LT1358 or LME49860 ??

[ygg-it]

I'm at a trade-off for my buffer and input pre stage: LT1358 or LME49860 ??
I'm listening both amplifiers, both are excellent but so different….
So specular that seems that the PROS of one chip appears to be the CONS of the other.


What you may like:

LME49860: <-----> LT1358:

LME49860: colorless and neutral <-----> LT1358: emotional, warm-toned and sweet
LME49860: accurate and clean <-----> LT1358: mellow and smoothing
LME49860: clear and unaggressive mids <-----> LT1358: forward and heavenly mid bass
LME49860: soft bass <-----> LT1358: punched and controlled bass
LME49860: airy and sharp high <-----> LT1358: polish at the high edges
LME49860: revealing on female voice <-----> LT1358: revealing on male voice

What you will not like:

LME49860:sometimes harsh-toned <-----> LT1358: sometimes muggy and confined soundstage
LME49860:flat and boring <-----> LT1358: lower resolution, higher distortion


Do you agree on my acoustical analysis?

[AndrewT]

a comparison of both to a B1 or a DCB1 would be helpful.

[abraxalito]

Originally Posted by ygg-it

I'm listening both amplifiers, both are excellent but so different….

Internally they're rather different too - the National is a traditional voltage feedback whereas the LT is CFB with an input buffer on the current mode input to make it VFB in practice. Have you tried comparing LM6172 against LT1358? They're much more similar parts design-wise but the LM is considerably cheaper. I'm getting excellent sonic results from LM6172 as a DAC I/V, its high bandwidth does need more care in layout and implementation though.

[ygg-it]

At the end, I can't give up the microdynamics of LME49860.....


Here is my final chain:

LME49860 (BUFFER IN & PRE) + LT1364//AD826 (BUFFER OUT)


Regarding the heavenly LT1358, I must say that at the end is not so natural and colorless...

Sergey Romanov says: "Coloring, particularly of vocals, is the addition of unnatural or irritating intonations to the timbre. Coloring often provokes a desire to switch the sound off but never to make it louder"

See schematics:
EARPHONE PURE AUDIOAMP II

[abraxalito]

Originally Posted by ygg-it

See schematics:
EARPHONE PURE AUDIOAMP II

That 'RF block ferrite' won't do much good where you've put it. If you check out impedance plots of ferrite beads at RF frequencies, you'll find they top out at a few kohms in the best case, in the worst a few hundred ohms. Yet your impedance looking in is 47k5 - so the best you can expect in your implementation is probably a 1dB reduction of RF. Ferrites are generally used when circuit impedances are much lower than this.

Secondly, don't make the input ground the same symbol as the rest of the circuit grounds then it won't get mixed up with them. If you want to keep your ferrite blocker, put it in the input ground, not the signal lead.

Third - your three terminal regs won't have much rejection above 100kHz, so as you appear to be concerned about RF, give them some input filtering. Oh and 10nF on the adjust pin is barely noticeable at all in ripple rejection terms - make it something substantial. What's the reason for non-polar electrolytic configuration on the reg inputs btw? If the input does go negative (it won't) you'll be waving goodbye to your LM317

If you'd like more feedback, just ask...

[ygg-it]

Hello, thanks!
I like reply as yours since seems to be sincere and not just criticism.

1) Ferrites are generally used when circuit impedances are much lower than this..

You are asbolute right. I took it away, does not make much sense here.
Now my low pass RF filter is only the serial resistance and the input opamp capacitance. I tested. It is ok !


2) here is my site and my Grounding Technique. Anyway my site is quite old and I have to redesign it (from E.P.A. AD826 to E.P.A. II).

Noise & Stability design solutions

3) here is about NP capacitor and low capacitance:

Less capacitance makes LM317/LM337 sound much better, despite higher noise. (ref. "LM317, understanding and listening" by Eric Juaneda). NON-POLAR (or better, BIPOLAR) electrolytics show substantially less distortion than the polar ones. (ref. "Capacitor sound 5&6" by Cyril Bateman; "A real time signal test for capacitor quality" by John Curl & Walt Jung).
I did a listening test and both work!

4) If the input does go negative (it won't) you'll be waving goodbye to your LM317

I did not understand what you suggest

5) If you'd like more feedback, just ask...

Yes please, as I said you are welcome!

6) did you noticed the 3x input capacitors MKT KONEK: they sound perfect and overreached the MKP in a blind listening test!

[abraxalito]

Originally Posted by ygg-it

Hello, thanks!
I like reply as yours since seems to be sincere and not just criticism.

You are welcome. Yes, this is intended to be constructive criticism

Now my low pass RF filter is only the serial resistance and the input opamp capacitance. I tested. It is ok !

I'd suggest you try with a bigger cap on the input. The opamp's own input capacitance is small (a few pF) and probably rather non-linear. In my own designs I go for a -3dB input frequency around 200kHz, determined by not wanting a perceptible droop in the response at 20kHz. -3dB at 200kHz gives around -0.1dB at 20kHz and I don't think I could hear that.

2) here is my site and my Grounding Technique.

Thanks - I tried the link but here it doesn't work. Perhaps being blocked by the Great Firewall.

3) here is about NP capacitor and low capacitance:

Less capacitance makes LM317/LM337 sound much better, despite higher noise. (ref. "LM317, understanding and listening" by Eric Juaneda).

OK I will search for that one and see what's new there. Thanks for the reference.

NON-POLAR (or better, BIPOLAR) electrolytics show substantially less distortion than the polar ones. (ref. "Capacitor sound 5&6" by Cyril Bateman; "A real time signal test for capacitor quality" by John Curl & Walt Jung).
I did a listening test and both work!

I have read Cyril Bateman's articles but it was quite a while ago. From memory they were about capacitors passing audio signals not power supply smoothing. In power supply smoothing we do need the capacitor to distort the signal.

4) If the input does go negative (it won't) you'll be waving goodbye to your LM317

I did not understand what you suggest

I was rather obliquely pointing out that here the output from the rectifiers is unipolar, quite unlike an audio signal. So you definitely don't need non-polar caps. But if you really like the sound, who I am to stop you

5) If you'd like more feedback, just ask...

Yes please, as I said you are welcome!

One other point I noticed is that although you're concerned about RF (rightly, IME) you have no mains input (common mode choke) filter. I'd definitely use one or even perhaps two in series. Pick them with the lowest current spec you can find (I've not found lower than 1A though). Also your transformers look a bit underpowered at only 2VA each.

6) did you noticed the 3x input capacitors MKT KONEK: they sound perfect and overreached the MKP in a blind listening test!

Yep I did notice that - but are those caps better than a straight wire? Given that you've got offset voltage adjust I was wondering why you needed them?

[ygg-it]

Since I cannot give up to the emotional warm-toned LT1358 too,
yesterday I found an excellent configuration that sounds heavenly (even if much different) and mix the PROS of the two!


LT1358 as buffer input

LME49860//AD826 as buffer output
The diving capability stays the same (I worried about the less driving capability of the LME49860...)

= 2.8 Vrms @ 33 ohm @ 1% THD+N

Release 030: much less analytical than the release 029 but much more emotional .

EARphone PURE AUDIOamp II with LT1358 + LME49860 (under testing) on Flickr - Photo Sharing!

[ygg-it]

@ abraxalito : i will reply soon...pls stay tuned...


LT1358 as buffer input is still too much coloured and mellow.
I'm moving it as buffer output.

LT1364 is too harsh

LME49860 is excellent as buffer input

AD826 is still perfect as buffer output

I'm testing the new chain: LME49860 + LT1358//AD826

....

[ygg-it]

-- -3dB at 200kHz gives around -0.1dB at 20kHz and I don't think I could hear that.

Unfortunately I’m able to hear a 100 pF capacitor on input....


-- I tried the link but here it doesn't work. Perhaps being blocked by the Great Firewall.

mmmm. please wait till my site will be rebuilt with the new version of the E.P.A. II
"http://ygg-it.tripod.com/id16.html"


-- From memory they were about capacitors passing audio signals not power supply smoothing.

The article is referred to biased capacitors (and power supplier supply rails do bias...) and I believe that in any amplifier the closed electrical loop of the sound signal slightly includes also the power supply capacitors even if there is a regulator after ...



--One other point I noticed is that although you're concerned about RF (rightly, IME) you have no mains input (common mode choke) filter.

I usually use a power supply network conditioner.
Anyway any network conditioning can modify (better (clean) or worse (less emotional)) the sound,
so i decided not to put at all


--Also your transformers look a bit underpowered at only 2VA each.

They deliver 110ma and the total quiescent current of my 3 opamp (LT1358, AD826,LME49860) is 2+2+6.8+6.8+5.1+5.1 = 27.8 ma.
I agree they might work quite saturated (probably before the opamps clipping..), but do you know how much is 80ma in an headphone ?


--Given that you've got offset voltage adjust I was wondering why you needed them?

Two reasons: my offset circuit is not a servo, so if I change the source, the input DC might change.
Second:as you may see I use huge resistor (1M6) to bias the opamp in order to lower the offset-circuit electrical and sound influence.
If I take away the capacitor, the impedance seen by the offset circuit significantly drops and also changes according to the volume knob setting

__________________


By now an excellent configuration in my amplifier is

LME49860 as buffer input and first preamp stage, AD826 as "master" buffer output, LT1358 as “slave” buffer output configured as a unity gain buffer

but I'm realizing that now it is becoming just a matter of personal taste....