opa1642 is a great little dual, you would need adapters as it only comes in soic8, but only 3 and its not as expensive. i love opa827, really great chip and i use it in one of my headamps, but I do not really think the layout and circuit is appropriate to get the best out of it and spending as much as the dac at this stage is not warranted IMO. the opa1642 is a VERY high performance jfet input opamp that is unity gain stable, so will need less trickery than many like AD797 to drop into the circuit. lme49990 is another nice chip, but a single. both of these are extremely close to the opa827, some could argue the lme is its equal, but i tend to prefer jfet input opamps for dac IV (the opa827 is jfet input)
using those the chips would cost you less than 20 for the 3 plus the adapters. I agree that fast video opamps are god for IV as they tend to deal with glitch very well, but I think it would take more than lowering the FB/compensation cap value
using those the chips would cost you less than 20 for the 3 plus the adapters. I agree that fast video opamps are god for IV as they tend to deal with glitch very well, but I think it would take more than lowering the FB/compensation cap value
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Why would that be? In the case of the AD827 the datasheet does not warn of potential instabilities, as it's done on the LM6172 data. Maybe it's not such a problem.
You said it: video (fast) opamps are good for I/V, but in this case that is not so really. I/V filtering (unfortunately) is done inside the chip. So the external chips only convert the balanced outputs to single ones.
A combination of chips might work here too. As the second chip would have to drive the signal, the AD827 might shine there; and a fet input type could be used on the unbalancing chips.
Hey thanks stratus. I'm not an EE so my knowledge of digital circuitry is very limited. I understand the basics, but I'm not a tech by trade. I had some vocational training years ago in HS, but never pursued it as a profession. I did like building Heathkit stuff over the years, and a little DIY occasionally. Now I have more time on my hands so I'm getting back into some audio DIY projects. My satisfaction comes in the challenge of planning and pulling everything together and creating a nice looking unit - that hopefully performs as well as it looks. diyAudio is a great site!
I didnt mention the AD827 at all, but my point is spending that sort of money (for 6 x OPA827) on what i consider to be a bit of a subpar PCB as a first upgrade would be misguided and the recommendation to spend almost as much on the chips as the whole dac is IMO irresponsible. dual soic8 adapters by themselves place the decoupling and ground plane too far away from the pins for my liking and although its supposed to be unity gain stable, i find this depends on the supply voltage and layout
voltage out/IV whatever there is still fast glitches that need to be handled (for the filtering process, nothing to do with the IV conversion), so video opamps are very good for the task, as are some current feedback chips but that would require a redesign. I do not consider blind opamp rolling with very pricey high performance chips a great idea, compensation and or layout needs to be considered for best performance and some way to verify performance preferred.
so to that end I recommended a very high performance dual jfet input unity gain stable opamp (opa1642) that doesnt break the bank and i dont think redjr should spend too much until there is work done elsewhere like power supply/decoupling
redjr, no they are most definitely not the same chip. for starters opa827 is a high priced single channel jfet input opamp. i dont know much about the AD827, but its a dual
the opa1642 doesnt have very high output drive, so depending on what you will be driving with it, yes a composite solution might be a good idea. the opa1642 on input and then if youre up to it AD797 for the 2 output chips (definitely READ THE DATASHEET with this one as its a little bit more than dropping it in to get the best performance) myself i would be tempted to throw a buffer in the output opamp's FB loop too
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It's OK to confuse the chips. The AD827 is a dual bipolar-input chip made by Analog Devices. The OPA827 is a single fet-input chip made by Texas.
I'm quite sure the AD827 will work fine, even with no additional mods, because it's offered as optional with another eBay kit using the same AD1955 DAC. The chip is quite affordable (three for $12) and it's a direct drop in.
http://www.ebay.com/itm/AD1955-WM88...452?pt=LH_DefaultDomain_0&hash=item2c639cd884
I also consider spending too much money right away on chips for this kit rather foolish, though not necessarily irresponsible. People are spending more money on the parts being changed on the AK4396 kit than with the kit itself, so it's a question of what you are looking for. But that should do gradually.
The problem with SOIC parts is that you need the adapter AND you need to solder the small part to the adapter, which I hate. You can buy it pre-soldered, and pay more.
In that sense is that I think DIP dual parts, like the AD827, LM4562, LME49720 and LME49860 are great. These last three apparently are the same, so buy the one you can get.
I'm quite sure the AD827 will work fine, even with no additional mods, because it's offered as optional with another eBay kit using the same AD1955 DAC. The chip is quite affordable (three for $12) and it's a direct drop in.
http://www.ebay.com/itm/AD1955-WM88...452?pt=LH_DefaultDomain_0&hash=item2c639cd884
I also consider spending too much money right away on chips for this kit rather foolish, though not necessarily irresponsible. People are spending more money on the parts being changed on the AK4396 kit than with the kit itself, so it's a question of what you are looking for. But that should do gradually.
The problem with SOIC parts is that you need the adapter AND you need to solder the small part to the adapter, which I hate. You can buy it pre-soldered, and pay more.
In that sense is that I think DIP dual parts, like the AD827, LM4562, LME49720 and LME49860 are great. These last three apparently are the same, so buy the one you can get.
agreed so many numbers it takes a while for the special part of the brain to develop to be oversized in diyers lol.
i didnt say it was irresponsible to spend that much yourself, thats personal choice and can certainly be worthwhile if everything is in place, i would consider something like that for the second round of upgrades; unless you go into a project knowing what you want to do from the get go and have experience with the gear and know what you like. What i did say was I thought it irresponsible to recommend someone else do it as the first upgrade
better get used to soldering soic8, the soic8 is rather large and if you cant do that there isnt going to be a lot of future in DIY for you. given correct technique its actually very easy, can be done with 2 swipes (one each side of pins). check out the vids and practice practice practice. get yourself a loupe or helping hand etc anyone can do it
i didnt say it was irresponsible to spend that much yourself, thats personal choice and can certainly be worthwhile if everything is in place, i would consider something like that for the second round of upgrades; unless you go into a project knowing what you want to do from the get go and have experience with the gear and know what you like. What i did say was I thought it irresponsible to recommend someone else do it as the first upgrade
better get used to soldering soic8, the soic8 is rather large and if you cant do that there isnt going to be a lot of future in DIY for you. given correct technique its actually very easy, can be done with 2 swipes (one each side of pins). check out the vids and practice practice practice. get yourself a loupe or helping hand etc anyone can do it
this has been denied somewhere by a national employee; AFAIK this is just rumor that took hold and rather strongly on this forum, i didnt actually realize that the 860 had been added to this too...
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That info I took from this same forum:
http://www.diyaudio.com/forums/chip-amps/107344-lme49720-vs-lm4562.html
They probably ARE different, or National wouldn't be using different names for them.
I personally didn't try any of them yet. Would like to.
Oh i'm aware of the prevalence of this popular opinion here, but as far as i know there is nothing real to substantiate it. also the latter 2 are about the same price, what would be the point of pretending its a different chip? its not like they have a lack of good designs and designers at National
anyway i think ive given enough lipservice on opamps, what else can the OP do for starters? improve local decoupling on all the chips? isolate the power supplies? take a look at analogue and digital ground loop areas and give any significant digital ground returns their own chunky bus back to star away from sensitive analogue lines.
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I went to have a look at my comments, and I don't think I recommended anything expensive. I even said going the OPA827 way was expensive.
But I do think and do recommend upgrading the output chips as a good move.
hey dont personalize it, you simply quoted me and commented on it, but inferred that I had said it was irresponsible for someone to buy them for their own dac with their own money, i felt i had to clarify that. my issue was with it being recommended by someone else at this stage.
i made the comment initially in my first post, then you went off on your tangent on AD827 which i didnt even name in my post
edit, i'm sorry i had to go back and look. so it was you, but you thought you were recommending AD827 but made a typo (I wondered about that typo comment lol). no worries. BIG difference on every level. in that case since i know bugger all about AD827 i have no comment
but my recommendations standsituation over. I totally agree that upgrading the output chips is a good idea, i just dont think it should be taken too far yet as the sound of the unit may well evolve from other mods and the OP still has to live with it for a while
calmart said:
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Well, the only person that was talking about using a better chip at the output was me, so I have to personalize it if what I'm saying is twisted.
There are many things on this eBay kits, particularly the DAC ones, that are promising and deserve improvements.
There are basically three areas in all of them that can be improved: passive parts, power supply and analog chips.
The most straightforward upgrade are the output chips, which usually are a budget compromise on those low-priced kits. If the chips are regular DIPs you only have to swap them, and THAT is what I suggested and recommend. The National chips seem like an affordable and good upgrade, and that should be the first move.
The AD827 is offered as an output option for the same AD1955, as shown. And it also seems affordable. Apparently a drop-in swap too.
Being a faster chip that is also dual and also DIP, it would be a second move.
To go further some passive parts might have to be upgraded too, but for that I would need the schematic.
A third move would be to add an input transformer to the S/PDIF digital input, as when things get clearer elsewhere that interface might need upgrading.
The last move would be upgrading the supply, but that needs more work, definitely more than many may find necessary for this kit.
There are many things on this eBay kits, particularly the DAC ones, that are promising and deserve improvements.
There are basically three areas in all of them that can be improved: passive parts, power supply and analog chips.
The most straightforward upgrade are the output chips, which usually are a budget compromise on those low-priced kits. If the chips are regular DIPs you only have to swap them, and THAT is what I suggested and recommend. The National chips seem like an affordable and good upgrade, and that should be the first move.
The AD827 is offered as an output option for the same AD1955, as shown. And it also seems affordable. Apparently a drop-in swap too.
Being a faster chip that is also dual and also DIP, it would be a second move.
To go further some passive parts might have to be upgraded too, but for that I would need the schematic.
A third move would be to add an input transformer to the S/PDIF digital input, as when things get clearer elsewhere that interface might need upgrading.
The last move would be upgrading the supply, but that needs more work, definitely more than many may find necessary for this kit.
"To go further some passive parts might have to be upgraded too, but for that I would need the schematic. "
Hi,
The schematic is here.
http://www.diyaudio.com/forums/atta...3073175-new-ad1955-da-build-ad1955_markii.pdf
Hi,
The schematic is here.
http://www.diyaudio.com/forums/atta...3073175-new-ad1955-da-build-ad1955_markii.pdf
haha sorry thats plain untrue. you actually DID recommend opa827; i realised just above it was a typo, but thats what you said, no twisting required. so i made comment on it and then went on to recommend upgrading the opamps myself to a lesser degree, which is a natural thing to recommend and i agree, i agreed and recommended it myself; just not 70 dollars worth. the op was confused and had searched for the price for opa827, so obviously i'm not the only one who thought you were recommending it
then you twisted MY words to say that i was saying he was irresponsible and it was all downhill from there; that is what happened
past that i'm out of here, because you seem to be incapable of understanding english subtlety
(not a big deal, its obviously your second language, but its causing issues here).
you keep on reading far too much into what i say and missing parts.
i'm sorry if you are offended for some reason, i have already stated its clear there was a misunderstanding yet you are still being all stroppy.
OP: good luck with your build, calmart has it covered pretty well actually, just watch out for spelling mistakes
also regularly assess where you are at and what money is required, because although with a few simple mods these dacs can perform quite well, the designs are often a little bit flawed and particularly grounding can be a bottleneck and past a certain point there is nothing to be gained and you only make matters worse.
digital input, grounding/decoupling and power supply are where I would start after the opamps and when you feel up to it a discrete buffer to replace the opamps
have fun!!
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Sorry, but you keep making things personal, not me.
First you said I was irresponsible, now you tell me I'm lying, being "plain untrue"?
I did NOT recommend the OPA827. You seem to imagine I did. Tell me where the words "recommend" and "OPA827" are on the same line on what I wrote?
I never used the OPA827, so there's no way I could recommend it without having done so.
So who's twisting who?
Believe me I'm quite capable of understanding English subtleties, even if it's not my native language. Portuguese isn't either. and I'm quite capable on it too. Language is not causing any issues, saying what I'm not saying is.
For me it's fine to leave it there though, as we discuss audio matters here.
First you said I was irresponsible, now you tell me I'm lying, being "plain untrue"?
I did NOT recommend the OPA827. You seem to imagine I did. Tell me where the words "recommend" and "OPA827" are on the same line on what I wrote?
I never used the OPA827, so there's no way I could recommend it without having done so.
So who's twisting who?
Believe me I'm quite capable of understanding English subtleties, even if it's not my native language. Portuguese isn't either. and I'm quite capable on it too. Language is not causing any issues, saying what I'm not saying is.
For me it's fine to leave it there though, as we discuss audio matters here.
qusp/carl -
Thanks for your comments. As with any project there's a point you reach of diminishing returns. If the upgrade won't yield a noticeable sonic improvement (that's subjective), then a decision needs to be made. Don't get me wrong guys, I also know there can be a cumulative affect on the sound with multiple upgrades too. You can play with the hardware forever, or just enjoy the music. I'm somewhere in the middle.
If I don't take somewhat of a scientific approach to the suggested mods, then I won't ever know which one had more of an impact over another. It's just my way of understanding the benefit of each mod. For starters I'll likely go with an inexpensive drop-in replacement for the op-amp before changing/upgrading passive components. Probably the AD827 to start. One step at a time. As far as redesigning the PSU, or even off-boarding it that will wait. I need to know the benefit and what to change. Bigger filter caps? Different regulator chips, etc.
I've not worked with the SOIC8 type chip before, but have no concerns or fears about my ability to perform the soldering task. It looks straight forward and if I'm going to be changing out opamps in future projects, I'll need to have some of them around in my parts inventory.
Thanks for your comments. As with any project there's a point you reach of diminishing returns. If the upgrade won't yield a noticeable sonic improvement (that's subjective), then a decision needs to be made. Don't get me wrong guys, I also know there can be a cumulative affect on the sound with multiple upgrades too. You can play with the hardware forever, or just enjoy the music. I'm somewhere in the middle.
If I don't take somewhat of a scientific approach to the suggested mods, then I won't ever know which one had more of an impact over another. It's just my way of understanding the benefit of each mod. For starters I'll likely go with an inexpensive drop-in replacement for the op-amp before changing/upgrading passive components. Probably the AD827 to start. One step at a time.
As far as redesigning the PSU, or even off-boarding it that will wait. I need to know the benefit and what to change. Bigger filter caps? Different regulator chips, etc. I've not worked with the SOIC8 type chip before, but have no concerns or fears about my ability to perform the soldering task. It looks straight forward and if I'm going to be changing out opamps in future projects, I'll need to have some of them around in my parts inventory.
If I understand you correctly, wouldn't I need 6 OPA827? Two per Browndog adapter? At Mouser prices that's ~$66 for the opamps and $9 for the adpaters. Not a stretch, but that's more than the DAC cost.
you seem to be having problems going back and understanding your own posts. so considering I said nothing at all on these pages it sure reads like you recommended it, are you now suggesting that redjr was imagining thing/delusional as well? I was giving you the benefit of the doubt with the language thing and now you take that as an insult and rule that out, so.....
clearly you did not even read the post of yours I quoted before, you only assumed you had said what suits your mind, that is the very definition of delusional and yet you are the one name calling and calling me deluded
read the above, actually READ it. its become clear now that you got caught in some kind of loop of typing opa827 when you actually meant AD827, but that wasnt obvious to me OR redjr and since then I have no idea what has happened to you, you need to settle down and take a breath.
man how you cope in Brazil with such a thin skin I have no idea
redjr: sure one step at a time mate, best way to tell differences anyway, i was just spelling out the areas i would look at, not suggesting you do it all straight away, or even at all.
yep, soic8 is no dramas, i think most peoples barrier to SMD is thinking they cant do it
hey BTW a little help above by saying you had misunderstood too, would have diffused this situation I think, although I understand you not wanting to get involved
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