ad627anz, ad8005
hello.
I just wondered if the ad627 and ad8005 is any good?
got some samples yesterday.
Anybody have a clue😕
Regards
PK
hello.
I just wondered if the ad627 and ad8005 is any good?
got some samples yesterday.
Anybody have a clue😕
Regards
PK
dunno, you tell me..
http://www.analog.com/en/prod/0,2877,AD627,00.html
http://www.analog.com/en/prod/0,2877,AD8005,00.html
the datasheets are on the top banner, just below the heading.
time to do your own thinking 😉
http://www.analog.com/en/prod/0,2877,AD627,00.html
http://www.analog.com/en/prod/0,2877,AD8005,00.html
the datasheets are on the top banner, just below the heading.
time to do your own thinking 😉
I dont still know!😕
I trust the ear more than the datasheets, and i don't understand them well.
I am noob. but after building my power amp soon i can test them😀 😀 😀
have anybody tested them??
anybody want to buy them and some ad797? Or maybe exchange them fore some opa627 or 541 or something else😉
thanks
PK
I trust the ear more than the datasheets, and i don't understand them well.
I am noob. but after building my power amp soon i can test them😀 😀 😀
have anybody tested them??
anybody want to buy them and some ad797? Or maybe exchange them fore some opa627 or 541 or something else😉
thanks
PK
Helpful link
Dunno if this has already been posted, but I found this link to help me get my head around things like this:
http://www.zero-distortion.com/tests/opamps/opamps.htm
He tends to favour the AD826 and AD829, BTW.
Cheers.
Dunno if this has already been posted, but I found this link to help me get my head around things like this:
http://www.zero-distortion.com/tests/opamps/opamps.htm
He tends to favour the AD826 and AD829, BTW.
Cheers.
Re: ad627anz, ad8005
The AD8005 requires probably a better pcb since it is faster. A bad pcb may not be good to the AD8005. AD627 is very good this I know fom personal expereince, AD8610 is also very good but I have never tested the A8005PKS said:
So what exactly are the sonic differences between the OPA627 and the OPA637? Apparently both sound great, but why would I want to use one over the other?
I'm glad I came across this thread because I just discovered that my Chord CPA-1800 preamp is based on the Burr Brown OPA604, which I gather from this discussion isn't the last word in sound quality.
So I want to replace these with something better. After looking through this and a couple of other threads it looks like the OPA627 or OPA637 are a good place to start - but which one?
Since the Chord pre already is set up with all sorts of regulators, etc., I think the best bet to start with would be a direct drop-in replacement. Are OPA627/OPA637 suitable as a direct replacement for the OPA604?
Also, in order to facilitate experimentation, I was thinking about using those sockets. Do these degrade sound quality substantially?
I've gleaned so much reading about your experiences - I'm not sure which op amp out of the 4 or 5 that look promising will give me the sound I seek, though. So many choices. 🙂
Thanks for your help,
KT
I'm glad I came across this thread because I just discovered that my Chord CPA-1800 preamp is based on the Burr Brown OPA604, which I gather from this discussion isn't the last word in sound quality.
So I want to replace these with something better. After looking through this and a couple of other threads it looks like the OPA627 or OPA637 are a good place to start - but which one?
Since the Chord pre already is set up with all sorts of regulators, etc., I think the best bet to start with would be a direct drop-in replacement. Are OPA627/OPA637 suitable as a direct replacement for the OPA604?
Also, in order to facilitate experimentation, I was thinking about using those sockets. Do these degrade sound quality substantially?
I've gleaned so much reading about your experiences - I'm not sure which op amp out of the 4 or 5 that look promising will give me the sound I seek, though. So many choices. 🙂
Thanks for your help,
KT
The 604 is a single opAmp. The 2604 is a dual.
So you need which ever of those OPA that is the single. The 627 is single.
In my opinion it sounds unlistenable. I know this flies in the face of popular opinion in this thread. I've used it in a few top quality sounding DACs and pre-amps, always with the same result. I used good bypassing and also tried the resistor from the +ve rail to the output. (which I found with some chips did take an unpleasant edge off) but the 627 always sounded the same, compressed, soft treble, odd bass, and kind of like there was a phase error though it where some frequency bands vied with others and some were sucked out and others dominated.
It's not just me either who came to the same conclusion. Two of my friends have some of the best sounding HiFi I ever heard, and that's saying something, and they both agreed when we tried it in a pre-amp.
They are apparently very good in the I-V position, I haven't tried them there yet as I don't have such a DAC yet. So maybe my £30 investment won't be wasted after all.
My preference at the moment seems to be the AD797 or the AD847. The former seeming to make the background quieter and the mid and treble simply leave the boxes, focus and detail, drama, but with with pleasantness. Can make the treble a little loud though. The 847 has an impressive dynamic edge and dynamic bass but can sound a little 'steely'. They do an AD827, which is a dual version. one of my friends has fitted these to his pair of Meridian M10 active loudspeakers. He'd tried many opamps before settling on this one. He also has the metal dome tweeter conversion but those old meridian amps may somewhat lack the treble due to the slower output devices. Which can offset any brightness or edgy treble due to op-amps.
However there is no shortage of treble extention in my setup and they seem to work well as the subtractor after my Philips 7350 DAC.
We recently tried the LM6171 single opamps. There was good detail and good rendering of 'inner information' within the music. But they were kind of jangly and became quickly fatiguing. We reverted to the softer sounding but better tonally balanced AD825 in that instance, they were there due to offset problems with that particular preamp when fitted with ad797 and no DC blocking caps. We felt it was better with the 'slightly lesser' 825 and no blockers than with the 797 and blockers.
So you need which ever of those OPA that is the single. The 627 is single.
In my opinion it sounds unlistenable. I know this flies in the face of popular opinion in this thread. I've used it in a few top quality sounding DACs and pre-amps, always with the same result. I used good bypassing and also tried the resistor from the +ve rail to the output. (which I found with some chips did take an unpleasant edge off) but the 627 always sounded the same, compressed, soft treble, odd bass, and kind of like there was a phase error though it where some frequency bands vied with others and some were sucked out and others dominated.
It's not just me either who came to the same conclusion. Two of my friends have some of the best sounding HiFi I ever heard, and that's saying something, and they both agreed when we tried it in a pre-amp.
They are apparently very good in the I-V position, I haven't tried them there yet as I don't have such a DAC yet. So maybe my £30 investment won't be wasted after all.
My preference at the moment seems to be the AD797 or the AD847. The former seeming to make the background quieter and the mid and treble simply leave the boxes, focus and detail, drama, but with with pleasantness. Can make the treble a little loud though. The 847 has an impressive dynamic edge and dynamic bass but can sound a little 'steely'. They do an AD827, which is a dual version. one of my friends has fitted these to his pair of Meridian M10 active loudspeakers. He'd tried many opamps before settling on this one. He also has the metal dome tweeter conversion but those old meridian amps may somewhat lack the treble due to the slower output devices. Which can offset any brightness or edgy treble due to op-amps.
However there is no shortage of treble extention in my setup and they seem to work well as the subtractor after my Philips 7350 DAC.
We recently tried the LM6171 single opamps. There was good detail and good rendering of 'inner information' within the music. But they were kind of jangly and became quickly fatiguing. We reverted to the softer sounding but better tonally balanced AD825 in that instance, they were there due to offset problems with that particular preamp when fitted with ad797 and no DC blocking caps. We felt it was better with the 'slightly lesser' 825 and no blockers than with the 797 and blockers.
Ian makes a very good point here, which is that depending on application an op-amp may give a very different character of sound.
I have only so far tried the OPA627bp in I/V in my CD player, where it absolutely blows away 2604 (harsh, horrid), JRC2114 (boring, muffled, closed in - original unit), OPA2134 (or 2132, can't remember) (good, but lacking the magic). OPA627 does miracles here, maybe the biggest upgrade of my life (well, the cd player's life). And it isn't even well bypassed yet..
Pending an imminent move to a different house (and much better listening room!!! :-D ) I've put on hold most hi-fi stuff...but I intend to come back to trying different op-amps in my Rod Elliot pre-amp. I will report on the suitability of these op-amps in my own system, used as gain.
I have only so far tried the OPA627bp in I/V in my CD player, where it absolutely blows away 2604 (harsh, horrid), JRC2114 (boring, muffled, closed in - original unit), OPA2134 (or 2132, can't remember) (good, but lacking the magic). OPA627 does miracles here, maybe the biggest upgrade of my life (well, the cd player's life). And it isn't even well bypassed yet..
Pending an imminent move to a different house (and much better listening room!!! :-D ) I've put on hold most hi-fi stuff...but I intend to come back to trying different op-amps in my Rod Elliot pre-amp. I will report on the suitability of these op-amps in my own system, used as gain.
KT,
the 637 needs to be used with a gain of 5 or greater to avoid oscillations. The 627 is happy ay unity gain. Apparently the 637 is slightly better in suitable circuits. Either will kill the 604 as a direct replacement.
the 637 needs to be used with a gain of 5 or greater to avoid oscillations. The 627 is happy ay unity gain. Apparently the 637 is slightly better in suitable circuits. Either will kill the 604 as a direct replacement.
Regarding sound....
Ian's opinion is as valid as mine, but I disagree 100% 😀
I think the opa627 is extremely natural sounding and very, very listenable. Get a couple from usacaps on ebay for about 10 bucks. Bargain 😎
627's are I/V stage supremos, and IMO work well as preamps.
I built a 627 based pre stage just to prove to myself that a passive pre will beat an active. The 627 was good enough to turn my opinion on its head. I used a gain of 3, 100uF + 100nF on the pins and +-12v from two lead acid batteries. Subjectively the 627 amp had better dynamics, image solidity AND detail, losing out only in stage width and a slight loss of tonal purity. This though was with a cheap mylar input cap and even worse RS electros across the batts. I'm about to re-do the circuit properly and expect to find it much improved.
So, IMO, you should definately try'em!
Ian's opinion is as valid as mine, but I disagree 100% 😀
I think the opa627 is extremely natural sounding and very, very listenable. Get a couple from usacaps on ebay for about 10 bucks. Bargain 😎
627's are I/V stage supremos, and IMO work well as preamps.
I built a 627 based pre stage just to prove to myself that a passive pre will beat an active. The 627 was good enough to turn my opinion on its head. I used a gain of 3, 100uF + 100nF on the pins and +-12v from two lead acid batteries. Subjectively the 627 amp had better dynamics, image solidity AND detail, losing out only in stage width and a slight loss of tonal purity. This though was with a cheap mylar input cap and even worse RS electros across the batts. I'm about to re-do the circuit properly and expect to find it much improved.
So, IMO, you should definately try'em!
While going through datasheets for a number of op amps looking for something I realized the striking similarity between OPA132 and OPA134. Surprisingly many data are identical and most diagrams are identical. That makes me wonder if these are indeed variations on the same design? Maybe 134 is newer and was intended as an improvement/replacement, but maybe didn't deliver in all aspects? Anybody who knows more about this?
float said:
Thanks for your opinions, guys.
Interesting how one person may prefer the sound of something while another may not like it at all - even in the best case scenario when the circuit, system, recording, and room are the same. Here we're also talking about different circuits, systems, music, and listening rooms, too. What pushes one person's buttons may be anathema to another.
But enough people have expressed positive opinions on the OPA627 that I think this is one I must try. I've also heard some very positive things about the AD825 though I've also heard this chip described as recessed in the midrange. Maybe I'll try that one, too (need a soic to dip adapter - those exist, right?).
If this sparks any suggestions, I usually prefer the sound of a good tube preamp - clear, open, sweet, dramatic, slightly warm but not the kind that's syrupy, bloated, or cloudy. If anything, I lean towards a more luscious but clear sound than a purely neutral one.
Any chips fit this description?
I'm really looking forward to do some chip rolling!
PS - The Chord SPA-1800 is set to a gain of 1.2, so the OPA637 is out of the question.
PPS - What's the difference between the AP and BP designated 627s?
Thanks again,
KT
KT said:
The OPA627 is not a generic drop-in replacement op-amp.
When well used, it is very good. But it is very sensitive to PSU bypass, PCB layout and the components around it.
That's why on some circuits it doesn't perform well, and who doesn't know it well will not be able to extract the performance from it.
There are much easier alternatives to try.
I also like very much the OPA847, as I reported several pages back.
But it's unfair... for a preamp, the AD815 eats everything for lunch.
😎
PS: I've seen (and heard) several so-called 'high-end' preamps and integrated amps with the OPA604 and I just wanna
.
carlosfm said:
Thanks for the suggestion, Float. I ordered some OPA627s from usacaps, but I had to read through this post before I felt comfortable enough that the chips are legitimate: http://tinyurl.com/bu7px
Carlos, I understand about getting everything right in order to wring the best out of the circuit. I'll start with what I have first and experiment from there. I may take some time before it really sings.
The AD815 sounds like an exceptional chip. I don't think I'm ready to tackle it yet, though.
Maybe later down the road. It'll be my reward for waiting and learning.
Looks like I'll have to consider the OPA847, though.
Best,
KT
Give the AD797 a go too.
I think I'm correct in saying it's the lowest noise chip made.
It needs low value resistors around it to get the benefits of the low noise. But even in a not so good circuit it's work well. Apart from the occasional large offset.
I would suggest trying to not use DC blocking caps at all.
Re the 627's, so many good reports, that why I bought some. I only got the less respected version though, didn't know any better then. Maybe that makes some difference.
Carlos, do you know, does the 627 need low value resistors? In the pre-amp the resistor values were very high, although Vishay, and all hard wired with no copper tracks. Black gate N 33mic caps with 100n XR7 dipped ceramics. Solid silver wire to and from the chips.
I think I'm correct in saying it's the lowest noise chip made.
It needs low value resistors around it to get the benefits of the low noise. But even in a not so good circuit it's work well. Apart from the occasional large offset.
I would suggest trying to not use DC blocking caps at all.
Re the 627's, so many good reports, that why I bought some. I only got the less respected version though, didn't know any better then. Maybe that makes some difference.
Carlos, do you know, does the 627 need low value resistors? In the pre-amp the resistor values were very high, although Vishay, and all hard wired with no copper tracks. Black gate N 33mic caps with 100n XR7 dipped ceramics. Solid silver wire to and from the chips.
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Joined 2003
Thanks for that schematic Carlos. My current preamp is Russ White's "Freebird" design, where he excludes the 330nF cap between +V and -V, and does not bias the op-amp to class-A with the 2K resistor.
Luckily I found a couple of 330nF caps in my spare parts and have installed them (that was a difficult trick). I don't have many resistors in my spare parts but I will grab the resistor from school and see what kind of difference it makes. I also plan to replace the 1n4002 diodes on my preamp supply with MUR110's as well 😉.
Since I have been quite ill the last few days, I spent a couple hours reading through this thread and got nice and educated. I am a computer nerd at heart, so sadly my source for my stereo is my computer. I use an M-Audio Audiophile 2496 soundcard that I have done a few mods to. First, I cut the connection between the DIN connectors ground and the chassis, which supposedly lowers the noise floor by removing a ground loop. Then from reading this thread I am making a few more modifications. The coupling caps at the output of this soundcard are of course electrolytic, so I removed them completely from the circuit creating a short. DC levels measured great at 3.4mV. Now the only DC coupling capacitor is at the amplifiers input and is a high quality MKP cap
The op-amps on this soundcard are NE5532. There are 4 of them, but 3 of them are on the audio input which I never use, so I only need to replace a single dual op-amp with a better one. After some reasearch I have come between two op-amps to choose from. The OPA2132 or the AD823.
I think first I will try the OPA2132 since I am a Burr-Brown fan, although the AD823 looks better on paper with it's better distortion figure, but I don't think the numbers really matter anymore when they are so small.
Luckily I found a couple of 330nF caps in my spare parts and have installed them (that was a difficult trick). I don't have many resistors in my spare parts but I will grab the resistor from school and see what kind of difference it makes. I also plan to replace the 1n4002 diodes on my preamp supply with MUR110's as well 😉.
Since I have been quite ill the last few days, I spent a couple hours reading through this thread and got nice and educated. I am a computer nerd at heart, so sadly my source for my stereo is my computer. I use an M-Audio Audiophile 2496 soundcard that I have done a few mods to. First, I cut the connection between the DIN connectors ground and the chassis, which supposedly lowers the noise floor by removing a ground loop. Then from reading this thread I am making a few more modifications. The coupling caps at the output of this soundcard are of course electrolytic, so I removed them completely from the circuit creating a short. DC levels measured great at 3.4mV. Now the only DC coupling capacitor is at the amplifiers input and is a high quality MKP cap
The op-amps on this soundcard are NE5532. There are 4 of them, but 3 of them are on the audio input which I never use, so I only need to replace a single dual op-amp with a better one. After some reasearch I have come between two op-amps to choose from. The OPA2132 or the AD823.
I think first I will try the OPA2132 since I am a Burr-Brown fan, although the AD823 looks better on paper with it's better distortion figure, but I don't think the numbers really matter anymore when they are so small.
Yes, thanks for that schematic Carlos.
Same design as the preamp we tried the chips in recently. But that came with 4k7 in, 120k FB, 43k to earth. I didn't try a 330n across the rails. I also didn't have the load resistor 100k after the 100r o/p. Another difference was that pre had a 50k pot and 30k to earth instead of the 100k you suggest. Even with a 100k it's still not going to be all that great with a 50k pot there and is why we had offset problems. That's probably going to be swapped for a 10k eventually. Maybe a single series r L-pad if it can be made to fit.
The other time I tired the 627, the bypassing was not quite that good, but the r's were around 5k in and 10k FB and used in the inverting mode with 100pf polystyrene across the 10k. All vishay and soldered to the socket pins. Pin 3 direct to earth.
Same design as the preamp we tried the chips in recently. But that came with 4k7 in, 120k FB, 43k to earth. I didn't try a 330n across the rails. I also didn't have the load resistor 100k after the 100r o/p. Another difference was that pre had a 50k pot and 30k to earth instead of the 100k you suggest. Even with a 100k it's still not going to be all that great with a 50k pot there and is why we had offset problems. That's probably going to be swapped for a 10k eventually. Maybe a single series r L-pad if it can be made to fit.
The other time I tired the 627, the bypassing was not quite that good, but the r's were around 5k in and 10k FB and used in the inverting mode with 100pf polystyrene across the 10k. All vishay and soldered to the socket pins. Pin 3 direct to earth.
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