Fostex HP-P1 Portable Amplifier and DAC for iPod/iPhone (Short REVIEW and Impressions Thread) - Page 2

Quote:

Originally Posted by Vitor Teixeira 

Hi qusp,

 

Does that mean that we can actually output 24/96 from an iPod/iPad?

So this is a dream came true! An iDevice and the HP-P1 is all we need to carry an outstanding music library!

But the downside it's that we cant sync those files with iTunes, right?

And for the iPad it's only possible with the camera conection kit?

I'm a bit confused..
 

 

ipad can output audio complying to the usb audio spec, some devices allow 24/96 and higher under the latest specification. the ipad firmware was recently upgraded to allow 24/96 playback currently this means only some movies and FLAC will play at this resolution. afaik the other idevices do not yet allow this, only ipad, but it will probably change soon enough. it works with some other devices too, some home docks will allow it, but CLAS doesnt, i dont yet know if the HP-P1 does, someone else will have to check. so as far as portable goes, only ipad and only with the cck both v1 and v2 ipad allow it; but it only works with dacs that will play it 

hey hey, you havent quite got it. yes lipoly and lifepo4 packs often come with charging circuitry to limit the input charge and make sure that they arent over discharged as well. aplies more to lipoly, not so much to lifepo4 because lipoly can literally explode in slow motion and cause fires, whereas you have to be pretty 'absentminded' to cause such a problem with quality lifepo4; its much more forgiving, but not immune. this is mainly for batteries that are sold to the public for use in a variety of devices, just as a backup. but i would say that the fostex has its own charging circuit to take care of this and the battery, being that it was sold to an oem producer, it is not required by law to have the circuit, as they now are for the packs sold to the public. 

no what i was saying, is that which ever chemistry it is, it will be a certain voltage and a certain capacity for example 13.2v (4 x 3.3 cells) and 2300mah (capacity) this will have been specified by fostex to get the best runtime in their specific amount of space. the energy density of batteries increases as time marches on, but in general each battery chemistry sticks to a nominal voltage per cell in the pack. for lifepo4 the nominal voltage is 3.3vdc per cell and from memory lithium polymer is 4.2v, this means that over its charge when fully charged it (lifepo4) will be closer to 3.6vdc per cell and near the end of its useful life more like 3vdc, but it spends most of the cycle between 3.4-3.3 dropping from 3.6 pretty quick and dropping from 3.3-3 pretty quickly also.

so the charger and charge manager/fuel gauge in the fostex, will be designed to charge based on the nominal, max and min thresholds of the chemistry its designed for. if you go and change that voltage or battery type, the charger will act on the wrong info, thinking the battery is full when its not, thinking its empty when its not etc and damage, or make the battery go al explody in your pocket. battery capacity is ok to increase, generally anyway, as the charger will be based on the voltage thresholds, not the capacity, it judges its actions on that and has no idea of the capacity, which is what gives you longer life anyway.

with me? sorry for the longwinded explanation; its what i do hehe. so all i'm saying is, as long as it will fit, its the right chemistry and the right number of cells that are wired in the correct way (series or parallel), it may well work even if its not the same custom made pack, but you absolutely must make sure thats all correct by checking with the manufacturer, dont take my word for it.

its all elementary anyway as i doubt very much it will be an issue you ever have to deal with.

Just put in my order for one of these with Performance Audio; thanks for locating that dealer.  Price is better than other places I've checked.  Did call in however to find out their first allotment has already sold out, so I guess we'll see when they'll get another batch and when they'll send me my order.  Looking forward to comparing this against my current setup!

-Ed

Jeremy, what is the source of this information please? (It's news to me. According to Vinnie, nothing in the design of CLAS limits high res. The issue is on the Apple side)

Ah, I see the issue now. High res may curently only be available through the iPad camera kit and therefore only to standard USB DACs. So this is a limitation in the current iPad firmware that may impact on the CLAS, Fostex, Wadia, Pure-i20 etc. Still it is early days as to how this will unfold.

How powerful is the amplifier?  Can it drive modern day can : LCD2, HE5, HD800

flac player doesnt have any limitation on ipad as least its confirmed to work at 24/96, pretty sure i read it regarding clas in there the other day, but it doesnt make any sense that it would work, as the ipad only does it via the usb audio spec, which clas does not comply to (being that you cannot use it with a pc). as it has its own proprietary way of transfering the data which is more likely to be causing problems if you are having any, the chances of the ipad supporting that protocol are very slim, but not impossible. the info was first posted on here by Benchmark, who discovered it would work with their dacs

I said noting about the CLAS doing the limiting, but its not the ipad, cck, or usb audio codec thats doing it, clas may do hires internally, but until they rewrite the software to allow hires with ipod/ipad natively, it will not happen, because that IS where the limitation is, the ipad was just catching up with the usb standard with that firmware update, which allows much higher than that now without a driver (32bit 384khz and multichannel)

The authentication chip coomunicatiun protocols are different. Within that, I don't know if the CLAS is different again from Fostex, Wadia and Pure i-20. This is an issue that I think we are going to hear a lot about. It is absurd if these high end units are denied high res. (Personally I don't care; I'm a dinosaur with my CDS, but a lot of people do.)

i dont think its a matter of being denied it, apple arent great for being open, but in this case i dont think it has to do with that. THEY have to rewrite their DSP software for it if they use proprietary software to transfer data (especially if they do it asynchronously of slave the idevice as clas does), , its them thats doing the limiting now. i dont know, but wadia will be using their own software, not sure about the others. the cck does not make this possible, it just happens to be the only device at the moment that handles the transfer within the standard i think. bit of conjecture there so i'm not stating a fact, but the pieces all fit.

Quote:

Originally Posted by kiertijai 

How powerful is the amplifier?  Can it drive modern day can : LCD2, HE5, HD800

No, it have quite weak output. I have problem to even get enough volumefrom it  with Sennheiser HD600, so it cant drive them to ideal SQ.

No, it have quite weak output. I have problem to even get enough volumefrom it  with Sennheiser HD600, so it cant drive them to ideal SQ

    Thanks,

    So I think we have to use it with the Grado's, Ultrasone, Sennheiser below 600,  JVC DX1000 , Sony MDR Z1000  and other IEM, CIEM.

That should be enough.