Aspen Headphone Amp

[Bigun]

Originally Posted by AKSA

TL431 shunt regulator

I shalln't argue with the Master.

but... this means we have an Opamp in our camp, hiding as it may within the psu

[keantoken]

I agree with Nico about the capacitance multiplier ramping the voltage. I had not thought of this. It should also not pop when you plug in the headphones, as too many do.

I also like the idea of using zero NFB buffers instead of opamps for the crossfeed.

I am starting to think someone really should ginnea pig all these ideas...

- keantoken

[AKSA]

Gareth,

The TL431 is a remarkable device. Even John Broskie uses them, and they are used in the Supratek preamp power supply (I know because I had a hand in it).

In any event, they don't pass signal, and they have a largish cap across them, which should be configurable to give soft turn on, a desireable quality.

Trialling each and every one of these ideas would take hundreds of hours. I have in fact done many of them already, and Nico has vindicated my choice of the amp topology. What will take the time now is the crossfeed and the power supply. I guess that's why design is tricky..... lots of man hours. Volunteers anyone?

Hugh

[MJL21193]

Originally Posted by keantoken

I am starting to think someone really should ginnea pig all these ideas...

- keantoken

I have a lot going on, but I may find time over the weekend to cobble it together. I have all the parts.
Now, listening...is another story. To me, most amps sound the same, if they are working properly. If there are Earth moving, subtle differences from one component choice to another, it is beyond my capacity to resolve.
Add to that is my hearing is on a steady downward trajectory ...

[AKSA]

Much appreciated John, we shall see very soon hopefully, I am grateful for your interest.

Hugh

[Nico Ras]

Hugh,

are you going to supply a complete kit of parts or only the PCB? Reason is why I am asking is that laying the PCB one must have a clue of the components the guys will want to use, for example headphone socket foot prints are not the same, nor are potentio meters. Capacitor pitch may differ, etc.

Supplying the kit would make sense and the PCB design would be much easier. Besides the amps will be consistent.

Who will draw the final schematic and select the components?

I do not have any project on the go, as I mentioned, I built my last amp and if you want a hand at PCB layout, it will be only with pleasure.

Nico

[AKSA]

Hi Nico,

No, this is an open design, and while I know different components have different footprints, and pleasing all comers is difficult, it's already starting to dominate my time and I won't be making a penny from it..... and right now I'm under the pump with orders, so development time is tricky. Hell, I'm simulating the power supply right now!!

Hugh

[Nico Ras]

Hi Gareth,

Since you are the appointed "Project Manager" could you start finalising the schematic - draw one from every ones wishlist as it appeared here, let the guys comment on what the final design will look like and then freeze it - NO FURTHER CHANGES. Don't allow the guys to just demand I want, they must show the schematic of what they want so others can agree or disagree with it.

You then need to suggest a bill of components that would most suit everyone, most important is outline drawings of the selected components, especially pots and large caps or esoteric stuff that is not common then post it here or forward it to me (nico_ras@telkomsa.net)

Next step would be to throw open a general PCB layout. i.e. where you want everything placed, volume control, input connector, headphone connector, etc.

Post your suggestion and again let every one have his/her say about it. Once you are satisfied then - FREEZE THE DESIGN no further changes.

I suggest you allow a time frame for both activities, say 3 days for the schematic and another 3 days for the PCB general layout.

This will take us to about Thursday next week. On Friday I will start the PCB layout and when finished I will e-mail it to Hugh for comments and when we agree it is workable it will be posted on the forum for final view and then it is up to you to apoint whomever will have the PCB made and arrange your group buy, etc.

Hugh if I missed something please shout out loud. Mind you anybody can have a say.

Have fun at it.

Kind regards

Nico

[Nico Ras]

Originally Posted by MJL21193

subtle differences from one component choice to another, it is beyond my capacity to resolve.
Add to that is my hearing is on a steady downward trajectory ...

Hi John,

I think the point here is to listen that there is no obvious flaw. I don't think any of us are capable of hearing something earthmoving without being able to compare it to something less earthmoving.

You are experienced in both designing and listening to spot a flaw in the sonic representation of the system and honest enough to give your real opinion, regardless whether it is good or bad.

Kindest regards

Nico

[MJL21193]

Originally Posted by Nico Ras

...and honest enough to give your real opinion, regardless whether it is good or bad.

This is true... I might candy coat it a bit but it can still be a bitter pill.

I'm not going to have time this weekend - too many things going on, but looking at the design, having simulated it, I doubt there will be a problem. It's simple and basically bulletproof. There may be some compensation issues, but that is best left till the board is finalized to tweak.