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The Opamp thread - Page 266

post #3976 of 4693

Quick question if anyone can answer on the PCM5102.

 

 

Feature 02US 03US 02 Dragon Comparison
         
         
         
DAC PCM1793DNR: 113 dB
THD: 0.001%
PCM1798DNR: 123 dB
THD: 0.0005%
PCM 5102DNR: 112 dB
THD:0.0022%
 
I/V OP275 MC33079 This is a voltage-out DAC so there is no need of I/V conversion

 

 

The Teac / Esoteric A-H01 uses this D/A chip as well.  However it doesn't have an RCA or COAX line-out (the UD-H01 has line-out, in dual-mono with 2x PCM1795).

 

So my question is... is the Dragon an ideal USB DAC for connecting to amplifiers via RCA, to experiment with op-amps in the amplifier section, or am I overlooking something?  Clearly a conventional DAC with I/V will potentially colour the experiments right?

 

Likewise, the Teradak 2.6 has passive I/V - http://www.teradak.com/en/product_view.asp?ID=206

 

I see portable devices like the Teclast T51 using OPA2604 for the 'line-out', is this standard or are there portable devices with true direct signal from the D/A?


Edited by kiteki - 6/14/12 at 3:45am
post #3977 of 4693
Quote:
Originally Posted by qusp View Post

ok mate, no worries, I reckon i'd be pretty curious too by this stage. Being DC coupled is a good thing for audio, particularly headphones as output caps tend to need to be large to allow driving low impedance headphones without rolling off the bass. they form a high pass filter at the output in combination with the headphone impedance and the amps output impedance (I will call impedance Z from now on). Electrolytics are not so linear and have lower damping factor (means high output Z) so the amp does not have quite as good electro-mechanical control of the driver, not such an issue with headphones some would say, due to being physically small, but I disagree.

 

DC coupling is not without its caveats though, the output caps help to protect the headphones from DC at the output if the amp, so the fact its a DC coupled amp, means although audio performance is good, if there is a failure condition in the amp that creates DC your headphones will see all of it.

 

indeed the temp sensor is handy for all sorts of things and most are pretty cheaply priced, so you didnt buy the fluke? would have been risky on ebay, fluke gear on the bay is often fake, as its a well known big brand.

 

Thanks qusp - I'm more convinced than ever that, using a DC coupled amp like the PB2, I don't want to risk the use of unstable op-amps.

 

Regarding Fluke 62 vs. RayTek MT6 - I found a couple of Fluke 62 reviews which say that the Fluke 62 is just a re-branded RayTek MT6 - they truly are identical except for color and branding.  

 

I picked up the RayTek for $52.00 instead of $86.00 for the Fluke.

 

 

Fluke_62.jpgRaytek_MiniTemp_MT6_-_Same_as_Fluke_62.jpeg

 

 

                         $86.00                                                                $52.00

 

 

Mike

post #3978 of 4693

I have a iBasso D-12 and a iBasso D12 with the topflight kit. I am interested in OPAmp rolling and try out the different sound.

I find the high freq response of the D-Zero better than the D-12 stock OPAmp.

Does anyone knows what OPAmp is used the D-Zero.

Also, is there any list of compatible OPAmps with the iBasso D-12?

post #3979 of 4693

D-Zero is AD8656.  I recommend you try a few AD chips until you find one of your liking.  You can start here.

post #3980 of 4693

kiteki, saw your Q, no time to answer till tonight

post #3981 of 4693
Quote:
Originally Posted by kiteki View Post

D-Zero is AD8656.  I recommend you try a few AD chips until you find one of your liking.  You can start here.

Thanks for the information and the recommendation. Ordered a AD712KN right away without checking if it a dual or single channel OPAMP tongue.gif

post #3982 of 4693
Quote:
Originally Posted by viveksaikia22 View Post

I have a iBasso D-12 and a iBasso D12 with the topflight kit. I am interested in OPAmp rolling and try out the different sound.

I find the high freq response of the D-Zero better than the D-12 stock OPAmp.

Does anyone knows what OPAmp is used the D-Zero.

Also, is there any list of compatible OPAmps with the iBasso D-12?

 

Check the D12 and D10 threads, there's plenty.  Most require soldering, if I recall correctly.

post #3983 of 4693
Quote:
Originally Posted by Mad Max View Post

 

Check the D12 and D10 threads, there's plenty.  Most require soldering, if I recall correctly.

 

yeah well they dont really make dip8 any more in new models, not for a while now

post #3984 of 4693

That's why many chips require soldering to adapters.  Otherwise, you are left with DIP8 chips, some of which are meh, some are super fast video opamps with a lot of need for compensation and whatever else.  I wouldn't complain about OPA602, neat chip, but probably not such a good buffer with only 20ma output.

post #3985 of 4693

If only alot of the one that was mention came in dip-8 vers.That way I don't have to send them off to get them soldered.

post #3986 of 4693

Is there any reason why a class-A biased OPA627 with some silly resistors would sound worse than a regular OPA627?  I don't like it.

 

When the PDF says absolute max +-18V that's 4x 9V batteries right?  What happens if I overclock the OPA627 to +-19.2V?


Edited by kiteki - 6/15/12 at 12:31am
post #3987 of 4693

1) All (well, maybe not all, but most) OA perform better when not loaded. Biasing in class A is load, so it could sound worse (depends on the value of that bias resistor = biasing current)

2) Yes, +/-18V = four 9V batteries. If you "overclock" it to +/-19.2V nothing serious would propably happen (it could perform worse, but to burn it you need much higher voltage).

post #3988 of 4693

Thanks for the swift answers Amarok!!  The loaded OPA627 doesn't sound very good.  I will experiment with voltage supply in OPA627 and OPA827 to see if I can hear the difference!

 

Edit:  My amplifier won't turn on when 4x 9V are connected.


Edited by kiteki - 6/15/12 at 12:59am
post #3989 of 4693
Quote:
Originally Posted by kiteki View Post

Quick question if anyone can answer on the PCM5102.

 

 

Feature 02US 03US 02 Dragon Comparison
         
         
         
DAC PCM1793DNR: 113 dB
THD: 0.001%
PCM1798DNR: 123 dB
THD: 0.0005%
PCM 5102DNR: 112 dB
THD:0.0022%
 
I/V OP275 MC33079 This is a voltage-out DAC so there is no need of I/V conversion

 

 

The Teac / Esoteric A-H01 uses this D/A chip as well.  However it doesn't have an RCA or COAX line-out (the UD-H01 has line-out, in dual-mono with 2x PCM1795).

 

So my question is... is the Dragon an ideal USB DAC for connecting to amplifiers via RCA, to experiment with op-amps in the amplifier section, or am I overlooking something?  Clearly a conventional DAC with I/V will potentially colour the experiments right?

 

Likewise, the Teradak 2.6 has passive I/V - http://www.teradak.com/en/product_view.asp?ID=206

 

I see portable devices like the Teclast T51 using OPA2604 for the 'line-out', is this standard or are there portable devices with true direct signal from the D/A?

 

I think you are misunderstanding the term line out. line out simply means line level voltage output, just a reference level voltage so that engineers know they arent going to blow or clip the input of their amps or mixers as they know what to expect. it has nothing to do with whether there is a circuit in the output and an IV convertor is simply there to give that standard level from a current output. this could be a simple resistor, a discrete jfet IV, or transformers along with many other types.

 

the above quoted specs I wouldnt take anything from the above, the 3 dacs have just taken the ideal datasheet performance from the dac chip, nothing to do with its performance in the application.

 

the below is a table for the line level single ended standard. in reality dacs are all over the place, the sabres balanced out for instance is about 3vrms @ 3.9ma which is about double the +6db SE standard, so pretty hot voltage, but lower than normal current.

 

Some current out dacs will handle passive resistive IV well, depending on their voltage compliance and current, others will not handle it well at all, with the sabre the THD+N is not great with passive IV, but some still prefer the sound. I personally dont like passive IV all that much; its a bit musical for my taste, top end lacking sparkle, easy to listen to, but for me dynamics are compromised, at least with the dacs i've tried it with.

 

Line levels and their nominal voltage levels.
Use Nominal level Nominal level, VRMS Peak Amplitude, VPK
ARD, Germany +6 dBu 1.550 (approximate) 2.192 (approximate)
USA professional audio +4 dBu 1.228 (approximate) 1.737 (approximate)
Consumer audio −10 dBV 0.316 0.447

 

the voltage out dacs, like the one you mention and wolfstons, should be buffered, not connected directly, they should not be loaded with capacitive cables etc and usually have an internal opamp anyway. so if you just have a well designed transparent IV stage that you leave constant during the tests, then this is just as valid as a baseline.

 

I generally prefer current out dacs as I like maintaining control of the IV stage, but i'm quite intrigued by the AK4399, so have picked up a couple of chips and a suitable proto board

post #3990 of 4693

most high performance opamp output stages these days are already pretty deeply biased, so with nominal load should be in class A anyway. It depends on the load, driving low impedance headphones directly would take most out of the class A envelope without extra bias, so it can be useful

 

I would be more likely to use a current source than a resistor anyway, like a jfet CRD, or a jfet wired as current source, this creates a much higher impedance current source so the noise on the PSU rail isnt injected directly.

 

not a fan of the adapters, they are a necessary evil though.

 

as for your batteries, realize that the voltage is a nominal rating, probably they start very slightly higher, spend most of their time around 9.4-9.6 and then drop down as they run out, depends on the chemistry what this curve will look like. probably the positive rail will drop much quicker, so watch that.


Edited by qusp - 6/15/12 at 3:26am
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