Linear versus Switching PSU in Mola-Mola Kaluga

FAQs | Applies to:


What are the differences between the Kaluga and the Theta Prometheus?


Answer:

A. In brief:

1. Lowest distortion input stage. Not available as an OEM component from Hypex.

2. nCore 1200 module with much higher quality components, selected by Bruno for their sonic qualities. Not available as an OEM component from Hypex

3. Switching power supply developed especially for Mola-Mola. Not available as an OEM component from Hypex

In full (from Bruno Putzeys):

The power amp module in the Mola-Mola amps is not strictly the NC1200. You may remember we sat down together to tweak a few parts and the improvement was not subtle. Based on those changes I made a new module specifically for the Kalugas. Also the input stage is a completely different affair. The one in the Kalugas is the same as in the Makua and is not available to anyone else. It has the lowest distortion I've ever seen on a buffer stage, and more importantly the most linear input impedance. This means it's much more forgiving towards the source impedance.

Regarding the supplies, the proof is printed black on white in fig 4. in the Stereophile review of the Prometheus. Those 60Hz related components are simply nonexistent in the Kalugas. The most likely cause of those in the Thetas is the big toroidal transformer combined with the big capacitor tank and the rectifiers + associated wiring putting out a stray field. It's often said that toroids don't have a stray field. They do, and it's located where the wires come out. The field you get there is very nasty, consisting of 60Hz harmonics going all the way up into the kHz region. It's so strong that it is easily picked up by the speaker wiring so the amp output could be clean and you'd still get a buzz in the speaker as a result of the few inches of wire between the amp module and the chassis.

The kalugas have no discernible hum or buzz and the construction of the power supply is part of the reason (the internal wiring explains the rest). Because of the fact that rectification happens on the primary side, currents are smaller. Also, for the same amount of energy storage the capacitors are physically much smaller so you can do a circuit board layout that has minimal current loops. The power transformer is run at 100kHz meaning it too can be smaller and its stray field (which contains no 60Hz related component!) is very easily shielded.

The designer of the SMPS has also done a custom job for Manley for microphone preamplifiers. When the people there realized that suddenly all the hum and buzz they'd been fighting for years was completely gone they went ape. It's really strange how lay people (especially those trained in the art of audiophilia by their peers who write for audio magazines) seem to think that switching power supplies are noisy. They're not. Given half a chance they're much quieter. All you need to take care about is of course the 100kHz and associated harmonics. Once I had that down the SMPS sounded much better than the big iron and copper affair that's incorrectly known as a "linear supply".

Cheers,

Bruno

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by On a Higher Note