The Aleph-X

[carpenter]

safer ground plane

Why not just mask the ground plane with a thick insulating layer such as polyurethane or something similar?

John Inlow

 

[skaara]

Are these the pcbs for grollins amp?

 

[carpenter]

Yes, these pcbs were designed from Grollins schematics by "tvi" and enhanced by me (carpenter). I added the Aleph off-board multi-transistor approach as well as flipping around a few components.

Please proof read before using. I'm careful, but human. I have etched myself a pcb and now have the components. After I finish my wife's home office, I'm going to put the pieces together. Until then, I have no physical proof to whether or not these circuits are layed out properly.

John Inlow

 

[vdi_nenna]

Sorry John, where did you say we can get a copy of your PCB?

Thank Vince

BTW- I built your heatsinks last year and they look great. I haven't had the chance to put them to work yet...maybe on the XA!

Thanks!

 

[carpenter]

pcb availability

Hi Vince,

I made the pcb myself. I attached a copy of the pcb art to a raw circuit board and pressed indentations where the pads go with a sharp pointed tool. I then added the dry transfers. I began with the pads and then layed on the circuit traces. After that came the etching. Very simple proceedure.

Thanks for the compliment regarding my chassis proceedure.

John Inlow

 

[stefanobilliani]

John,

Just to know that I have understand well , the sense terminal is were I put the source of each mosfet.


And if can be of help: the drain of Q10 is signed two times ; one of these is the drain of Q11.

Thanks very much.

 

[vinay]

Scale for the PCB layout

John,

When I open the pcb layout in photoshop, at 100% the image size is 8inch by 12inch. What is the actual dimensions of the PCB.

Thanks,

Vinay

 

[carpenter]

pcb size

The actual pcb size is 4"x6". I enlarged the drawings for clarity. I go to a photo shop to have my layout transferred to film. They do a 1/2 reduction and because of the process the detail is fantastic.

John Inlow

 

[carpenter]

nice catch stefanobilliani

This is why I'm so glad you folks are proof reading. I have made the correction to my drawings. Q10 drain (located next to R44/45 on the right hand side of the stuffing drawing) is incorrectly labeled and should be tagged Q11drain.

John Inlow

 

[carpenter]

perhaps you'll like this.....

I enhanced Grey's schematics to my liking. I added the Aleph off board concept in blue boxes. Does anyone see any flaws?

Thanks,

John Inlow

 

[eLarson]

Is R21 (3 W, 3 ohm resistor) strictly necessary beneath D2/D3 and D4/D5? Also, why not tie each path to ground with its own resistor rather than tying them together with a resistive path to ground?

Erik

 

[hifiZen]

PSRR?

🙁 It weems my last question got lost in the noise and forgotten after the discussion diverged on some random tangent... so let me ask again:

The balanced nature of the Aleph-X should give it excellent PSRR... however, real life so rarely conforms to such ideals. I really want this to be a <i>quiet</i> amp... for me, active regulation is out, simply because of the complexity and power wasteage (and I don't think it will have much advantage over a pi-filter anyway), but is a pi-filtered supply warranted, or will a standard cap-only supply be sufficient?

Let's hear from those who have already built and listened to this amp... what are your experiences with power supply noise in the outputs?

 

[Lisandro_P]

Don diss a capacitance multiplier... i had great sucess with mine.

 

[rtirion]

Quiet amp

I have finished both channels (circuit) and am working on the
final PS and case. During test runs I have used both PS with and
without PI filter (74mF-2,2mH-74mF). With the PI filter everything
is dead quiet. Without PI filter there is very, very little hum.

Regards

 

[Nicwix]

Hi rtirion

Well done!

Are you using the circuit that you published on 17 July with the 12V rails, or have you updated it?

Best regards
Nix

 

[rtirion]

Nix,

Yes I am using the circuit with the 12V rails.
I have experimented a lot with the famous resistors, and for now
will stick with the 1k value.
No other changes.

 

[hifiZen]

rtirion:

Excellent! Thanks for the info... that's just what I was looking for. I'll make room for the pi filter in my design then. Somehow, I still had my fingers crossed that the PSRR would be good enough to reject the ripple of a cap only supply, but in the back of my mind, I knew it would be too good to be true.

Lisandro_P:

I'm not dissing active regulation at all, but with only 15V rails and high current... the additional power loss is a significant penalty. If I were to go with active regulation, I would most likely choose a cap multiplier type design, specifically for it's ability to track changes in mains voltage, thereby allowing a smaller voltage drop and minimizing power dissipation in the pass element. Anyway, I like the simplicity of passive only power supplies... the more projects I build, the more I appreciate simplicity.

 

[hifiZen]

Actually, I haven't ruled out the possibility of a CRC filter or maybe a CLRC filter... I'll have to run some simulations to do a comparison with straignt CLC, but it would be nice to damp or eliminate any possible resonance modes in the audio band...

 

[jwb]

What is the meaning of the letter "m" in the values of, for instance, R25, R24, R45, R29, et cetera in your schematic?

 

[jwb]

Nevermind, I just realized that all the resistors labelled "m" are the 5W power resistors. Thanks a lot for contributing your schematic. I'm actively pondering a two-device headphone amp made from this design.