The X front end is great for a preamp and there is even an example of this in the patent. However, if you plan to use unbalanced connection between preamp and amp, i'd probably tend to use something else.
rljones said:
I can only agree in this, just finished a linelevel preamp with the same OPAMP and a LM431 wich is the same as the ZR431. Dual regulation, OSCON 47uF/25V (Low ESR ~ 37mOhm) and in parallel with WIMA FKP2 10nF as supply bypass. Feedback network on the AD8610 (gain +2) is done with WMA0204 resistors. And volume pot the old fashion way.
There is no bluring of the soundstage! Good really GOOD! I can only recommend it!
Sonny
hi sonny,
how do you think the sound compares to a good discrete design, or even the ultimate reference, a straight wire bypass? or at least a passive preamp. i think IC opamps can sound excellent, better than a lot of people give credit for, but here are some deficiencies i've noted about their sound quality.
- there is a diminishing of atmosphere and "air" around performers
- dynamics do not sound completely linear, there is some slight compression of both micro and macro contrasts
- there is some ringing phenomenon with high frequency and impulse-like signals which blurs the leading edges of transients, cymbals, etc.
- there is at times some hashiness and/or hardness to the upper midrange and treble
note that these are the really highest-level nitpicks. again i think ICs can sound quite good but the very last degree of resolution and purity seems to be lost. how do you think the AD8610 holds up?
marc
how do you think the sound compares to a good discrete design, or even the ultimate reference, a straight wire bypass? or at least a passive preamp. i think IC opamps can sound excellent, better than a lot of people give credit for, but here are some deficiencies i've noted about their sound quality.
- there is a diminishing of atmosphere and "air" around performers
- dynamics do not sound completely linear, there is some slight compression of both micro and macro contrasts
- there is some ringing phenomenon with high frequency and impulse-like signals which blurs the leading edges of transients, cymbals, etc.
- there is at times some hashiness and/or hardness to the upper midrange and treble
note that these are the really highest-level nitpicks. again i think ICs can sound quite good but the very last degree of resolution and purity seems to be lost. how do you think the AD8610 holds up?
marc
Dorkus
It seems like the innovative stuff that you are discussing is the "front end" - The switching, level controls, remote, etc.
If you could just pull this off it would be a great accomplishment.
It almost seems like the amp circuitry is less important- there are various pre-amp gain stages out there. If you standardize on connectors, people (including you)could develop boards for different designs.
i.e. a single channel Pass line stage. Someone else might make a board for op amp modules- then we can compare.
I guess some of the circuits have different requirements,
but can't you have adjustments for that?
It seems like the innovative stuff that you are discussing is the "front end" - The switching, level controls, remote, etc.
If you could just pull this off it would be a great accomplishment.
It almost seems like the amp circuitry is less important- there are various pre-amp gain stages out there. If you standardize on connectors, people (including you)could develop boards for different designs.
i.e. a single channel Pass line stage. Someone else might make a board for op amp modules- then we can compare.
I guess some of the circuits have different requirements,
but can't you have adjustments for that?
AD8610 vs AD825
i just checked out the datasheet for the 8610 and it looks pretty nice. some excellent specs, esp. the comparisons to the AD627. i'm wondering how the sound compares to the AD825. i haven't tried it yet but it also looks good, i esp. like the wide open-loop frequency response and relatively low open-loop gain.
i just checked out the datasheet for the 8610 and it looks pretty nice. some excellent specs, esp. the comparisons to the AD627. i'm wondering how the sound compares to the AD825. i haven't tried it yet but it also looks good, i esp. like the wide open-loop frequency response and relatively low open-loop gain.
Re: AD8610 vs AD825
So do I. I have just replaced the opa627 as I/V in the Elektor 96/24 DAC with upsampling, with AD825 as filter/ouput. The sound is much better than with the 627, with the upper mid grain gone. Using the 825 as I/V results in a smoother sound than with the 8610. Only long term audition will reveal the preference, and then this will be system dependent. The DAC has much better componets than standard.
------------------------------------------------------------------dorkus said:
So do I. I have just replaced the opa627 as I/V in the Elektor 96/24 DAC with upsampling, with AD825 as filter/ouput. The sound is much better than with the 627, with the upper mid grain gone. Using the 825 as I/V results in a smoother sound than with the 8610. Only long term audition will reveal the preference, and then this will be system dependent. The DAC has much better componets than standard.
hi variac,
you are right, a lot of the work i'm doing is in the front-end. as you point out there are a lot of gain stages out there but i'm trying to get a level of refinement to the operation of the preamp that most DIY projects are missing. i'm all for "hack" projects that sound great but require a knowledge of circuit design to operate (e.g. my roommate currently has no idea how to work my system) but after a while you get tired of plugging things in and out and hoping your speaker voice coils won't jump out of their gap one of these days. i want something that is a pleasure to both use and listen to.
you are all right in advocating plug-in modules for maximum flexibility, and i will probably prototype things this way. i'm still hoping the final product will be a completely polished and integrated design however. after the amount of work i'll have to put into this to get to that point, i'll probaby have no desire to continue to tweak with different modules endlessly... i'd end up spending more time soldering than listening, and that i believe would be an unfortunate outcome. 😛
marc
you are right, a lot of the work i'm doing is in the front-end. as you point out there are a lot of gain stages out there but i'm trying to get a level of refinement to the operation of the preamp that most DIY projects are missing. i'm all for "hack" projects that sound great but require a knowledge of circuit design to operate (e.g. my roommate currently has no idea how to work my system) but after a while you get tired of plugging things in and out and hoping your speaker voice coils won't jump out of their gap one of these days. i want something that is a pleasure to both use and listen to.
you are all right in advocating plug-in modules for maximum flexibility, and i will probably prototype things this way. i'm still hoping the final product will be a completely polished and integrated design however. after the amount of work i'll have to put into this to get to that point, i'll probaby have no desire to continue to tweak with different modules endlessly... i'd end up spending more time soldering than listening, and that i believe would be an unfortunate outcome. 😛
marc
Marc,
How about a differential amplifier like the Pass but current sourced and the outputs buffered. This would give balanced or single-ended in and balanced or single-ended out without having to resort to phase inverters and such.
Jam
How about a differential amplifier like the Pass but current sourced and the outputs buffered. This would give balanced or single-ended in and balanced or single-ended out without having to resort to phase inverters and such.
Jam
jam
It looks like we have a volunteer....... Nice weather we're having isn't it?
H.H.
Every talks about the weather but no one does anything about it.
Mark Twain
It looks like we have a volunteer....... Nice weather we're having isn't it?
H.H.
Every talks about the weather but no one does anything about it.
Mark Twain
hi all,
HPotter: i'd love to go discrete but no one's seriously suggested anything yet! 😛
jam: hey, here's our first suggestion. 🙂 that sounds like a good start. which topology are you referring to, something like BOSOZ? how would you like to go about the buffer circuit?
also, i'm wondering if we'll need an input buffer for the attenuator, maybe do a distributed gain arrangement as i mentioned earlier. altho i like to avoid extra active stages wherever possible, we may get better optimizations of impedances and noise performance this way.
harry: yeah weather is pretty nice over here too.
btw, does anyone have any opinion on DC servos to control offset?
cheers,
marc
HPotter: i'd love to go discrete but no one's seriously suggested anything yet! 😛
jam: hey, here's our first suggestion. 🙂 that sounds like a good start. which topology are you referring to, something like BOSOZ? how would you like to go about the buffer circuit?
also, i'm wondering if we'll need an input buffer for the attenuator, maybe do a distributed gain arrangement as i mentioned earlier. altho i like to avoid extra active stages wherever possible, we may get better optimizations of impedances and noise performance this way.
harry: yeah weather is pretty nice over here too.
btw, does anyone have any opinion on DC servos to control offset?
cheers,
marc
Something smells in Texas!
Harry is up to something!
Marc,
I suggest a simple current sourced and possibly cascoded mosfet for the buffer (Groans of agony from Grey).
I think that DC servos for the most part suck ( or hose if you are from Canada ) as they impose a sonic signature on the sound. The only way to make them work is to design them with a very low time constant which might be a problem with some circuits.
I would stick with the old Black Gate unless our much loved guru Harry has some ideas.
Jam
Harry is up to something!
Marc,
I suggest a simple current sourced and possibly cascoded mosfet for the buffer (Groans of agony from Grey).
I think that DC servos for the most part suck ( or hose if you are from Canada ) as they impose a sonic signature on the sound. The only way to make them work is to design them with a very low time constant which might be a problem with some circuits.
I would stick with the old Black Gate unless our much loved guru Harry has some ideas.
Jam
ok. i guess i will have to ditch the DC coupled criterion, oh well...
i'm interested to see you mention Black Gates. are these your coupling caps of choice for larger (e.g. +10uF) sizes? i've used them only once, for the DC blocking cap in the feedback loop of an amp, and thought they sounded pretty nice, smoother and less "etched" than the film caps i was usin previously (8uF RelCap metallized PP film bypassed by .1uF Solen), but i still felt it had a sonic signature of its own... maybe a little euphonic?
mmm, cascodes... the debate will begin again i'm sure. i'm perfectly willing to try both cascoded and non-cascoded flavors and see how they sound.
i should put up a web page for this project soon...
i'm interested to see you mention Black Gates. are these your coupling caps of choice for larger (e.g. +10uF) sizes? i've used them only once, for the DC blocking cap in the feedback loop of an amp, and thought they sounded pretty nice, smoother and less "etched" than the film caps i was usin previously (8uF RelCap metallized PP film bypassed by .1uF Solen), but i still felt it had a sonic signature of its own... maybe a little euphonic?
mmm, cascodes... the debate will begin again i'm sure. i'm perfectly willing to try both cascoded and non-cascoded flavors and see how they sound.
i should put up a web page for this project soon...
OK, let me be the first one to place schematic here. I didn't try it so I don't know (actually I don't have any experience with preamps because I don't use them) how it sounds. It looks good on paper, it is SE, it is different than Nelson Pass designs and it comes from Erno Brobely. It is ALL-JFET design so Harry should be happy, it has balanced in and out, it has current sources and output buffers. It is similar to early John Curl designs for Mark Levinson. Any comments?
For further reading this is the link: http://www.borbelyaudio.com/
For further reading this is the link: http://www.borbelyaudio.com/
Attachments
well, at least we have something tangible to argue about now.
it looks fine by me, i'm willing to mock it up and give it a listen after i collect some comments/suggestions/possible improvements.
it looks fine by me, i'm willing to mock it up and give it a listen after i collect some comments/suggestions/possible improvements.
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