Mooly,
I have been very busy today and did not have the time to come to the forum until late at night.
Thanks for your write-up. Your description is very clear. I spent a couple of hours reading through that thread - very interesting discussions.
I have spent a substantial amount of time learning to get the grounding right. I think for now mine is very similar or the same as one of the last posted pictures. I only did a bit more, that any lifted grounds via a resistor have a suitable capacitor to shunt RF to the chassis, and I found this very important to obtain clear treble. I lifted the signal ground from the circuit common via a 10R. I lift the ground from chassis via 22R (also with a bridge). The chassis is isolated from mains earth via a 35A bridge (that should provide safety). I shunt RF from the chassis to earth via a small capacitor.
The main difference is perhaps that I use LRCLRCC filter and I made the star point right at the last C.
I think I will try this tomorrow for my power amp:
1) Remove the 10R resistor which sepeartes the signal ground from the star ground and see if it makes things better or worse.
2) Try put the input shield directly on the star ground.
I still need to think through how I may do the grounding for my line level XO/EQ opamp cricuits. The tricky bit is that, I run 3 seperate shunt regulators after the RAW LCLC supply, each driving treble, midrange and woofer circuits respetively. So there must be 3 local "star ground" coming from the same RAW PSU ground. The Input ground must be seperated into 3 to branch into 3 seperate circuits.
Please let me know if anything I said does not sound right.
Regards,
Bill
I have been very busy today and did not have the time to come to the forum until late at night.
Thanks for your write-up. Your description is very clear. I spent a couple of hours reading through that thread - very interesting discussions.
I have spent a substantial amount of time learning to get the grounding right. I think for now mine is very similar or the same as one of the last posted pictures. I only did a bit more, that any lifted grounds via a resistor have a suitable capacitor to shunt RF to the chassis, and I found this very important to obtain clear treble. I lifted the signal ground from the circuit common via a 10R. I lift the ground from chassis via 22R (also with a bridge). The chassis is isolated from mains earth via a 35A bridge (that should provide safety). I shunt RF from the chassis to earth via a small capacitor.
The main difference is perhaps that I use LRCLRCC filter and I made the star point right at the last C.
I think I will try this tomorrow for my power amp:
1) Remove the 10R resistor which sepeartes the signal ground from the star ground and see if it makes things better or worse.
2) Try put the input shield directly on the star ground.
I still need to think through how I may do the grounding for my line level XO/EQ opamp cricuits. The tricky bit is that, I run 3 seperate shunt regulators after the RAW LCLC supply, each driving treble, midrange and woofer circuits respetively. So there must be 3 local "star ground" coming from the same RAW PSU ground. The Input ground must be seperated into 3 to branch into 3 seperate circuits.
Please let me know if anything I said does not sound right.
Regards,
Bill
Hi Bill,
Only you know the grounding layout of the PCB's etc... just make sure you don't inadvertantly isolate one completely by accident... that could be destructive in a power amp.
It really does help to think in terms of DC analysis and volt drops. Imagine applying say 1volt at the input and say the output is perhaps supplying 10 volts across 10 ohms (1 amp flowing).
Now put in imaginery values in ohms for the ground leads etc, and think, does that current cause any volt drop that can corrupt the signal at all.
Only you know the grounding layout of the PCB's etc... just make sure you don't inadvertantly isolate one completely by accident... that could be destructive in a power amp.
It really does help to think in terms of DC analysis and volt drops. Imagine applying say 1volt at the input and say the output is perhaps supplying 10 volts across 10 ohms (1 amp flowing).
Now put in imaginery values in ohms for the ground leads etc, and think, does that current cause any volt drop that can corrupt the signal at all.
Hi all
has anyone here tried ADA4627BRZ from Analog Device? some diyer's from asia claim it bettered OPA627, I have received 4pcs samples from Analog Device(it's single opamp, similar to OPA627) but haven't tried it yet
right now I'm using LM4562 both plastic and can type (TOC8) and found the can type bit more transparent and clearer sounding than plastic (dip8) type.
I read somewhere forum that hifinutnut likes OPA627 than LM4562, I think you should try ADA4627BRZ
I will write the follow up on ADA4627 sooner
has anyone here tried ADA4627BRZ from Analog Device? some diyer's from asia claim it bettered OPA627, I have received 4pcs samples from Analog Device(it's single opamp, similar to OPA627) but haven't tried it yet
right now I'm using LM4562 both plastic and can type (TOC8) and found the can type bit more transparent and clearer sounding than plastic (dip8) type.
I read somewhere forum that hifinutnut likes OPA627 than LM4562, I think you should try ADA4627BRZ
I will write the follow up on ADA4627 sooner
Theoretically, the single OpAmps can deliver a better quality. BUT... you are already in the diminishing returns area - you might not HEAR the improvement.
Some people claim they do, but I'll take that with a grain of salt.
For me LM4562 provided a very good sound quality. Tried some LT1028 with adaptor and besides overloading the PS, I didn't hear an improvement. I don't say it wasn't, just that I didn't hear it.
Some people claim they do, but I'll take that with a grain of salt.
For me LM4562 provided a very good sound quality. Tried some LT1028 with adaptor and besides overloading the PS, I didn't hear an improvement. I don't say it wasn't, just that I didn't hear it.
Ada4627brz
Hi eherdian,
I've been using the ADA4627BRZ's for a couple of weeks now, and have to say that I like them quite well. I've not had a chance to test/listen to the 627/637/827's yet so I can't really compare them for you.
I DO know that I prefer the sound of the ADA4627BRZ to the ADA4627ARZ in the same circuit and prefer either of them to the 4562 which, to me, sounds a bit bright with slightly lacking deep bass.
Dan
Hi eherdian,
I've been using the ADA4627BRZ's for a couple of weeks now, and have to say that I like them quite well. I've not had a chance to test/listen to the 627/637/827's yet so I can't really compare them for you.
I DO know that I prefer the sound of the ADA4627BRZ to the ADA4627ARZ in the same circuit and prefer either of them to the 4562 which, to me, sounds a bit bright with slightly lacking deep bass.
Dan
I don't get how people can believe that a piece of silicon (OpAmp) can "lack bass" or it can be "bright"... The chip it is not a filter, but rather the circuit that was used in was not designed for a bipolar OpAmp.
Usually, if you put a LM4562 in place of a JFET OpAmp, you might find that the lower input impedance require an increase of the existing coupling capacitors, changing the polarization network... It is not the LM4562 fault, but the technical error or rolling blindly the OpAmps in the circuit without paying attention of the details.
Usually, if you put a LM4562 in place of a JFET OpAmp, you might find that the lower input impedance require an increase of the existing coupling capacitors, changing the polarization network... It is not the LM4562 fault, but the technical error or rolling blindly the OpAmps in the circuit without paying attention of the details.
I've not compared opamps myself but it seems totally reasonable to me that people do hear differences. Note its not necessary for them to believe anything, just hear something. Perception is relative and if the mid/highs have more detail then our attention is drawn to those details with the result that we perceive a lack of bass. Try as an experiment listening to just the tweeter (or just the mid range if you have a 3-way) of your speakers . I've done this and it sounds rather horribly bright/shouty alone, but when melded with the rest its fine. So the perception of sound is all about balance.
If opamps doesn't sound different from each other, there's no reason to believe discrete amplifiers sound different from each other either. No need to strive for progress? Is LM4562 the end of the line?
"I don't get how people can believe that a piece of silicon (OpAmp) can "lack bass" or it can be "bright"... The chip it is not a filter, but rather the circuit that was used in was not designed for a bipolar OpAmp.
Usually, if you put a LM4562 in place of a JFET OpAmp, you might find that the lower input impedance require an increase of the existing coupling capacitors, changing the polarization network... It is not the LM4562 fault, but the technical error or rolling blindly the OpAmps in the circuit without paying attention of the details." -SoNic_real_one
Well, I'm not in the habit of doing anything "blindly" (but I do make mistakes).
The original circuit was designed for NE5532P or LM833N op-amps which are, according to the data that I have, bipolar. I do realize that FET/diFET input devices can have different requirements for loading, coupling etc. and try to make allowances/modifications for these factors.
To my ears the LM4562's sound as described in that particular circuit in that particular device. In future, I'll qualify my observations as such.
Sadly, I can't afford a 'scope to better quantify what my ears tell me. It might make all of this a lot easier-but a lot less fun.
BTW, the OPA2111 (also bipolar, according to TI) does sound rather nice in the same circuit, giving back some bass extension and eliminating some of the "peakiness" that I found as very minor "weak spots" in the LM4562.
I'd also put them on the "must try" list.
Dan
Usually, if you put a LM4562 in place of a JFET OpAmp, you might find that the lower input impedance require an increase of the existing coupling capacitors, changing the polarization network... It is not the LM4562 fault, but the technical error or rolling blindly the OpAmps in the circuit without paying attention of the details." -SoNic_real_one
Well, I'm not in the habit of doing anything "blindly" (but I do make mistakes).
The original circuit was designed for NE5532P or LM833N op-amps which are, according to the data that I have, bipolar. I do realize that FET/diFET input devices can have different requirements for loading, coupling etc. and try to make allowances/modifications for these factors.
To my ears the LM4562's sound as described in that particular circuit in that particular device. In future, I'll qualify my observations as such.
Sadly, I can't afford a 'scope to better quantify what my ears tell me. It might make all of this a lot easier-but a lot less fun.
BTW, the OPA2111 (also bipolar, according to TI) does sound rather nice in the same circuit, giving back some bass extension and eliminating some of the "peakiness" that I found as very minor "weak spots" in the LM4562.
I'd also put them on the "must try" list.
Dan
"blind" testing is a virtue in subjective comparisons
sighted manual rolling in one instance of a circuit isn't the most convincing method of comparison - you really should have at least 2 complete copies of the test circuit, one with each of the op amps - and they should be "blueprinted" - trimmed to match in all particulars - level and frequency response to better than 1% over the audio range
1st establish that you can't hear a difference in the two copies - with the same op amp type in both
a good soundcard can be cheap tool to aid the process - Juli@ still has good price/performance and soemthing like Audio DiffMaker should help identify objective measurable differences in the circuit performance - and you should eliminate those not specific to the op amp choice
then do a blinded ABX with the different op amps in each
fast, quiet, "clueless" switching using short term memory tests as higher resolving but if you think you need more time and less "performance pressure" there's no explicit need for a short listening time in a blinded test
(ABX needs careful investigation of possible clues from extraneous differences such as switching delays, DC mismatch pops, noise in one channel, anything in the test setup that allows identifying A vs B)
a surprising amount of "clearly heard" difference can't be found in blinded, controlled testing:
http://www.diyaudio.com/forums/solid-state/12752-blind-listening-tests-amplifiers-28.html#post152392
if Stereophile's reviewers couldn't tell the difference in cheap SS vs "High End" Tube power amps when EQ'd and trimmed then much of the uncontrolled op amp rolling subejctive commentary seems suspect to me
sighted manual rolling in one instance of a circuit isn't the most convincing method of comparison - you really should have at least 2 complete copies of the test circuit, one with each of the op amps - and they should be "blueprinted" - trimmed to match in all particulars - level and frequency response to better than 1% over the audio range
1st establish that you can't hear a difference in the two copies - with the same op amp type in both
a good soundcard can be cheap tool to aid the process - Juli@ still has good price/performance and soemthing like Audio DiffMaker should help identify objective measurable differences in the circuit performance - and you should eliminate those not specific to the op amp choice
then do a blinded ABX with the different op amps in each
fast, quiet, "clueless" switching using short term memory tests as higher resolving but if you think you need more time and less "performance pressure" there's no explicit need for a short listening time in a blinded test
(ABX needs careful investigation of possible clues from extraneous differences such as switching delays, DC mismatch pops, noise in one channel, anything in the test setup that allows identifying A vs B)
a surprising amount of "clearly heard" difference can't be found in blinded, controlled testing:
http://www.diyaudio.com/forums/solid-state/12752-blind-listening-tests-amplifiers-28.html#post152392
if Stereophile's reviewers couldn't tell the difference in cheap SS vs "High End" Tube power amps when EQ'd and trimmed then much of the uncontrolled op amp rolling subejctive commentary seems suspect to me
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Hi jcx,
In a perfect world or under laboratory conditions you are totally correct. (or if I were a professional audio equipment reviewer or manufacturer)
I'm lucky in that I have 4 essentially identical devices that I use for the comparisons. All have the same modifications applied and utilize the same circuit boards and power supplies. The only "wild" condition is that I can't count on the tolerance of each component on each board as they heat, cool or age.
We just look for whatever sounds most like "real" music.
Counting not on my ears alone, I have a group of friends who also get exposure to live music on a frequent basis, from classical to jazz, from big band to solo piano, from rock to Gregorian Chants. Not "golden ears" at all, but people who enjoy listening to a wide variety of live music. For them it is essentially "blind" testing.
As a side note, I remember a TON of controversy concerning blind or ABX testing. I won't even go there.
We don't always reach a consensus (as our hearing varies, as does our reaction to what we hear), but, in the end, the goal is music and its enjoyment.
If two chips in (virtually) the same circuit sound different, there is a whole raft of possibilities as to why. If all of these factors can be quantified and results are repeatable then there would/should/could be one and only one op-amp design that would work consistently and perfectly every time. I don't know that there is a totally "transparent" or "perfect" op-amp. If we accept that premise, it might stand to reason that each one adds its own mild (or not) colorations that, to some, will sound better or worse than another in a specific application.
If there were that one perfect device there would be no need to ever improve or update it, as perfect is forever (like the old ads for the first CDs- "Perfect music forever.")
Or am I totally off base here?
In a perfect world or under laboratory conditions you are totally correct. (or if I were a professional audio equipment reviewer or manufacturer)
I'm lucky in that I have 4 essentially identical devices that I use for the comparisons. All have the same modifications applied and utilize the same circuit boards and power supplies. The only "wild" condition is that I can't count on the tolerance of each component on each board as they heat, cool or age.
We just look for whatever sounds most like "real" music.
Counting not on my ears alone, I have a group of friends who also get exposure to live music on a frequent basis, from classical to jazz, from big band to solo piano, from rock to Gregorian Chants. Not "golden ears" at all, but people who enjoy listening to a wide variety of live music. For them it is essentially "blind" testing.
As a side note, I remember a TON of controversy concerning blind or ABX testing. I won't even go there.
We don't always reach a consensus (as our hearing varies, as does our reaction to what we hear), but, in the end, the goal is music and its enjoyment.
If two chips in (virtually) the same circuit sound different, there is a whole raft of possibilities as to why. If all of these factors can be quantified and results are repeatable then there would/should/could be one and only one op-amp design that would work consistently and perfectly every time. I don't know that there is a totally "transparent" or "perfect" op-amp. If we accept that premise, it might stand to reason that each one adds its own mild (or not) colorations that, to some, will sound better or worse than another in a specific application.
If there were that one perfect device there would be no need to ever improve or update it, as perfect is forever (like the old ads for the first CDs- "Perfect music forever.")
Or am I totally off base here?
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there's no controversy that in controlled, blind ABX testing a statistically significant portion of listeners can distinguish level differences down to 0.1 dB ~= 1 % over wide enough frequency range
but below a few dB we don't generally recognize the difference as perceived loudness change
any subjective listening test is expected to find "differences" when levels aren't matched
also “expectation”/“placebo” effect is well known to be strong, interacting groups are even worse – social pressure causes us to “rewrite” memory, sensory input to go along
what our eyes see and our brain has been primed to expect really do change our sound perception – but we are interested presumably in which part/op amp really affects the electrical signal and resulting sound waves hitting our ears
without reading a good perceptual psychology text, preferably with psychoacoustic slant many people simply don't appreciate how unreliable, malleable our brain's interpretation of sensory input is
given the good quality of hi res soundcards it seems a major time waste to me to not let measurements have the 1st say, and eliminate and control electircally measureable effects
and within the psychoacoustic known limits I'll choose good measurements over my or other people's informal, uncontrolled listening impressions until I see good, controlled, blinded perceptual test evidence of audible differences - that would prompt development of new measurements
but below a few dB we don't generally recognize the difference as perceived loudness change
any subjective listening test is expected to find "differences" when levels aren't matched
also “expectation”/“placebo” effect is well known to be strong, interacting groups are even worse – social pressure causes us to “rewrite” memory, sensory input to go along
what our eyes see and our brain has been primed to expect really do change our sound perception – but we are interested presumably in which part/op amp really affects the electrical signal and resulting sound waves hitting our ears
without reading a good perceptual psychology text, preferably with psychoacoustic slant many people simply don't appreciate how unreliable, malleable our brain's interpretation of sensory input is
given the good quality of hi res soundcards it seems a major time waste to me to not let measurements have the 1st say, and eliminate and control electircally measureable effects
and within the psychoacoustic known limits I'll choose good measurements over my or other people's informal, uncontrolled listening impressions until I see good, controlled, blinded perceptual test evidence of audible differences - that would prompt development of new measurements
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That's a really interesting read... thanks for the link.
Now, I'm going to quote from memory something Doug Self put in print in his original articles on "blameless class B".
Doug reckoned that if you didn't like the sound of the amp (blameless) it would perhaps be possible to add a "niceness" control upstream to introduce for example 2nd harmonic distortion etc etc.
It makes you wonder
don't wonder my friend, try it! this Trident EQ has a "saturation" knob: Trident A-Range Equalizer by Softubeit would perhaps be possible to add a "niceness" control upstream to introduce for example 2nd harmonic distortion etc etc.
It makes you wonder
with music: ImageBam / with movies: ImageBam
basically it adds a very very delightful analog color...the perfect fix for digitis to my ears
BTW, I got a tricky question for you
I've had the same issue TWICE w/ the same dual LT1028ACN8 opamp...I really have no idea wth is going on
first, this sound card: ImageBam
you can see that I've got sockets on the browndog and on the soundcard...low end bass was VERY percussive, and totally mind blowing!
then I tried to solder some 1028AC directly on a browndog, and the low end bass was dull and not percussive anymore?!
second, my Firestone Spitfire DAC: ImageBam
same story, a socket on the PCB and 2 sockets on the browndog: very percussive bass!
so I thought, WTH! and decided to solder the 1028AC on the browndog = much clearer sound, wider center channel(on headphones) and the same low end bass percussion = best sound I had ever head = me in heaven...feeding high quality opamps w/ toslink on a discrete linear DPS does pay off!
then I decided to go an audio repair shop, and the guy ditched the PCB socket and soldered my soldered browndog onto the DAC PCB = low end bass percusson is gone, and the low end bass is utterly dull.
question: why?
I've been told that sockets add impedance? anyway, lesson learned! I will ask the guy to put back the stock socket on the PCB...and forget about hard mods
a friend of mine is gonna send me some ADA4627-1B, and what's a roller w/o a socket duh
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As always you need to measure what's happening. Best guess if the effect is as extreme as you say is that the IC's are borderline unstable in all the sockets.
Yes they do add "impedance" making instability more likely, and a good test would have been to dab a small cap across the supply pins of each IC (and even better with a 'scope looking at the supplies, opamp output etc).
Yes they do add "impedance" making instability more likely, and a good test would have been to dab a small cap across the supply pins of each IC (and even better with a 'scope looking at the supplies, opamp output etc
).