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View Full Version : Chips or Discrete opamps, Can you here the difference?



Ian Mackenzie
04-23-2004, 02:32 PM
This thread is bound to stir a rousing debate.

The idea is to talk about subjective experiences rather than tech hype.(but please lets keep the flaming to Pms is there has to be any)

I'll start,

Like many I always thought chips or opamps were just that, an accepted part of modern electronics.

About 10 years ago I opened up my Phase Linear 3300 Series 11 pre amp and found a bunch of chips, NE5532 in the phono stage and output buffer and TL072 in the tone controls.

At the time I was a diy convenor at the local audio club so one afternoon we swapped in and out different chips.

After many swaps I concluded yes it did change the voicing of the pre amp but they were all just different.

None better or worse, and it was a case of blending associated equipment for the most pleasing result.

I then did similar things with a DAC and had the same experience.

A friend then bought over a Parts Connection Pre kit he built This was a discrete opamp affair, a simple Jfet diff pair and souce follower baised into class A.

We plugged it in. The difference was an obvious improvement, more fine details, for bass clarity, better imaging and a purity which I never thought possible.

In comparion both my consumer Phase Linear pre amp and Harman Kardan control preamp (5532) sounded flat, etched and thin.

I have since binned both to the Lab scap heap and use a discrete opamp preamp.

An audio engineer was over the other night for a look at the bad boys. The comment was "those slots and horn are very impressive. They are obviously that accurate that inferior electronics spoil their performance".

Ian



:duck:

jbl
04-23-2004, 02:52 PM
There are differences between packages. Your friend is correct. You may be more likely to hear difference(s) with your slots and horns because they are very accurate. When I replaced the capacitors and resistors in my amp and pre amp, the noise floor lowered considerably. That difference would'nt be as great on anything but a horn. As a result, the dynamic range of my system increased. You should be able to hear a difference between chips. Don't forget that the chip manufactures, unless they are customed made for a particular manufacturer or design application are mass produced. The tayloring of the final result depends in large part on the associated components and the intended result anticipated.

scott fitlin
04-23-2004, 11:01 PM
Any extremely efficient speaker system, especially horns, and horn tweeters will show up any flaws in ones electronics. IC,s are flawed, but some are able to sound quite good in well designed circuits.

Discrete is the best, and the difference is very audible. If you have a discrete unit that has the sound you like, that will always be the best, and cleanest sound.

Ian Mackenzie
04-23-2004, 11:40 PM
One thing I found was that the better chips, like the opa 627 and AN 797 have a copper substrate to dissipate the power, they nearly always sound better.

Biasing them into class A by applying a negative voltage to the output oftern improve performance. People like Hafler and others always do this when using chips and use improve supplies.

But chips can usually only swing a milliamp if that, and then revert to A/B mode, certainly not 10 or even 40 milliamps.

Even simple CRC supplies with nice BG filter caps kill all three pin series regulators when using opamps, I think that is where so called opamps can get a bad name. Also lack of correct Pole compensation in certain applications lead to harsh sounding CD players in the early 80's.

I while back Jensen put out a good discrete opamp for pro use, and Forsyth more recently, then there are elaborate designs by Borbely. More recently Pass has turned discrete audio opamp design full circle with very simple 2 stage balanced cascoded dual diff pair designs, with a 2nd stage as a source follower using very little feedback.

He refers to his patented technique as Super Symmetry, or X Theory where very little traditional feedback is used only to match both side of the opamp so distortions cancel out perfectly.

The performance of these very simple designs is stunning. Sterophile magazine has ranked them among the best pre amp & power amps pitted even against the Kells and Mark Levinsons.

But getting back to conventional 8 Pin opamps, I like the TL072 as a good alrounder, it does most things well and unless you need a very quiet preamp, is preferred to the NE5532 IMHO

Ian

scott fitlin
04-24-2004, 01:01 PM
I totally agree with everything you said in this last post!

Incidentally, the discrete 990 op amp from Jensen did and still does sound very good. Summit audio used this in their products, and they are clean, and sweet and musical sounding!

:cool:

Chas
04-24-2004, 01:44 PM
Shouldn't this thread be off-topic? But I will jump into the frey, anyhow - it's just too interesting.

I think that good audio engineering can extract very high performance from a tube, discrete or chip based op-amp design. You make your choice and squeeze every bit of performance you can out of it.

Personally, I use simple SE and fully balanced tube designs with no global feedback and regulated power supplies as my benchmark. Of course, I wouldn't ever consider tubes for say, a phono preamp - there are just too many obstacles to conquer. So, I am referring to preamp line stages, crossovers and power amps.

I have heard great stuff using all the devices available to us, however for a DIY'er that is just getting into building things, IC op-amps, in my experience, can run with the best of them.

I am surprised to hear of TLO's being still appreciated these days, I haven't used them in twenty years. Maybe, I should have a listen.

I like AD744's and AD 845's depending on the application. But, and this is a BIG BUTT, they must have super low impedance power, preferably with two stage regulation. This peculiarity for power seems to make or break an IC op-amp based circuit for some reason.

Ian Mackenzie
04-24-2004, 04:06 PM
Sorry I should have posted in off topic.

Chas, I think we are all showing our age, TL072 I mean...LOL

So you are a Tube Dude, well as they say if it don't glow, it don't go.

Great to see there are some of use would mess with this sort of thing on the forums.

I'm amazed how well the vintage JBL's brush up with AAA electronics, their reputation is even more well deserved.

Ian

jtgyn
04-25-2004, 05:52 AM
To quote from "B.Ludwig@mx.Uni-Saarland.de" a DIYer for amp modifications....

"Most of the music we listen to nowadays has passed through more than one 5534 in the studio-equipment anyway."

Regards Scott

Chas
04-25-2004, 07:26 AM
"Most of the music we listen to nowadays has passed through more than one 5534 in the studio-equipment anyway."

Very true! Hey, maybe that's why I like 50's and 60's jazz on vinyl?
:D