volts
____ 24 vac
____ 30 vac
____ 34 vac
The transformer is 500va surely there must be a way i can hook this up and use it for my amplifier if anyone can help me with a schematic on how to do this it would be greatly appreciated.
____ 0 volts
____ 24 vac
____ 30 vac
____ 34 vac
The transformer is 500va surely there must be a way i can hook this up and use it for my amplifier if anyone can help me with a schematic on how to do this it would be greatly appreciated.
The way you describe the XFMR is that it has one secondary winding with 2 Taps. There is no tap at 1/2 so there is no way to get balanced or centered DC supplies. One way to maximize the transformer and power out is to develop a single DC voltage DC using the maximum 34VAC. Using a full bridge rectifier and single large cap to produce a single supply 0.95(34x1.4) - 2Vdiode or ~ 43 Vdc. so not nearly enough voltage to get 200 W into 4 ohms. There are capactor coupled output bridged amps to get the most out of this XFMR for audio giving close to 200W at 4 ohm.
2 full wave bridges, run of the the zero and 34 volt tap. One bridge for positive, one pridge for negative. Or 2 single diodes, one for plus and one for minus, and large filter cap (half-wave rectifier). Then bridge output. If stereo, pushes power limits on transformer - but would be OK for music. YMMV. My 2 cents.
The only way you can do it is by two half wave rectifiers but then the ripple is way too high for a power amp.
For a high power amp it would certainly work, but not too good. At some point, clipping or compression will occur. A larger capacity for the filter caps may or may not improve the situation. I think there is a "point of no return" where more caps only push the transformer at its current limit without providing a stable voltage anymore (think low pass). Creating a center tap by using two of those transformers is the answer here IMHO.
I still get away with using the half-wave rectifiers because my amp never has to drive more than 25 Watts RMS for each channel (max RMS for the speakers) and I have a transformer with quite some reserves.
I still get away with using the half-wave rectifiers because my amp never has to drive more than 25 Watts RMS for each channel (max RMS for the speakers) and I have a transformer with quite some reserves.
yea but you are throwing away a good portion of the XFMR VA when you do this! Also you need double the bulk C and beefier diodes to match. Ripple is now 60Hz so as you said it is higher in magnitude. see Full Wave Voltage Doubler see link here Again most XFMR efficiency and economy is using bridged amps and single voltage PS using full wave bridge. Speakers don't go to DC so there is no reason the amp needs DC coupling either!
current delivery imho is not much of an issue, it is the voltage dropping that is the issue.....
a full wave bridge with center tapping to provide split rails can be seen as really 2 voltage doublers in 1......
yes, you are right. The voltage drops very badly as current demand increases.
It is a current delivery problem!
DOH! DON'T TRY THIS AT HOME. (thanx to Andrew T for pointing this out) I set this down on paper and looked at where the electrons flow - it won't work. Somebody correct me if I'm wrong, but for any given current, wouldn't doubling the capacitance in a half wave circuit give the same ripple (but different frequency) as a full wave circuit? (based on V=q/C where q would be the integral of the current over time) Another vote for big capacitors and beefed up diodes. Another 2 cents down the drain.
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