The Mini-A's current draw varies with the signal. If you want a constant current draw in a single-ended design, you'll need to look at the original Zen amp where an unmodulated constant current source defines the current draw. By definition, the Aleph current source is modulated--otherwise it would have no reason for existing.
Switching power supplies have advantages in that they're rather small and light weight. They have disadvantages in that they react poorly to some loads and generate RF; a large part of the problem with AC line pollution we face these days.
I've used a computer power supply to run an old car radio so as to have background music in my shop, but that's as far as I'm willing to go. I can't say that I'm real excited about their use in decent audio equipment. By the time you make a switching power supply that performs anywhere near as well as a normal analog supply, you've:
1) Designed it from the ground up
2) Spent nearly as much money as you would on an analog supply
3) Created something of hideous complexity with the attendant increase in possibilities for failure
Buying a switching power supply from an online surplus supplier is tempting because they can often be had cheaply, but you have to ask yourself if they're really suitable for audio.
Grey
Switching power supplies have advantages in that they're rather small and light weight. They have disadvantages in that they react poorly to some loads and generate RF; a large part of the problem with AC line pollution we face these days.
I've used a computer power supply to run an old car radio so as to have background music in my shop, but that's as far as I'm willing to go. I can't say that I'm real excited about their use in decent audio equipment. By the time you make a switching power supply that performs anywhere near as well as a normal analog supply, you've:
1) Designed it from the ground up
2) Spent nearly as much money as you would on an analog supply
3) Created something of hideous complexity with the attendant increase in possibilities for failure
Buying a switching power supply from an online surplus supplier is tempting because they can often be had cheaply, but you have to ask yourself if they're really suitable for audio.
Grey
Beautiful amp!
I've been planning on using the SMPS' from apex (theyre sitting in my drawer) for my mini-A, but I do have a spare 300VA 20+20 toroid in my drawer as well.
I'm definitely no power supply expert (I stick mostly to modding turntables), how would I reduce the voltage as I'd expect ~24V after rectification?
Or would I be better off doing a RC bank after the SMPS? Would this give the best of both worlds?
I've been planning on using the SMPS' from apex (theyre sitting in my drawer) for my mini-A, but I do have a spare 300VA 20+20 toroid in my drawer as well.
I'm definitely no power supply expert (I stick mostly to modding turntables), how would I reduce the voltage as I'd expect ~24V after rectification?
Or would I be better off doing a RC bank after the SMPS? Would this give the best of both worlds?
I hope that heatsink is grounded by a very low impedance connection, and even then I'd be concerned about EMI from the fan motor.ojg said:
This thread made me smile actually, as I was considering switching my computer's cooling system to massive copper heatpipes to two large passive heatsinks forming the sides of the PC's tower case--total silence. It's the exact opposite thing of what you're doing--using active cooling for an application that almost always sees passive cooling.
I think this is not the case for constant current loads--the noise of an existing supply can be dealt with by good quality shielding (preferably more than one level of shielding) and a series of RC filters. Perhaps you still end up with a lot of capacitors, but you retain the advantage of avoiding a large transformer. The saving in size and weight would still be significant in really high power cases. The fact that the presence of high frequency switching does not necessarily interfere with audio is obvious in something like the outstanding sound quality of Berning's ZOTL. Finally, don't forget precision scientific supplies are usually switchers as as well.GRollins said:
As long as the supplies do not both use ground as a reference (which is why he had the only-two-pin power connector mention), just hook up - of one to + on the other. That gives 24 V from the free - to the free +, with the common connection in the middle (which can then be referenced to ground).
I did something similar with my Zen V5 with the sj74/sk170 jfets on the front end. I connected two 19.5V 3.5A laptop power supplies together to make a +/- 19.5V SMPS (two laptop supplies/channel). I dialed in a 1.5 - 2 Amps (around 25 watts/channel??) on the bias and she actually sounds good.
I also took four 4"x6" heatsinks and arranged them like an aleph 5. I bolted them together with 1x1 angle in a square fashion. The four sinks have one of the four IRF9240/240 bolted to it with a KAPTON Isolator.
Under the sinks I have all four laptop supplies in a Hammond 1650 enclosure. The four sinks bolt onto the top of the enclosure.
The amp is driven via a jfet BOZ with a Lightspeed attenuator in front all in another smaller Hammond enclosure.
She looks and sounds sweet.
I would post a pic of it, but in the middle of a cross country move.
I also took four 4"x6" heatsinks and arranged them like an aleph 5. I bolted them together with 1x1 angle in a square fashion. The four sinks have one of the four IRF9240/240 bolted to it with a KAPTON Isolator.
Under the sinks I have all four laptop supplies in a Hammond 1650 enclosure. The four sinks bolt onto the top of the enclosure.
The amp is driven via a jfet BOZ with a Lightspeed attenuator in front all in another smaller Hammond enclosure.
She looks and sounds sweet.
I would post a pic of it, but in the middle of a cross country move.
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