New Posts  All Forums:Forum Nav:

The Opamp thread - Page 264

post #3946 of 4752

Hi,

 

Quote:
Originally Posted by Avro_Arrow View Post

Have you tried stacking your BUF634U?

You can quite literally stack them one on top

of the other...

The "best bang for the buck" stack is four, but

it is not uncommon to see as many as eight.

In your situation, though, two is probably the

limit your board will support.

In proper use, each buffer would have it's own spot

on the board...but in a pinch they can just be stacked

one on top of the other.

LME49600 can also be stacked.

 

LME49990 and LME49600 (BUF634) is a pretty

good combination.

 

I can not say how they will perform in your situation, though.

Layout will determine the maximum performance as much

as proper component selection.

 

Thanks for the recommendation.  Ignorance speaking here, but I thought that even though stacking yields more current, it comes with the expense of even less transparency - as a rule.  Is that true?   (School me!)

 

Thanks!

 

Mike

post #3947 of 4752
Quote:
Originally Posted by SpudHarris View Post

Mike, I told you that you can get OCD about rolling. But you are right to draw a line in the sand and take some advice from the 'Gurus'. I've been doing this for a long time and I'm probably no further along than yourself but I have learned a few things along the way.

 

Even if you get a combo that you like and it's not causing hassle, you will be searching for the holy grail again within a week. I went through the same thing as you, I got so bogged down by trying to find the perfect sound for me that I lost track of why I was listening at all. Take my advice and find something that you like (OPA1612 by the sounds of it is your flavour) stick in the HA5002 buffers close up the PB-2 for a minimum of a week and just start enjoying your tunes again. The problem with obsessive rolling is that not only do you not get to enjoy your music, you rarely get to know what difference the OpAmps make before you are dropping them again for the new best thing.

 

Get back to your tunes and chill beerchug.gif

 

I believe every word of this, Spud!  I kid you not, I've had sessions as long as six hours straight, rolling, rolling, and rolling some more.  Three to four hours straight is commonplace.  I've gone koo-koo!

 

And yes, I've only once gone an entire week without rolling.  rolleyes.gif

 

But yeah, I'm in the "chill phase" for now, just enjoying the OPA1612s with dummy buffers, but I'm not sure that's "safe".  

 

Sheesh - I should have bought an SR71B to go balanced - no brains required.  biggrin.gif   If it weren't for the fact that I actually hear differences, I wouldn't be so tormented.  (First world problems!  I'm so spoiled!)

 

Mike

post #3948 of 4752
Quote:
Originally Posted by leeperry View Post

the really funny thing is that OCD'ed opamp rollers can rave about an opamp, even though it's oscillating like hell in their gear(AD797 anyone?) and yet properly implemented cheapish opamps such as OPA627AP and OPA2132P can sound out of this world when put together by a skilled EE who also happens to have ears(which is very rare apparently).

 

I don't think you could ever get anything good out of 5532's or 49720's, but the chips I just mentioned can sound mind blowing when properly implemented within a dual mono design(don't push your luck by using dual opamps on stereo signals, though ^^)

 

rolling opamps w/o an oscilloscope is like trying to calibrate a display to D65/2.3 w/o a colorimeter, good luck w/ that tongue.gif

 

I hear you leeperry!   I needed a spanking!  biggrin.gif

post #3949 of 4752
Quote:
Originally Posted by Avro_Arrow View Post

Have you tried stacking your BUF634U?

You can quite literally stack them one on top

of the other...

The "best bang for the buck" stack is four, but

it is not uncommon to see as many as eight.

In your situation, though, two is probably the

limit your board will support.

In proper use, each buffer would have it's own spot

on the board...but in a pinch they can just be stacked

one on top of the other.

LME49600 can also be stacked.

 

LME49990 and LME49600 (BUF634) is a pretty

good combination.

 

I can not say how they will perform in your situation, though.

Layout will determine the maximum performance as much

as proper component selection.

 

oh lordy yes it is L3000.gif am I doing it right?

 

got buffers? very_evil_smiley.gif

 

LPUHP pair w 18W8531_10Jun2012_1007 sm forum.jpgLPUHP pair w 18W8531_10Jun2012_0994 sm headfi.jpgLPUHP pair w 18W8531_10Jun2012_1010 sm.jpg

 

 

LPUHP pair w 18W8531_10Jun2012_1018 sm.jpgLPUHP pair w 18W8531_10Jun2012_1016 sm.jpg

 

^^ pictured with a pair of Scanspeak 18W/8531 G0 6.5" mid/woofers, which will take me down to about 30Hz in a ported enclosure till I add some larger 10" Volt pro woofers.

 

 

and an lme49990 based balanced input 'instrumentation amp' underneath

instrument LPUHP first channel_01May2012_0877.jpg

 

The above is opc's 'the wire' LPUHP (Low Power Ultra High Performance) parallel buffers taken all the way baby, to make a 15W/ch dual mono low wattage power amp with the craziest numbers and audio youve ever seen. i'm using it for my tweeters in a ESS dac based quad mono balanced digital crossover for some speakers i'm building (like a hardcore JH3A for speakers).

 

This is correct use of X7R caps, see there are no other nearby caps of similar size to cause resonance and I needed a larger value than available in np0 because of that; its also a high end build so a few bucks isnt worth saving, but X7R is best suited for the job. These are 1206 size 10uf with the only caps beforehand being in the main PSU and they are 4700uf.

 

the ones on the lme49990 are also X7R, but only 1uf due to much lower current demand, but even though the power delivery is via solid planes and vias, the main supply caps are a fair way away and a physically small 1uf cap was needed, no suitable np0 was available and probably not even desireable.

 

the buffers use plenty of current in this format, so larger caps from each supply pin to ground are most definitely needed, its a 3 layer PCB so the middle is basically all ground plane and the other 2 are for signal and power routing.

 

The design has been publicly poked, prodded and probed to within an inch of its life with no signs of instability. Its designed to drive 15W into an 8ohm speaker load so it needs larger than a .1uf, these are acting as decoupling caps and small reservoirs for transients.

 

I'm also going to bring it along to the next headfi meet with a novelty HE5/6 cable, I think its going to suit them down to the ground. except extreme loading conditions the copper in the PCB is enough to take the heat, but in summer it'll need its heatsink, which will be custom CNC for a couple of our group for bater.

 

For those that care, wires are 20awg VHAUDIO UPOCC copper in foamed PTFE and the insane overkill output wiring is VHAUDIO 10AWG twisted pair UPOCC in FEP (this is actually AC wiring, but its so nice I thought it was perfect)

 

 

and heres its little brother in balanced mode on the output of one of my dacs, breadboard testing, not final layout, as you can see i'm testing a thermonuclear device for transparency =) . Thats a pair of balanced HD600 (with lemo 4 pin connector), directly on the output out of frame. The bal-bal wire is acting as the output stage/IV for the dac and headphone amp, sounds magic! so yeah opamp rolling is fun, but it soon leads you to this madness haha

 

fifo-akd12p testing lock 09May2012_0936.jpgfifo-akd12p testing lock 09May2012_0937.jpg

 

are we having fun yet?


Edited by qusp - 6/11/12 at 2:04pm
post #3950 of 4752
Quote:
Originally Posted by zilch0md View Post

 

I hear you leeperry!   I needed a spanking!  biggrin.gif

 

dont worry about him, he was one of the craziest roll by ear users on this forum for a long time, that would not listen to anyone. I qualified for that title too for quite a while, well perhaps a bit less doggedly. the pros often dis opamp rollers, but I disagree, its often where you get the taste for electronics on more than a surface level and if you have the hunger for learning, I guess thats when the training wheels come off. I wonder if LP actually has a scope himself, he certainly wouldnt have even entertained the thought a couple of years ago

 

please dont label me Guru, i'm far from a guru, i'm still learning every day and the ins and outs of this particular area wrt phase i'm just poking around on the surface. I need to get more time on sims, unfortunately spice doesnt come on mac and I havent gotten around to installing windows on here yet, solely for sims etc

 

@ Spud, dont worry, I saw the inverted commas on guru :D


Edited by qusp - 6/11/12 at 11:22am
post #3951 of 4752
Quote:
Originally Posted by qusp View Post

snip awesum stuff

 

are we having fun yet?

can I buy a set? looks seriously awesum.

post #3952 of 4752
Quote:
Originally Posted by zilch0md View Post

I hear you leeperry!   I needed a spanking!  biggrin.gif

 

You apparently do autralia%201.gif

 

But no worries, blind rolling is hell fun! too bad the best chips will never be stable w/o a EE background in order to know how to get them stable.....I've given up on opamp rolling altogether and I also avoid gear using 45xx/553x/497xx's. So far, so good very_evil_smiley.gif

 

Having access to an oscilloscope is mandatory, but afterwards you'll need to know how to overcome those nasty oscillation issues....otherwise you'll have no clue what to do. If you're lucky, adding decoupling caps will help.....but the most pesky and arguably best sounding chips will be far more finicky to deal with. It's actually a job in its own right, all it takes is a mere EE diploma if you fancy playing God in a more serious manner than the "look, ma! no hands" blind rolling hit & miss experience normal_smile%20.gif


Edited by leeperry - 6/11/12 at 11:07am
post #3953 of 4752

I been thinking about trying some op-amps that has a sound signature similar to tube but I don't know any that has that sound signature. Mainly Dip-8 so i don't have to try to get some one to solder it. i do have a adapter in case it's single channel.
 

Mainly a tleast tube sound signature while not being too bright and have a tight bass it having a big sound stage is a plus but not a most.

post #3954 of 4752

The OPA627 is often called coloured, analog etc., perhaps use 072D as a buffer, random thought.

post #3955 of 4752
Originally Posted by leeperry View Post
 "look, ma! no hands" blind rolling hit & miss experience 

 

What's so hard about it though, there should be a tutorial on op-amp environments, it feels like there's an ivory tower surrounding basic electronic circuits and capacitors.

 

Like, I'd love to improve the 50 cent or less op-amps in devices like the Teclast T51 or Colorfly CK4 to $5 op-amps however the reaction is usually "I suspect you need to understand x/y/z in the circuit or there will be solar flares"  is not really helpful.

 

Edit:  At the same time half this forum thinks all op-amps will sound identical in their ideal circuit, and op-amp rolling is really only messing with voltage / colour / distortion, which isn't helpful either.  It's like saying "don't mess with your TV image / laptop / air-conditioner an EE has already calibrated it to perfection in it's ideal circuit" ...


Edited by kiteki - 6/11/12 at 7:46pm
post #3956 of 4752

The MUSES and some other rare op-amps arrived today, will experiment with them when I'm in the zone.

post #3957 of 4752
Quote:
Originally Posted by kiteki View Post

 

What's so hard about it though, there should be a tutorial on op-amp environments, it feels like there's an ivory tower surrounding basic electronic circuits and capacitors.

 

Like, I'd love to improve the 50 cent or less op-amps in devices like the Teclast T51 or Colorfly CK4 to $5 op-amps however the reaction is usually "I suspect you need to understand x/y/z in the circuit or there will be solar flares"  is not really helpful.

 

Edit:  At the same time half this forum thinks all op-amps will sound identical in their ideal circuit, and op-amp rolling is really only messing with voltage / colour / distortion, which isn't helpful either.  It's like saying "don't mess with your TV image / laptop / air-conditioner an EE has already calibrated it to perfection in it's ideal circuit" ...

I agree completely its very daunting for a beginner. There is simply no tutorial. And there should be one, a big one, explaining the equation, bipolar vs fet and the dangers and some notable exclusions (AD8599). Also oscillation, and bypassing. Then slew rate and bandwidth. There is s much that I barely get.

 

maybe an article should be made where more then one person can contribute? just lay out the headers and take it from there.

post #3958 of 4752

There is already one of the best sources of information online...the manufacturers Data Sheet.

Tanget has some good articles on op amps here.

Look in the section titled "Op-Amps in Detail".

 

Designers have some goal in mind when they create a layout which may include

some sever compromises such as limited size or designers experience...

These compromises can limit the maximum usable bandwidth that you can

get out of the board no matter what components you stuff into it.

 

Quote:
Originally Posted by WiR3D View Post

I agree completely its very daunting for a beginner. There is simply no tutorial. And there should be one, a big one, explaining the equation, bipolar vs fet and the dangers and some notable exclusions (AD8599). Also oscillation, and bypassing. Then slew rate and bandwidth. There is s much that I barely get.

 

maybe an article should be made where more then one person can contribute? just lay out the headers and take it from there.

post #3959 of 4752
Quote:
What's so hard about it though,

 

 

nothing that hard about it, past knowing how to verify what you have done has actually improved matters, I agree LP did present it a little too extremely, but thats what he does for effect =) however there is most certainly truth in what hes saying. there is no general guidelines of which chip will go well where, replacing X for Y, Each chip has its own set of preferred operating conditions and each circuit represents a set of parameters of its own, even when the parts are the same, the lead, or trace inductance, grounding, gain, compensation, power supply voltage and load current, capacitance, as well as parasitic and/or parallel capacitance, inductance etc; all have influence on these parameters.

 

bipolar or fet is a minor thing, that will tell you little and cannot be used to make decisions. the datasheet and knowing how to read a layout, as well as having some way to verify performance is the only way to do it. simulation can help to a degree too, but even when spending a great deal of time creating complex models there are still some elements that will be unknown until its done in reality and thats if you can get an accurate model, or be able to trust the datasheet enough to build one based on that. the best models come from building and measuring the real thing, then you have the change from loading....

 

a basic scope can be had for pretty cheap and unless you are really needing to play with high bandwidth parts, should be enough to get a rough idea. handheld ones are starting to become more useful, but you still cannot beat an old analogue scope for value.

 

of course as mentioned, I didnt even touch dealing with the incompetence of the designer, or otherwise compromised designs

 

that being said, there are ways to make sure what you are doing is safe, or likely to cause damage, many of which have been discussed in the last few pages; you can still have fun, but know when to recognize the signs something is really wrong. you WILL hear differences, because of the change in conditions, some may even be preferred, whether you have made an improvement or not is all relative, if you like the sound better and the amp isnt going to kill itself or your headphones, then hey I call that a win.

 

do remember though and this is important, we are talking about audio bandwidth here, the blinkered chase for high slew rate and wide bandwidth at all costs is not all that relevant for our purposes; in the same way that oven controlled oscillators are not relevant either, only the OCX do tend to be a higher grade part overall, nothing to do with being ovenised

 

@WiR3D: which build were you talking about? the LPUHP amps? the GB is over, there was a single run of blank PCBs, no kits were available, the PCBs sold out in less than 24hrs!! I ran the group buy for the passives, custom transformers from sumR and keratherm thermal interface material to drive the cost down, people sorted the actives out themselves. there will not be another run of PCBs


Edited by qusp - 6/12/12 at 6:39am
post #3960 of 4752

Excellent comments, everyone, but a datasheet in the hands of a beginner is what led me to trying the AD797s in the buffer stage of my PB2, with OPA1612s in the L/R - a combination which sounds great to my ears - I truly can't hear anything undesirable - quite to the contrary, it sounds wonderful, but for everything getting so hot I have to remove the top of the case to use it - and now that I've been warned that the op-amps themselves might still get so hot as to destroy my LCD-2s, I'm deprived of this wonderful sound - and completely incapable of discerning whether or not there really is an actual risk of damage, because I have neither the knowledge nor the test equipment of an experienced EE and throwing money at the test equipment is easy enough, but even then I wouldn't know how to use it.

 

Back to the AD797 datasheet having pointed the way to this fiasco, it was these words that gave me the light-bulb idea to drop them into the buffer stage:

 

Quote:
The low distortion and 16-bit settling time of the AD797 make it ideal for buffering the inputs to Σ-Δ ADCs or the outputs of high resolution DACs.

 

I knew perfectly well that my PB2 is not a sigma-delta ADC or DAC, but the word "buffer" was all I needed to see to imagine their use in the buffer stage of my PB2.  The sound is so wonderful to my ears, colored, yes, not neutral, but warm, with lots of control in the bass, very little loss of detail across the spectrum as compared to running the OPA1612s with dummy buffers, but I'm having to exercise self-discipline to avoid using this ear-candy combination!   Like a former cigar smoker who just found a rare Cuban in the bottom of his humidor, I can't have it because it might give me cancer.

 

Conclusion (I'm not as bitter as this may sound, but it's the truth, just the same):   Rolling op-amps is a complete joke for all but a relative handful of people who truly do have the knowledge and the test equipment.  Everyone else should just stick to buying off-the-shelf designs. If you want a different sounding amp, buy a different sounding amp.  

 

Still, it has been a lot of fun.  And, undermining my own arguments, above, it will no doubt continue to be a lot of fun, cause I'm gonna smoke them Cuban cigars!

 

Mike

New Posts  All Forums:Forum Nav:
  Return Home