Question of rail splitter

[Q00 0]

My PPA will be AC powered, so no need rail splitter. The ground will be from the transformer. But I will use Op-Amp to isolate the source ground, but in this case, no need for high current capacity.

 

Op-Amp will sounds better with high supply voltage. So I will use as high voltage as possible for the supply. To me, it's kind of inapropriate to use battery with PPA.

I suppose so but i would advise u to have some sort of voltage protection in place and sum really good caps. Our main source voltage isnt exactly 'clean'.

 

I think the main reason some people use batteries is for the flat voltage and quietness that a battery provides in a circuit from what i read in head-fi.

[bpribadi 0]

bpribadi, ok, I can understand that. If the transformer you will use is small enough to fit into my casing I won't mind going that way too. Have you decided which transformer you will use? Unfortunately I know nothing about the rectification diodes etc.

 

Hi Heady,

 

I will use toroid transformer from Farnell (I don't know cheaper place to get the toroid transformer).

 

The case you want to use is it the Hammond casing we bought? I will use it as well for the PPA? So we will look for toroid with just the right size

 

Actually I have one 50VA toroid already, but I think it is too big.

[mukegile 0]

I suppose so but i would advise u to have some sort of voltage protection in place and sum really good caps. Our main source voltage isnt exactly 'clean'.

may be we want to explore some articles on balance power;

eq; ,.

http://www.equitech.com/articles/bpng.html

 

 

[bpribadi 0]

I suppose so but i would advise u to have some sort of voltage protection in place and sum really good caps. Our main source voltage isnt exactly 'clean'.

 

I think the main reason some people use batteries is for the flat voltage and quietness that a battery provides in a circuit from what i read in head-fi.

 

Yeap... this is my strategy:

 

1. Use AC socket with filter. I know it is not really recommended for high current equipment such as big power amp, but for headphone amp should be ok.

 

2. Single stage regulation for the high current circuit, and Dual stages regulation for the low current circuit.

 

3. Three stages of capacitors, Panasonic FC / Nichihon for Elco, Sanyo Os-Con near the Op-Amp, and another MKP/MKS very near the Op-Amp.

 

I think should be 'clean' enough

 

My concern with battery is, to much battery to get high voltage. I think for the cleanness of battery vs. the high slew rate with AC powered high voltage regulated PS, I prefer the high slew rate for the effect is more audible than the clean voltage of battery. Anyway, the regulated PS is already clean enough for the Op-Amp, since Op-Amp also have some capability to reject PS ripple.

Edited October 28, 2004 by bpribadi

[huangyong 0]

Think should use AC for my amp, and omit the virtual ground. use the real ground instead.

but is it true that real ground is noisier than virtual ground?

 

i found some cheap & used toroidal transformers in SLT. may be good for experiment.

 

bripadi, what is the point of using 2-stage regulator? better?

Edited October 28, 2004 by huangyong

[bpribadi 0]

may be we want to explore some articles on balance power;

 

But that's what we always use in the audio eqpt PS..., can you enlightened us where is the difference?

 

bripadi, what is the point of using 2-stage regulator? better?

 

I know my handle is difficult to spell Just call me Bram that's fine with me...

 

Well it is just my idea, how good it is should be seen in Oscilloscope. Do you have oscilloscope in your lab for us to test it?

[bpribadi 0]

but is it true that real ground is noisier than virtual ground?

 

All depends on the power supply circuits and design... and that's also the reason why we use regulators

[huangyong 0]

 

I know my handle is difficult to spell Just call me Bram that's fine with me...

 

oops.. Sorry

[bpribadi 0]

No problem with me.. Don't take it seriously, it is just to make it easy for everyone, to type my real name is much more easier than my nick....

[aaa 0]

I'm planning to use 20 Sanyo 2100mAH NiMH AA cells in series to power my future PPA.

Sanyo 2100mAH is bcos it is $3 a piece, I can't find cheaper NiMH AAs.

NiMH is for the low internal resistance and not so sig memory effect.

the number 20 is a compromise between feeding enough voltage to the OPA627/637 and not buring the AD8610 (absolute max rail to rail 27V)

there in a protection diode that will take up 0.75v and the Q3 will eat up some more voltage.

 

Thinking of a build-in Trickle charger.

Where to find cheap 5v to 30v (or +-15 should do as well) DC-to-DC adaptor? (charge by USB cable)

or should I just add a AC to DC adaptor inside(for charging).

 

Edited October 28, 2004 by aaa

[bpribadi 0]

I'm planning to use 20 Sanyo 2100mAH NiMH AA cells in series to power my future PPA.

 

Wow...., man, I appreciate your effort to take the inconvenience way to power your PPA for the sake of clean DC supply (will you be able to hear the difference ?).

 

Sanyo 2100mAH is bcos it is $3 a piece, I can't find cheaper NiMH AAs.

 

Same price for Sanyo 2300 mAh at W Cube at Adelphi 3rd floor.

 

NiMH is for the low internal resistance and not so sig memory effect.

 

True, but if you put them in series, the internal resistance will become significant.

 

 

Well, for me, I want to enjoy music, and to charge and discharge batteries for PPA is just too inconvenience to me

[jtfoo 0]

Well, for me, I want to enjoy music, and to charge and discharge batteries for PPA is just too inconvenience to me

But in the spirit of the PPA, the designers themselve designed them to be portable, one of the 'P' stands for in PPA. Else it'll be a 'PA' amp, without the 1st P confusing?

[aaa 0]

Same price for Sanyo 2300 mAh at W Cube at Adelphi 3rd floor.

If fact I will prefer cells with lower energy density, even if price is the same.

(Where to buy industral NiMH cells???)

That's becasue cells with higher energy density tense to have higher self-discharge rate, less cycling life, and these are what I care more about.

 

True, but if you put them in series, the internal resistance will become significant.

I'm planning to use HD650, with 300ohm imp

power=I^2*R

lets say I will be listening at 100mW/channel power (that's rather loud)

0.1w=I^2*300

I=18.26mA (dynamic current, exclude the static current drawn by op-amp & buf)

since PPA has 3 channels, that's about 55mA dynamic current drawn

 

lets say each AA NiMH cell has a internal resistance of 0.025ohm

(from Sanyo date sheet for AA NiMH 2100 @1Khz after discharge to E.V.=1.0v)

0.025x20=0.5ohm

 

Since V=IR

the load-modulated ripple voltage= 0.5ohm x 0.055A = 27mV

 

that is very low in my view

 

Well, for me, I want to enjoy music, and to charge and discharge batteries for PPA is just too inconvenience to me 

I plan to have a build-in triggle charger, So I leave it charging while not in use.

You AC power will be plugged while in use, this is not that much of a difference in my view.

Edited October 29, 2004 by aaa

[aaa 0]

But in the spirit of the PPA, the designers themselve designed them to be portable, one of the 'P' stands for in PPA.  Else it'll be a 'PA' amp, without the 1st P    confusing?

I can assure you that Bram's PPA will be far more portable than mine.

I'm planning to use a case of 105x285x60mm without any empty space inside left.

with 20AA NiMH (on a 2nd layer battery board) inside it isn't going be light either.

I'll only be use it in a portable setup when I'm traing for a backpacking trip...

If I have the chance to design it again I will make it smaller.

 

anyway these will only be a problem after I get my PPA done and working...

[digi01 0]

Thinking of making the rail splitter above. but the current output capability seems not good (below 100mA). Any idea how to improve the current output?

 

put a few opamps in series? parallel? or use a high power opamp.

opamps in series,I think this way is ok.

 

 

digi

Edited October 30, 2004 by digi01