[miceblue]

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Mike Jobs died today?

Ehm, you meant Steve Jobs, right? If so, yes he died today.... R.I.P. Steve Jobs...he was truly an iconic innovator who helped shape today's standard in mobile technologies.
 

 

[lee730]

Quote:

Ehm, you meant Steve Jobs, right? If so, yes he died today.... R.I.P. Steve Jobs...he was truly an iconic innovator who helped shape today's standard in mobile technologies.
 

lol sorry. I meant Steve Jobs.
 

 

[kiteki]

 
Hmm I heard that LOD's on iPhones are just a 'scam', and that it's the same thing as the HO at max volume.
 
EIther way, even if the iPhone 4 could compete with the Teclast T51, or let's just say hypothetically that it rivals the T51, it's still $750 versus $130.
 
 
Actually, it's a shame the T59 was cancelled in 2007 as the "iPhone killer"... come on Teclast, 3 1/2 years, are you releasing the T59 or just talking talk talk talk

 

[qusp]

hmm, well i find that whole thing kinda funny really, a digital attenuator in this case, at full volume IS a pass through line out, there is no 'extra circuitry' to go through. but thats a rumour that is unsubstantiated anyway and gets pulled out every now and then. 

 

[Anaxilus]

Quote:

hmm, well i find that whole thing kinda funny really, a digital attenuator in this case, at full volume IS a pass through line out, there is no 'extra circuitry' to go through. but thats a rumour that is unsubstantiated anyway and gets pulled out every now and then. 

Still passing through the same opamp though yeah?  Wouldn't an idevice w/ a LOD adapter be even better in theory? 

 

[qusp]

pretty sure the later ipods and iphones are set up to drive the headphones directly with an integrated class D or G driver and there is probably just a different pin for the lineout. afaik there has never been an ipod with a separate opamp. there might be an on die section that is bypassed, but my point is, turning the volume up, does not amplify, turning it down attenuates, so turned up is just a state where there is no attenuation 

 

[Anaxilus]

Quote:

pretty sure the later ipods and iphones are set up to drive the headphones directly with an integrated class D or G driver and there is probably just a different pin for the lineout. afaik there has never been an ipod with a separate opamp. there might be an on die section that is bypassed, but my point is, turning the volume up, does not amplify, turning it down attenuates, so turned up is just a state where there is no attenuation 

Right, I get that, but it's not exactly LO performance but next best seems to me.  I'd imagine the T59 would still have the headphone amp section to pass through.
 

 

[qusp]

lineout only refers to a voltage reference/compliance level so that it is sufficiently high in dynamic range, but not too hot as to over drive the input stage of the amp you are connecting to. Pretty much every dac either has line level created by external or internal amplifiers to create 2v output referenced to an internal voltage reference, it has to be converted from usually a small amount of current (just a few mA usually). with the internal settings set to output 2v (usually less for portable devices) or higher for balanced output. only current out dacs with passive IV conversion do not do this and these are pretty much, if not totally unheard f for portable. so this popular thinking that lineout bypasses amplifiers is false. previously and still with some devices there will be an external dsp, amplifier, filter, damping resistor, capacitor etc to help drive headphones and this will (hopefully) be bypassed in the lineout in those cases, but given the ipods of today are voltage out, DC coupled and have on die amps and dsp, probably all that happens for lineout is certain processes are bypassed, rather than actual circuitry except perhaps for the small output damping resistors to protect from cable capacitance, or short circuit

 

[RAFA]

Quote:

sorry you do know what lineout is right? lineout only refers to a voltage reference/compliance level so that it is sufficiently high in dynamic range, but not too hot as to over drive the input stage of the amp you are connecting to. Pretty much every dac either has line level created by external or internal amplifiers to create 2v output referenced to an internal voltage reference, it has to be converted from usually a small amount of current (just a few mA usually). with the internal settings set to output 2v (usually less for portable devices) or higher for balanced output. only current out dacs with passive IV conversion do not do this and these are pretty much, if not totally unheard f for portable. so this popular thinking that lineout bypasses amplifiers is false. previously and still with some devices there will be an external dsp, amplifier, filter, damping resistor, capacitor etc to help drive headphones and this will (hopefully) be bypassed in the lineout in those cases, but given the ipods of today are voltage out, DC coupled and have on die amps and dsp, probably all that happens for lineout is certain processes are bypassed, rather than actual circuitry except perhaps for the small output damping resistors to protect from cable capacitance, or short circuit

What is then the desirable max output voltage for HO? (I know it depends on how much Ohm the HP have) I only ask, because I find it kind of difficult to understand this stuff. At the moment I want to build an amp section, feeded by an AD1955. The voltage, that the AD1955 puts out is 2.4V. Isn't this enough for a headphone?
 
BTW it seems that the T59 will come out in 11 months or in the eleventh month. In this source: http://bbs.imp3.net/thread-10459929-1-1.html it is not better specified. Kind of confusing...

 

[qusp]

yeah as you say it depends on the headphone impedance and sensitivity so i cant really answer such a generalized question, how is that 2.4v measured, point to point or vrms? for many headphones yes that will be enough voltage, but probably not enough current and depending on the output stage, possibly not low enough output impedance, also most dacs do not like being loaded with such a reactive load, probably it will effect the performance.
 
For higher impedance headphones its not going to be enough voltage either, i find for >/=300r 4-5vrms minimum is needed, preferably 6-7

 

[RAFA]

Quote:

yeah as you say it depends on the headphone impedance and sensitivity so i cant really answer such a generalized question, how is that 2.4v measured, point to point or vrms? for many headphones yes that will be enough voltage, but probably not enough current and depending on the output stage, possibly not low enough output impedance, also most dacs do not like being loaded with such a reactive load, probably it will effect the performance for higher impedance headphones its not going to be enough voltage either.

 
The reference current of the measurement is 0.960 mA. Your answer helped quite a bit. In the end: the purpose of opamps is actually to enhance current. With the data given by the headphones: DT1350 80ohms + 100mW max -> I can back calculate most of the components. (I presume)
 
Also gain-settings are now much clearer to me.
 
 

 

[Anaxilus]

Thanks for the tech brief.  Let me express my question in simpler terms and remind you I was asking about the T59 and your comment about just maxing the volume for LO sound since it's digital to remove attenuation.
 
IME, DACPort LX sounds better than the DACPort w/ volume maxed or at any other setting.  In fact, the regular DACPort sounds best at about 70% on the pot, max sounds noisy and congested by comparison.  Same result to a lesser degree w/ the iPod Nano when using a cheapie Crossroads LOD.  In neither case does the device via HO ever match the SQ of the same unit run via LO even though the iPod isn't even true LO.
 
So, you are saying the T59 would present a true LO sound maxing the digital pot of the T59 correct?  I can appreciate the possibility if that's due to the digital pot but otherwise my experience w/ other devices doesn't seem to mesh.
 
Another question, are all pots both digital and analog set to be 0 attenuation at max setting always?

 

[qusp]

Quote:

Thanks for the tech brief.  Let me express my question in simpler terms and remind you I was asking about the T59 and your comment about just maxing the volume for LO sound since it's digital to remove attenuation.
 
IME, DACPort LX sounds better than the DACPort w/ volume maxed or at any other setting.  In fact, the regular DACPort sounds best at about 70% on the pot, max sounds noisy and congested by comparison.  Same result to a lesser degree w/ the iPod Nano when using a cheapie Crossroads LOD.  In neither case does the device via HO ever match the SQ of the same unit run via LO even though the iPod isn't even true LO.
 
So, you are saying the T59 would present a true LO sound maxing the digital pot of the T59 correct?  I can appreciate the possibility if that's due to the digital pot but otherwise my experience w/ other devices doesn't seem to mesh.
 
Another question, are all pots both digital and analog set to be 0 attenuation at max setting always?

still dont think you are quite with me, but i'll just cover the q's above as best i can rather than rehashing. given the same circuit and appropriate gain/dsp/filter settings or lack thereof in the output stage in both instances, then yes a digital pot (which this isnt) will behave the same as LO, there is a difference between a digital pot and a dac chip which has integrated digital attenuation. if set to zero attenuation the latter is the same as line out, but the former also often has gain. i dont know about the t59, so i cant answer specifically whether the voltage is correct or higher than LO, which would overdrive/clip the input stage of the amp you connect to it, which is probably why you found 70% worked best and became distorted above that. if the digital pot is a separate device in the circuit rather than just an mcu changing the dacs registers to change the volume, then set to max may not be as transparent as it still has to pass through another DSP than if it were sent directly out.
 
so if the volume control is either integral to the dac chips dsp section, or occurs previous to the DAC stage, then full volume is just like not being there at all ie LO, in fact given sufficiently high bit depth (32bits or higher) in the volume control, even when attenuated its often like its not there at all, because there is 8 bits of dynamic range before the audio data starts being truncated.
 
basically though, without knowing the design of the t59 i cant give a definitive answer, there are digital volume controls and digital volume controls, there is no correct generalized answer. 
 

 

[Anaxilus]

Quote:

still dont think you are quite with me, but i'll just cover the q's above as best i can rather than rehashing. given the same circuit and appropriate gain/dsp/filter settings or lack thereof in the output stage in both instances, then yes a digital pot (which this isnt) will behave the same as LO, there is a difference between a digital pot and a dac chip which has integrated digital attenuation. if set to zero attenuation the latter is the same as line out, but the former also often has gain. i dont know about the t59, so i cant answer specifically whether the voltage is correct or higher than LO, which would overdrive/clip the input stage of the amp you connect to it, which is probably why you found 70% worked best and became distorted above that. if the digital pot is a separate device in the circuit rather than just an mcu changing the dacs registers to change the volume, then set to max may not be as transparent as it still has to pass through another DSP than if it were sent directly out.
 
so if the volume control is either integral to the dac chips dsp section, or occurs previous to the DAC stage, then full volume is just like not being there at all ie LO, in fact given sufficiently high bit depth (32bits or higher) in the volume control, even when attenuated its often like its not there at all, because there is 8 bits of dynamic range before the audio data starts being truncated.
 
basically though, without knowing the design of the t59 i cant give a definitive answer, there are digital volume controls and digital volume controls, there is no correct generalized answer. 
 

Great, thanks!
 

 

[chengdude]

This is a really interesting thread...8 pages of speculation.  It's true that in the last week or two, there's been several "leaks" (read: company PR) to sites like imp3 and ZOL, which typically means a product will be officially announced soon.  The more frequent the "leaks", the sooner the announcement. 
 
As far as specs, who knows?  True again, one of the  "leaks" mentioned 24/96, but beyond that nothing is known.  From the illustration, which as was mentioned, comes from the OEM doing the work for Teclast, you can see a DC power jack.  A "portable" device with a DC power plug and, by conclusion, a wall wart...not to mention a large-ish rotary volume knob?  The T59 is probably more intended as hybrid, semi-portable desktop hi-res music player.  At least they appear to have acknowledged that (assumed) power-hungry components require something more practical than a single Li-ion battery charged over USB.  Then again, who knows since it's all speculation.
 
By the way, Teclast is a shell company that markets MP3 players, PMPs, e-readers, MIDs, laptops, webcams, USB flash drives, and DVD drives.  They are most definitely not a "videophile" company, whatever that's supposed to mean.  They buy designs from different OEMs and market them under the Teclast name.  That's why there's a Nationite s:flo2.  Or, if you have the money, an (insert your name) version of the T51.
 
By the way (part 2), that "original design" of the T59 from 2007 pictured in a couple of earlier posts was fan art...original, yes; Teclast, no.