New Aleph Mini PCB GB

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#661
fcel said:
I'm patiently waiting for my parts from Jason. Chassis is all ready to go.
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I'm sorry i can't send your parts till you show us pics of the chassis 😀

OK all the kits are done.. I went out and bought another static strap because i lost mine in my last move.. ALL i have to do now is seperate the Output fet's and then start shipping.. Those who bought psu kits will have to send me $$ for shipping..

J
 
#667
I finished my first project using these boards and am on my way with two more. For my first project, I did something completely different, and built an Aleph headphone amp customized to mate with my Grado Labs headphones and BZLS preamp.
 

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#671
Interior view. You can't quite see it from this pic, but there is 0.2F in the powersupply in a CRC configuration. I also used Ultrafast Soft Recovery diodes from International Rectifier for the rectifier bridge. Major overkill for a headphone amp, but this supply is deadly quiet even without using a regulation stage. I left room in the chassis to add separate regulators for each channel in the future if I change my mind. I designed for +/-15V rails, but ended up with /-17V. Gotta luv Plitron trafos.
 

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#672
Closer view of the stuffed amplifier pcbs's. Nothing exotic used here. Matched the IR9610's to less than 0.1mV, and ended up with +8mV and -11mV DC offsets for the left and right channels respectively, probably due to resistor mismatches. The bias is set at 0.25A and the CCS at 50%. Max power into the Grado's is 3W.

How does it sound? Was real bright at first listen but after 10-15 hours of burn in time, the sound came right back to neutral. The sound is very dynamic, and I have never heard such deep and well controlled bass in my life. Crisp and clear but not etched or fatiguing. Amazing reproduction of vocals, very natural.

Oh yeah, I almost forgot to point out that the output transistors are not missing, but are underneath the pcb's and mounted to the chassis for heatsinking. Used IRF610's for the outputs.
 

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#673
Great job, Metalman🙂 Now lets see, in order to scale this thing for a headphone amp: Supply rails +/- 15V, output devices irf610,
source resistors 1 ohm, output resistor 0,47 ohm. Smaller trafo. Thats what I gathered from your posts and pics. Is there any other changes needed?

Steen.🙂
 
#675
metalman said:
Interior view. You can't quite see it from this pic, but there is 0.2F in the powersupply in a CRC configuration. I also used Ultrafast Soft Recovery diodes from International Rectifier for the rectifier bridge. Major overkill for a headphone amp, but this supply is deadly quiet even without using a regulation stage. I left room in the chassis to add separate regulators for each channel in the future if I change my mind. I designed for +/-15V rails, but ended up with /-17V. Gotta luv Plitron trafos.
Click to expand...

Hey there Tin Man, those caps look good.

What value are those power resistors in the PSU?

Regards

Anthony
 
#676
Originally posted by steenoe
Is there any other changes needed?
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A few of the resistor values need to be adjusted, but not many. I'll put together a complete schematic for you and post it.

Originally posted by Coulomb
What value are those power resistors in the PSU?
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3 x 27 ohm on each rail. Quite high in comparison with what you would use on power amplifiers, but as this is only dealing with 0.5A total current, I could really ramp it up to drop the ripple, which measures at 0.5 mV(peak to peak).

Cheers, Terry
 
#677
metalman said:

A few of the resistor values need to be adjusted, but not many. I'll put together a complete schematic for you and post it.


3 x 27 ohm on each rail. Quite high in comparison with what you would use on power amplifiers, but as this is only dealing with 0.5A total current, I could really ramp it up to drop the ripple, which measures at 0.5 mV(peak to peak).

Cheers, Terry
Click to expand...

Thanks Terry, I tried 5 x 50R all the way down to 2 x 50R on my Mini A's and the rail VD was half the Supply voltage. I figure that when using one PSU with two Mini A's 5 x 500R is going to be required to suppress ripple without crushing the rail voltage.

Regards

Anthony
 
#678
I could use a little direction in choosing some PCB screw terminals. That's to obviate problems with my ready-fire-aim chassis design process.

I would like to know the general consensus of the group on Phoenix, On-Shore & 3M. What do you like?

I am specifically looking to terminate

AC0/AC0, AC1/AC1 (8mm pitch?)
-V, Gnd, & +V (5mm?) on the PS boards.

I am additionally looking for the 3 position PCB 90 terminal for

Out/Gnd.CGnd (5mm?)
2 position SG/UN

I would just like to avoid ordering the wrong terminals three times. Digikey has about 5000 choices.
 
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