[cyanbomb]

I have to say it: I just visited Xin's website, which looks like barely organized chaos. lol... pardon the oxymoron.

At the order page, there are lists of OPAmps, and to a non-EE educated person like me, numbers like AD8397, and LMH6643 make no sense. Can someone do a small write-up about OPAmps, and describe the sonic qualities of some of the more famous/common ones, etc?

I'd love to get involved in this whole OPAmp rolling business!

 

[onvn]

I think Tangent has a great page all about op-amps he has reviewed.. and he has a page on op-amp choice for the cmoy, which is a great guide even if it is specifically articulated for the cmoy..

 

[Pete7]

http://tangentsoft.net/audio/opamps.html

 

[NelsonVandal]

It's not really up to date, but the sum up is priceless. Do some searching here on HeadFi, at Xin's place, Diyaudio etc. There are many reviews. We all like to disagree about opamps

since they are the single most important compenent by far in this kind of amps. Buy a couple of the very good but cheap opamps like LME49720 (= LM4562), AD8397, AD8599, AD8066 and maybe the old workhorse OPA2134 to have some kind of reference. I'd say avoid the more expensive like AD8620, OPA2107 until you're sure about what kind of sound you want.

And it's very important for you to know at what voltage they'll be running. Some are spec'd max 12V some are spec'd min 10V etc. And beware, some opamps only come in single channel, and you need two of them mounted on a special adapter like the AD744, AD825, OPA627 etc. And beware again, some opamps will give you huge amount of DC-offset and can only be used with tweaks or in a buffer position.

Even more warnings - some opamps have a very low output current like the LME49720 and the crappy but popular AD823, and should only be used in front of buffers.

Happy rolling.

 

[tnmike1]

OR stick with an amp where you don't have to mess with such things. Unless, of course, you enjoy tinkering with electronics

 

[cyanbomb]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif It's not really up to date, but the sum up is priceless. Do some searching here on HeadFi, at Xin's place, Diyaudio etc. There are many reviews. We all like to disagree about opamps since they are the single most important compenent by far in this kind of amps. Buy a couple of the very good but cheap opamps like LME49720 (= LM4562), AD8397, AD8599, AD8066 and maybe the old workhorse OPA2134 to have some kind of reference. I'd say avoid the more expensive like AD8620, OPA2107 until you're sure about what kind of sound you want. And it's very important for you to know at what voltage they'll be running. Some are spec'd max 12V some are spec'd min 10V etc. And beware, some opamps only come in single channel, and you need two of them mounted on a special adapter like the AD744, AD825, OPA627 etc. And beware again, some opamps will give you huge amount of DC-offset and can only be used with tweaks or in a buffer position. Even more warnings - some opamps have a very low output current like the LME49720 and the crappy but popular AD823, and should only be used in front of buffers. Happy rolling.

Oh. My. God.
I feel like I need to buy a textbook on basic electronic engineering.

Let's say I wanted to buy a SuperMacro-IV, and wanted a warm sound, with a detailed, large soundstage. What Opamp would I be looking at?

 

[TzeYang]

teh opa2107. Though some might find it overly warmish. I kinda like it if i don't have a choice. If i have a choice, i'll use 2x OPA627 instead.

 

[tomb]

Quote:

Originally Posted by cyanbomb /img/forum/go_quote.gif Oh. My. God. I feel like I need to buy a textbook on basic electronic engineering. Let's say I wanted to buy a SuperMacro-IV, and wanted a warm sound, with a detailed, large soundstage. What Opamp would I be looking at?

The problem with Dr. Xin's amps are that he uses unique circuitry and voltage. If I remember correctly, his amps use a buck-boost circuit based on low-voltage batteries. Chances are, you should stick with whatever he designs and don't roll opamps, per se, unless he recommends them.

Refer to Tangent's "Notes on Opamps" and if you find something that Dr. Xin recommends in there, then maybe you can use that to make your choices. Don't get me wrong - what Xin does with his circuitry is magnificent, but that also means it's probably not that flexible with other design circuitry that follows conventional practice.

Other headphone amps that use 2x9V or 18-24VDC power supplies fit the norm when it comes to rolling opamps and you have a little more latitude. Generally speaking - very generally - Texas Instruments' Burr-Brown opamps (OPA627, OPA637, OPA2134, OPA2132, OPA2107, etc.) are warm with pretty good imaging and detail. Analog Devices' opamps (AD823, AD825, AD8065/66, AD8610/20, AD843, AD845, etc.) are more aggressive with loads of detail, but sometimes bordering on harsh, depending on the circuit.

Some opamps are based on BJT input circuitry, whereas the previously mentioned ones are all FET input. You don't have to necessarily know what that means except that BJT opamps are very aggressive and sensitive to the circuit. FET opamps, on the other hand, are very tolerant of the surrounding circuitry, power supplies, and input/output. One reason the CMoy is such a success is that the OPA2134 or OPA2132 is wonderfully warm and detailed, yet outrageously tolerant of the wide variance in construction and quality of the homebuilt Mint Tin headphone amp.

However, a BJT opamp such as the AD8397 may not be entirely successful even in a quality PCB. The two types are rarely compatible in the same circuit. One exception is the OPA2227, which is actually a BJT opamp, but is "slow" enough to work in the same circuits as an FET opamp.

Hope that helps and wasn't too confusing ...

 

[ssportclay]

Quote:

Originally Posted by cyanbomb /img/forum/go_quote.gif I have to say it: I just visited Xin's website, which looks like barely organized chaos. lol... pardon the oxymoron. At the order page, there are lists of OPAmps, and to a non-EE educated person like me, numbers like AD8397, and LMH6643 make no sense. Can someone do a small write-up about OPAmps, and describe the sonic qualities of some of the more famous/common ones, etc? I'd love to get involved in this whole OPAmp rolling business!

What you describe is nice in theory.It just seems that new opamps are coming out so quickly that it is very difficult to keep track of them.The best sounding amplifiers that will become available within the next 2 years will most likely be using opamps that aren't even available yet.

 

[cyanbomb]

Guys, I'm very very grateful for your kind (and enormously detailed!) explanations, and will check out the links you recommended.

Hopefully one day soon I'll be rolling my own OpAmps.

One last question: Is there a website where I can buy OpAmps from?

 

[d-cee]

Quote:

Originally Posted by cyanbomb /img/forum/go_quote.gif Guys, I'm very very grateful for your kind (and enormously detailed!) explanations, and will check out the links you recommended. Hopefully one day soon I'll be rolling my own OpAmps. One last question: Is there a website where I can buy OpAmps from?

digikey, mouser, farnell