[ppl]

Jeff Guidry> if you would consider an opamp that performed better on one type of music than another then consider the sonic differences between AD and BB Opamps. the AD's have guts with lots of Punch in the bass. The Midrange is right in your face on some AD devices and less so on others. The BB opoamps on the otherhand are polite and some like the OPSA-627 also are detailed AD opamps tend to be less detailed but more forgiving of bad recordings. I would sugest you listen to each to be sure. then there is other manufactures like Intersil that is somewhat like the AD sound as is elantec opamps. Like tangent says it is mostly a system Thing. you can't make a silc purse out of a sows ear but the reverse is often true.

 

[tangent]

As sweeping generalizations go, I agree with ppl's capsule description of op-amps. There are holes you can poke in it, but I'm not going to -- just realize that specific chip reviews are going to tell you more.

Thinking more about this, I suppose that if you were a fan of bad old rock recordings that tended to be recorded over-bright, and that you were also a Grado fan, that the more forgiving, dark, laid back Burr Brown sound might mesh better with your music. Again, though, I would say that this is not a matter of Burr Brown chips being good for rock, but rather that they match with your tastes better. This isn't limited to Grados and Burr Brown chips and old rock music. You could imagine similar setups for other equipment and music types, but in all cases, something is broken, and you should simply view this as compensation for a flaw. Expanding these examples to say "chip X is good for music style Y" is probably wrong, for any particular X or Y you can name. Maybe in your system with your recordings and your ears and your headphones and your source it's true, but I doubt you can find a rule I can't kick the legs out from under.

I think that it's not asking too much to find a chip that sounds good with all of your recordings. Uh, oh, another sweeping generalization, and this time I will poke some holes: you might find that some recordings are too bad to listen to on a chip that makes everything else sound good. I would call those recordings "culls".

 

[andrzejpw]

tangent: how forgiving do you think the 8610 is in the meta circuit? Is it very analytical? Or is it smooth?

 

[Duncan]

Wowee... a mini update...

I'm still running the BB OPA2604AP, and still with the same Duracell Ultra Battery that I had the last time I posted in this thread...

The voltage is now at 7.91v and the BB op-amp is still singing sweetly... i'll let you know when it gives up, at what voltage...

The 9v cell i'm using, to the best of my knowledge, i've had the META42 running for at least 20~25 hours... and at a volume substantially louder than most of you guys listen at... so, are Duracell Ultras really THAT good, or is the META an extremely economical design in terms of power usage?

Thanks

 

[tangent]

Quote:

how forgiving do you think the 8610 is in the meta circuit?

Forgiving sonically or electrically?

Quote:

The voltage is now at 7.91v and the BB op-amp is still singing sweetly

That's not unexpected. My review says 9V is the minimum, but keep in mind that the test is done with a very difficult recording with a CMoy type amp and evil headphones. Getting an extra volt or three with reasonable recordings, a buffered amp design and nicer headphones is expected.

When you deem the op-amp starved, let us know what headphones you were using at the time. Then for grins, if you would, plug in your Grados and see what you find. I'll bet you find that it sounds good again for awhile.

On the efficiency issue, the biggest single draw in most META42s is the op-amp chip(s). The 2604 will typically draw 10.5mA for both amplifier channels (12mA max). The two output EL2001s will draw about 1.5 mA apiece at rest, and if there's a third EL2001 buffering the virtual ground it will add another 1.5 mA. The LED is another 1-2 mA, and the whole rest of the circuit is probably under 1mA total. So, your amp at rest will draw 17 mA max, and probably less. When driving headphones, it might go up to 20 mA or so. With a 600 mAh battery, then, you would expect 30 hours of run time, or more if your particular amp is configured to draw less than 20 mA, which it probably is.

To get that 600 mAh, though, you have to run the battery down to about 5-6V. You probably won't be able to quite hit that mark with that chip.

 

[Duncan]

I speeded things up, by using a rechargeable 9V cell that refused to play on my CHA47 anymore... and it bummed out at 6.94v... I'm not sure how current really works (I've got a multimeter but don't know how to use it... not all that electronically minded) in any case, the current reading didn't reflect anything 200µ nor 2000µ 0.03 at 20m at 0.3 at 200m (whatever on earth that all means)

Whereas, my Duracell now measures at 7.2V and a current of 0.25 at 20m and 2.5 at 200m and is still working fine

I hope that makes sense to you Tangent, because it doesn't to me

I personally couldn't notice any degradation in the sound quality right until the last moment, when it just sloped off... coughing and spluttering... thats using my 32ohm Sonys... so, I daresay the Grados would be the same?!

 

[tangent]

Sorry, Duncan, you did lose me. "0.03 at 20m" is two unitless numbers...I can't make anything of that.

What I'm talking about when I mention minimum voltages for op-amps has to do with the point where the op-amp becomes starved for voltage. It has little to do with batteries specifically. It affects wall-powered amps the same way.

Now, batteries vary in their ability to deliver current under load, and batteries drop in voltage at different rates depending on the cell type and how heavily you've been using them. And, there's the issue of rechargeable batteries wearing out. All of these things also figure into the issue at hand in complicated ways.

What I'm trying to get across is that my "minimum voltage" numbers for op-amps have a number of assumptions built into them, and when you change the conditions the op-amp's behavior will change, too. For example, in my tests I use a benchtop power supply, which will supply as much current as any op-amp could want. Your heavily-used rechargeable battery can't supply as much current as the amp wants, so its measured voltage is beside the point.

 

[ppl]

"As sweeping generalizations go, I agree with ppl's capsule description of op-amps. There are holes you can poke in it, but I'm not going to -- just realize that specific chip reviews are going to tell you more" By tangent.

Ok Kid's more sweeping Generalzations~ IMHO the AD-8610 & 8620 Are the Best Bang For the Ma. That being Current drain of the Opamp. The Dual 8620 Draws 6.3 Ma with (2) 9 volts and the AD-823 Draws 8.2. The Draw of the AD-823 is dependent upon the Supply voltage as the voltage is rased the Current draw gose up. The AD-8620 on the Other-hand remains constant at different Supply Voltages. The AD-8620 Has better performance in all Parameters than the AD-823 with the Exception of operation at low supply voltages. The 8620 works fine from (1) 9 Volt but i use two. I also think the AD8620 sounds way better than the AD-823. the 823 sounds Bloated in the Midbass while this may be good to some it makes voice sound unnatural on my MDR-7506's Also the AD-823 sounds Rough not smooth at all. I Like Smooth. The 8620 has the best combo of smooth, Detail, Imaging, Low Noise, of any other Opamp i have tried that is battery frendly. It is a wounderfull alternative to the OPA-627, although I think the OPA-637 is somewhat more revealing than Eather the AD-8620 and the OPA-627, But the 8620 draws half the Curent of the BB chips and will also sound good on lower supply voltages. somthing that the OPA-627,OPA-2604,OPA-2107 will not do. So for the Life of me I can't Imagine why one would use anyother opamp for battery use than the AD-8610, AD-8620. Oh BTW the 8610 & 8620 are one of the few opamp types that the Dual sounds as good as the single. i did a review of the 8512 search

DISCLAIMER
The Above is only my view of this topic and your millage may vary. The above is based upon My Musical tastes that include almost everything and with the Equipment i use. Sure holes may be in any general overview of a subject but sutch an overview is IMHO the best way to Cover alot of different issues.

 

[Fixup]

Just finished my mini META and I found OPA2134 and LMH6643 is a good match - warm, sweet and detailed, slightly better than the AD823+LMH6643 comb.

In the Aug. 22 issue of EDN, AD claims LMH6643 as based on National's VIP10TM process technology, excellent AC performance, lower distortion and improved pulse response. Also in this issue, John Bittner wrote an application brief on using LMH6643 to transfer color video on 1,000 feet of twisted-pair wire! Very promising.

The most unique feature of LMH6643 is its low voltage - true 3V (+-1.5V).