Originally Posted by zilch0md
More confused than ever...
So, does this mean that if my PB2 is equipped with op-amps rated for an absolute supply voltage of +- 18V, I can feel free to connect a 36VDC external power supply?
I suspect you will answer, "No," but I don't understand why you will say, "No" other than to advise me to stick with the manufacturer's recommendation to not exceed 16V DC at the external supply jack.
(the villiage idiot)
that depends on how the power supply is handled, or more specifically, how the ground reference is generated and; as covered, whether there is any type of DC switching/upconverting performed to boost voltage, or generate the negative rail voltage. of course if the manufacturer says not to exceed 16vdc, do not exceed 16vdc, they will have reason for saying this.
the use of a voltage doubling circuit is not all that common in high end headphone audio, even portable. 1. because it is a process that generates noise, mostly switching noise (out of band noise, but noise all the same) 2. it means a virtual ground is created and this is higher impedance than a real split supply 3. most headphones are perfectly happy with the swing available from +/-8-9vdc rails, with only 600ohms needing more IMO. for instance in my portable balanced dac-.amp i'm 'only' running a 4 series connected A123 LiFePO4 for a total of +/-6v6->7vdc, this is regulated down to +/-5.9vdc with a dual mono/bipolar supply and I challenge anyone to go past 60% with HD600. these batteries are capable of 140A bursts, thus I dont use them directly lol even though their noise and output impedance is lower than the regulators (2 x LTC3032)
Jan has some clever tricks in the stepdance overall, but i'd rather balanced than pseudo balanced and i'd rather bipolar rather than pseudo bipolar, both mechanisms introduce noise and impedance
Originally Posted by SpudHarris
Mike, there are other components in there that may limit what you can safely pump in.
what he said
Originally Posted by zilch0md
I can readily imagine that's true, and would not want to exceed the manufacturer's documented maximum permissible external supply voltage, but I was hoping to gain an understanding of how it is that kiteki can use 36V DC battery packs to supply power to op-amps that have the same +-18V absolute maximum Vs rating as many of the op-amps that I use (including the AD797 - which we both use).
I have no problem understanding that a swing from -18V to +18v is 36V (doh!), but does this mean that if kiteki were to use only two 9V batteries in series (for a total of 18V) instead of four 9V batteries (for a total of 36V), kiteki's op-amps would only be getting HALF their maximum permissible supply voltage? If the answer to that question is, "Yes," then does this mean that when I use a 16V external DC battery pack with my PB2, I'm only getting a swing of -8V to +8V, which is less than HALF of my op-amps' maximum permissible +-18V supply voltage? I don't think so. Here's why:
Jan Meier once told me that the Meier Stepdance uses a "voltage doubler" that will take an internal 9V battery up to 18V or an external 15V supply voltage up to 30V.
Maybe that's what's going on with the PB2, also - when I connect a 16V external power supply, the op-amps see 32V because of some sort of voltage doubling circuit - and maybe kiteki's amp doesn't have this voltage-doubling feature...
I think kiteki is playing with the output stage of his dac, arent you? but yeah everything else is covered above. i've not looked at the pelican PSU, I really dont see the need for +/-16v, but hey...
Originally Posted by kiteki
I'm not aware of any volting doublage, though I am interested in one since I can't fit 4x 9V batteries in a portable amplifier lol.
Do not put a class-A biased OPA627 in the wrong way, I turned on the DAC and it looked like it was going to catch on fire.
Edit: Threw away the chip all fixed.
haha yeah batteries will do that, no current limiting
Edited by qusp - 6/16/12 at 12:14am