Hi everyone
This is my first post at DIYaudio. Apologies, in advance for any breach(es) of protocol. ;-) This post relates to op-amps in (high-gain) phono stages and (low gain) pre-amps.
Firstly, I run a 60dB gain (low-output MC) dual-mono phono stage that utilizes 2 pairs of DIP-seated Burr Brown OPA37GP op-amps. Sonically it's fine but I'm unrelentingly curious. Does anyone know if Burr Brown OPA637's are direct electrical drop-in replacements, and if so, what sought of changes might occur? Any other more modern designs that could also suit?
Secondly, shortly I'm about to road test another dual-mono phono stage which utilizes 2-stage gain comprising (don't gag, not my design!) one pair TI TL-071 followed by another pair Burr Brown OPA660 or unknown brand CA3280. How easy is it to swap out the TL071 for a more modern op-amp design?
Thirdly, if one was designing a premium quality line-level op-amp-based pre-amp, maybe combining functions of headphone amp and USB DAC as well, which op-amp(s) would suit best?
Fourthly, is the ultimate low-ripple, noise-free DC power supply design based upon Walt Jung's 'super-regulator' principles? Should one use Schottky diodes above HEXFRED and other fast-soft recovery types?
I should add that I've listened to countless devices incorporating op-amps, most of which sound harsh and distorted. Of those components that seem to deliver the sonic goods, I've found all are made by Burr Brown.
At the risk of creating undue controversy, it appears that each op-amp brand has a vaguely familial sound. AD op-amps almost always sound brittle and artificially forward, even their pricey, premium ones.
And that brings me to some of DIYaudio more animated technical debates. It's crucial to focus on basic electrical parameters in designing circuits with op-amps, and graphs and data have their place. However at the end of the day, one should always relate their activities back to what each component contributes to the overall sound quality, viz, how closely an original recorded event is reproduced/replicated by your audio equipment. This process will automatically disqualify anything to do with digital compression (MP3 and the like). How any audio print media can dare to seriously review MP3 players and computer sound cards as viable audio devices is beyond me!
nightcap
This is my first post at DIYaudio. Apologies, in advance for any breach(es) of protocol. ;-) This post relates to op-amps in (high-gain) phono stages and (low gain) pre-amps.
Firstly, I run a 60dB gain (low-output MC) dual-mono phono stage that utilizes 2 pairs of DIP-seated Burr Brown OPA37GP op-amps. Sonically it's fine but I'm unrelentingly curious. Does anyone know if Burr Brown OPA637's are direct electrical drop-in replacements, and if so, what sought of changes might occur? Any other more modern designs that could also suit?
Secondly, shortly I'm about to road test another dual-mono phono stage which utilizes 2-stage gain comprising (don't gag, not my design!) one pair TI TL-071 followed by another pair Burr Brown OPA660 or unknown brand CA3280. How easy is it to swap out the TL071 for a more modern op-amp design?
Thirdly, if one was designing a premium quality line-level op-amp-based pre-amp, maybe combining functions of headphone amp and USB DAC as well, which op-amp(s) would suit best?
Fourthly, is the ultimate low-ripple, noise-free DC power supply design based upon Walt Jung's 'super-regulator' principles? Should one use Schottky diodes above HEXFRED and other fast-soft recovery types?
I should add that I've listened to countless devices incorporating op-amps, most of which sound harsh and distorted. Of those components that seem to deliver the sonic goods, I've found all are made by Burr Brown.
At the risk of creating undue controversy, it appears that each op-amp brand has a vaguely familial sound. AD op-amps almost always sound brittle and artificially forward, even their pricey, premium ones.
And that brings me to some of DIYaudio more animated technical debates. It's crucial to focus on basic electrical parameters in designing circuits with op-amps, and graphs and data have their place. However at the end of the day, one should always relate their activities back to what each component contributes to the overall sound quality, viz, how closely an original recorded event is reproduced/replicated by your audio equipment. This process will automatically disqualify anything to do with digital compression (MP3 and the like). How any audio print media can dare to seriously review MP3 players and computer sound cards as viable audio devices is beyond me!
nightcap
Hi nightcap,
Good thread topic.
It seems to me that all op amp based signal amplifiers may have a "sound". Whether you can hear it depends a great deal on your system, and you. I think PCB layout is just as important as the op amp you use.
This seems to be a topic worth exploring.
Cheers!
-Chris
Good thread topic.
It seems to me that all op amp based signal amplifiers may have a "sound". Whether you can hear it depends a great deal on your system, and you. I think PCB layout is just as important as the op amp you use.
This seems to be a topic worth exploring.
Cheers!
-Chris
This is my basic "first look" to see if op-amps are plug compatible. First, download the datasheets for both parts. Is the supply voltage of the new part greater than what's being supplied? Are the basic input, output, and power signals on the same pins? What's the minimum stable gain, and is the circuit set up for that or greater? Finally, look at the compensation and offset pins. Usually they're not used, but different op-amps use different polarities and configurations for offset. If it's used, make sure it's wired like the data sheet. Ditto any compensation used. If the new part meets the above, it will usually work well enough to dig deeper into how to optimize it and how it sounds. I've used the OPA627 in scientific instrumentation, and it's a fantastic part in terms of low offset and low noise. The OP37 is a higher bandwidth version of the old OP27, and they're both aimed primarily at precision lower frequency applications. I think they're bipolar, but would have to check. IMO, they're pretty old designs. Again not sure, but I think the 627 is jfet or cbfet or something, but it has way lower input currents, and IMO has little in common with the old 27/37 parts. Unfortunately, it's quite expensive, and may or may not be any better sound-wise than (man is my memory shot- forgive p/n errors) the 833/797 parts commonly used.
Thanks Chris and Conrad.
Certainly will compare specs, and agree that overall circuit design, materials and parts selection, and attention to detail optimise sonic outcomes.
It'd be good to hear from DIYers who might share brutal first-hand experiences, whether in fact, there is any merit in swapping out older op-amps; if so, any gain, and how much pain? Also those related aspects of DC power supply and pre-amp design......
nightcap
Certainly will compare specs, and agree that overall circuit design, materials and parts selection, and attention to detail optimise sonic outcomes.
It'd be good to hear from DIYers who might share brutal first-hand experiences, whether in fact, there is any merit in swapping out older op-amps; if so, any gain, and how much pain? Also those related aspects of DC power supply and pre-amp design......
nightcap
Op-amp viewpoints welcome
OPA2134,LM4562 and AD8066 are worth looking at. The OPA2134 is a good choice for replacing devices such as NE5532, 4558 etc. LM4562 is more revealing than the OPA2134, but worth trying. It is still the "flavour of the month" (I think)
AD8066 is another very revealing opamp, but only comes in SOIC .
It requires close bypassing. It usually sounds better using normal 100nF bypass capacitors instead of the recommended 100nF ceramic, PROVIDED that voltage regulators are fairly close by,for stability reasons.
SandyK
OPA2134,LM4562 and AD8066 are worth looking at. The OPA2134 is a good choice for replacing devices such as NE5532, 4558 etc. LM4562 is more revealing than the OPA2134, but worth trying. It is still the "flavour of the month" (I think)
AD8066 is another very revealing opamp, but only comes in SOIC .
It requires close bypassing. It usually sounds better using normal 100nF bypass capacitors instead of the recommended 100nF ceramic, PROVIDED that voltage regulators are fairly close by,for stability reasons.
SandyK
Op-amp viewpoints welcome !
Nightcap
If you want more information on op-amp "rolling" and subjective reports on the effect of using different types of op-amps. Have a look at the Rock Grotto Audio Forum. They have tested most of the better opamps in various types of equipment.
SandyK
http://rockgrotto.proboards39.com/index.cgi
Nightcap
If you want more information on op-amp "rolling" and subjective reports on the effect of using different types of op-amps. Have a look at the Rock Grotto Audio Forum. They have tested most of the better opamps in various types of equipment.
SandyK
http://rockgrotto.proboards39.com/index.cgi
Hi sandyK,
Interesting forum that's just starting up. Sounds like their heart is in the right place and I wish them well.
If you search on this site, you will see many op amp comparisons and discussions. The results from your search may be more than you wish simply due to the number of members posting here, so refine your search and read in little bits.
Are we the other "big forum"? Anyway, everyone is welcome and membership in other forums is a good thing. It helps everyone share knowledge, so don't be shy about it.
-Chris
Interesting forum that's just starting up. Sounds like their heart is in the right place and I wish them well.
If you search on this site, you will see many op amp comparisons and discussions. The results from your search may be more than you wish simply due to the number of members posting here, so refine your search and read in little bits.
Are we the other "big forum"?
Anyway, everyone is welcome and membership in other forums is a good thing. It helps everyone share knowledge, so don't be shy about it.-Chris
Op-amp viewpoints welcome
Chris
I mentioned Rock Grotto because some of the less experienced
people may feel intimidated by the sheer size and more technical side of this forum. There is also an unfortunate tendency here for some members to "snipe" at some of other peoples designs, although most members try to be helpful. I originally registered as a member on Rock Grotto because I wished to post a project about modifications to the Musical Fidelity X-DAC V3 without being subjected to minor technical criticisms. But as someone who has been constructing electronics projects for >30 years, I do enjoy the technical excellence of DiyAudio Forum.
BTW, I have previosly visited this forum on and off, for several years.
Kind Regards
SandyK
Chris
I mentioned Rock Grotto because some of the less experienced
people may feel intimidated by the sheer size and more technical side of this forum. There is also an unfortunate tendency here for some members to "snipe" at some of other peoples designs, although most members try to be helpful. I originally registered as a member on Rock Grotto because I wished to post a project about modifications to the Musical Fidelity X-DAC V3 without being subjected to minor technical criticisms. But as someone who has been constructing electronics projects for >30 years, I do enjoy the technical excellence of DiyAudio Forum.
BTW, I have previosly visited this forum on and off, for several years.
Kind Regards
SandyK
Nurturing Intelligent Audio Design
Forums such as this and Rock Grotto assist participants from diverse backgrounds and interests in exploring fresh audio territory. It benefits all if we can keep open minds!
Having supported democracy, I also feel there are sobering caveats in the field of audio, something akin to ground rules, that must underpin any fruitful discussion. These include my opening salvo regarding the sheer insanity of considering MP3 devices and PC sound cards as premium audio sources.
With >30 years in music - composing, performing, recording, engineering, broadcasting, reviewing; in audio - retail and installation; in computer hardware and digital multimedia; in cable design and assembly - I remain eager to listen and learn. My next challenge is to develop a proper grasp of thermionic and SS circuit design, ultimately to complete my own projects from scratch rather than just modify.
My trusty ears tell me that with 16-bit red book CD digititis (very few exceptions) recorded music standards have actually regressed in the last 25 years. Yes folks, analogue remains the reference point if you intend to seriously and realistically assess audio equipment! SACD had a chance of establishing itself until the industry ineptly undermined it. Now they're onto Blu Ray already and planning for the next stage of wanton, sped-up obsolescence. Innit marvellous?
Anyway life goes on. BTW thanks for the pointer on the "flavour of the month" op-amps, Sandy. Read a whole heap on-line. This coming week promises intense auditioning. New phono stage is scheduled to arrive Wednesday. There'll be slightly more current drained in my house than normal.....
nightcap
Forums such as this and Rock Grotto assist participants from diverse backgrounds and interests in exploring fresh audio territory. It benefits all if we can keep open minds!
Having supported democracy, I also feel there are sobering caveats in the field of audio, something akin to ground rules, that must underpin any fruitful discussion. These include my opening salvo regarding the sheer insanity of considering MP3 devices and PC sound cards as premium audio sources.
With >30 years in music - composing, performing, recording, engineering, broadcasting, reviewing; in audio - retail and installation; in computer hardware and digital multimedia; in cable design and assembly - I remain eager to listen and learn. My next challenge is to develop a proper grasp of thermionic and SS circuit design, ultimately to complete my own projects from scratch rather than just modify.
My trusty ears tell me that with 16-bit red book CD digititis (very few exceptions) recorded music standards have actually regressed in the last 25 years. Yes folks, analogue remains the reference point if you intend to seriously and realistically assess audio equipment! SACD had a chance of establishing itself until the industry ineptly undermined it. Now they're onto Blu Ray already and planning for the next stage of wanton, sped-up obsolescence. Innit marvellous?
Anyway life goes on. BTW thanks for the pointer on the "flavour of the month" op-amps, Sandy. Read a whole heap on-line. This coming week promises intense auditioning. New phono stage is scheduled to arrive Wednesday. There'll be slightly more current drained in my house than normal.....
nightcap
Op-amp viewpoints welcome
Nightcap.
I think that the reason for the virtual extinction of SACDs
and DVD-A (I own some of each) is due to the general public not giving a damn about quality, just as long as they can hear their favourite music wherever they are. This has been made possible for them by formats like MP3, and the fact that manufacturers are allowed to label any shiny toy as HI-Fi ,without having to qualify their claims.
Interestingly, a better source of music tracks is often present in deluxe edition CD releases, in the form of "the making of"
bonus DVDs. The content is often 48KHZ LPCM, or 5.1 Dolby Digital. As an example the deluxe version of "Norah Jones-Not Too Late" CD has a few music videos, as well as the earlier live performances,with LPCM audio. The live performances have much better dynamic range and sound quality approaching that of SACD/DVD-A.
Currently, their are quite a few 48KHZ LPCM "promo" music videos posted on the Internet. It is a damn shame that the CD audio isn't usually up to the standard of the music companies promo videos. Incidentally, some of these LPCM promos can sound very good indeed, if bit depth is increased to 24bits with appropiate software . Providing of course, that the playback chain is good enough. I use a Music Fidelity X-DAC V3 which upsamples to 24bit 192KHZ for playing this material via SPDIF .
It pays to replace the switchmode bridge rectifier diodes in the typical player's switchmode PSU with UF4007, or , better still
(in my opinion) the even faster, slow recovery type BYV26C. Some judicious placement of sound deadening material in the player, such as self adhesive felt, will also improve the audio quality via SPDIF.
Video quality usually improves too, even via HDMI !
SandyK
Nightcap.
I think that the reason for the virtual extinction of SACDs
and DVD-A (I own some of each) is due to the general public not giving a damn about quality, just as long as they can hear their favourite music wherever they are. This has been made possible for them by formats like MP3, and the fact that manufacturers are allowed to label any shiny toy as HI-Fi ,without having to qualify their claims.
Interestingly, a better source of music tracks is often present in deluxe edition CD releases, in the form of "the making of"
bonus DVDs. The content is often 48KHZ LPCM, or 5.1 Dolby Digital. As an example the deluxe version of "Norah Jones-Not Too Late" CD has a few music videos, as well as the earlier live performances,with LPCM audio. The live performances have much better dynamic range and sound quality approaching that of SACD/DVD-A.
Currently, their are quite a few 48KHZ LPCM "promo" music videos posted on the Internet. It is a damn shame that the CD audio isn't usually up to the standard of the music companies promo videos. Incidentally, some of these LPCM promos can sound very good indeed, if bit depth is increased to 24bits with appropiate software . Providing of course, that the playback chain is good enough. I use a Music Fidelity X-DAC V3 which upsamples to 24bit 192KHZ for playing this material via SPDIF .
It pays to replace the switchmode bridge rectifier diodes in the typical player's switchmode PSU with UF4007, or , better still
(in my opinion) the even faster, slow recovery type BYV26C. Some judicious placement of sound deadening material in the player, such as self adhesive felt, will also improve the audio quality via SPDIF.
Video quality usually improves too, even via HDMI !
SandyK
Hi Guys,
Add to this that they've been told time and time again that their old 70's equipment is junk (okay, the speakers weren't up to today's standards) then on to last years gear being superseded by the new shiny thing. The new shiny things are not really repairable and spares are generally not in stock. Can you blame them for giving up? The music software and music hardware industries got too greedy and the public turned on them.
I don't think rectifier changes are the proper way to fix a poor power supply design. We've made a big circle of preferred devices and really, the original 400x series work very well. The problem seems to stem from both board layout, toriod transformers and filter capacitors that are too large. That and the use of three terminal regulators that have poor high frequency rejection. With little consideration given to the power supply, there are noise problems throughout the device.
Listening tests and part swapping have some value, but generally go wrong unless they are preceded by some bench time and a little technical expertise. Everyone wants to believe that they are improving the product. I never judge my own stuff until they have been listened to by some brutally honest friends. Children are great here. Wives too sometimes.
-Chris
This topic is also based in the general publics refusal to constantly replace their libraries of a new media type. They don't seem to mind replacing a worn out LP though.
Add to this that they've been told time and time again that their old 70's equipment is junk (okay, the speakers weren't up to today's standards) then on to last years gear being superseded by the new shiny thing. The new shiny things are not really repairable and spares are generally not in stock. Can you blame them for giving up? The music software and music hardware industries got too greedy and the public turned on them.
I don't think rectifier changes are the proper way to fix a poor power supply design. We've made a big circle of preferred devices and really, the original 400x series work very well. The problem seems to stem from both board layout, toriod transformers and filter capacitors that are too large. That and the use of three terminal regulators that have poor high frequency rejection. With little consideration given to the power supply, there are noise problems throughout the device.
Listening tests and part swapping have some value, but generally go wrong unless they are preceded by some bench time and a little technical expertise. Everyone wants to believe that they are improving the product. I never judge my own stuff until they have been listened to by some brutally honest friends. Children are great here. Wives too sometimes.
-Chris
and of course the only valid way to proceed with mods is to own at least 2 of the device so you have the unmodded device in front of you to switch A/B, level matched, same source material/test signal - not a hrs or days old "memory" of the unmodded sound - people are really poor in the long term sonic memory department
Op-amp viewpoints
Chris and jcx
I didn't want to go there about greedy record companies and the release of mainly back catalogue stuff. I did manage to get a couple of new releases in both new formats before the record companies gave up on mainstream releases. I agree 100% on the issue of linear power supplies. In fact, I use a little known PSU add-on design by John Linsley Hood to dramatically reduce the output impedance of the power supplies out to >100KHZ. This add-on also greatly reduces noise level, results in a far more neutral sound, as well as increasing channel separation. I was referring to the increasing use of switchmode power supplies in CD/DVD players. These types of modifications are well documented elsewhere.
Are many members of this forum aware that ill informed politicians are legislating to make the use of "intelligent "
switch mode PSUs MANDATORY ? Yes, linear PSUs will be illegal !
Regarding listening tests, 3 of us discuss our mods before implementation and listen to the results as a group. We also use a compilation CD specifically for this purpose , in conjunction with other high resolution material. We are also able to audition unmodified equipment againt modified equipment. This includes Silicon Chip magazine designed amplifiers and preamplifiers, in original and modified states. We also have 2 Oppo DV981HD players (check out their capabilities. They also have an undocumented feature that allows digital volume control via SPDIF, if O/P is set to LPCM) available for comparison, as well as 2 Pioneer DVD-A/SACD players.One of us also owns a Marantz SA11 DVD player.Speakers used include an old Ohm Walshe (Dalek) fitted with plasma tweeters, DCM QED and Infinity speakers fitted with very recent high quality Raven tweeters.
SandyK
Chris and jcx
I didn't want to go there about greedy record companies and the release of mainly back catalogue stuff. I did manage to get a couple of new releases in both new formats before the record companies gave up on mainstream releases. I agree 100% on the issue of linear power supplies. In fact, I use a little known PSU add-on design by John Linsley Hood to dramatically reduce the output impedance of the power supplies out to >100KHZ. This add-on also greatly reduces noise level, results in a far more neutral sound, as well as increasing channel separation. I was referring to the increasing use of switchmode power supplies in CD/DVD players. These types of modifications are well documented elsewhere.
Are many members of this forum aware that ill informed politicians are legislating to make the use of "intelligent "
switch mode PSUs MANDATORY ? Yes, linear PSUs will be illegal !
Regarding listening tests, 3 of us discuss our mods before implementation and listen to the results as a group. We also use a compilation CD specifically for this purpose , in conjunction with other high resolution material. We are also able to audition unmodified equipment againt modified equipment. This includes Silicon Chip magazine designed amplifiers and preamplifiers, in original and modified states. We also have 2 Oppo DV981HD players (check out their capabilities. They also have an undocumented feature that allows digital volume control via SPDIF, if O/P is set to LPCM) available for comparison, as well as 2 Pioneer DVD-A/SACD players.One of us also owns a Marantz SA11 DVD player.Speakers used include an old Ohm Walshe (Dalek) fitted with plasma tweeters, DCM QED and Infinity speakers fitted with very recent high quality Raven tweeters.
SandyK
Hi Sandy,
My comments are directed towards the average group of tweakers. Those who do not follow any kind of scientific or documented process. You should see the volume of destroyed equipment in North America!
Over here an idiot with a soldering iron is called a plumber by some. No shortage of plumbers.
-Chris
My comments are directed towards the average group of tweakers. Those who do not follow any kind of scientific or documented process. You should see the volume of destroyed equipment in North America!
Over here an idiot with a soldering iron is called a plumber by some. No shortage of plumbers.
-Chris
Op-amp viewpoints welcome
Chris
I should have mentioned that we have between the 3 of us,
3 x MF X-DAC V3 and a V2. So we have been able to do comparisons all along the way. As a result, 2 of the VB3s are modified as I mentioned in the email. The 3rd is not currently using the 8066, but is using an outboard dual regulated PSU plus OPA2134s internally. Yesterday I replaced the generic front channel IC in a SoundBlaster X-FI card with an OPA2134 with excellent results. I baulked , however at the posted suggestion (elsewhere) of shoving in the highest capacity, most expensive filter capacitor you can find, in place of the existing main filter capacitor. I did however fit a parallel 100nF poly capacitor.
SandyK
Chris
I should have mentioned that we have between the 3 of us,
3 x MF X-DAC V3 and a V2. So we have been able to do comparisons all along the way. As a result, 2 of the VB3s are modified as I mentioned in the email. The 3rd is not currently using the 8066, but is using an outboard dual regulated PSU plus OPA2134s internally. Yesterday I replaced the generic front channel IC in a SoundBlaster X-FI card with an OPA2134 with excellent results. I baulked , however at the posted suggestion (elsewhere) of shoving in the highest capacity, most expensive filter capacitor you can find, in place of the existing main filter capacitor. I did however fit a parallel 100nF poly capacitor.
SandyK
Hi Sandy,
Since I am intending to use this card as a piece of test equipment, I wanted to be cautious. Loop back tests will be run before and after. Did you try this also? I was also going to use small shunt caps and I'm trying to figure out a metal shell for the card to cut down on external noise from the computer. I have two cards.
-Chris
Odd you should have mentioned this. I have the OPA2134 and the X-FI music (good card). I am about to do the exact same thing that you have. I haven't read anything on the subject at all.
Since I am intending to use this card as a piece of test equipment, I wanted to be cautious. Loop back tests will be run before and after. Did you try this also? I was also going to use small shunt caps and I'm trying to figure out a metal shell for the card to cut down on external noise from the computer. I have two cards.
-Chris
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