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The Opamp thread - Page 281

post #4201 of 4794

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Quote:
Originally Posted by zilch0md View Post

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

post #4202 of 4794

Hello, I've been browsing this thread and another (Claro Halo thread) for some time to see if I could find some information. Now, what I am most curious about is replacing the Opamps on the Claro Halo. Looking around, I have seen that the AD797BR is one of the most favored opamps. Looking around on ebay, I have found a few for sale. Now, the Claro Halo requires 2 channel (Stereo?) opamps so I would need an adapter for two AD797s to fit in one slot. I've found one on ebay, http://www.ebay.com/itm/270924926938, that appears to be a match. Now, as this is my first few steps into opamp rolling I'm not certain if I have this correct. From initial appearances it looks good. This is why I'm asking you gentleman if you could offer me any guidance or advice in my endeavors?

 

Furthermore, in case the AD797BR is the wrong choice, what other opamps should I look at? There's so many, it's a bit intimidating. I listen to a mix of genres, ranging from classic rock, alt rock, and rap to electronica music. Any suggestions and tips are very much welcome!

post #4203 of 4794
Besides tonal differences, can opamps affect separation of vocals and the instruments? If so, are there any in particular that can improve that?
post #4204 of 4794
Quote:
Originally Posted by itshot View Post

Besides tonal differences, can opamps affect separation of vocals and the instruments? If so, are there any in particular that can improve that?

Definitely. AD797, LME49990.

post #4205 of 4794
Quote:
Originally Posted by MSalinas View Post

Hello, I've been browsing this thread and another (Claro Halo thread) for some time to see if I could find some information. Now, what I am most curious about is replacing the Opamps on the Claro Halo. Looking around, I have seen that the AD797BR is one of the most favored opamps. Looking around on ebay, I have found a few for sale. Now, the Claro Halo requires 2 channel (Stereo?) op-amps so I would need an adapter for two AD797s to fit in one slot. I've found one on ebay, http://www.ebay.com/itm/270924926938, that appears to be a match. Now, as this is my first few steps into op-amp rolling I'm not certain if I have this correct. From initial appearances it looks good. This is why I'm asking you gentleman if you could offer me any guidance or advice in my endeavors?

 

Furthermore, in case the AD797BR is the wrong choice, what other opamps should I look at? There's so many, it's a bit intimidating. I listen to a mix of genres, ranging from classic rock, alt rock, and rap to electronica music. Any suggestions and tips are very much welcome!

This is were I got my pre-soldered AD797BRs from, I would say to replace all three(?) of the stock op-amps (keeps them all matching).

http://www.ebay.com/itm/mod-1x-AD797BR-Dual-Mono-Op-amp-module-ultralow-noise-replace-dual-op-/261100530695?pt=LH_DefaultDomain_0&hash=item3ccacdec07

post #4206 of 4794

OP rolling .... I am a little bit confuse, many studio equipment facturers use the old 5532/5534 OPA's still again

post #4207 of 4794
Quote:
Originally Posted by PurpleAngel View Post

This is were I got my pre-soldered AD797BRs from, I would say to replace all three(?) of the stock op-amps (keeps them all matching).
http://www.ebay.com/itm/mod-1x-AD797BR-Dual-Mono-Op-amp-module-ultralow-noise-replace-dual-op-/261100530695?pt=LH_DefaultDomain_0&hash=item3ccacdec07

Could you plug that particular item into an m-stage?
post #4208 of 4794

FritzS do you mean you're confused why new studio equipment is still using the NE5532 / 5534?

 

It could be a lack of interest since they are more focused on expensive microphones, ADC, equalizers, software etc., and it's pretty difficult to 'hear' op-amps in the actual music, via playback equipment! 

 

So, if they can't hear or sense the difference between NE5532 and AD847 or whatever in the recording chain, via playback, then I imagine they're not in a rush to use the AD847.

 

I have a feeling the higher-end studio equipment really does use the more sophisticated chips like AD797 and MUSES8920 though, if you look at how much they spend on microphones, speakers, room acoustics etc. then if they have a clue... xx top-end IC's are complete pocket change.

 

 

Another perspective is for example my latest amplifier purchase used AD8620 on the line-in, LME49720 at the power supply, and NE5532 as the headphone driver!, this is called an 'audiophile' amplifier. 

 

While the NE5532 is not the ultimate in resolution or transparency it's still pretty high-end sounding and has a favourable tone / character / quality to some users.

 

So either it just has a nice colour in it, or it's a thin woven mask on so much of 80's and 90's music that when people hear it it's naturally evocative like an emotional reflex.

 

I wouldn't personally use it in any studio eqiupment though unless the IC's have to cost 50 cents.  If the aim is natural, high-rez and transparent that's what IC's like the MUSES8920 are designed for.


Edited by kiteki - 11/5/12 at 5:34pm
post #4209 of 4794

AD847?? Why don't I have these??

 

Are they good?

post #4210 of 4794
Quote:
Originally Posted by SpudHarris View Post

AD847?? Why don't I have these??

Are they good?

nothing really special about them mate, they are a low power video opamp, thus it does have pretty high slewrate, but that doesnt always make it an easy dropin replacement for audio. its current feedback video slinging brethren such as AD811 are superior video opamps when used for audio, but these are not dropin either, due to being current feedback (847 is voltage FB afaik). basically theres nothing that sets it apart from others you already have. the MUSE is a bit lame if you ask me as well.
Quote:
Originally Posted by fritz 
OP rolling .... I am a little bit confuse, many studio equipment facturers use the old 5532/5534 OPA's still again

yes they do, because they are cheap, well performing and very well known/modeled. this means their simulators are able to model the performance of the circuit using these chips quite accurately because the models are very accurate, that cannot be said for many others.
Edited by qusp - 11/7/12 at 1:30am
post #4211 of 4794
zilch0md: sorry I didnt reply to the above mate, theres a significant amount of time involved in a proper reply for that that covers a lot of research I did over the last 2 years and to be honest I not only dont realy have the time, but it also involves research involved in a possible product development. I wouldnt use that alarm though, it will not be designed for audio ie. it will not have been designed wrt the amount of noise it spills back into the power
Edited by qusp - 11/7/12 at 1:55am
post #4212 of 4794

Thanks for the feedback Jeremy, appreciated mate. I'm rolling with the Fi-quest again, man I forgot what a great amp this is. I'm using AD797BRZ's at the moment with 5 stacked BUF634AU's for each channel. It powers my HE-6 better than anything else I have, desktop or otherwise. You still using yours?

post #4213 of 4794
Quote:
Originally Posted by qusp View Post

zilch0md: sorry I didnt reply to the above mate, theres a significant amount of time involved in a proper reply for that that covers a lot of research I did over the last 2 years and to be honest I not only dont realy have the time, but it also involves research involved in a possible product development. I wouldnt use that alarm though, it will not be designed for audio ie. it will not have been designed wrt the amount of noise it spills back into the power

 

Understood.  Thanks for getting back to me!

 

Mike

post #4214 of 4794
Originally Posted by qusp View Post

the MUSE is a bit lame if you ask me as well.

 

Ask Esoteric. =)

 

I think you mean you think the specs are a bit lame for your liking, and / or the pricing of the MUSES01 / MUSES02,... or have you speculated it's some kind of JRC4556 die plus marketing?

 

I think at least we can agree that studio equipment today still using NE5532, or statements that that chip is at or beyond the threshold of all human perception is certainly 'lamer'. =]

 

I had the desire to defend NE5532 for a moment but whatever it's not high-end and it's coloured.

 

I recall you hating on NOS sound a few dozen pages back, just thought I'd mention in passing I can't extract much joy out of my NOS DAC's as of yet.

 

 

 

Originally Posted by FritzS View Post
Originally Posted by kiteki View Post

/ however right now I'm preferring the more pristine unfettered highs of the AD823!

 

I am going the reverse way in my GSP Audio Solo, I use a metal can OPA LME49720HA instead of the AD823 with better performance.

 

Actually today I finally tried the LME49720, in the place of AD823 and I like it!!  I don't know how to put it in words but the AD823 was glassy and rivetting while the LME49720 just seems slighty more airy and natural like the smell of a forest. =)

 

Later I put AD823 where LME49720 used to be and now the hiss and RFI in this amp is very close to zero.  How could a company even release an amp with so much hiss and RFI if the solution was just using the 'right' op-amp?!  I fixed the hiss / RFI and don't have a clue!

 

I wish someone could explain how all of this works in plain speak.  Like showing an exploded view of the die to us, how everything works at low level within the die, how they improved on that design and why we perceive the IC's as sounding different, even within X versus Y high performance IC's.

 

Not just "well the high capacitance loads and ceramic decoupling into thermal value parasitics no one can  hear under 0.01% P.S. the LME49990 is cleaner sounding than OPA627 caveat: if you're an EE.".

post #4215 of 4794

Hi kiteki,

Quote:
Originally Posted by kiteki View Post

[snip]

 

Actually today I finally tried the LME49720, in the place of AD823 and I like it!!  I don't know how to put it in words but the AD823 was glassy and rivetting while... 

 

the LME49720 just seems slightly more airy and natural like the smell of a forest.  =)

 

[snip]

That has to be one of the most poetic choice of words I've ever seen for describing the sonic characteristics of an audio component - but I get it!  L3000.gif

 

The LME49990s in my iBasso PB2 deliver a similar neutral but open and organic quality relative to AD797s.

 

Mike 

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