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The Opamp thread
Jul 20, 2009 at 8:16 PM Post #226 of 7,383
Quote:

Originally Posted by LingLing1337 /img/forum/go_quote.gif
No, you see, the DAC is a, erm... Beresford. So no spec sheets. I could try contacting Beresford NA and see if they know. I'll let you know if I find out. Jeff from Beresford NA, when I previously asked him about discretes, said that the unit they tried worked very well.


The Beresford 7520 have a line voltage of 10V in the opamp area.
 
Jul 20, 2009 at 9:11 PM Post #227 of 7,383
Quote:

Originally Posted by finax /img/forum/go_quote.gif
The Beresford 7520 have a line voltage of 10V in the opamp area.


Thanks. Any other valuable information such as this regarding the 7520 you care to share? (By the way, for some reason this post sounds very sarcastic. It is not.)
 
Jul 20, 2009 at 10:46 PM Post #230 of 7,383
Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif
It is impossible to know exactly how the power is utilized in the circuit from the input voltage. You can have a 12V input and have many different voltage swings for the amplifier section, including +/- 12 V. Which is more then enough power for the discrete opamps. It is hard to know exactly what is being supplied to the opamp without measuring it directly.


@LingLing1337
Do you have any type of manual or spec sheet which would outline the voltage swings for this opamp in the circuit?
Aside from measuring the opamps directly you could contact the company that makes the unit and ask them what the + and - supply voltages are for the 5532 in this design.


If he uses the Beresford dac the opamp is supplied from a single regulated +10v, (7810 regulator)
Negative pin of the op-amp is tied to ground

The noise of those Audio GD op-amps is not good with low supplies , 10v is NOT suitable
 
Jul 20, 2009 at 10:50 PM Post #231 of 7,383
Quote:

Originally Posted by LingLing1337 /img/forum/go_quote.gif
And if 10v isn't enough to plug in an Audio-GD unit, then what is a natural, analog-sounding opamp to cure my digitis?


Have you tried any op-amps with FET input? these can sound a little smoother than bipolar input types
 
Jul 21, 2009 at 12:15 AM Post #232 of 7,383
Quote:

Originally Posted by zoiberg /img/forum/go_quote.gif
If he uses the Beresford dac the opamp is supplied from a single regulated +10v, (7810 regulator)
Negative pin of the op-amp is tied to ground

The noise of those Audio GD op-amps is not good with low supplies , 10v is NOT suitable



This may be the case, I told him to check it over with the company to verify the voltages. The point being unless you know how the circuit is operating you cannot just guess because of the 12V Wallwart.
There are many ways to change this input to higher voltages and positive and negative swings.

If the internal circuitry is running at 10V then the circuit is not suitable for discrete opamps.
 
Jul 21, 2009 at 1:31 AM Post #233 of 7,383
Quote:

Originally Posted by leeperry /img/forum/go_quote.gif
"new"? "different" ? you're looking for the best op-amp and you call the 49720NA "new"
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this chip kicks butt!
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are you saying that the 49722MA is not as good as the 49720NA? I still wanna try it anyway
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some photos of what you call "new package" would be much appreciated
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so I shouldn't bother w/ LT1358/1355/1364/1469 etc etc??


You do realize you are trying to reason with Andrea don't you ? At the best of times his logic is hard to follow.....best ignore the troll...his post will soon disappear along with his latest persona.

Peete.
 
Jul 21, 2009 at 4:23 AM Post #234 of 7,383
I'm just amazed that someone SO deeply obsessed w/ op-amps.....didn't bother trying the 49720NA.

and now all the blabla about the LT chips has become m00t?! even the LT rep I talked to told me "Audio is not an application that we have focused on, but our parts are often selected for high-end systems."

at least National did this LME serie ONLY for audio circuits...and they had some pretty bad ass audio equipment for QA, from what audioman54 said on diyaudio.com
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Jul 21, 2009 at 6:00 AM Post #235 of 7,383
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Jul 21, 2009 at 7:42 AM Post #236 of 7,383
When you learn how to use the AD797, especially the BRZ suffix series, other op-amps stop to matter. This is why I stopped discussions about any op-amps. The idea is to properly use pin 8 in order to adjust THD and bandwidth compensation. No dual op-amp provides access to other parts of the op-amp architecture than inputs and outputs. For top notch performance it doesn't suffice. The AD797BRZ looked to me as the best op-amp many times, with proper decompensation it's far better. It outperformed my last favorite OPA228P being decompensated by default. Read the AD797 datasheet carefully and good luck in experiments! Similar functionality for far less money you have with the AD8021 but this one is nasty and doesn't accept supply voltages more than 26.4V total.
 
Jul 21, 2009 at 8:08 AM Post #237 of 7,383
Quote:

Originally Posted by dead can dance /img/forum/go_quote.gif
Jim Williams said...


I don't know who it is, and I don't want to know. It's obvious this guy hasn't tried the BRZ series and/or he didn't manage to have proper bandwidth compensation. The AD797BRZ is like I stated in my review - the OPA627 and the AD797ANZ qualities put in one chip, with no their flaws transfered. This is with pin 8 left alone. When you hit the spot with the capacitance - around 30pF to ground in my circuit, it improves strongly. If you want to stay with Jim's claims, it's your choice and be happy with unsuccessful op-amp rolling during next two years. :p
 
Jul 21, 2009 at 8:36 AM Post #238 of 7,383
The LT1028ACN8 (I burnt the CN8 pair the other day, so no comments) is a bit drier and with narrower soundstage than the AD797BRZ, both default and decompensated. The AD797ANZ is drier than both. I can try them decompensated and see what the difference will be against the BRZ series.
 
Jul 21, 2009 at 8:56 AM Post #239 of 7,383
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Jul 21, 2009 at 8:57 AM Post #240 of 7,383
Quote:

Originally Posted by dead can dance /img/forum/go_quote.gif
for my Super Pro the best opamps so far have to be the LME49720 and LT1355


ok cool! well I've ordered some samples and adapters, so I'll be trying the 49722 and LT1028CS8...plus all these LT DIP8 samples, if I ever receive them
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but, indeed, the 49720NA doesn't make you wanna roll opamps anymore...you get to think "what for?"
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