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The Opamp thread
Apr 4, 2010 at 3:38 PM Post #2,461 of 7,383
Quote:

Originally Posted by Mad Max /img/forum/go_quote.gif
Stock. I have AD744KN as well, and it is not much of an improvement over the J version. I haven't modded any of the opamps, and I'm pretty sure you'll love the metal can version. It synergizes better with my ipod than my Compass DAC, making my portable rig more natural sounding. It is a very tight fit in my amp, so no mods yet. I'll try the OB mod later, though.

I can't decide whether I like 4627-1B or 744AH better.
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I too like the ADA4627...it's in my top 5 for sure. I ordered a set of the 744AH from the Ebay link so thank you for that! I think I'll try them stock first for a week or so before doing the bypass mod.
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Apr 4, 2010 at 5:59 PM Post #2,463 of 7,383
Quote:

Originally Posted by ecclesand /img/forum/go_quote.gif
I too like the ADA4627...it's in my top 5 for sure. I ordered a set of the 744AH from the Ebay link so thank you for that! I think I'll try them stock first for a week or so before doing the bypass mod.
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Wow, just reminded me. I have a few of these that need to be put on some adapters for testing. So many units and so little time!
 
Apr 5, 2010 at 5:53 AM Post #2,464 of 7,383
Quote:

Originally Posted by ihrm /img/forum/go_quote.gif
Hey all, noob here. I'm not at all sure what an opamp. Could anyone try to explain or link me to some good reading?


An opamp (Operational Amplifier) is a particular kind of differential amplifier (that is, it has two intputs, and amplifies the difference between them). It has very high input impedance, very low output impedance, and extremely high gain.

Since all opamps have these properties, they can be treated as a fundamental electronics building block. (Historically, this isn't quite true, but it's been basically true since the u741, invented in 1968).

Some notes on their operation and history can be found at : Operational amplifier - Wikipedia, the free encyclopedia

While some notes on their usefulness can be found at:
Operational amplifier applications - Wikipedia, the free encyclopedia

Along with their uses as small-signal amplifiers, they can also be used as elements in analogue computing (adders, integrators, differentiators), control circuits (zero level detectors, Schmitt triggers), and to do some rather nifty things (inductance simulators, negative resistance simulators)

Here, though, we mostly use them as gain stages in headphone amplifiers and buffer stages in Digital to Analogue converters. Much of the discussion centres around which opamps sound the best, although realistically, there are now many modern opamps with distortion levels so low they should be indistinguishable from each other.
 
Apr 5, 2010 at 7:22 AM Post #2,465 of 7,383
Apr 5, 2010 at 7:43 AM Post #2,466 of 7,383
Quote:

Originally Posted by foureight84 /img/forum/go_quote.gif
I've been looking for the OPA627SM for my soundcard, and I found this on eBay 2 pcs of BB OPamp IC OPA627SM (OPA627) + DIP adapter - eBay (item 120354248036 end time Apr-18-10 06:58:46 PDT)

It seems too good to be true. The price is really cheap for the 627sm and it comes with the DIP adaptor which looks exactly like what auzentech sells on their website. Has anyone ever bought from this seller? I want this for my headphones and front channel (running on the auzentech bravura).


Meh probably not a good idea since I just saw that the seller is based in Hong Kong. If it's too good to be true it probably is right? heh
 
Apr 5, 2010 at 2:28 PM Post #2,467 of 7,383
Quote:

Originally Posted by theSeekerr /img/forum/go_quote.gif
An opamp (Operational Amplifier) is a particular kind of differential amplifier (that is, it has two intputs, and amplifies the difference between them). It has very high input impedance, very low output impedance, and extremely high gain.

Since all opamps have these properties, they can be treated as a fundamental electronics building block. (Historically, this isn't quite true, but it's been basically true since the u741, invented in 1968).

Some notes on their operation and history can be found at : Operational amplifier - Wikipedia, the free encyclopedia

While some notes on their usefulness can be found at:
Operational amplifier applications - Wikipedia, the free encyclopedia

Along with their uses as small-signal amplifiers, they can also be used as elements in analogue computing (adders, integrators, differentiators), control circuits (zero level detectors, Schmitt triggers), and to do some rather nifty things (inductance simulators, negative resistance simulators)

Here, though, we mostly use them as gain stages in headphone amplifiers and buffer stages in Digital to Analogue converters. Much of the discussion centres around which opamps sound the best, although realistically, there are now many modern opamps with distortion levels so low they should be indistinguishable from each other.


Ok thanks! That clears things up. I was looking at the wikipedia article earlier, but it didnt really give me a good idea of what we would use them for. I'm looking at buying a Zero DAC off eBay and there are 2 opamp options. OPA627 or the OPA2604. Whats the difference between them? Is it worth spending the extra money on the OPA627? Thanks again
 
Apr 5, 2010 at 3:19 PM Post #2,468 of 7,383
Quote:

Originally Posted by foureight84 /img/forum/go_quote.gif
Meh probably not a good idea since I just saw that the seller is based in Hong Kong. If it's too good to be true it probably is right? heh


this is a very serious seller AFAIK, ask him if they're genuine and if you can see the TI box they come in
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for this price you can get a whole bunch of OPA-Earth, or a Burson V2...so they'd have to be genuine, and sound really good!

Andrea is poisoning me to try AD845KN...must resist
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Apr 6, 2010 at 1:31 AM Post #2,469 of 7,383
Quote:

Originally Posted by foureight84 /img/forum/go_quote.gif
Meh probably not a good idea since I just saw that the seller is based in Hong Kong. If it's too good to be true it probably is right? heh


You have to watch some ebay sellers as they sell counterfeit components.
I have no experience with the sellers you posted but just saying be carful.
 
Apr 6, 2010 at 4:01 AM Post #2,470 of 7,383
Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif
You have to watch some ebay sellers as they sell counterfeit components.
I have no experience with the sellers you posted but just saying be carful.


Yea it's a good idea. I thought it's kinda cheap since the OPA627SM goes for $70 each... This is $50 for two, so it does sound really too good. I noticed that he has sold a bunch and with 100% + feedback, he seems legit. I emailed the seller for more information as you guys suggested. Going to confirm with TI after.
 
Apr 7, 2010 at 8:17 AM Post #2,472 of 7,383
I finally settled and bought a pair of OPA627AU.
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I can't wait to try them out.

I have a question though, I have a Auzentech Bravura sound card and it's setup with a pair of Audioengine A2 with a Polkaudio PSW111 sub connected through the speakers. Will I get better bass if I were to connect the sub to my soundcard via a y-adapter and replace the sub channel's opamp with one known for deeper bass?
 
Apr 7, 2010 at 8:26 AM Post #2,473 of 7,383
So I got my LT1028 today - how do I easily measure DC offset before frying heapdhones (only have a cheap DMM at hand right now)? Could I use a mini to mini on the HP out and the DMM with that?
 
Apr 7, 2010 at 8:30 AM Post #2,474 of 7,383
Quote:

Originally Posted by foureight84 /img/forum/go_quote.gif
I finally settled and bought a pair of OPA627AU.
smily_headphones1.gif
I can't wait to try them out.

I have a question though, I have a Auzentech Bravura sound card and it's setup with a pair of Audioengine A2 with a Polkaudio PSW111 sub connected through the speakers. Will I get better bass if I were to connect the sub to my soundcard via a y-adapter and replace the sub channel's opamp with one known for deeper bass?


Most likely.


Quote:

Originally Posted by buz /img/forum/go_quote.gif
So I got my LT1028 today - how do I easily measure DC offset before frying heapdhones (only have a cheap DMM at hand right now)? Could I use a mini to mini on the HP out and the DMM with that?


I think so.
 
Apr 7, 2010 at 2:01 PM Post #2,475 of 7,383
Quote:

Originally Posted by buz /img/forum/go_quote.gif
So I got my LT1028 today - how do I easily measure DC offset before frying heapdhones (only have a cheap DMM at hand right now)? Could I use a mini to mini on the HP out and the DMM with that?


that's how I do it! but I've never got any DC on the 1028...OTOH on 1363/797B
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