AudioCircle
Other Stuff => Archived Manufacturer Circles => Aspen Amplifiers => Topic started by: bhobba on 21 Mar 2009, 04:40 am
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Hi Hugh and All
Just tinkering around again and finding out a bit more about one of my favorite products, the LM 4562 op amp; an op amp that was actually, horror of horrors, designed not just using theory, but by listening (heaven forbid). Found out some really high end stuff is using them biased into class A and with an emitter follower output stage capacitor coupled. Seems they recon the better capacitors these days are so good it is close to copper (I presume they mean stuff like the platinum sonicaps) and that in class A the LM 4562 is so good its not worth going discreet.
Anyone any thoughts, observations, comments, ideas or whatever? Maybe something to consider for a future Aspen product?
Thanks
Bill
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Hi Hugh and All
Just tinkering around again and finding out a bit more about one of my favorite products, the LM 4562 op amp; an op amp that was actually, horror of horrors, designed not just using theory, but by listening (heaven forbid). Found out some really high end stuff is using them biased into class A and with an emitter follower output stage capacitor coupled. Seems they recon the better capacitors these days are so good it is close to copper (I presume they mean stuff like the platinum sonicaps) and that in class A the LM 4562 is so good its not worth going discreet.
Anyone any thoughts, observations, comments, ideas or whatever? Maybe something to consider for a future Aspen product?
Thanks
Bill
Hi Bill,
Have you seen any comparisons of the LM 4562 vs. other "popular" opamps? From memory, a middle-European guy with the moniker "DVV" used to post here and his site contains some comparative reviews ... although they must be 5-10 years old, now. He liked the AD826 as it had a good bass response. (But I've lost his website! :( )
Regards,
Andy
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Bill,
I seem to recall this opamp being picked up by Silicon Chip for a preamp. It's claim to fame was extremely low measured distortion; I'm always suspicious of this, because in my experience very low distortion usually means mostly higher order, which sounds clean but sterile.
That is not to condemn it, but until I've built one and listened extensively, I wouldn't like to say either way.
Cheers,
Hugh
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That is not to condemn it, but until I've built one and listened extensively, I wouldn't like to say either way.
Cheers,
Hugh
Hello Hugh
That would be a very good ideas, you can have, without problems, LM4562 samples from National Semiconductor.
Have you try and listen any others opamps, like the AD825, OPA637, OPA627, OPA2134, etc... ?
Bye
Gaetan
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Hello guy's
Maby we are better with the oldies, like the AD825, OPA637, OPA627 ?
Those high speed low distortions opamp like LM4562 need a very high nfb and a very good decoupling.
They don't show, in the data sheet, the distortion spectrum, but I would not be surprise of higher order distortions in the LM 4562, and some say that the LM4562 do have a quite flat soundstage.
Here is the distortions vs output of the LM4562, even taking account of the noise floor it goes quite high at low level output;
(http://img403.imageshack.us/img403/8651/captureg.jpg)
Bye
Gaetan
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Maybe we are better with the oldies, like the AD825, OPA637, OPA627 ?
Gaetan
Can you explain what the difference is between the AD825 & the AD826?
Thanks,
Andy
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One thing that never ceases to amaze me about Silicon Chip is that they never comment on how the end product sounds. I actually think Silicon Chip does a lot of good for audio electronics and their magazine has given me a lot of reading pleasure and has also taught me a lot.
However even some of their so called "objective measurements" just don't seem to add up when I look at the various graphs published. I borrowed some magazines from my local library and have been reading their analysis on this amp. The claim of having "typically 0.0006% THD" just does not appear on the graphs and is far closer to 0.001%, this is still very good but it is not what they are claiming.
Music is far more than just measurments as Hugh and others have stated, there is much more to audio reproduction that just THD. If it was that simple why is it that a Stradavarius sounds so good? The first, and only time, I heard a Stradavarius was a defining moment for me. A friend had shouted me to a trip to a concert and the guest violinist was just amazing and the clarity and tone was a stand out. I only discovered that it was a Stradavaruius being played afterwards when I read the program notes and this insight made a big impression on me to show that there is more to music that just frequency measurements in a lab.
Bluesky
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Hi
The LM4562 is currently the opamp for use in the Orion crossover, but I haven't tried it yet. Some others like West have, I think. There is also some comment on the newest range of National op-amps on DIY Audio. (http://www.diyaudio.com/forums/showthread.php?s=&threadid=132471&perpage=25&pagenumber=1)
Regards
Mike
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Mike,
I'm mainly using the OPA2107, mixing in the LM4562. It's going to take some time, frankly a lot of time, but I hope to find a nice mix.
-West
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I've built 2 of the Silicon Chip "Professional" Preamps using the OPA2134 Opamps.Sound was very cold, which is characteristic of most opamps but was'nt helped by the fact that application notes which specifically state that they (the OPA2134) perform better in inverting mode than non-inverting mode were ignored. In addition there were far too many coupling caps (non-polarised electrolytics) in the circuit. I ditched most of them and used Blackgate N were they were required. Also used Blackgates for the power supplies.
These preamps went to 2 of my nieces together with valve power amplifiers. The combination of OPA2134 based preamp and 6V6 tube based power amp sounded pretty darn good.
Just a variation on Hugh's theme of tube based preamp and SS based power amp.
Cheers,
Ian
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Hi Bill,
Have you seen any comparisons of the LM 4562 vs. other "popular" opamps? From memory, a middle-European guy with the moniker "DVV" used to post here and his site contains some comparative reviews ... although they must be 5-10 years old, now. He liked the AD826 as it had a good bass response. (But I've lost his website! :( )
Regards,
Andy
Hi Andy,
Dejan's site yes, he swears by the AD826 for everything and as a drop in for Marantz Cd players too, I always found his site somewhat misinformative especially when it came to overbiasing Class A/B amps but he did spend alot of time listening. Tangentsoft also has a comparison of OpAmps for headphone amp use. atleast most of the well known ones. After years of fiddling with opamps Ive learned there is no one since fits all, they all sound different, some subjectively better or worse, but this always changes based on application hence why discreet will never lose popularity among the pickiest. Ic's are damn easy to work with though, make designing a cinch but Ive always found every Ic benefits from a discreet buffer follower, always, even in a preamp to these ears..I tend to agree with Hugh these days in that the THD distribution is more important with a descent from the 2nd harmonic onward rather than a general THD figure which is very vague in all opamp datasheets.
Colin
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I think it was the Silicon Chip headphone amp that Hugh was thinking of, it has the LM4562 specified.
The guys over at Rock Grotto Audio reckon the metal can version LM4562HA is the go.
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THe DEQX I own is revamped in AU by the manufacturer by replacing multiple opamps for the LM 4562
The sound is not sterile but very very transparent and dare i say musical for a digital device.
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I'm no expert in the OpAmps but I really lke the LM4562 in my Shanling T 200A
It is very musical and the soundstage is very wide.
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Adding to the mix:
I'm using them in my CDP and while I agree about the transparency and soundstage, there's a certain amount of edginess in the top-end that I don't like all that much. They've been in there for nearly a year now and I'm quite used to them but based on my initial impression, I'll be replacing them audio-gd discrete component op-amps [similar to Burson devices]. Going back to what Hugh, gaetan and others have said, distortion seems a likely culprit.
Jules
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Maybe we are better with the oldies, like the AD825, OPA637, OPA627 ?
Gaetan
Can you explain what the difference is between the AD825 & the AD826?
Thanks,
Andy
Hello Andy
The AD825 are for audio and have a 41mhz bandwith, 125 v/us slew rate, with 12 nv/hz noise at 10khz.
The AD826 are for video and have a 50mhz bandwith, 350 v/us slew rate, with 15 nv/hz noise at 10khz.
Some was prefered the sound of the AD826.
Bye
Gaetan
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Hello carusoracer and Jules
Is the LM4562 do better than the AD825 for transparency, soundstage and sweet musicality ?
For me a 3D deep and wide soundstage are very important.
Thank
Bye
Gaetan
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Hi gaetan,
sorry, I can't give an opinion on the AD825 v LM4562. For what it's worth, the LM4562 is v good on 3D, soundstage and transparency but as I said above .......
Jules
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Hi gaetan,
sorry, I can't give an opinion on the AD825 v LM4562. For what it's worth, the LM4562 is v good on 3D, soundstage and transparency but as I said above .......
Jules
Hello Jules
You mean the edginess in the top-end...
Hum... I'm very sensitive to mid and high frequency distortion or harshness.
Thank
Bye
Gaetan
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I'm using them in my CDP and while I agree about the transparency and soundstage, there's a certain amount of edginess in the top-end that I don't like all that much. They've been in there for nearly a year now and I'm quite used to them but based on my initial impression, I'll be replacing them audio-gd discrete component op-amps [similar to Burson devices]. Going back to what Hugh, gaetan and others have said, distortion seems a likely culprit.
Jules
Hi jules,
Why did you pick the audio-gd discrete-component opamp over the Burson "opamp"? I have heard people comment on a harsh top-end with the Burson buffer and I wondered whether the Burson opamp replacement would sound as harsh?
I'm interested in trying out a "discrete opamp" replacement for the opamp used in the GK-1 phono stage.
Regards,
Andy
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Hello Andy
The AD825 are for audio and have a 41mhz bandwith, 125 v/us slew rate, with 12 nv/hz noise at 10khz.
The AD826 are for video and have a 50mhz bandwith, 350 v/us slew rate, with 15 nv/hz noise at 10khz.
Some was prefered the sound of the AD826.
Bye
Gaetan
Thanks, Gaetan, :D
From the specs, surely it seems the AD826 should be better for audio ... except for the higher noise figure? (And, as far as noise is concerned, the signal in each of the 3 channels of my active XOs passes through 3 AD826s, yet with CD selected and my GK-1 turned up full (but no CD playing), I can put my ear against each driver and basically don't hear any noise! (A real tribute to the AKSA products, IMO! :thumb: ) )
Regards,
Andy
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I'm using them in my CDP and while I agree about the transparency and soundstage, there's a certain amount of edginess in the top-end that I don't like all that much. They've been in there for nearly a year now and I'm quite used to them but based on my initial impression, I'll be replacing them audio-gd discrete component op-amps [similar to Burson devices]. Going back to what Hugh, gaetan and others have said, distortion seems a likely culprit.
Jules
Hi jules,
Why did you pick the audio-gd discrete-component opamp over the Burson "opamp"? I have heard people comment on a harsh top-end with the Burson buffer and I wondered whether the Burson opamp replacement would sound as harsh?
I'm interested in trying out a "discrete opamp" replacement for the opamp used in the GK-1 phono stage.
Regards,
Andy
Hello Andy
Which opamp are used in the GK-1 phono stage ?
Thank
Bye
Gaetan
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Hello Andy
Which opamp are used in the GK-1 phono stage ?
Thank
Bye
Gaetan
Sorry, don't know, Gaetan (Hugh scrubs the markings off them!). :lol:
Regards,
Andy
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I've used the LM4562, AD825 and OPA2134 on CD player outputs and my preference is in that order. I hated the AD826 but could have been fakes. I also hate the OPA627 even though it is loved.
It's a very good opamp (very neutral) and did a little buffer comparing it against a Nelson Pass B1 and a Burson. In fact I preferred it to the Burson which sounded overblown in comparison and it was almost as transparent and neutral as the B1. It bettered the B1 in extension and dynamics in a system (uses a tweaked AKSA 55N+) that goes down to 30Hz and I think that's due to the high output impedance of the B1.... mine's capless and 330R but the suggested B1 uses caps and is 1K. Used in a system >40Hz and the B1 wins but the LM4562 is not shamed.
To me, the LM4562 was a pleasant surprise and is my choice for CD player outputs.
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Hello
I'm interest in high end op-amp for best transparency, soundstage and sweet musicality, because I will use an old Onkyo receiver, I will take out it's amp circuit, and also replace the phono and line stage MJM4559 Ic op-amp by the best opamps.
So I would use those op-amps for the line preamp and phono preamp section of this receiver.
Thank
Gaetan
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Gaetan
try these forums out http://www.audioasylum.com/index.htm
for instance digital general http://www.audioasylum.com/audio/digital/bbs.html
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I'm always suspicious of this, because in my experience very low distortion usually means mostly higher order, which sounds clean but sterile.
Hugh
Yes, that's the LM4562! Still one of the best monolithic opamps.
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I'm always suspicious of this, because in my experience very low distortion usually means mostly higher order, which sounds clean but sterile.
Hugh
Yes, that's the LM4562! Still one of the best monolithic opamps.
Sorry sos ... how can it be sterile yet "still one of the best monolithic opamps"?
Secondly, can you explain what a "non-monolithic" opamp is?
Regards,
Andy
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I built a really simple single stage preamp using a 4562 and I absolutely loved it. Worth the time to try at least, just a few resistors and caps:
(http://img529.imageshack.us/img529/9135/dsc08988hb1.jpg)
Very musical and not sterile at all...even with Solens. :D
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Thanks Bill,
I'm getting interested...... :finger:
Hugh
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THe DEQX I own is revamped in AU by the manufacturer by replacing multiple opamps for the LM 4562
The sound is not sterile but very very transparent and dare i say musical for a digital device.
Speaking of the devil, my DEQX is Oz bound for upgrades to HDP-3 status which includes tearing out all the old opamps and replacing with LM45462s. Initial reports confirm what you are hearing, that it is a big improvement. Of course, there is more going on in the HDP upgrade so it won't be an apples to apples comparison for me.
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I've used the LM4562 in my DAC output (Zhaolu) and found it to be a bit sterile as well. Very transparent, for sure, but somewhat mechanical in nature, no matter what I did to try and give it some additional "musicality". Overall the AD2107 seems to fill that void for me better than the LM4562.
Bob
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Oddly, I consider myself fortuneate in having a less elegant, prior implementation of Bob's dac, the Zhaolu 2.0. Because my Zhaolu 2.0 provides balanced outputs, it uses a typical app note implementation of each phase of a channel feeding its output to an op amp (which provides the balanced outputs) and after, the 2 phases combined in another op amp to provide single ended outputs. [This is the same topology as found in the SB Transporter]
I use the single ended outputs, which allows me to tune the subjective results by using different opamps for dac filtering and balanced to single ended output. For the dac chip (CS4398) output filtering I use 1 dual OPA2107/channel (each phase served by its own amp in the dual), and for the balanced to single ended combining and output to the external world, one dual LM4562, with each of its amps serving its own channel. In total, 3 dual opamps for the analog section of the DAC for both channels.
In reality, this topology is no more complicated than that in Bob's Zhaolu 2.5. My 2.0 has an additional opamp per channel, as each phase, gets its own amp, rather than both phases of a channel filtered and combined in a single opamp, and then buffered. But most importantly, it allows me to use different monolithic opamps for the filtering and single ended output functions, and get what I want subjectively. (nor do my choices compromise objective measures)
This also leads me to the sad conclusion that audio reproduction is far more 'additive' than I'd like from a superficial intellectual perspective. I've not evaluated the newer Zhaolu 3.0 which provides single ended outputs from a single opamp per channel, combining phases, filtering and output in one stage. Perhaps the LT1028, or the new SiGe opamps from TI. But I've yet to encounter a monolithic opamp that 'does it all'.
FWIW,
Paul
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Hi Guys,
I've sold my Zhaolu 2.5C with a Zapfilter and moved on but tried a lot of different opams before going to the Zapfilter and couldn't find one that sounded good to me while I owned it.
So, that brings me to my question. Have any of you played with HDAM opamp replacements? Audio-gd sells them and they get very good reviews on the Head Fi forum. http://www.audio-gd.com/enweb/pro/diy/OPA.htm
Jim
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Hello
I did only try the OPA627 last year and it was a very sweet and precise op- amp with a 3D tube sound.
There was a web site where a guy test somes op-amps for the distortions spectrums, but I've forgot where was that web site.
There is few discrete op amp schematic thread in the diyaudio forum.
I've look at the HDAM opamp web site, they are more affordable than some others discretes op-amps.
Bye
Gaetan
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Hello
I did only try the OPA627 last year and it was a very sweet and precise op- amp with a 3D tube sound.
There was a web site where a guy test somes op-amps for the distortions spectrums, but I've forgot where was that web site.
There is few discrete op amp schematic thread in the diyaudio forum.
I've look at the HDAM opamp web site, they are more affordable than some others discretes op-amps.
Bye
Gaetan
Gaetan,
I think your referring to Doug Selfs site where he goes through most of the popular opamps, AD797,opa2134 etc.. I wholly agree on the Opa627 though, it sounds very very close to a tube with very subtle differences that really take alot of listening to seperate, the only area I have found strongly better Opa627 vs tube is the soundstage width, its huge and surprisingly not clinical from this Op. There are steps to get the absolute best out of it, but out of the box its quite good. The ad744/ad811 almost completely caused me to abandon opamps for anything musically related, then I dragged back out this trusty old bugger with a new approach ;)..
Colin
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Hello Colin
I know that page of Doug Self, but there is a more complete analyse with spectrum analysis, from S. Groner, done in 2008, I just founded it on my hard disk and traced it on the web, here is the document link;
http://www.sg-acoustics.ch/analogue_audio/ic_opamps/pdf/opamp_distortion.pdf
Btw, this weekend it's the Audio Show in Montreal at the Sheraton in downtown, I will be there.
http://www.salonsonimage.com/en/visitors/index.html
Thank
Bye
Gaetan
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Gaetan,
I wholly agree on the Opa627 though, it sounds very very close to a tube with very subtle differences that really take alot of listening to seperate, the only area I have found strongly better Opa627 vs tube is the soundstage width, its huge and surprisingly not clinical from this Op. There are steps to get the absolute best out of it, but out of the box its quite good. The ad744/ad811 almost completely caused me to abandon opamps for anything musically related, then I dragged back out this trusty old bugger with a new approach ;)..
Colin
Hello Colin
You mean pushing the OPA627 into class A ?
As an example, Thorsten Loesch, in his revised Analogue Addicts Phono Preamplifier, push the Op-Amp output to operate as single ended class A emitter follower, he connect a 6K8 resistor from the output to the positive supply.
Thank
Bye
Gaetan
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Thanks Bill,
I'm getting interested...... :finger:
Hugh
High Hugh.
Yes it does look interesting. Certainly interesting enough to try. Like I said read reports that in class A and output buffered with a transistor sounds really sweet.
Thanks
Bill
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Hi Gaetan,
Yes Class-A is correct, I originally used the resistor trick a long time back, found that even a simple Bjt,Led,resistor current source sounded much better, also a drawn current of 5ma,a buffer and nested feedback really improved this chip for a voltage gain stage.
Colin
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Hi Gaetan,
Yes Class-A is correct, I originally used the resistor trick a long time back, found that even a simple Bjt,Led,resistor current source sounded much better, also a drawn current of 5ma,a buffer and nested feedback really improved this chip for a voltage gain stage.
Colin
Hello Colin
I've modified the analog addicts phono preamp. Using a ccs but the ccs resistors value are approximative.
Is, in my image, it is like you said and resistors value ok for 5 ma ?
Thank
Bye
Gaetan
(http://img441.imageshack.us/img441/5047/analogaddictsphonopreamg.png)
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hi
after trying a lot of AOP ( ad825 , 5532 , 627 , 2604 , 2132 , ad845 , 8620 , ths4062 and 8066 ) in CD players output stages or input buffer in preamps , i've got the best results with AD826 and THS4032
Alain
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Hi Gaetan,
For the CCs, I assume you are using a Green Led?, in that case a 270R resistor will suffice for a little over 5ma. Also, the 2k from collector to output is not really neccessary as this is a high impedence junction as it is and offers little and is absolutely not neccessary for any sonic benefit, ive tried with and without and never noticed a difference in the slightest. For ythe opa627, negative rail biasing is best, it makes much more sense if you take a gander at the datasheet and simplified schematic as to why you will want to pull current from the Upper half, youll notice from the schematic that the positive rail half is in the same drive configuration as a diamond buffer which is very sonically good, now there is the advantage on running 1/2 single ended which in the opa627 is the upper half, the lower half is a standard EF... For the CCS use a very low capacitance bjt, my favorite for opamp biasing is 2sc2705, 1.5pf cob, and connect to the negative rail exactly as you have drawn with the pnp in the schematic....If you have any questions feel free to PM me, as I dont want to hijack the LM thread ;)...
Colin
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Hello Colin
Thank for your help, I will do as you suggested.
Bye
Gaetan
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Hello
I have read again some texts of Doug Self and
found somethings interesting about the LM4562
in his web page "Designing With Opamps"
It seem that the distortion figures tets in the
Nat.Semi. data sheet are done with a shunt
feedback circuit, giving better figures with less
common-mode distortion in the input stage and
less distortions at HF.
The Doug Self LM4562 distortions tests done
with a series feedback mode circuit do have
much higher distortion at HF compared with
a circuit using shunt feedback mode. And the
distortions should be higher in a real life use
with musics and transients.
Since some circuits and most phono preamp circuit
use series feedback mode, maby it is explain the
certain amount of edginess in the top-end for the
LM4562.
Bye
Gaetan
First image are LM4562 in series feedback mode
circuit test. Second image are LM4562 in shunt
feedback mode circuit test.
(http://img141.imageshack.us/img141/9231/lm4562distgraph.gif)
(http://img150.imageshack.us/img150/1913/lm4562distgraph2.gif)
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Hi Gaetan,
Have you tried the metal can series for the LM4562HA. It seems like Mark and couple of guys from DIYaudio swear by it. They feel that it is a more refine version. :drool: I also wonder how they perform as a non-inverting unity gain buffer as compare to the other configurations.
BTW, does anyone knows if it is a good idea to skip the buffer at the cdp output(4.5kohm) as there is a unity gain buffer after the attenuator.
KK
Can't wait to get my hands on my Soraya. :drool:
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Hi KK,
Welcome to you, and Colin, and Gaetan, to the forum!
Today I auditioned the new Soraya (update 2009 version as discussed) in a good friend's system, with Squeezebox, Burson Buffer, and VSonics.
Stunning, exceeded specifications, I can continue without any worries at all. Compared to the older model it offered more resolution, much better layering of instruments, and huge bass articulation. I'm over the moon, results better than expected.... :thumb:
Colin, you there?? Are you in for a surprise! :drool:
Cheers,
Hugh
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Hugh!,
Im here now ;), haha, I emphatically agree, I cant find a fault with it thus far in any way shape or form at this moment, from the Lows to the highs to the Soundstaging, natural, very 3d and most importantly non fatiguing whatsoever...My Jaw dropped with the 50w prototype, at 100w(retail version) its at its best in terms of resolution and drive...This was all conceived during Hugh's outpouring of madness, it required a pogo stick to keep up with the speed of his changing ideas!, :icon_lol:
Colin
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Hi Colin,
You are certainly being charitable here, but I'm really pleased you like it too, and I cannot overstate the contribution in practical and creative ways that you have made to my audio madness in years past.
It is a great shame we live on different continents....... thank you sincerely. :thankyou: :beer:
Cheers,
Hugh
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Hi Hugh,
Non-Charitable, its a culmination of taking the conventional amplifier, finding the weaknesses and finding a practical and hopefully simplistically elegant solution the weaknesses.Also its driven by a mad passion to experiment with new ideas rather than to re-introduce an old design with minore parts changes which can be often at the small corner of empirical differences. Ears are essential here, as we have both found, the well known area of measurement does very little to dictate sound "quality", so the Ears are both a first and last defense while we all still retain something to call hearing ;). As always its great to try and correlate what we measure to what we hear, truly and utterly impossible with straight THD exams, the biggest difference being IM and how the Thd unfolds across the band with music which still gives creedence to the rightfully sought after monotonically decreasing figures 1khz and up. Slew Rate too seems to play a pretty good indicator surprisingly, and then this is affected by many parameters,choice of frequency compensation, gain, nfb-db, Ft and Phase Shift within the amp. Tells me, while Tube amps had acheived their peak of the Art, SS amps still have creative life in them..Hugh, your going to need to set up a Soraya HTX review page pretty soon! :D..
Colin