500V, 50W lamps mean 100 mA idle current, and 5K resistance.
To get maximal negative swing on 2.7K primary calculate voltage drop on a voltage divider formed by 2.7k and 5k, of 500V, and get 175.3 Volt. It is a peak negative swing that defined by resistor (25W lamps in series) to the load (output transformer primary). It is not limited by a tube itself, it is limited by resistance of lamps that supplies current through the load. Maximal non-distorted power is 5.485 Watt.
However, if to disbalance the amp and set idle current higher (magnetizing transformer's core) you can get more of power. Now, it is your turn to calculate power obtained such a way, if a tranny is toroidal.
To get maximal negative swing on 2.7K primary calculate voltage drop on a voltage divider formed by 2.7k and 5k, of 500V, and get 175.3 Volt. It is a peak negative swing that defined by resistor (25W lamps in series) to the load (output transformer primary). It is not limited by a tube itself, it is limited by resistance of lamps that supplies current through the load. Maximal non-distorted power is 5.485 Watt.
However, if to disbalance the amp and set idle current higher (magnetizing transformer's core) you can get more of power. Now, it is your turn to calculate power obtained such a way, if a tranny is toroidal.
Michael; I suggest you to go from schematic, rather than from numbers given by author. Please see my previous posts.
You may swap a lamp and a negative PS and get this well familiar picture:
when it is well balanced max power is limited by resistance of lamps, and is 5.485W.
For more power you have to dis-balance it biasing the transformer.
You may swap a lamp and a negative PS and get this well familiar picture:
when it is well balanced max power is limited by resistance of lamps, and is 5.485W.
For more power you have to dis-balance it biasing the transformer.
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Holy smackeroos!!
Wavebourn has got it right! 5.485 Watts tops without magnetizing the OT. I've been assuming it could get the same current swing up as the tube pulled down from the idle current. Not so. The tube can only pull down as much voltage as the resistor (bulbs) can pull it back up, to maintain current balance (volt-second balance actually) in the OT. So the measured 9.75 watts is actually with the OT badly magnetized. Working from Wavebourn's calc. of 5.485 Watts, this thing would draw over 2000 Watts if scaled up to 29 Watts per channel.
Wavebourn has got it right! 5.485 Watts tops without magnetizing the OT. I've been assuming it could get the same current swing up as the tube pulled down from the idle current. Not so. The tube can only pull down as much voltage as the resistor (bulbs) can pull it back up, to maintain current balance (volt-second balance actually) in the OT. So the measured 9.75 watts is actually with the OT badly magnetized. Working from Wavebourn's calc. of 5.485 Watts, this thing would draw over 2000 Watts if scaled up to 29 Watts per channel.
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Right. I edited my comment as you posted this! There is a Norton equivalent thought of in terms of current loops and there is a Thevinin equivalent thought of in terms of a voltage divider. Either way, the answer is the same. That is, 175 volts peak swing.
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Holy smackeroos!!
Wavebourn has got it right! 5.485 Watts tops without magnetizing the OT. I've been assuming it could get the same current swing up as the tube pulled down from the idle current. Not so. The tube can only pull down as much voltage as the resistor (bulbs) can pull back up, to maintain current balance (volt-second balance actually) in the OT. So the measured 9.75 watts is actually with the OT badly magnetized. Working from Wavebourn's calc. of 5.485 Watts, this thing would draw around 2000 Watts if scaled up to 29 Watts per channel.
That's a great way to put it. It's SE, and asymmetry wil induce DC magnetization in the OPT
I was assuming from the tube's point of view that there was another tube. Well there is but it's a really lazy one that needs to be dragged uphill. So with the symmetry assumption in place, I get 175V peak swing each way for a grand total of... 5.5 watts that's at the primary side of the OPTI knew I was going to learn something today! and it's barely noon yet...
It is what I wanted to discuss with the Original Designer from the moment I chimed into the thread, but he run away complaining that we are bad jealous guys and don't like a non-famous genius... I wanted to help him to improve the thingy, actually: from problems to solutions, from solutions to achievements, as I usually do... It's sad, he did not want to.
Well, maybe the designer is still tuning in. Seems that the easiest fix would be to re-configure so that a cap could be put in series with the primary. That should get up to around the 10 Watt mark (if it doesn't run out of voltage someplace). That just makes the bulbs run a lot hotter then though. The other major problem is the bulbs wasting output power. How about a switched high frequency inductor to replace them. Have to do a bit of scratch pad scribbling to see if that is easy or a big headache. I think it would require a gapped ferrite core with two windings for the two switching transistors. Having to deal with plate circuit KVs would be a show stopper, but this can probably be used to power a LV buck winding on the OT. Nice exercise to solve anyway, since I would like an efficient CCS to try out on the Edcor GXSE SE OTs I added buck windings to (see earlier).
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It looks as he already "improved" it: the first amp had a cap coupling. Removing it he allowed some magnetizing of a tranny getting more of dirty power.
The next improvement was to redraw it in Cyclotron-like fashion to "hide ideas" from non-competent people.
Additional low voltage winding and a modulated CCS would be wast improvement; it would eliminate non-reliable and non-linear bulbs, need for second high-voltage source, and improved output power per percent of distortions.
...but it is what we discussed here already many times over last years.
Let's close the topic. It is over.
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