Aleph-X Economy Grade.

[mrfeedback]

I am keen to build a low cost, low power version of the Aleph-X for my PC workstation, where my nearfield levels are typically quite low.
Currently I am using an old all tube reciever rated at 10W + 10W or so, and usually I am using less than 1 watt or so.
In the interests of economy, I am keen to utilise PC switchmode supplies that I have hanging around, and as these are rated at 20 Amperes and more at 5V, I figure these would be a good soloution if......so....
Can the Aleph-X output stage be operated at 5V supply, what current is required at 5V, and what power output is to be expected into 4 or 8 ohms ?.

Eric.

 

[alaskanaudio]

How low can we go.

The answer is yes and no.

It is not possible to run a X from a five volt supply directly. You would need a switching power supply to boost the five volt level to something more reasonable.The same method as used in most higher powered car audio amps. Scrapping this idea would be the best choice.

John Fassotte
Alaskan Audio

 

[mrfeedback]

So what is the output stage (output transistors) minimum voltage requirement then ?

Eric.

 

[jwb]

PC power supplies have 12V rails too. That would be just right.

 

[dlharmon]

You do need to provide a 1A minimum load on the 5V though for it to operate properly. A 5ohm 10W resistor would work well. I ran a SOZ on a few of these in series for a while. The ground is connected to earth ground, but it only requires cutting a trace to fix. These can usually do 8A on the 12V output. Mine would start up with no problems with 32000uf on the outputs. I replaced them with transformers and rectifiers.

Darrell Harmon

 

[mrfeedback]

More what I meant is can the outputs be powered by 5V, and the input transistors and CCS by 12V ?.
I am seeking to build a baby version using el-cheapo heatsinks and output transistors in a compact box, all out of my junkbox excepting the output transistors.
If the whole amp is powered from 12V, what output power is available ?.

Eric.

 

[AudioFreak]

If you reorganise the front end current source to work at a lower voltage, you could probably get this working on about +/- 7V which should give a little over 6W output into 8ohms.

 

[mrfeedback]

Power Losses......

Thanks, that is the info I am looking for.
Because I will only be using a couple of watts, I can live with the inefficiency of a low power version.

Eric.

 

[cowanrg]

a computer power supply actually generates 5, 12, AND 7 volts.

if you combine a 5v and 12v lead, you can get 7v. trust me, i had a switch in my old computer that i could switch my fan's voltages from 5, 7, or 12, depending on how quiet i wanted it.

 

[Variac]

It would be cool to use those thousands of PC power supplies piling up! Can you run the output of one switching supply into another to jack up the voltage? The 12 volt out puts are usually pretty low amps the 5 v are the high output,

You can use CPU cooler heatsinks with fan to cool the output transistors. After all, you have the computer with fans right there anyway.

And if you use the a speaker design with a hard drive voice coil you have used another computer part:

http://ohmslaw.com/speaker.htm

http://www.diyaudio.com/forums/showthread.php?s=&postid=84478#post84478


Jwb: If I ever finish anything you will have to come listen to it!

 

[dlharmon]

It would be cool to use those thousands of PC power supplies piling up! Can you run the output of one switching supply into another to jack up the voltage? The 12 volt out puts are usually pretty low amps the 5 v are the high output,

And if you use the a speaker design with a hard drive voice coil you have used another computer part:

If anyone wants help with running these is series just ask me and I will try to explain the modifications to make it isolated. 5V is usually 20A and 12V is usually 8A (230W supply)

Darrell Harmon

 

[hifiZen]

Hmm... I've got a couple spare computer supplies sitting around doing nothing too. I considered sending them to the trash bin, but it seemed a waste of a perfectly functional piece of electrical equipment. Maybe they will find a renewed purpose in life! 😉

As far as modifying the supplies to be isolated, don't you have to crack the sucker open and cut the ground connection between the input (mains) side and the other side of the little transformers? Is that all there is to it? I'm honestly not too familiar with switching power suppies, and computer supplies in particular.

 

[dlharmon]

Hmm... I've got a couple spare computer supplies sitting around doing nothing too. I considered sending them to the trash bin, but it seemed a waste of a perfectly functional piece of electrical equipment. Maybe they will find a renewed purpose in life! 😉

As far as modifying the supplies to be isolated, don't you have to crack the sucker open and cut the ground connection between the input (mains) side and the other side of the little transformers? Is that all there is to it? I'm honestly not too familiar with switching power suppies, and computer supplies in particular.

There are some 200V 560uF caps usually. These may be charged. Check them with a meter and discharge with a resistor if necessary before doing any other work on the supply. They usually have bleeder resistors, but with these cheap supplies you can't trust that.

In the really common cheap ones all that needs to be done is to use some nylon washers and screws to mount the output side of the board. The frame is where it gets its ground. The input side should remain attatched with metal screws for safety reasons. Most of the supplies output is grounded only by attatchment to the frame at the corner where the wires come out, and another option is to cut that trace.

Be very careful with these supplies and don't try anything you are not sure about. Don't just cut the ground wire in the cord. That will leave the input section ungrounded also.

Another use for these supplies, even blown ones is to use the ferrite transformer core to build you own smps.



Darrell Harmon