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Old 23rd August 2008, 09:42 PM   #1
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Default absolute noobie has opamp question

Two questions I would like to ask here.
1. I purchased a headphone amp form a diy'er about a year ago and it has been great. I opened it up and it runs off two AD823AN's that are socket'ed. Can I upgrade these to OP-627's? This amp runs off of a single 9v. If I can not are there other options that would be a good upgrade to the AD823AN?

2. If I cannot do the swap above is there a basic headphone amp kit or what not that I can get my feet wet with that uses the OP-627 opamps? Are there any good crash course in basic signal amplication and opamps I can look at or buy?

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Old 24th August 2008, 02:36 AM   #2
lineup is offline lineup  Sweden
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do nothing

AD823 is so much hi-fi op-amp - real top class Analog Devices amplifier -
it is almost impossible to upgrade

suppose you should try with OPA627 or OPA637
then the circuit would have been setup for AD823 use
and you may not be able to get better out of OPA627,
unless you design a new circuit to support your OPA627 chip
... probably you could only do only worse

is when we CAN do better
otherwise will only be a downgrade, in some respect

Lineup - audo regards
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Old 24th August 2008, 06:08 AM   #3
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That is a fair reply. The amp doesn't sound bad. Perhaps I will try to roll my own Pimeta or have one built with the burr-brown opamp.
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Old 24th August 2008, 06:37 AM   #4
lineup is offline lineup  Sweden
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the audio elite makes preamp circuits/buffers with OPA627
If you search forum for OPA627
you will find a bunch of good schematics/applications for this top of the top Op-Amp.
Only drawback with OPA627 is the price .. not The Performance, for sure

Your amplifier was designed with AD823 in mind.
Think you do good let is stay that way = original.

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Old 24th August 2008, 04:16 PM   #5
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OK so stupid question. Is a preamp circuit with a buffer added what is typically considered a headphone amp?
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Old 9th September 2008, 12:16 AM   #6
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I did some digging through my paypal reciepts and it turns out that I don't have a CMOY. I have a Z-Audio Mu. It has socketed dual AD823's that are self buffered. Does this change the possibility of opamp rolling?
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Old 9th September 2008, 12:31 AM   #7
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What is it that you dislike about your headphone amplifier?
Its like: "Step 1: Identify the problem."

Crash course in amplifiers? Okay. http://myweb.tiscali.co.uk/nuukspot/decdun/ and http://headwize.com/projects/index.htm
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Old 10th September 2008, 04:04 AM   #8
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I have read through quite a few of these articles. I am having to look a lot of the terms up but some of it is quite informative. I don't dislike my amp but I would like to see how different opamps sound. It is sort of like saying I like coffee but there are different blends of coffee I like. The only particular flaw I can find is the amp gets a little harsh in the upper midrange at reasonable volumes using either my grados or senn 580s.
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Old 10th September 2008, 05:07 AM   #9
lineup is offline lineup  Sweden
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good question, espressogeek

i like to know how my opamp sounds
& how sounds different opamps

the keyword here is sound

opamps are quiet
they do not make sound .. not even transistors make sound we can hear
a well designed audio opamp & a good application of this opamp
will be 'transparant' in terms of influence on output

now, louspeakers make sounds .. no doubt
this is what they SHOULD DO, if no sound .. throw it in your garbage

same with headphones
they make sounds
with much less distortion, influence on sound quality, than Speakers

so you have MORE CHANCE to hear something of those previous stages in your sound system
if you listen in HeadPhones,
but!!! must be HeadPhones of very high quality

speakers usually have at least 10 times higher distortion
than good Phones (see Sennheiser )
Good Phones destroys the electrical signal like only 0.2%
this is the level of distortion of World's finest Phones
for example by http://www.sennheiser.com/

now, opamps
are advertised having 0.00003 % distortion

Even 0.001 % DISTORTION .. is one very tiny drop in the SEA of Sound distortion.

And with regards to music signal + opamp system
The only thing you would hear is music .. nothing else.
For one normally good opamp in one normal good audio circuit.

.. these are the facts
.. now, let's listen to all or some of The Myths .. of audio sounds

so post on people
& our golden, golden ears ... some poor boy may believe you

Lineup Audio LAB - Opamp designs for Hi-fi HeadPhones


Lineup - not stupid enough to be looking for his one drop
put into the Atlantic Ocean Waves
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Old 27th September 2008, 03:58 PM   #10
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I built a Cmoy based on the JDS board and when it was working (eh, see another thread about that, my own fault) it clobbered the sound of this little amp when listening to my HD-580s. I built it using an OPA2227. I was reading on Tangent's site about how little current the 823 op amps in the Mu can put out compared to other op amps and I believe that is part of the problem. I have several new op amps coming to use in building my own amps (working on a PPAv2 right now, should be finished very soon when the parts arrive monday) but I will try to replace these 823's with something more robust such as a 2227 or LM4562NA. In reviewing this amp I do have another question. Why would you run two dual channel op amps , one for left and another for right, when you could run just a single channel op amp in each side? I've tried googling for an answer but I can't seem to find an explanation.
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