Can someone tell me WHY op-amps sound so good?

Hantra · « **on:** 9 Jun 2003, 02:58 pm »

All:

I just got a pair of LM3875 based monoblocks from Scott Nixon, and they murder my Aloia amp. They sound way better, even with the Black Gate break-in issues. Why?

According to National Semiconductor, the LM3875 is a class B design. Shouldn't class A sound better according to conventional logic? This is all foreign to me pretty much, b/c I don't know the technical details. I do know what my ears tell me, and I do know that these are killer amplifiers. Aloia is one of the best solid state amps I have ever heard, and for it to be smashed by this is quite astonishing.

OTOH, the best SS amp I have ever listened to is Linn's Klimax Solo monoblock. After reading in Stereophile last week that they are OP-AMP based, this makes it even more intriguing for me.

So, is it purely the short signal path that makes these amps sound so good? Is it the simplicity? I mean, NS's site says the LM3875 would be GREAT for "high-end stereo television sets".

Hmm. . .

Tyson · « **Reply #1 on:** 9 Jun 2003, 04:06 pm »

I remember talking to Michael Barnes of nOrh about this a while back, and to the best I can remember it had to do with the fact yes, OP AMPS are class B, but they are able to switch so fast and so precisely that for all intents and purposes you are able to get class A type sound from them. The limitation on them is of course in ultimate power and current deliver compared to discreet output designs.

Jay S · « **Reply #2 on:** 9 Jun 2003, 04:17 pm »

I was quite amazed how good my Le Amps sounded when paired with Guan's DeZorel Audio Reference Senior power filter. IC-based amps don't get the same respect as discrete amps but in my mind they certainly can deliver great sound and a reasonable amount of current.

Maybe there would be someone in your area with Le Amps and you guys could do a comparison with your new Scott Nixon IC based amp!

JohnR · « **Reply #3 on:** 9 Jun 2003, 04:22 pm »

One of the theories that was propounded by 47 Labs was that the feedback path can be made very short. I'm really not so sure I believe it but hey! Scott offers his AmpKit as a... ahm, kit, so maybe someone with less projects lined up than me should try it

Curt · « **Reply #4 on:** 9 Jun 2003, 04:43 pm »

Quote from: Hantra

All:

I just got a pair of LM3875 based monoblocks from Scott Nixon, and they murder my Aloia amp. They sound way better, even with the Black Gate break-in issues. Why?

According to National Semiconductor, the LM3875 is a class B design. Shouldn't class A sound better according to conventional logic? This is all foreign to me pretty much, b/c I don't know the technical details. I do know what my ears tell me, and I do know that these are killer amplifiers. Aloia is one of the best solid state amp ...

The LM3875 is not an op-amp, it's a full audio amplifier in one package.

There is an input stage, a voltage gain stage, and two pairs of output transistors. The circuit design is very similay to discrete amplifiers.

Today a well done class B discrete amp can approach the class A amp sound, semiconductors have improved. When you make things smaller, like the LM3875s all-in-one-pkg IC design many noise and distortion problems dissapear or are greatly minimised improving the sound quality.

The National Overture series IC amps (and some other integrated circuit audio amplifiers) sound pretty good at low levels. Their limitations are: Watts output (due to package hear dissapation rating) and current output (which is internally limited).

For this IC I find the low current output 4-6 amperes to be the biggest problem. At 56W (100W peak output) in a small room with efficient loudspeakers you are OK volume wise but with 4 ohm loudspeakers that even have slight impedance dips say 3 ohms the current may not be enough to deliver the proper bass and maintain cone control.

This is the LM3875s biggest problem, low current output. But, it does sound good when not stressed.

Hantra · « **Reply #5 on:** 9 Jun 2003, 05:58 pm »

Quote

Maybe there would be someone in your area with Le Amps and you guys could do a comparison with your new Scott Nixon IC based amp!

I did not know that the LeAmps were similar in topology. I don't say this to be mean, or take stabs at anyone, but I have to say the LeAmp is one that I do not care for at all. I had a friend who ordered a pair in advance, and after they broke in, we did some listening. In short, in BOTH of our systems, the Arcam AVR-100 receiver bested the LeAmps. They just didn't do well for either of us.

Nevertheless, I say this to suggest that you get some other amps in your system to try out. The Arcam receiver is a good piece, but hardly as good as many other amps I have had that cost around the same as the LeAmp.

I appreciate the information, and the answers make lots of sense. I have a small room, and my speakers are 89db.

How in the world does Linn get 500 watts into 8 ohms with circuits like this?

B

cjr888 · « **Reply #6 on:** 9 Jun 2003, 07:35 pm »

Not much, but some background here on the Klimax's...

http://linfo.linn.co.uk/binaries/3941C843-BE2B-11D5-A3570002B33574A8/klimax_twin_user_manl.pdf

Read it all, but check out pages 15-21..

http://www.linn.co.uk/spec_sound/products.cfm?range=Power%20Amplifier#160

randytsuch · « **Reply #7 on:** 9 Jun 2003, 09:18 pm »

Hantra,
What's Scott Nixons web page address. I saw it a while ago, and noticed he was going to sell a gain clone, but lost the address.

I am very interested in this because I am in the parts gathering stage of building a gain clone of my own. I am planning on using the LM3886 which puts out a little more power than the LM3875. The 3886 specs a little better than the 3875, but I have seen reports the 3875 sounds better. Will probably build with both of them before I am done.

I am probably going to bridge a pair of 3886, to increase the power/current capabilities. Getting some advice on the best way to bridge them.

But, to get a lot of power from this type of device, National has an app note on how to parallel and bridge them, to the point where I think you can get as much power as you want, as long as you get the heat out.

Randy

cjr888 · « **Reply #8 on:** 9 Jun 2003, 10:45 pm »

Quote from: randytsuch

Hantra,
What's Scott Nixons web page address. I saw it a while ago, and noticed he was going to sell a gain clone, but lost the address.

I am very interested in this because I am in the parts gathering stage of building a gain clone of my own. I am planning on using the LM3886 which puts out a little more power than the LM3875. The 3886 specs a little better than the 3875, but I have seen reports the 3875 sounds better. Will probably build with both of them before I am done.

I am probably going t ...

www.scott-nixon.com

gonefishin · « **Reply #9 on:** 9 Jun 2003, 11:37 pm »

Randy...them little gaincard clones are great! I've heard a couple different versions and you really cannot beat them for easy power for a low dollar.

If I ever get done with my other projects...I've got to build me one of these. But, I still have my plate full right now...and I'm a slow eater

Check out diyaudio's website...they've got alot of people building gainclones.

cjr888 · « **Reply #10 on:** 9 Jun 2003, 11:47 pm »

Regarding Kurt's comments about output, the SACD/SET/Lowther Review (http://www.lowther-america.com/pf_robinson.htm) and if I remember correctly, that Scott has a high sensitivity setup....

...I have to wonder if all these little amps really, really show they magic with exceptionally easy loads even more so... Anyone given them a shot with speakers with very opposite needs? Wondering if given the right scenario really, really thrive...

Hantra · « **Reply #11 on:** 9 Jun 2003, 11:54 pm »

Quote

easy power for a low dollar.

While I agree with the above statement, I do think it is a bit misleading. These are not only the most cost effective amps I have had in my system, but they are the BEST amplifiers I have ever had in my system. Barring none, these sound better than any I have had, and they are not broken in. Far from it. . . .

The amps I have had in my system, in case you are interested are:

Aloia 13.01
McCormack DNA-1 Deluxe
Audio Note Soro SE
Roksan Caspian
Arcam A-75
n0rh LeAmp
Marantz MA700
Dynaco ST-70
Kora Explorer 90

Hantra · « **Reply #12 on:** 9 Jun 2003, 11:57 pm »

Quote

I have to wonder if all these little amps really, really show they magic with exceptionally easy loads even more so... Anyone given them a shot with speakers with very opposite needs? Wondering if given the right scenario really, really thrive...

That's a good question, and one I think I can shed at least a bit of light on. Mine are 89db, and 4 ohms. I have heard many people saying that the Gaincard will drive a very wide range of speakers. Since this is sort of the same concept, but better, it should as well. I suppose it all depends on your room, and volume needs. . .

B

gonefishin · « **Reply #13 on:** 10 Jun 2003, 01:13 am »

Hantra...didn't mean for it to sound like that. From what I've heard from these amps...they can sound great...and for very little money. If you ask me...they should be on everyones "must build" list.

I haven't heard the amps with alot of speakers...but the ones I have heard them on were high eff. speakers. Altec and Lowthers...Sometime in the future I should be able to have a listen to the clone on Edgar TiTans...and When I get my speakers done...I will certainly give them a try on my new speakers too. Of course...building my own gainclone is about third on my "build list". Getting my speakers done is one...then a 300B tube amp...then probably the gainclone.

Take care>>>>

Hantra · « **Reply #14 on:** 10 Jun 2003, 01:18 am »

So, let me understand this. . .

Is it that you think you can better the 300SE, so you are going to build one? Just asking b/c I have never heard one. What don't you like about it ?

B

JohnR · « **Reply #15 on:** 10 Jun 2003, 02:16 am »

Heh, I'm guessing that 'fishing is a bit like me, has a load of projects lined up to build, just wants to try everything

Curt · « **Reply #16 on:** 10 Jun 2003, 08:44 am »

Hantra,

The IRD MB-100s use the same output IC that Linn has used. They simply parallel ICs, like other companies parallel transistors, to get more output power and current.

This MOSFET IC has a 10 ampere output current which is enough (to make sense, this statement, needs to consider the amplifiers rail voltage) to drive all but the most difficult of loudspeakers. It operates in class A mode at normal listening levels and MOSFETS have no crossover distortion. This IC can sound very high-end in a good design.

The LeAmps you had may have had the nOrh DC blocking caps, which effected the sound and imaging. (BTW: IRD never sold MB-100s with DC blocking caps.)

The sound of the MB-100/LeAmp is pretty darn good when used with decent upstream components. But, I'd be the first to say they are not the right choice for large difficult to drive loudspeakers.

JohnR · « **Reply #17 on:** 10 Jun 2003, 09:00 am »

Quote from: Curt

It operates in class A mode at normal listening levels.

Really? What power level is that?

Curt · « **Reply #18 on:** 10 Jun 2003, 09:31 am »

Quote from: JohnR

Quote from: Curt
It operates in class A mode at normal listening levels.

Really? What power level is that?

Hi John,

Class AB means class A operation until some load condition where the bias changes (by being pulled down) effecting the circuit to perform class B.

As you play an MB-100 system louder you will reach a point where you can (slightly) hear the difference, the change from A to B.

The class change varies with the loudspeaker load. It’s probably safe to estimate 50-65W (with average 2-way loudspeakers) at class A.

In my system (currently using ProAc 1SCs) I run very clean to about 80W.

JohnR · « **Reply #19 on:** 10 Jun 2003, 09:34 am »

I know what Class AB means...

How do you figure you can get 50 Watts at class A with a bias current of 30 mA?