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The Opamp thread - Page 286

post #4276 of 4812

Now you're actually making me want to buy them!  I only have one discrete op-amp which is made by a different company in Taiwan.

post #4277 of 4812

Sun is fun!

post #4278 of 4812

I have 3 OPA 2107 I received from TI, I have decided against getting the LDI+ and will be getting an Asgard. So no need to keep them. Brand new, unused, still in anti-static bag, just opened it to verify contents.

Got them for free, will sell them for free. Just pay me for postage and you can have all 3 - I won't split them up because I'd have to get different cases for each. Will ship them in 2-3 weeks, so we can do it then, just wanting to put this out there early so it's all set up and ready to go when the day comes. First response gets them, just PM me!


Edited by SurfWax - 12/16/12 at 6:58pm
post #4279 of 4812

Hmm I just found this http://www.twistedpearaudio.com/digital/cod.aspx

 

 

The "current-out DAC" which allows for passive / external I/V.

 

 

Cusp weren't your bashing passive I/V concepts a wihle ago?  This DAC is released by the same company as your Buffalo...............


Edited by kiteki - 12/17/12 at 10:17am
post #4280 of 4812
i'm sorry, whats the question?

ANY current out dac allows passive or active IV stages. I V stands for Current (I) to Voltage (V) conversion
Edited by qusp - 12/17/12 at 7:44am
post #4281 of 4812

I thought you thought current-out / passive I/V designs are inherently flawed, well it seemed that way at the time, I didn't expect to see a passive I/V DAC from Buffalo.

 

I don't know, I suppose I connected you to Buffalo, and was thinking "qusp = buffalo" and then saw "buffalo = passive I/V", so was interested in your thoughts on that model, I suppose, since you know a lot about DAC's 'n stuff.

post #4282 of 4812
what in what I just said makes you think i'm FOR passive IV?

you still havent read up on Ohms law have you?

put resistance in the way of current, it turns into voltage, put resistance in the way of voltage, it turns into current....that conversion can be done passively with a simple resistor, or it can be placed at the output of a current feedback amp, discrete follower/buffer or in the feedback loop of an opamp so that the amp or active device in the active IV stage is driving the resistor to convert to voltage for your amp to amplify.

this means that the dac can be allowed to drive a very low impedance, not as hard work. its a current source remember, not the voltage source we spoke of before driving headphones, if you want current to stay current, you need to provide a low impedance

passive IV with ES9018 is Dumb, you need a really robust current source to use passive IV, even then i'm not a big fan, but with ESS you lose performance significantly, could be as much as 20dB THD lost. the ESS is a pretty wimpy current source, not low current, but not high impedance, an ideal current source has infinite impedance, es9018/12 is only 195ohms output impedance in stereo mode, so you need a REALLY low impedance

some companies still persist in using passive IV with ess, not many though

the COD is just a current out dac (PCM1794A) wit power supply, its a VERY rudimentary design, the dac is kinda just there, its a current out dac, but the 1794A has a higher (but still not that high) output impedance, so will work with passive IV better than es9018, that being said the ess will still win out, but with a lot of wasted potential.
Edited by qusp - 12/17/12 at 10:49am
post #4283 of 4812

I don't know about you, but I'm noticing a pattern in high-end audio that it's taking the path of either one of these two...

 

- NOS / passive I/V / PCM1704...

- 128x oversampling / 192kHz upsampling / OPA16XX / LME49XXX / ES9018...

 

You and someone else had me fairly convinced that passive I/V is inherently flawed, I'm surprised / confused Buffalo is selling it as well, just like I was surprised the Hifiman HM-901 changed from PCM1704 to ES9018 recently, worlds apart, yet always next to eachother?, lol.


Edited by kiteki - 12/17/12 at 11:00am
post #4284 of 4812
why are you surprised? ESS is the name on everyones lips, what makes you think the change was about anything more than that and the fact the DX100 was massively outselling the HM801?
OT (Click to show)
I dont really agree with dual mono, the ESS is already made of 16 parallel balanced dacs and the power supply topology is already set up for dual mono with one chip, so there is no added separation from using 2 and unless they actually exceed the analogue spec offered by the single chip, which is already a task, then its just using battery. i'll be interested to see what they come up with, but I feel there are other areas that should be taken care of before adding another dac chip; particularly if theyve had to make compromises to make it happen

twisted pear isnt selling passive IV.... they dont sell an IV board that does passive IV; they simply mention its an option so as not to alienate those who like passive IV and as a matter of completeness. passive IV is an option with ANY current output dac.

besides, I do use a buffalo II in my transportable because its compact and easily powered, nothing else in the build is twisted pair and I modified the dac board too, I think it was their last really good design, but my home dacs are ackodacs, i'm not a huge fan of the way the TP design has developed and dont regret jumping ship.

there are some nice voltage dacs too like the AK4399 from AKM, but generally (and with some trouble I might add) you can get higher performance with current out dacs when all your ducks are in a row, while something like the AKM is more easily applied and more robust, perhaps a better choice for some of the BIII builders i've seen and honestly some of the commercial ESS designs ive seen, itts not an easy dac to apply properly and many seem to miss the mark

anyway enough OT
Edited by qusp - 12/17/12 at 11:36am
post #4285 of 4812
Quote:
Originally Posted by kiteki View Post

 

So a DT770 / 600 ohm is low current, and a sensitive 16 ohm IEM is high current?  I don't get it, but thanks anyway.


Ahhh just happened to drop in this thread and this is driving me nuts. lol

 

How about this, 600 Ohms is high impedance so high voltage, 16 Ohms is low impedance so low voltage.

Voltage being inversely related to current at any given impedance, therefore 600 Ohms is low current and 16 Ohms is high current.

 

You got 4 Ohms & 8 Ohms speakers don't you?

Intuitively you wouldn't think these deserve just some low current TL072 right?

 

--

a side note, qusp you really have the patience of a superman!


Edited by hoshiyomi - 12/19/12 at 3:49pm
post #4286 of 4812
Hi everyone, apologies upfront if I may have missed any info anywhere (this is an overwhelming forum).

I'm new to this, and Xmas started slightly early for me as I have just been given a iBasso D12. As well, I was handed a few opamps (I think) and was wondering if these are ok to plug into the D12. I was told they are all duals, meaning I should only plug one in at a time? They all look the same, black with 8 pins and have the following written on them:

UTC UAA2 MC1458BL YA
JR15ABE3 LMC64 82AIN
96A4K9M RC4558P
JC73RA LM 833N

Any insight is greatly appreciated.

Cheers
post #4287 of 4812
Quote:
Originally Posted by Soun View Post

Hi everyone, apologies upfront if I may have missed any info anywhere (this is an overwhelming forum).
I'm new to this, and Xmas started slightly early for me as I have just been given a iBasso D12. As well, I was handed a few opamps (I think) and was wondering if these are ok to plug into the D12. I was told they are all duals, meaning I should only plug one in at a time? They all look the same, black with 8 pins and have the following written on them:

UTC UAA2 MC1458BL YA
JR15ABE3 LMC64 82AIN
96A4K9M RC4558P
JC73RA LM 833N

Any insight is greatly appreciated.
Cheers

 

Hi Soun,

 

You are very smart to have asked before trying those op-amps!

 

I'm not nearly as experienced at rolling op-amps as several others on this thread, but I've never heard of any of those, so unless you receive encouragement from someone else, I would say do not plug any of those into your iBasso D12.  

 

Wait for someone to make a recommendation of what they have tried successfully...

 

Mike

post #4288 of 4812

I think a very important idea for anyone new to this thread is that the thread contents may in fact not be "valuable information" - but are rather mostly "noise" - are based on dubious "socailly constructed" ideas

 

several conceptual errors collide here - naive "just listen" "subjective evaluation" and ignorance of op amp qualification by application circuit differences, not recognizing different performance demands in preamps, DAC I/V, filters, buffers, headphone driving

 

 

naive "just listen" "subjective evaluation" - is the mode throughout the audiophile world - overwhelmingly represented in the press, marketing - but ignores real human limitations, known perceptual psychology - try learning some of the science

 

 

and there are hundreds of op amps made for the very reason that they have different mixes of noise, frequency response, gain, slew rate, output current... each op amp's mix of specs may suit different circuit applications - since nothing practical can be built with "the best" specs for every application

 

but the overwhelming majority of "recommendations" here ignore/don't mention the circuit application, or even the power supply Voltages - and even within a category of a specific audio circuit type the engineer can make differing decisions on circuit details that affect op amp choice

 

 

obviously the idea of op amp rolling is compelling, people like playing - but most of the posts here are technically, psychoacoustically without value - a few could be harmful to your equipment

 

 

note to moderators - and committed kool aid drinkers (or "committed subjectivists") - I only point this out at very infrequent intervals - thousands of posts go by between "critical" posts - and I am addressing newbies - such as have recently posted - they deserve pointers to alternative opinions, information on the scientific, engineering basis of their hobby - to decide for themselves where to spend their time, money


Edited by jcx - 12/22/12 at 10:47am
post #4289 of 4812

Please give us said pointers.

post #4290 of 4812
Quote:
Originally Posted by Soun View Post

Hi everyone, apologies upfront if I may have missed any info anywhere (this is an overwhelming forum).
I'm new to this, and Xmas started slightly early for me as I have just been given a iBasso D12. As well, I was handed a few opamps (I think) and was wondering if these are ok to plug into the D12. I was told they are all duals, meaning I should only plug one in at a time? They all look the same, black with 8 pins and have the following written on them:
UTC UAA2 MC1458BL YA
JR15ABE3 LMC64 82AIN
96A4K9M RC4558P
JC73RA LM 833N
Any insight is greatly appreciated.
Cheers

 

MC1458

LMC6482

RC4558

LM833

All are dual-channel opamps indeed.  After inserting one in the right position and orientation, turn on the amp without your headphones plugged in and check and see if the chip gets very hot.  If so, then turn the amp back off and remove it.  Don't bother with those overheating chips, although all of these should work okay since they're all slow opamps.

 

LM833's datasheet says that it is for preamplification, among other things, so perhaps you should avoid putting that chip in the buffer position just to be safe.

 

Make sure that you don't put them in backwards or you will damage the opamp and possibly the D12.  Each chip has a notch that indicates which side of the chip that pins 1 and 8 are on.  Or there will be a printed or embossed dot next to pin 1.  Judging by this photo, when you insert an opamp into the D12, pins 1 and 8 should face your left if you are looking at the front of the amp with the headphone output and volume knob.

Edit: the linked photo shows single-channel opamps in the amp, make sure that you do not insert those dual opamps in the same manner!  I think that the duals go in the middle somehow.  Another D12 user should be able to confirm.


Edited by Mad Max - 12/22/12 at 1:07pm
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