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.
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.
Hi Siva,
You should try ASAP...
I'm enjoyoing the Fremen Edition beta now, it sound gorgeous
You should try OPA827, it's an incredible subjective performer on I/V.
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
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).
Siva, can you give me an opinion on post #8's grounding problem?
Also my SACD player uses dual opamps for I/V, I've mounted OPA827s on browndog adapter with GREAT results.
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
, 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
Kindly excuse this basic question
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.
Here's a sneak peek at that discrete opamp design:
http://www.diyaudio.com/forums/analog-line-level/207871-lf03-discrete-opamp.html#post2928775
Please post follow-ups related to that design on that thread to avoid clutter here.
Pure current amp might be fine if you are using active crossovers. But if you are driving commercial speakers that were designed for voltage source amplifiers, then you get sonic imbalance. This does not happen with the MyRef type design with voltage feedback.Kindly excuse this basic question
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
Hi
I tried 3 different caps in position C5 and want to share my experience.
1st was Wima MKP10 0.1uf/250v : Musical sound, very good definition, wide soundstage, overall very good cap.
2nd was russian K71-7 polystyrene 0.1uf/250v : bit wider soundstage than MKP10, slightly worse definition and a slight "grey" colour to the sound. Wasnt thrilled.
3rd was Rifa PME271M (m. paper) X2 0.33uf/275v : This is a winner! Musical sound, blacker background, excellent definition and seperation. Although the cap is huge and Dario suggested a small cap in that position, im very glad i tried it. This cap is higly recommended!
One question: Is this positive change to the sound, related to the increased capacitance of the Rifa cap?
Im using Dario's BOM for the audiophile parts with the exception of sonicap instead of the mundorf as input cap and MUR 860's in the rectifier
I tried 3 different caps in position C5 and want to share my experience.
1st was Wima MKP10 0.1uf/250v : Musical sound, very good definition, wide soundstage, overall very good cap.
2nd was russian K71-7 polystyrene 0.1uf/250v : bit wider soundstage than MKP10, slightly worse definition and a slight "grey" colour to the sound. Wasnt thrilled.
3rd was Rifa PME271M (m. paper) X2 0.33uf/275v : This is a winner! Musical sound, blacker background, excellent definition and seperation. Although the cap is huge and Dario suggested a small cap in that position, im very glad i tried it.
This cap is higly recommended!One question: Is this positive change to the sound, related to the increased capacitance of the Rifa cap?
Im using Dario's BOM for the audiophile parts with the exception of sonicap instead of the mundorf as input cap and MUR 860's in the rectifier
Are you talking about C4 (rail-to-rail bypass near the LM3886) or C5 (snubber cap across AC rails)?
C4 can make a huge difference to sonics, but C5 probably will not have significant impact. C5 is "visible" to the rest of the circuit only in the brief periods when the rectifiers conduct on each half cycle. Its impact is limited to quietening the background hash of 50/60 Hz harmonics.
Hi siva.
I am talking about C5. The differences among the caps i tried were not subtle, the rifa cap being the clear winner. My knowledge of electronics is virtually non-existant so i cannot backup my claims-but the perceived differences among the caps where more than evident. Maybe the Rifa cap filters garbage from mains more efficiently? I cant really say
I am talking about C5. The differences among the caps i tried were not subtle, the rifa cap being the clear winner. My knowledge of electronics is virtually non-existant
so i cannot backup my claims-but the perceived differences among the caps where more than evident. Maybe the Rifa cap filters garbage from mains more efficiently? I cant really say
Everyone refers to the MyRef RevC schematic. C5 is in the power supply part of the schematic.