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The Opamp thread - Page 121

post #1801 of 3880
11/24/09 at 11:16am
You can't use not unity gain stable opamps on the HD2, the gain is too low. LT1028, AD797, OPA(2)228, OPA637 etc all don't work or oscillate. The only one's that're stable and I don't know if they're unity gain are AD8022 and AD8397.

It's a voltage out DAC chip (AK4396) so the opamps have a gain of just 1 to supply current and make it single ended. The layout isn't designed to make a gain of 1 good enough for something like the LT1028 and it's never gonna work for uncompensated BB's
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post #1802 of 3880
11/24/09 at 11:27am
well, you told me yesterday that AD797 was a good choice in PM : "Although some chips in some apps, like the AD797, are just as good as its discrete counterpart. Only when you use 'em as a direct followup to the DAC though"

it should have read "but not on the HD2" then...ah

so 4*LT1028ACN8 will also be a waste of time then? I'll roll 4*LT1363CN8 in a moment, this should work
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post #1803 of 3880
11/24/09 at 11:37am
Thread Starter 
I would be surprised if he listened seeing how he wants to learn everything the hard way. Carful, you will go on ignore also!
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post #1804 of 3880
11/24/09 at 11:37am
Quote:
Originally Posted by leeperry View Post
so 4*LT1028ACN8 will also be a waste of time then?
No, if the source impedance is made to be 500 ohms or more. Here you might be more lucky.

My friend used two OPA2228P in his HD2 with success, it sounded better than OPA2604 to him. For the output buffer he used AD8599. People in most cases place AD8022 or AD8599 there. Both create great combos with OPA2604's in the first stage. The OPA228 is different from the OPA637 because you can compensate it for gains as low as 2. The OPA637 will never work for noise gains lower than 5. AD797 is unity gain stable by default but you can decompensate it for higher gains.
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post #1805 of 3880
11/24/09 at 11:59am
Quote:
Originally Posted by Slash47 View Post
You can't use not unity gain stable opamps on the HD2
from what I see LT1124ACN8 isn't either(A-VCL that is), and it sounds amazing..

OPA228P and LT1126ACN8 are decompensated, that's a big no-no indeed.
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post #1806 of 3880
11/24/09 at 12:09pm
Thread Starter 
@Majkel, I wouldn't even bother giving him anything useful.
He seems to slap away your hand when you offer it...
Let him learn on his own.
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post #1807 of 3880
11/24/09 at 12:16pm
Well, all of those sound pretty bad on the HD2 to me, including the 2228. I'd just use 'm for I/V myself. But I don't like OPA2604 -> AD8022 either (AD8599 is much, much better to me), so let's all just disagree

And leeperry, what I said to you is both accurate (I didn't say 'some' included the HD2 anywhere), I 'shouldn't' anything and it's a private message; isn't it pretty bad etiquette to discuss that openly? Even though the subject is pretty, uhm, bland.

Anybody here have a M3? I'm thinking of doing one with OPA827 or the new AD thingy and use it as a preamp and hp amp. Good idea?
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post #1808 of 3880
11/24/09 at 12:24pm
hehe ok, thing is I only care for the HD2 right now...well, most of the usual suspects in this thread are on my ignore list, we can speak freely...it's not like you gave me the pw to the pentagon firewall root account

I still rest my case that LT1124ACN8 doesn't appear to be unity gain stable(the PDF doesn't mention it) and it still sounds amazing..decompensated op-amps are another story altogether indeed.
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post #1809 of 3880
11/24/09 at 12:26pm
Thread Starter 
Slash47, here you might want to follow up over here as they are dicussing your info:
The best sounding audio integrated opamps - Page 39 - diyAudio
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post #1810 of 3880
11/24/09 at 12:27pm
Quote:
Originally Posted by ROBSCIX View Post
@Majkel, I wouldn't even bother giving him anything useful.
He seems to slap away your hand when you offer it...
Let him learn on his own.
It's just for the sake of people reading and curious of the answer. Modded CD1000 and a headphone out from an entry level "audiophile" sound card are disputably reliable components to evaluate op amp abilities. If the headphone driver is the NJM4580 then I understand his mental condition.
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post #1811 of 3880
11/24/09 at 12:35pm
Thread Starter 
Yes, the 4580 would definately color the output further.
I guess, some people think with a few months of reading other peoples opinions they suddenly have it all figured out.
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post #1812 of 3880
11/24/09 at 12:39pm
THD has almost nothing to do with perceived sound quality. If it were so tube amps would totally be out of the question. When designing discrete amps a lower THD can be achieved by higher open loop gain and increased feedback. Does it make the amp sound any better, well I don't think so. Some tweaks like current mirrors as LTP load reduces the THD dramatically but make the amp sound worse. If local feedback is applied to a two stage opamp based amp (opamp + buffer), the distortion of the amp as a whole will increase but I don't think the amp will sound any different.

Then there's the harmonic spectrum. Even order is claimed to sound more musical/natural to the ear and odd order gives a more "detailed" and "faster" sound. Higher order distortion is said to sound unnatural and harsh, especially 7th order. A typical modern opamp has almost no even order harmonics and is dominated by third harmonics. Most discrete amps are dominated by 2nd and have some 3d. What you like is a matter of taste. In blind tests it has been shown that some people prefer 2nd order while about just as many prefer 3d.

There are other theories that try to explain why amps sound good or not. This is one of them Memory Distortion Philosophies

I don't think you can judge amps from looking at their THD.
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post #1813 of 3880
11/24/09 at 12:40pm
I confirmed that JRC4580 is even on the Advance DE PCB. I'd replace it at once with the AD8397 for instance, or AD8022 as I did in my CD player. The improvement was obvious. Watching landscapes and sunsets through a dirty window makes no sense IMHO.
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post #1814 of 3880
11/24/09 at 12:44pm
Thread Starter 
Quote:
Originally Posted by NelsonVandal View Post
THD has almost nothing to do with perceived sound quality. If it were so tube amps would totally be out of the question. When designing discrete amps a lower THD can be achieved by higher open loop gain and increased feedback. Does it make the amp sound any better, well I don't think so. Some tweaks like current mirrors as LTP load reduces the THD dramatically but make the amp sound worse. If local feedback is applied to a two stage opamp based amp (opamp + buffer), the distortion of the amp as a whole will increase but I don't think the amp will sound any different.

Then there's the harmonic spectrum. Even order is claimed to sound more musical/natural to the ear and odd order gives a more "detailed" and "faster" sound. Higher order distortion is said to sound unnatural and harsh, especially 7th order. A typical modern opamp has almost no even order harmonics and is dominated by third harmonics. Most discrete amps are dominated by 2nd and have some 3d. What you like is a matter of taste. In blind tests it has been shown that some people prefer 2nd order while about just as many prefer 3d.

There are other theories that try to explain why amps sound good or not. This is one of them Memory Distortion Philosophies

I don't think you can judge amps from looking at their THD.
Who said you can judge opamps based on their THD values?
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post #1815 of 3880
11/24/09 at 12:46pm
Thread Starter 
Quote:
Originally Posted by majkel View Post
I confirmed that JRC4580 is even on the Advance DE PCB. I'd replace it at once with the AD8397 for instance, or AD8022 as I did in my CD player. The improvement was obvious. Watching landscapes and sunsets through a dirty window makes no sense IMHO.
Yes, the are a generic units similar to the NE5532,JRC2114D..etc. Like the NE5532 they still seem to be part of many designers toolboxes and reference designs either because of cost or component familiarity.
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