Gaucho said:
So for the passive method, the PS noise is impressed on the output, runs around the feedback loop into an input pin, is not common-mode, and gets amplified... like that?
OK, so now i've got two possible active solutions, the 2N4304 FET with a resistor feedback, and a LM334Z with a programming resistor (different name, same job🙂. The later device having much more 'stuff' inside. Are there good reasons to choose one over the other? Maybe noise factors?
BTW: the LT1028 and LT1037 sure look interesting.... tnx for the nudge to go wander amongst their data sheet forest.
Regards,
LarryO
Larry, the negative feedback will work to reduce the noise at the output in the same relative manner that the open loop signal is attenuated by the feedback network.
I'm sure both will do the job. If you've got the time and motivation prehaps give both a whirl and see what sounds best to your ears.
Gaucho said:
So the PSRR goes to zero dB, got it.
At +50 my brain questions the sensory apparatus so engineering to metricable specs becomes more salient at times. Not to say that's the paramount of experiential evidence, but certainly an expeditious beginning. So i repeat my query, are there good reasons to choose one over the other?
Cheers,
LarryO
OPA602
Hi everybody.
I have tested subjectively -that is, with my ears- a lot of opamps, including some of the best of them -opa627/637, ad825, etc-.
In a preamp based in the Pavel´s audio buffer schematics, modified to add some gain -it´s a pre, not a buffer- , and bypassed as Carlos has often suggested, I have obtained the sonic results best suited to my ears with OPA602.
Previously , I tested a lot of opas without buffering at all, and in that opportunity the same opamp gave the most musical sound of the bunch. Even my daughter, when opa602 was in the pre, told my that she liked a lot the sound: I mention this, anecdotically, as a way to put aside a bit my own subjetivity and to reassure myself that I wasn´t the only one hearing the difference.
Sould I have to describe the sound of that opa, I would say that is lush, a little warm, but very accurate in the microdynamic and detail items. Maybe not as detailed as opa627/637, but, to my ears, more musically satisfaying. I think it´s worth trying it wit an adapter to see what happens. As a note of interest, It doesn´t showed signs of distress, nor audible nastiness, because of the use of sockets.
Another OPA that gave my a lot of fun and pleasure is the venerable AD OP275 -a dual one, discontinued but still attainable, I suppose-. Thanks to it, I was able to change the sound of a Phillips DVD player to an extent that I thought was impossible: previously the Philips was sounding distorted, strained and -worst of all- compressed. After the modification, now sounds very, very nice. A little bassy, perhaps, but soooo musical and colourful!
In a first instance I tried, in the same DVD player, an opa2604, but the sound wasn´t appealing to me. Sort of black and white, cold and compressed.
Maybe this digression would be of interest to some of you.
Cheers.
Hi everybody.
I have tested subjectively -that is, with my ears- a lot of opamps, including some of the best of them -opa627/637, ad825, etc-.
In a preamp based in the Pavel´s audio buffer schematics, modified to add some gain -it´s a pre, not a buffer- , and bypassed as Carlos has often suggested, I have obtained the sonic results best suited to my ears with OPA602.
Previously , I tested a lot of opas without buffering at all, and in that opportunity the same opamp gave the most musical sound of the bunch. Even my daughter, when opa602 was in the pre, told my that she liked a lot the sound: I mention this, anecdotically, as a way to put aside a bit my own subjetivity and to reassure myself that I wasn´t the only one hearing the difference.
Sould I have to describe the sound of that opa, I would say that is lush, a little warm, but very accurate in the microdynamic and detail items. Maybe not as detailed as opa627/637, but, to my ears, more musically satisfaying. I think it´s worth trying it wit an adapter to see what happens. As a note of interest, It doesn´t showed signs of distress, nor audible nastiness, because of the use of sockets.
Another OPA that gave my a lot of fun and pleasure is the venerable AD OP275 -a dual one, discontinued but still attainable, I suppose-. Thanks to it, I was able to change the sound of a Phillips DVD player to an extent that I thought was impossible: previously the Philips was sounding distorted, strained and -worst of all- compressed. After the modification, now sounds very, very nice. A little bassy, perhaps, but soooo musical and colourful!
In a first instance I tried, in the same DVD player, an opa2604, but the sound wasn´t appealing to me. Sort of black and white, cold and compressed.
Maybe this digression would be of interest to some of you.
Cheers.
I am using 4x OPA627's in my DAC(Elektor2000). Installed a lot of the mods mentioned here. Tried a set of 4x AD8610's in the DAC and changed back again. Don't know which is best. The OPA627 sure has some detail and bass. Will try the 8610's next week again. Anyone an opinion on these 2?
OPA2111 anyone?
I was surf'n the data sheet forest recently and the OPA2111 caught my eye...
especially the open loop phase response, dead flat throughout the audio range. I may be "too slow" for some, but i'd sure like to know what those that have toyed with it think.
Cheers,
LarryO
I was surf'n the data sheet forest recently and the OPA2111 caught my eye...
especially the open loop phase response, dead flat throughout the audio range. I may be "too slow" for some, but i'd sure like to know what those that have toyed with it think.Cheers,
LarryO
Re: Why these LT OpAmps are......
some of us have been using LT devices for a while.
we just don't talk much about it.
🙂
maybe some folks remember the LT1010 buffer and condemned the whole product line?
mlloyd1
some of us have been using LT devices for a while.
we just don't talk much about it.
🙂
maybe some folks remember the LT1010 buffer and condemned the whole product line?
mlloyd1
zinsula said:
lgo51 said:
Wow those Readers Digest word power exercises can really pay off for some people! Your quite a linguist!😀
Well I'm not too sure what's best (probably a resistor 😉) but I would try the 2N4304 route first, the LM334's slew rate seems perhaps a bit low, this may reduce the extra voltage swing advantage of the CCS at high frequencies.
I believe the PSRR just goes down somewhat because a PP output is much better at 'bucking' any symetrical PS noise leaving less noise at the output before feedback is applied.
what about this?
Carlos, Gaucho, and everybody else, instead of the resistor output to neg rail have you tried a resistor from output to earth, perhaps 2k4 or 4k7? Would this cause more current to flow through both halves of the OpAmps output stage.
Or is current flow not the point, but unbalancing the opAmp so the +ve side is used more.
Or something else?
Carlos, Gaucho, and everybody else, instead of the resistor output to neg rail have you tried a resistor from output to earth, perhaps 2k4 or 4k7? Would this cause more current to flow through both halves of the OpAmps output stage.
Or is current flow not the point, but unbalancing the opAmp so the +ve side is used more.
Or something else?
That is just output load , like earphones .
In connection where output is laoaded by resistor to neg. supply rail , one output transistor is fighting with oposite polarity. The resistor is current source.
In connection where output is laoaded by resistor to neg. supply rail , one output transistor is fighting with oposite polarity. The resistor is current source.
Re: what about this?
Ian, yes it would increase current flow but it won't increase the idle current as is required for class A push-pull operation.
IMO alot of the point is to avoid switching distortion, also single-ended operation has a certain sonic character that many find perferable over even PP class A.
IanAS said:
Ian, yes it would increase current flow but it won't increase the idle current as is required for class A push-pull operation.
IMO alot of the point is to avoid switching distortion, also single-ended operation has a certain sonic character that many find perferable over even PP class A.
Got some OPA627BP on Brown Dog adaptors through an Ebay sale the other day... put 'em in last night (nearly breaking some other components in the process) and left it on repeat over night...
Had a listening session with a mate this afternoon....
😀
This has possibly been the biggest revelation of my audio hobby so far... The detail, the dynamics, the warmth. The sound oozes class. I've never heard this kind of precision and detail combined with real warmth and texture before. Simply, I'm blown away.
Joni Mitchell - Hits, Bee Gees - This is Where I Came in, Radiohead - OK Computer, Neil Young - Harvest .... all taken to unbelievable new heights by the OPA627. I've not even done proper bypassing yet.
Had a listening session with a mate this afternoon....
😀
This has possibly been the biggest revelation of my audio hobby so far... The detail, the dynamics, the warmth. The sound oozes class. I've never heard this kind of precision and detail combined with real warmth and texture before. Simply, I'm blown away.
Joni Mitchell - Hits, Bee Gees - This is Where I Came in, Radiohead - OK Computer, Neil Young - Harvest .... all taken to unbelievable new heights by the OPA627. I've not even done proper bypassing yet.
So in my humblest opinion, this is how I rank the op-amps I've heard in the I/V stage of my Marantz CD63ki:
1 - OPA627BP
2 - OPA2132AP
3 - OPA2604
4 - JRC2114
1 and 2 are obvious in their superiority, 1 is leagues ahead tho. 3 and 4 sound cr@p, in this application.
I have LM6172 to try, but I can't see it matching what I've heard from the OPA627s!!!
2132 is polite and pleasant, but uninspiring, 2604 is exciting but false and quite nasty, 2114 was just poor allround, bearing in mind it had no close bypassing. 627 has the least smear and glassiness, combined with the best detail (by a mile) and fullest, richest, most lovely sound.
1 - OPA627BP
2 - OPA2132AP
3 - OPA2604
4 - JRC2114
1 and 2 are obvious in their superiority, 1 is leagues ahead tho. 3 and 4 sound cr@p, in this application.
I have LM6172 to try, but I can't see it matching what I've heard from the OPA627s!!!
2132 is polite and pleasant, but uninspiring, 2604 is exciting but false and quite nasty, 2114 was just poor allround, bearing in mind it had no close bypassing. 627 has the least smear and glassiness, combined with the best detail (by a mile) and fullest, richest, most lovely sound.
SimontY said:Got some OPA627BP on Brown Dog adaptors through an Ebay sale the other day... put 'em in last night (nearly breaking some other components in the process) and left it on repeat over night...
Had a listening session with a mate this afternoon....
😀
This has possibly been the biggest revelation of my audio hobby so far... The detail, the dynamics, the warmth. The sound oozes class. I've never heard this kind of precision and detail combined with real warmth and texture before. Simply, I'm blown away.
Joni Mitchell - Hits, Bee Gees - This is Where I Came in, Radiohead - OK Computer, Neil Young - Harvest .... all taken to unbelievable new heights by the OPA627. I've not even done proper bypassing yet.
Hey man.have you buy it from supersoundangel ?🙂
SimontY said:
Yep!
Actually I made them 🙂.I'm very happy about you satisfied with deal.Hopefully all was well.
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