[DRKreiger]

That's good. Transparent and accurate is what i am after. The preamp will handle the soundstage quite well. I need a clear, and very undistorted signal.

Running this Sound card to a 6AK5/5654W preamp, and then to a converted Conn 12ax7 and 7868 Organ amp.

Thank's for the input. Did you add decoupling caps to the circuit? I am a bit concerned that I will need to improve on the power conditioning on the TH Omega card.

 

[imran27]

That's good. Transparent and accurate is what i am after. The preamp will handle the soundstage quite well. I need a clear, and very undistorted signal.

Running this Sound card to a 6AK5/5654W preamp, and then to a converted Conn 12ax7 and 7868 Organ amp.

Thank's for the input. Did you add decoupling caps to the circuit? I am a bit concerned that I will need to improve on the power conditioning on the TH Omega card.

LME49720 is very sensitive to RFI. You will need good shielding.
On my XD-05, decoupling provided no change. Neither better nor worse, no change at all. I guess it's because it is very well bypassed in the circuit itself, any more decoupling is sort of redundant in my case.

Do note though, LME isn't good at layering the sounds properly. Subtle tone variations often go unnoticed. You may want OPA1612 or Burson V5i-D for that purpose. Those 2 are also pretty good opamps.

 

[rikk009]

My experience with LME49720 and LME49990 was....Former one sounds more laidback and musical and later one more punchy bass and dynamics. So I use 990 for fast music and 720 for everything else. Mind you I am comparing 720(single) vs 990(dual on an adaptor) in Mstage HPA-1.

 

[Rroff]

That's good. Transparent and accurate is what i am after. The preamp will handle the soundstage quite well. I need a clear, and very undistorted signal.

Running this Sound card to a 6AK5/5654W preamp, and then to a converted Conn 12ax7 and 7868 Organ amp.

Thank's for the input. Did you add decoupling caps to the circuit? I am a bit concerned that I will need to improve on the power conditioning on the TH Omega card.

I've no experience of the JRC4580 but I've used TI's version the RC4580 a fair bit and its pretty decent if you are looking for accurate, neutral and largely transparent sound so I suspect the JRC is the same - like many that are largely transparent it is a bit "raw" sounding and lacks the "musicality" of some other op amps but for reference use its pretty close to ideal. (Along similar lines if you are using current hungry headphones the NJM4556A is pretty good where you value accuracy and transparency but personally I don't rate it with high impedance, less current demanding headphones like the Sennheiser HD600 series where I've heard it struggle at times and again is a bit "raw" sounding).

The LME49720 comes across as a bit clearer and a bit crisper sounding but that is partly because it also seems a touch "lean" as someone else noted - I've found all of that line up seem very sensitive to power supply noise and RFI if you want distortion free as well (The LM4562 very easily starts to sound a bit metallic with power supply noise and is often greatly enhanced with extra decoupling capacitors in my experience though I've never scoped it, etc. for hard data - I've only a fairly basic oscilloscope and most of my limited training in using one is for electronics in general and not so much audio engineering).

The OPA1612 is a pretty excellent op amp that I've never noticed struggling for articulation, etc. but its a touch light in the bass a touch bright towards the upper end and seems to takes a good bit of use before it loses a bit of a "synthetic" kind of colouration to the sound - I've never really been much of a believer in "burn in" with op amps but this one definitely takes awhile before the sound becomes more natural and it isn't just me getting used to it as I've a few dozen of them and its very noticeable when picking out a new one that I've not used before - one of my most used headphone amps is a reworking of the O2 I did for USB power using the OPA1612 for gain and LMH6643 for buffers and its immediately noticeable if I change the OPA1612 out - personally I highly rate it as an op amp for audio but for reference use it close but not perfect. If you aren't 100% looking for reference but want accurate and transparent but with a good musical "signature sound" then one of the OPA16xx line like the OPA1612 would probably be ideal.

 

[DRKreiger]

OK.. thank you, great info. I am looking at the OPA1612, and it seems only a surface mount is available. Would this require an adapter to fit into the DIP8 socket on my card? I am seeing some already mounted to adapter ones available, and pricing is not too bad.

 

[Rroff]

Yeah requires an adaptor unfortunately - at least I've never seen them available in DIP format - most of the OPA16xx series is either SOIC or stuff like VSON which is even worse for DIYing heh.

 

[DRKreiger]

So this would be the easiest option then for that solution?
https://www.ebay.com/itm/1PCS-TI-OP...770539?hash=item33dae4f6ab:g:LWMAAOSwUchaB6-h

 

[DRKreiger]

Alright.. So the LME 49720's are all in the card. Running some music to get a bit of current through them before i analytically listen. But they are definitely a wider soundstage than the JRC 4580's. The mids are a bit fuller, and tighter bass. The biggest thing i can attest to is the clearer 5k and above.

 

[Rroff]

So this would be the easiest option then for that solution?
https://www.ebay.com/itm/1PCS-TI-OP...770539?hash=item33dae4f6ab:g:LWMAAOSwUchaB6-h

Assuming its the genuine op amp then yeah that would make it easier - if you've got a reasonably precise soldering iron, some flux designed for soldering ICs (helps to hold the IC in place and reduces chance of accidentally bridging connections) and some moderate soldering experience its pretty easy to mount them on an adaptor yourself and the adaptors can be bought really cheap.

 

[raoultrifan]

I have a bunch of ST4580 in my Mackie MR6mk3 active speakers (about 6 x ST4580 per speaker), sound is very good actually...everything sounds neutral. I like most that despite such an opamp is being used, noise is very well kept under control: unless I'm placing my ear 10" in front of the tweeter I can't hear any noise (and this test was done at 1 AM when a single fly could sound really noisy).

Under most circumstances opamps should not sound different, unless there are "visible" differences in their datasheet. Although, we all know that opamps may sound different because:
- They have different CMRR/PSRR figures and the PSU from the circuit may be noisy or having high ripple, then the opamp having a better CMRR/PSRR will sound less grainy and with better details and transients.
- FET/JFET-input may sound different than BJT-input opamps (it may worth reading OPA604 datasheet regarding odd/even harmonics).
- Different noise specs will make a difference, especially if used in Voltage Gain (pre-amplification), but also in Low Pass Filter of a DAC.
- The circuit around the opamps may be configured for some opamps only (usually related to opamp decoupling, but also input or output impedance match with the circuit in front or after the opamp.
- Some opamps may oscillate and sometimes the addition of many undesired harmonics may sound better to some ears.

 

[imran27]

I have a bunch of ST4580 in my Mackie MR6mk3 active speakers (about 6 x ST4580 per speaker), sound is very good actually...everything sounds neutral. I like most that despite such an opamp is being used, noise is very well kept under control: unless I'm placing my ear 10" in front of the tweeter I can't hear any noise (and this test was done at 1 AM when a single fly could sound really noisy).

Under most circumstances opamps should not sound different, unless there are "visible" differences in their datasheet. Although, we all know that opamps may sound different because:
- They have different CMRR/PSRR figures and the PSU from the circuit may be noisy or having high ripple, then the opamp having a better CMRR/PSRR will sound less grainy and with better details and transients.
- FET/JFET-input may sound different than BJT-input opamps (it may worth reading OPA604 datasheet regarding odd/even harmonics).
- Different noise specs will make a difference, especially if used in Voltage Gain (pre-amplification), but also in Low Pass Filter of a DAC.
- The circuit around the opamps may be configured for some opamps only (usually related to opamp decoupling, but also input or output impedance match with the circuit in front or after the opamp.
- Some opamps may oscillate and sometimes the addition of many undesired harmonics may sound better to some ears.

Add to that:
- Input capacitance
- Open loop gain effects
- Phase response
- Input current/voltage noise density
- Output impedance over spectrum
- EMI/RFI sensitivity

 

[raoultrifan]

Well, most are already included in the "datasheet differences".

Again: a circuit is usually created across a dedicated opamp, so usually a possible upgrade should be done with an opamp having similar specs (but better CMRR/PSRR and lower noise and THD), at least in regard with "input bias current", "offset voltage", "output impedance".

've noticed myself improvement in LPF stage when swapping LME49860 with MUSES8820, but never noticed any differences when swapping LM4562 with LME49720 or vice-versa, mostly because these opamps are internally sharing an identical schematic.

I've also noticed improvement in I/V when using MUSES8920 and MUSES01 against NE5532 or LME49720, but never noticed any difference if swapping LME49702 with LM4562.

 

[imran27]

Well, most are already included in the "datasheet differences".

Again: a circuit is usually created across a dedicated opamp, so usually a possible upgrade should be done with an opamp having similar specs (but better CMRR/PSRR and lower noise and THD), at least in regard with "input bias current", "offset voltage", "output impedance".

've noticed myself improvement in LPF stage when swapping LME49860 with MUSES8820, but never noticed any differences when swapping LM4562 with LME49720 or vice-versa, mostly because these opamps are internally sharing an identical schematic.

I've also noticed improvement in I/V when using MUSES8920 and MUSES01 against NE5532 or LME49720, but never noticed any difference if swapping LME49702 with LM4562.

LM4562, LME49720 and LME49860 are basically the same opamp.
LME49720 is LM4562 with a better manufacturing.
LME49860 is LME49720 with higher power supply range.

 

[DRKreiger]

A ton of good info to research.

I think I may add decoupling caps to the 49720. Oscillation can h have pretty pronounced impact on a tube amp. I had a zobel (RD Network) across the primary side on my output transformer fail. That was very noticeable. We shall see how these perform, then think of decoupling
Improvement.

I have a few .47uf caps I can donate to the experiment. 2 in parallel should be enough.

 

[imran27]

A ton of good info to research.

I think I may add decoupling caps to the 49720. Oscillation can h have pretty pronounced impact on a tube amp. I had a zobel (RD Network) across the primary side on my output transformer fail. That was very noticeable. We shall see how these perform, then think of decoupling
Improvement.

I have a few .47uf caps I can donate to the experiment. 2 in parallel should be enough.

I tried the panasonic 82uF/35V, 20% tolerance caps on my opamps, especially the LME, didn't make any difference.
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