[eric343]

Quote:

Originally posted by Possum Wasn't the PPA supposed to be an amp done ppl's way?

Ppl's portable amplifier schematic (the one this amp is based on) has already been published and is an amp done entirely ppl's way (since he worked on it without any external input). I get the feeling that the PPA is more than simply a PCB layout of that amp; Tangent and Morsel are providing their own input. Whether this is for the better or worse remains to be seen...

 

[Possum]

It'd be nice, when the PPA is finished, if ppl gives us a "no compromise" version that he'd make.

 

[Squalish]

Why not go so far as to request a "PPL's Desk Amplifier"?

The goal of this was to fit the best circuit possible into a brick-sized portable amplifier. Making it bigger would require that it lose its portability. If you want something that uses up all the space it can use, either design your own or request it explicitly, don't ask that the PPL's Portable Amplifier(PPA) be made too big to be portable.

Personally, if you guys work well as a team and get finished with the PPA, I wouldn't mind another non-portable DIY headamp design.

 

[morsel]

Possum said: "Wasn't the PPA supposed to be an amp done ppl's way? ... It'd be nice, when the PPA is finished, if ppl gives us a "no compromise" version that he'd make."

Without Team PPA there would be no PPA. Together, we are designing a more practical amp with broader appeal and will actually get boards made and delivered to the community. We have detailed discussions on our private mailing list and talk to each other on the phone. I will be at Kurt's all day tomorrow helping to build and test the new prototypes. Tangent is invaluable with his wealth of parts knowledge, assembly experience, practical electronics, battery board design, and financial backing. Kurt has just joined us but has already contributed with testing FET CCS issues as well as tempering our somewhat volatile personalities with his level headed perspective. PPL is our chief EE guru and design engineer. I have been managing the project, doing the pcb layout, and contributing to the circuit design. We also listen to input from Head-Fi and Headwize.

Eric is correct. The PPA is much more than a PPL Pocket Amp. Go take a look at one of the published schematics and see for yourself.

"Tangent and Morsel are providing their own input. Whether this is for the better or worse remains to be seen..."

Differential output is my baby. Kurt and I get to find out how good it is tomorrow.

Squalish, we may eventually come out with an AC only amp, but it is way too early for such speculation. After the PPA is done Tangent and I will need to work on META42 v3.

Let's get back to the power supply, OK?

 

[Nisbeth]

Looks like you've got the calender filled for a while, Morsel

Have you completely abandoned the idea of a battery supply or is this still being considered?


/U.

 

[tangent]

Quote:

Have you completely abandoned the idea of a battery supply or is this still being considered?

The AC supply being discussed in this thread doesn't replace the battery supply, it complements it. The PPA will not run from alkalines, only from rechargeables, so we need to make a custom power supply anyway that is capable of the relatively high voltages and currents required to charge the battery pack. If people choose to run their PPA only from the custom wall supply, that's fine, too.

"No alkalines" isn't a ruler's decree, by the way, it's a statement of fact. A typical PPA will draw 50mA or more, levels which will cause alkalines' life to go down faster than linearly w.r.t. current draw. We have no choice but to power this amp from rechargeables for portable use.

 

[aos]

I just realized you are actually incorporating transformer / rectifier into the amplifier? Why not use a wallwart? A proper power supply will not care if its input is wallwart or a custom rectifier or even batteries - I'm speaking from experience. Ripple and noise will be eliminated either way. You're going to lose tons of space on board and on the rear panel too (for the
IEC socket). I don't know if there's even space for it in that enclosure you're planning to use. Wallwart is also more convenient for a portable as you can take it with you if you want and leave it at home if you don't. You can also have multiple wallwarts at your different locations. Net effect is lighter and smaller unit, ultimately more portable. I consider this one of the key tricks to keep the size / weight / complexity down. Also far less possiblity of hazard while you work on it when there's no high voltage in the box. The only drawback is that power supply has to be more elaborate in order to deal with higher ripple and potentially noise from non-Schottky / non-bypassed rectifier diodes.

 

[guzzler]

correct me if I'm wrong, but I don't think the supply was to be built into the PPA enclosure??

g

 

[tangent]

The PPA power supply will be external for this iteration. Maybe later we'll do an AC-only space-no-object PPA with the power supply on the same board.

 

[Possum]

Quote:

Originally posted by morsel Without Team PPA there would be no PPA. Together, we are designing a more practical amp with broader appeal and will actually get boards made and delivered to the community.

Ah, my misunderstanding of what the project was about.

EDIT: If you keep track of all the compromises you decdie to make to meet your project goals, you could have the information available to create somewhat of a less practical and more optimal home amp. Or the information could be available to DIY'ers who would like to build the amp themselves based on the circuit.

 

[Possum]

Quote:

Originally posted by Squalish The goal of this was to fit the best circuit possible into a brick-sized portable amplifier. Making it bigger would require that it lose its portability. If you want something that uses up all the space it can use, either design your own or request it explicitly, don't ask that the PPL's Portable Amplifier(PPA) be made too big to be portable.

I don't think 2 regulators, as mentioned in the post I had in mind when I replied, would take up that much space if cleverly designed. But I guess it depends on who's designing it.

 

[tangent]

Quote:

Wasn't the PPA supposed to be an amp done ppl's way?

This statement rankled me when I first read it, but I didn't have a ready answer. But on thinking about it, I see where the disconnect lies: there's a big difference between "an amp done ppl's way" and "an amp with every idea ppl has ever come up with or ever will come up with". It's true, the PPA does not incorporate every single idea ppl has ever run past the community, or even past the team via private email.

ppl has made several "pocket amps", and no two have been exactly alike. He's tried lots of variations, and mentioned most of them publically. Should the PPA incorporate every last one of those ideas into a massive hodge-podge, especially given that we're trying for an amp that's at least nominally portable?

That's my piece.

Now let's get back to the point of this thread: talking about the power supply, not the dynamics of Team PPA.

 

[aos]

Ok, if this is an external regulator (and even if it were internal), which is fed by AC, you should definitely include at least one regulator. I am still of firm belief that biggest part of differences in sound between different pieces of electronics that use same components is the quality of their power supply. In power amps it is rarely practical to have full voltage regulation but in a headphone amplifier it should be utilized to our advantage. I'm not saying that you should leave cap multiplier to speaker amps; use it if you like it, but include a regulator in front of it as well. From what I remember, it takes many capacitors to equal one regulator in ripple rejection.

Second, given the use of rail splitters, it is probably best to have a simple + and GND supply instead of dual rails (where would you connect them anyway?).

And third, since this regulator is not run from batteries, Jung's super reg should probably be worth evaluating. I've designed a board for it that I never got chance to use so if I have time I could donate one to the project for evaluation. But this brings another question, if this regulator is external that means that for battery operation there is no regulation whatsoever. Have you considered an on-board regulator where the power lines come to it, and then leave the option of populating it to the builder? You can even do it all surface mount, on the bottom side if there's no space, and then people can jumper it out if they don't want / can't solder it. All it takes is a SOIC chip, two resistors and perhaps a capacitor.

 

[morsel]

A capacitance multiplier is a relative regulator, as opposed to an absolute regulator. It regulates the voltage to a percentage of the input rather than an absolute voltage. In our circuit we are using a zener to limit the maximum voltage. If the circuit is always operated in saturation then it effectively becomes an absolute regulator.

I don't want to speculate too much. We have our hands full with PPA testing and the TLE problem. We will get around to power supply tests. If the capacitive multiplier is not good enough then we will reconsider our plans.

The dual rail version is intended for amps that require dual rails. One could use it rail to rail for the PPA, ignoring the ground connection.

We have discussed on board regulators. We may turn to them if we feel it is necessary.

 

[dta116]

I am currently working on a similar P/S for my audio projects.

The capacitor multiplier that includes a TL431 shunt regulator.
I feel this is probably the best of both worlds but have not quite got the results I want yet...

I will follow this thread with intrest....

Thanks guys, (and gal).