I know wiring transformer secondaries in parallel is a big NO. However, what about if they are isolated by a bridge like so (see pic).
Please note the differing voltages of T1 and T2 ... the idea is as the T2 rails sag with load, a helper transformer T1 , can provide support at rail minus 2 volts and keep it better regulated. I just happen to have several transformers available and wondering how to utilize them in power amps.
Please note the differing voltages of T1 and T2 ... the idea is as the T2 rails sag with load, a helper transformer T1 , can provide support at rail minus 2 volts and keep it better regulated. I just happen to have several transformers available and wondering how to utilize them in power amps.
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To use all those transformers, I would go dual mono instead. Maybe also build separate supplies
for the input/driver circuit and the output stage.
To double the VA, you could use two transformers by paralleling the secondaries on each transformer,
and then series connecting the doubled secondaries to form a center tap. This would give the same voltage as one,
but with twice the VA. The only drawback electrically could be small differences in the voltages, which would
increase the ripple voltage.
for the input/driver circuit and the output stage.
To double the VA, you could use two transformers by paralleling the secondaries on each transformer,
and then series connecting the doubled secondaries to form a center tap. This would give the same voltage as one,
but with twice the VA. The only drawback electrically could be small differences in the voltages, which would
increase the ripple voltage.
Yes, as long as the rails do not sag below 20v equivalent, the 22v Trafo does all the work. However with higher amplitudes, without T1, the rails would sag to 15 or 16v. And in this region 15-20v), T2 would carry the load equally. And in doing so, increases the RMS capabilities of the amplifier for a given load ( assuming the rest of the components can handle the load).
I see you have not noted anything catastrophic in the circuit, apart from it being unconventional... yes?
I see you have not noted anything catastrophic in the circuit, apart from it being unconventional... yes?
Given the realities of psychoacoustics, there is little to be gained.
Even if you managed to increase the output power by 30% (relatively optimistic, taking into account the unequal transformers), this will be barely noticeable.
In a direct A-B comparison, you will easily tell the difference, but if you listen to the two configurations at different times, say 10 or 20 minutes apart, you won't notice the difference.
If the "high" transformer is really high -say 50% higher than the other- and the reservoir caps are large enough, it will give the impression of a more powerful system, capable of an occasional and isolated punch, but it will crumble in the presence of sustained bass.
That's the principle of cheap sound systems, but the result is achieved with a single, under-dimensioned transformer.
Even if you managed to increase the output power by 30% (relatively optimistic, taking into account the unequal transformers), this will be barely noticeable.
In a direct A-B comparison, you will easily tell the difference, but if you listen to the two configurations at different times, say 10 or 20 minutes apart, you won't notice the difference.
If the "high" transformer is really high -say 50% higher than the other- and the reservoir caps are large enough, it will give the impression of a more powerful system, capable of an occasional and isolated punch, but it will crumble in the presence of sustained bass.
That's the principle of cheap sound systems, but the result is achieved with a single, under-dimensioned transformer.
I don’t disagree with your findings, I also see it a different way ( putting a marketing hat on) one could say the higher volt/ lower current T2, gives better Dynamic output ( music is Dynamic anyway) and the lower volt/ higher current T1 helps with sustained bass. Best of both worlds in a situation where T1 is an add-on to an existing amplifier design.
Naturally if one were to design from scratch, this would be an unnecessary implementation.
So apart from everyone discouraging the idea, no one has come out and said this will blow the amp or the PSU or the bridge rectifiers.... correct?
Naturally if one were to design from scratch, this would be an unnecessary implementation.
So apart from everyone discouraging the idea, no one has come out and said this will blow the amp or the PSU or the bridge rectifiers.... correct?
You need to find out at which load the 22 Vac tranny drops to 20 Vac. If this is yet beyond it's capability, there's nothing to be gained by your idea, 'cause as the total load increases, that trannie's load also increases furthermore.
Remember: A transformer's nominal secondary voltage complies with it's maximum VA load.
Best regards!
Remember: A transformer's nominal secondary voltage complies with it's maximum VA load.
Best regards!
I mean, I would try it out in LTspice first just in case, but nope, probably not.
This might be useful for avoiding excessive power supply drooping with low-impedance loading as seen in some AV receivers:
2x 109 W / 4 ohm --> 5x 23 W / 6 ohm (Yamaha RX-V475).
So you could provide substantial peak headroom without things entirely going south under load.
A Class G amplifier probably is the better solution still, given that it also cuts down on idle power dissipation and is way more likely to keep output transistors in SOA when the output is accidentally shorted.
Yes but, beyond 20v it will fall at a much lower rate... till T1 also saturates, but by that time both trafos' should act like one large Trafo .
This your circuit looks weird a bit but if you have a lot of free transformers and enough space for them then it can work with some circumstances:
if 20 V trans is a bit powerful then 22 V one (or have lover enough impedance) then the sence of this circuit increases.
If 20 V transformer is less powerful then the sence of this circuit tends to zero.
With a difference less then 10..20% in parameters (and the same secondary voltages) we can of cause safely parallel transformers without any diodes.
Erm, why? Transformer sagging happens due to the windings' DC resistances, and as copper, like almost any other metallic conductor, shows PTC characteristics, more sagging is to be expected if the windings rapidly heat up under overload conditions.
Best regards!
ran some tests on a Kenwood M2 power amp. Its rated for 220w/8e.
I measured clipping at 221watts (line voltage had sunk to about 115v with the long extension cord I had, but this was a baseline anyway).
I had a second M2 power supply I got from ebay and paralleled that PSU (post rectification) feeding the main caps for the M2. So just doubling of transformers and rectifiers, no added capacitance.
With the second PSU hooked on, both channels now clipped at 282 watts into 8 ohms...
On a single channel (when AC lines were closer to 117v) I had got 242 watts and 313watts respectively.
So adding a second PSU to an existing commercial amp yielded an additional 60 watts, its not a lot, but its not unremarkable either. At these levels, the auditory volume delta is not very noticeable, but the bass (since its felt also by the body etc) can feel a bit more.
So... is it worth it? I don't know... bragging rights .... maybe, but so what?
I measured clipping at 221watts (line voltage had sunk to about 115v with the long extension cord I had, but this was a baseline anyway).
I had a second M2 power supply I got from ebay and paralleled that PSU (post rectification) feeding the main caps for the M2. So just doubling of transformers and rectifiers, no added capacitance.
With the second PSU hooked on, both channels now clipped at 282 watts into 8 ohms...
On a single channel (when AC lines were closer to 117v) I had got 242 watts and 313watts respectively.
So adding a second PSU to an existing commercial amp yielded an additional 60 watts, its not a lot, but its not unremarkable either. At these levels, the auditory volume delta is not very noticeable, but the bass (since its felt also by the body etc) can feel a bit more.
So... is it worth it? I don't know... bragging rights .... maybe, but so what?
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