Thicker PL400 faceplate with new analog meters...
- Thread starter Gepetto
- Start date
How about using two of these - one for the left channel & one for the right. Avel Lindberg Y236904
Mount them left and right to balance (in weight) the unit. Still would be a heavy mother.
Mount them left and right to balance (in weight) the unit. Still would be a heavy mother.
Hmm. I wonder if the transformer needs to be 75 volts to be able to put out say 400 watts. 400 watts at 8 ohms is about 57 vac (or 800 watts at 4 ohms). Rectified (with no load) a 60 volt transformer will produce a DC voltage of 85 volts. I would think this will still be adequate. As the amplifier is asked to produce more power, the load on the power supply gets heavier and I would expect the DC voltage of the power supply will get dragged down and clipping occurs. I think it's more about the VA's than the volts. 1600VA's is a lot of power.
we are used to 200-250 watts at 8 ohms per channel with 80 v rails ( rough calculations 57v ac through bridge is 80 volt rail
to get 350-400 watts per channel you need 100 v dc rails so 72 volts minimum.
from What I remember talking to Bob Carver the transformers he uses in the 700 amps is rated over 2000va. When we approach clipping that transformer can not hold rail voltage. You do see it power out.
if you can help with the concept on dragging down rails and clipping.vs higher va transformers I’m all ears
to get 350-400 watts per channel you need 100 v dc rails so 72 volts minimum.
from What I remember talking to Bob Carver the transformers he uses in the 700 amps is rated over 2000va. When we approach clipping that transformer can not hold rail voltage. You do see it power out.
if you can help with the concept on dragging down rails and clipping.vs higher va transformers I’m all ears
Nope - can't find it. Secondary goes from 55v to 60v to 110v - nothing between 60 and 110.
How about rails of 170 volts? Eliminate the transformer altogether and go direct to the 120v (actually this puts the transformer outside your house on the power pole). Is that just too hot? Could the amp be driven with rails that high?
How about rails of 170 volts? Eliminate the transformer altogether and go direct to the 120v (actually this puts the transformer outside your house on the power pole). Is that just too hot? Could the amp be driven with rails that high?
Nice try. With main power first you would have 170v each rail for about 340 v Between the rails. Way over limit of transistors we use. Second very dirty signal on main supply. I just measured my main power now and it is 1.9% THD+N. With it being Saturday am it’s probably the cleanest you will get with industrial operations shut for the weekend . And third there is no insulation from the grid.
The sagging of rails is primarily due to load regulation caused by ohmic losses in the transformer windings. The EI core has limited window area and limits the size (AWG) wire that can be wound successfully to fit into that window. The solution to that is to use a much larger EI core that will have a much larger window area which will allow the use of larger diameter wire. That size increase is often intolerable due to either the amount of physical space allowed or due to intolerable cost factors. PL was contending with both factors.
Other factors contribute, such as larger loss in the bridge rectifier at higher currents and more ripple in the bulk capacitor voltage leading to lower average output voltage BUT the dominant sag cause is winding losses in the transformer.
Other factors contribute, such as larger loss in the bridge rectifier at higher currents and more ripple in the bulk capacitor voltage leading to lower average output voltage BUT the dominant sag cause is winding losses in the transformer.
Sorry, I'd just like to pull on this thread a bit. Which transistors are being subject to the full + and - rail voltages? Worst case (I see) is either the + rail voltage or the - rail voltage. Not both added together.
Secondly, dirty power - isn't that dirty power just coming through the transformer attenuated a bit by the inductance and capacitance of the transformer, but surely the rectification and the bulk capacitors will remove that to whatever extent you want. You could even add line filters (better be big ones) to reduce the incoming noise.
So, here's another try (with toroidal transformers). Instead of one transformer for the right channel and one for the left, use one to generate the positive rail voltage and another transformer to make the negative rail voltage. These should work: Toroidal Transformer 75v
So it's rated at 2x35 volts at 115vac, which would be 2x38 volts at 125vac, producing between 70 and 76 volts for each leg. There are other transformers that would allow even greater rail voltages (but with decreasing current capacity).
Secondly, dirty power - isn't that dirty power just coming through the transformer attenuated a bit by the inductance and capacitance of the transformer, but surely the rectification and the bulk capacitors will remove that to whatever extent you want. You could even add line filters (better be big ones) to reduce the incoming noise.
So, here's another try (with toroidal transformers). Instead of one transformer for the right channel and one for the left, use one to generate the positive rail voltage and another transformer to make the negative rail voltage. These should work: Toroidal Transformer 75v
So it's rated at 2x35 volts at 115vac, which would be 2x38 volts at 125vac, producing between 70 and 76 volts for each leg. There are other transformers that would allow even greater rail voltages (but with decreasing current capacity).