The Opamp thread - Page 280

and what part of my post made you think I wasnt aware of that?

the thing is, whoever that idiot was, said that the opa637SM was 'harsh' when its the top spec part, is either attributing something else to the opamp, using it incorrectly (it needs to be used at 5x gain at least to be stable), or just making stuff up.

it was probably the same person that said
this is the really stupid part, someone comparing AM and HA and saying A's were lower quality is just trying to sound smart, because they are the lowest spec metal can for 2 different companies and cannot even be compared, one is not even graded against the other. National and Ti used to be 2 different companies, only very recently Ti acquired National, but they are still not graded against one another. they do not make an OPA637HA and nor do they make an LME49710AM, so there is no basis for comparison.

the quality levels are not even really quality levels. to grade the parts they will just take a batch of the devices and bin them on performance in harsh environments, ie. how much they change/drift as they heat up (tempco: mostly if the parameters will drift in temperatures above 85 degrees....) they will call one lot SM, one lot BM and another AM based on the result. Because they have tested them they can then assure this level of performance/stability to customers, who may be using the parts in mission critical applications where lives, or large amounts of money are on the line if something goes wrong (like a plane or spaceship dropping out of the sky)

this process takes time and costs money, many will not even be tested because they know they wont sell as many SM parts, so there will be parts that could be graded SM in the stock sold as AM, as its not worth their time to test them, but they know they can call all of them at least AM. at the temperatures we use them at and the frequencies used in audio, we are not even close to stressing the lowest level.

what? AU that came out 2 months ago? the opa637 datasheet was last updated in 2000 and released before that, I personally have a set that i've had for nearly 3 years.

I can tell you without doing that test, forget it, hes gotta be having a laugh, some people are stupid, 250 is a joke, buy something else, buy a better amp. is that each or a pair? either is beyond crazy, but $250 each is criminal …

yes I ignored that, because i'm not sure they make high quality opamps wit da goodz kickin bazz... you are much better off adding a proper headphone buffer. I gather the dac section of the board is fairly well done, but the headphone amp could definitely use some work and swapping an opamp isnt going to fix it. what it needs for tight and controlled bass, is good high current and low output impedance headphone drive.

or you could just use EQ to bump the bass....
Edited by qusp - 10/5/12 at 2:05am

kiteki:


there is no such thing as ESS 'current mode' its a term that is erroneously bandied around. the dac puts out all voltage into higher impedance loads and all current into zero impedance loads and a mix of the 2 at all the levels in between. I wouldnt go near the fun thing, or his ESS dac.

mate ARZ vs BRZ? hmm they sure dont measure any differently. I use the BRZ.... just because.... but I think any large difference is going to be in your mind.

I'll tell you what is interesting for AD797 fans who dont mind a bit of DIY, the designer of the chip, Scott Wurcer is currently working on a DIY project with some other notable designers!! They are developing a discrete high performance balanced Jfet input opamp design for audio and publicly too. Eventually there will be small PCBs made available; i'll probably start bread-boarding one of the versions this weekend.

Its being designed to be small enough to plug into an opamp adapter, or close at least and not use hundreds of parts, just high performance using well matched low noise jfets and transistors. not a novice build if you have to do the matching, but if you can get the parts it probably wont be too difficult and performance should be superb! the parts will absolutely need to be matched, like the AD797 its going to be a very high performance and likely somewhat cranky thoroughbred, it will need good power supply too, as its PSRR wont be as good as an IC.

heres an early version prototyped up by one of the members, there are parts on the other side too



perhaps with Scotts permission when something more concrete is ready, I will see if we can run a GB for kits over here, perhaps with the matched BF862 jfets or similar already soldered for those not confident with SMD.

There will likely be either a matching buffer needed, or a higher current output buffer included in a modified design, if people want to drive low impedance headphones. so far the load impedance is only tested for 600 ohms and up. Its a general purpose audio opamp, not a headphone amp by itself, so could be teamed with lme49600/10, or simple class A discrete buffer/follower in a design, or without buffer in the line stage or IV stage of an existing design.

i'm sure there will be a version made available that will drive lowZ, we have already been talking about it. its a way off yet and I have no claim to fame, i'm only involved as a hobbiest and big fan of Scotts (who is over the moon that this is happening!)

I cannot guarantee I can get permission to make this happen, but there WILL be PCBs at some point from someone, i'll make sure to update you guys when its ready. The design is being made publicly available, so I would think if I ask and as long as i'm not making a product with it, it should be ok. we'll see
Edited by qusp - 10/5/12 at 2:25am

 

The ANZ and BR have different input offset voltage, input bias current, input offset current, different open loop gain and something about "plastic" versus "standard".

 

 

I didn't test them with the same DAC so I'm not completely sure, could be a synergy issue but they don't seem to sound identical to me. =/

 

 

Thx for the info on the DIY discrete coming up.

 

 

 

 

 

You said the ESS ES9018 sounds and measures better every time in 'current mode' using an external I/V.  http://www.diyaudio.com/forums/digital-line-level/190745-differences-between-voltage-dac-current-dacs.html#post2604083

 

 

Why not go near the NFB-11.32?  I hope it's not Buffalo or AckoDAC favoritism ...

Howdy!

  Yeah that was from a post that was rather old!  LOL!  Those prices were outdated.

Just posted it for fun.  Nice Analysis!!

 

So basically im lookin at either  LME49720HA ,  opa 627SM,  and OPA2111,  all to-99 cans.

 

I have heard it said that the Burr Brown's are "warmer" sounding.

 

I also saw some reviews about the LME49720HA sounding slightly warmer than LME49710ha.

 

The Ortofon x5-mc I am using really extracts the highs from the music.

But it also extracts alot of the stylus noise in the groove,  raspy sounding crap!!

 

I can get rid of it with the Diamond Cut Audio I have with the crackle filter.

 

Soundstage and imaging is great with LME49710HA.  Sometimes I can get 5 different channels playing back at once.  A center sound two inner stereo

bands,  and one that is way to the outside of the inner bands.  It's very 3d and I like that.    So wondering if staying in the

LME family will keep me happy?

 

Dunno if getting one single opa2111 to test out Burr Brown Sound is wiser than getting two OPA627SM's?

 

I dunno,  I don't have a engineering degree.   Its a sound card,  and I really listen to it through my desktop speakers, and a Marantz sr7300 into 3 pairs of speakers in series lol!!   It looks like top of Empire State Building,  3 speakers stacked on each other!!!  Auzentec made it with a really nice Analog recording sections.

http://www.auzentech.com/site/products/x-meridian2g.php

 

So i have Digital Dacs in Card,  and Digital Dacs I can turn on in the Amp,  along with Analog settings on both as well!!  Lots of settings!!!!

Card does warm up in 48 and 44khtz digital passthrough on the sound card.  Bass extender sweetens the highs as well.

Just the Analog section has best detail,  just is less "juicy" shall we say.

 

So basically hmm......  whats warmer with good detail and Bass.   My mids are dry with the LME49710HA's thanks to the ORTOPHON,  but detail is incredible!!

Definetly keepers for mastering vinyl!!! 

 

I also modded my turntable wires with silver!! 

http://www.vinylengine.com/turntable_forum/viewtopic.php?p=323623

 

So that makes the trebles treblyer!!!  And the bass is so detailed its fantastic!!!

 

Also this tube passthrough device I am thinking about as well.

http://secure.oatleyelectronics.com//product_info.php?cPath=100_104&products_id=922

 

And here is headphone one:

http://secure.oatleyelectronics.com//product_info.php?cPath=100_104&products_id=885

 

Thanks for chattin me up.....  Decisions decisions......

 Oh another quick question,  the LME49720HA needs a single or dual adapter?

 

If im right the opa2111 is a single adapter. i.e. it is dual channel or dual output.  Not sure of the terms.

 

And the opa627sm ineeds a dual to-99 adapter for stereo output in a dip8?

 

It's called oscillation

 

I dunno, try 2*OPA132U soldered onto adapters? or OPA2132P if you're not DIY savvy.

Edited by leeperry - 10/7/12 at 8:12pm

For Kiteki, about the NFB-11 (Click to show)

 

The funny thing is I came to this thread to see about OPAMPs, because I was just about to get the Otomatsu amp out I built and run some OPAMPs through it, so I wanted to see what ones are being discussed at present.

Are there any other alternatives under $600 using ESS ES9018?

Edited by kiteki - 10/8/12 at 2:47am

Warning: Spoiler! more on the ESS theme for kiteki (Click to show)
the opa1652 is pretty sweet if you need a dual Currawong, but really its still hard to beat lme49990 for singles if youve not tried that.
Edited by qusp - 10/8/12 at 4:16pm

 I found this little review and it helped greatly.

 

http://www.xbitlabs.com/articles/multimedia/display/auzen-xfi-home-theater-hd_6.html#sect0

 

After reading through it I went and ordered a LME49860 to try.  Said it almost beat

a OPA637SM. 

 

49990 I might try too.

 

Still its weird,  the trebles seemed to have de harshed,  I think it's just my

cartridge breaking in.  The bass output has risen,  and the treble is not so

harsh.  I find it dependent upon when the Vinyl was pressed.  I guess it also

depends on how it was recorded.  Songs like the Police ,  where that drummer

is wailing on the high hat can become terrifying experiences!!  Really hot and ear

cutting. 

 

Earlier recordings with the 15degree cutting head angle are nice and never harsh,

the later ones where they went to 20 degrees,  they can really have a lot of harshness in

the treble.  It just depends at what level they are at in the recording mix.  up front or

with effects and blended in lower.

 

When I get the dispensable income I might try some other to-99 opamps. 

I am starting to wonder if the lme49710HA's can really be beat.  When I put on

the Auzentech bass Crossover thingy, it adjusts from like 60 to 250 htz,  it is like a tube amp has been turned on.

It really sweetens the mix.   I just forgot to turn it on,  cause when I record I want a unbiased signal.

Edited by smengy1 - 10/8/12 at 10:28pm

Hey qusp,

 

 

This goes back a while, but reading this again, I'm very curious about the regulating, dual mono/bipolar supply that is sitting between your 4S LiFePO4 pack and your load.

 

I have almost no DIY skills, but I'd like to get my hands on something, anything, that can be inserted (externally) between a LiPo pack and the power jack of an amp - to limit maximum possible current to about 3A.  Everything I've read on the subject (reading without much understanding) points to using something like an NTC thermistor as a current inrush limiter, but I don't have the first clue if that's what I really need, much less how to deploy it.  

 

I'm probably dreaming, but do you have any knowledge of something I can purchase off-the-shelf, maybe that's made for RC hobbyists, that will limit a LiPo pack's current?  I'm coming up empty-handed when looking for such a device - which amazes me, considering how useful it would be across many portable applications - not just audio.

 

Thank you!

 

Mike

yes, go to digikey and type varistor, or MOV, I did a quick search, first part that came up was a 445-2533-1-ND, a small 8 volt 3 amp current limiting device. this one is a surface mount, meaning it has no leads. this makes it a bit trickier to solder to, but it is very small. I am sure one could be found that is through hole (has leads) that would be easier to work with, although bigger.

can I ask why you need 3A? i'm using a low noise bipolar regulator, you unlikely need bipolar, or 3A. thermistors will limit current yes, but they are hardly low noise and they do not regulate, they just limit voltage. the amount of voltage drop, like a resistor, will vary with current draw. what is your application? what is the real current limit, there are not many low noise higher current IC regulators
Edited by qusp - 10/19/12 at 6:41pm

H22 and qusp,

 

Thank you for your replies!

 

OK, here's my application:

 

I want to power a DACmini CX using a hardcase, 4-cell, 5000mAh LiPo pack (16.8V when fully charged):

 

 

http://www.hobbypartz.com/98p-40c-5000-4s1p-hardcase-direct.html

 

For H22's benefit, as I can tell from the post I quoted that you're probably already aware of this, qusp...  

 

RC LiPo batteries are rated at their nominal voltage - assuming 3.7V per cell, but when fully charged, they deliver 4.2V per cell, thus a battery like this one, which has a "4S1P" designation (4 cells in series, with no parallel connections), can deliver 16.8V when fully charged (4.2V x 4 cells), despite being labeled as a 14.8V battery (3.7V x 4 cells.)  

 

A "5S1P" battery has an 18.5V nominal rating, which sounds attractive, at first consideration, for use with the DACmini CX, given the fact that the DACmini CX can accept any voltage from 9V up to 19V, but a 5-cell LiPo (like the Energizer XP8000 and XP18000) can deliver 21V when fully charged (4.2v x 5 cells), and thus, would need voltage regulation in addition to current limiting.

 

As you know, these LiPo packs can deliver A LOT OF AMPS.  The C rating of a LiPo battery can be used to calculate the number of Amps it's capable of delivering continuously.  The 5000mAh battery pictured, above, has a 40C rating.  To calculate the number of amps that can be delivered with a continuous load (peak current is typically 50% higher still), just multiply the C rating by the mAh rating and divide by 1000:

 

40 * 5000 / 1000 = 200 Amps! 

 

 

The DACmini's switch-mode AC power adapter is rated at 2630 mA.

So... I already see that I'm going to have to teach myself how to solder - even IF I can get my hands on a schematic for a noise-free device that can be inserted, inline, between the LiPo pack and the DACmini CX.   In an ideal world, this imaginary device would limit current to 2630 mA (3000 mA would be fine), without voltage regulation.

 

There's no need to regulate the voltage of a 4-cell pack.  It can start out at 16.8V (4.2V per cell) and discharge down to 12.0V (3.0V per cell) - at which point, this audible alarm (that I currently use with a different LiPo pack application) would signal that it's time to recharge the pack:  

 

 

http://amzn.com/B003Y6E6IE

 

The DACmini CX can handle anything from 9V to 19V, so an input that decays from 16.8V to 12V is ideal.  David McKrell, of CEntrance, has assured me that the DACmini's internal power supply takes any voltage that's coming in and converts it to a constant supply voltage at the rails.  Input voltage has no impact on sound quality, as long as there are enough amps and it fits the range 9V to 19V.

 

Comments?

 

Thank you, again!

 

Mike

Buy my Op-Amps!!!

http://www.head-fi.org/t/633854/opamps-2x-opa602bp-2x-opa827-2x-ada4627-multiple-adapters-capacitors