My "audiophile" LM3886 approach

[ClaveFremen]

Originally Posted by soongsc

The X cap, Dario had posted a pic a while back.

They're Kemet/Arcotronics R46

[skouliki]

Hi. Today i used 2n5484 FETs to bias LME49720 in class A in my AK4396 dac, and i must say it sounds wonderful. Has anyone tried biasing LM318 in MyRef?
Is there any reason not to do it?

[linuxguru]

Originally Posted by skouliki

Has anyone tried biasing LM318 in MyRef?
Is there any reason not to do it?

Yes, I've done it in my LF01 hybrid/discrete opamp module. The output stage bias current of the LM318 is set at ~1.5 mA, sourcing out of the LM318, i.e. upper transistor is always on. This in turn drives another Class-A biased discrete voltage-follower.

My audible impressions : Smoother, more airy, less edgy than the stock LM318. No significant regression has been observed yet, but similar audible improvements can probably be obtained from Dario's shunt-regulator upgrades alone. Maybe the shunt-regulator upgrades + LF01 will be even better, but that's still on the to-do list.

I've been distracted for the last few weeks running simulations on a discrete opamp designs, so I didn't get around to doing the shunt-regulator upgrades or anything else related to the MyRef.

[linuxguru]

Originally Posted by skouliki

Hi. Today i used 2n5484 FETs to bias LME49720 in class A in my AK4396 dac, and i must say it sounds wonderful.

Slightly OT - what's the bias current, and is it sourcing out of or sinking into the output of the LME49720? FWIW, I found the stock LME49720 a bit disappointing as an I/V converter in comparison to its specs. OTOH, the stock LT1361 sounds very good indeed, even better than the LT1364 and the dark and detailed OPA1612A. It's possible that some of these will sound better in Class-A operation.

[ClaveFremen]

Originally Posted by linuxguru

I've been distracted for the last few weeks running simulations on a discrete opamp designs, so I didn't get around to doing the shunt-regulator upgrades or anything else related to the MyRef.

Hi Siva,

You should try ASAP...

I'm enjoyoing the Fremen Edition beta now, it sound gorgeous

Originally Posted by linuxguru

Slightly OT - what's the bias current, and is it sourcing out of or sinking into the output of the LME49720? FWIW, I found the stock LME49720 a bit disappointing as an I/V converter in comparison to its specs

You should try OPA827, it's an incredible subjective performer on I/V.

[skouliki]

Originally Posted by linuxguru

Slightly OT - what's the bias current, and is it sourcing out of or sinking into the output of the LME49720? FWIW, I found the stock LME49720 a bit disappointing as an I/V converter in comparison to its specs. OTOH, the stock LT1361 sounds very good indeed, even better than the LT1364 and the dark and detailed OPA1612A. It's possible that some of these will sound better in Class-A operation.

I used the lone FET method described in tangentsoft. Biasing Op-Amps into Class A

I have to agree with you about LME49720. Although it sounds wonderful biased in class A i still prefered stock AD8066 in that position. AD8066 was much better in terms of resolution and seperation of instruments, plus it had a huge soundstage. I didnt try biasing AD8066 in class A because all of a sudden it stopped outputing in one of the channels

[linuxguru]

Originally Posted by ClaveFremen

I'm enjoyoing the Fremen Edition beta now, it sound gorgeous

You should try OPA827, it's an incredible subjective performer on I/V.

Great to hear that the Rev FE has come to life!

I'll try to get hold of a few OPA827s and give it a try - they're single opamps, so I'll have to mount it on a dual SOIC8 to single DIP8 adapter like the Sjostrom type C or similar (the Marantz CD4000 uses a DIP8 dual opamp for the I/V converter).

[ClaveFremen]

Originally Posted by linuxguru

Great to hear that the Rev FE has come to life!

Siva, can you give me an opinion on post #8's grounding problem?

Originally Posted by linuxguru

I'll try to get hold of a few OPA827s and give it a try

Also my SACD player uses dual opamps for I/V, I've mounted OPA827s on browndog adapter with GREAT results.

[kuldeepsingh]

Kindly excuse this basic question , but i want to know that wherher this audiophile approach circuit or other my_ref circuits of LM3886 are basically current-drive amplifiers??

And whether it works in current-feedback as shown on this page - Lenard Audio - Education - Amplifiers.

So that the impedance variation of speaker with frequency variation of sound will taken care with variable gain of amplifier. If its true, it means awesome sound

[linuxguru]

Originally Posted by kuldeepsingh

Kindly excuse this basic question , but i want to know that wherher this audiophile approach circuit or other my_ref circuits of LM3886 are basically current-drive amplifiers??

And whether it works in current-feedback...

The output stage is a transconductance amplifier - i.e. a V-I converter known as the Howland Current Pump. The transconductance of the output stage is independent of the load impedance, so it could be considered as current-drive, not voltage-drive.

However, it is not a current feedback topology - the GNFB loop is still a conventional voltage-series feedback loop from the load. Nevertheless, the topology and compensation schema are novel and unique, giving it outstanding sonics even with a commodity opamp and chipamp.