[Mad Max]

797B has the edge against 4627-1B as far as soundstage. Or that's what my Minibox-E+ + AD700 showed me.

I have 1357, I got tired of it after a while. I'd say it is more or less on par with 1363 and has bright highs with warm, slightly energetic mids and rounded bass in my gear - very colored and fun. The first time I popped it in it had Grado-like energy with AD700 in the mids, but it lost some of the energy with use. I haven't used it again in a long time.

 

[Mad Max]

*double post*

Edit: How was it again one does class A biasing of mono opamps? And output-bypass?

Edit2: So it's a 2.2k to 10k resistor between pins 6 & 7 for Class A and join pin 5 to 6 (on certain opamps) for output bypass. Thanks, ecclesand.

 

[leeperry]

well, the SS on 1028A is far wider than on 797B, but it's also less versatile...it's kind of triangle shaped(a huge triangle, though

), where 797B would be like a big rectangle, but not as large.

anyway, the sound is a lot "thicker" and impressive on 1028A, and the SS a lot more versatile on 797B...they make for a perfect combo IMHO, 797B on DAC stage and 1028 for final buffer

 

[ecclesand]

Quote:

Originally Posted by Mad Max /img/forum/go_quote.gif *double post* Edit: How was it again one does class A biasing of mono opamps? And output-bypass?

http://www.head-fi.org/forums/f6/opa...ml#post6012420

Use a 2.2k or higher resistor for class a. I have used 2.2k up to 10k.

 

[Mad Max]

What does that resistor do, exactly? How do you know which value between 2.2k to 10k is best or is it experimentally determined?

Edit: I see AD744 there is special because of pin 5 being for "compensation." What is the compensation? None of the other opamps I have have this according to their datasheets, and for 2141A pin 5 is some kind of offset. So pin 5 having some kind of use makes the output bypass mod possible?

 

[12Bass]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif I think many consider that transparency the lack of "color" or the ability to just allow the sound of the amp to come through with no additional influences from the opamps. I think many of use are looking for that and from a purist point of view we should all be looking for that however, some like coloring as it helps with synergy for certain systems. What do you look for 12bass, transparency or some coloring? Just a question to hear different opinions.

Difficult to put into words. I like the idea of transparency... or parts which don't add any coloration to the signal. On the other hand, some components add a pleasing coloration... so it depends. Also varies based upon the application. For musical use, I tend to go more for a sound that accentuates the tonality of the instruments, while hi-fi applications lean more toward clarity and minimal coloration.

 

[ROBSCIX]

Quote:

Originally Posted by 12Bass /img/forum/go_quote.gif Difficult to put into words. I like the idea of transparency... or parts which don't add any coloration to the signal. On the other hand, some components add a pleasing coloration... so it depends. Also varies based upon the application. For musical use, I tend to go more for a sound that accentuates the tonality of the instruments, while hi-fi applications lean more toward clarity and minimal coloration.

I guess it just depends on what you after. Some people like coloring and others don't.

 

[diditmyself]

Quote:

Originally Posted by Mad Max /img/forum/go_quote.gif What does that resistor do, exactly? How do you know which value between 2.2k to 10k is best or is it experimentally determined? Edit: I see AD744 there is special because of pin 5 being for "compensation." What is the compensation? None of the other opamps I have have this according to their datasheets, and for 2141A pin 5 is some kind of offset. So pin 5 having some kind of use makes the output bypass mod possible?

Pin 5 on AD744 is a compensation pin. You're supposed to connect a capacitor from this pin to ground or one of the supply rails. The exact value depends on the circuit and what bandwidth you're after... but this pin is a direct output from the voltage amplification stage and can be used to bypass the internal output stage and use an external output stage instead.

Since the VAS in AD744 is single end it can't operate in anything but class A. There's no need for further Class A biasing when used as described above. A resistor from neg rail to pin 5 does nothing but mock up the circuit.

In general ClassA biasing of opamps might be theoretically appealing, but I don't think it holds up in a blind test. The resistor (or better a constant current source) is choosen to class A bias the output stage to a point where you're certain it will operate in single end class A at all levels.

 

[Spacehead]

Now listening AD8397 directly in a tweaked cmoy-core. I added 10 ohm output resistors and ferrite beads. Dc offset is 8 mV per channel.

AD8397 sounds quite delicious, like orange, nice to rip open and then enjoy bitter sweetness. But actually it is too sweet and oscillates very easily.

I can't yet tell final verdict because there is some oscillations.

When I used this chip on my buffered 100% stable amp, there was less sweetness and more sharpness, but good transitions and bass. Highs are recessed.

 

[12Bass]

What sort of supply bypassing are you using with the AD8397?

 

[Spacehead]

Quote:

Originally Posted by 12Bass /img/forum/go_quote.gif What sort of supply bypassing are you using with the AD8397?

In that poorer cmoy-core I had 0.1 uF from -V to G and +V to G
multilayer ceramic capacitors

In this better buffered cmoy-core I have one Panasonic FC from +V to -V and it seems to keep things stable , as well as being buffered, getting the load of from op amp. (or is 50 ohm resistor too low between WJ buffer and op amp)

I was just about to post that I really like this AD8397. It gives life to music and sounds.


And btw. I just try and test every possible option to get things working. I don't understand that much, but I read a lot.
I have balanced inputs in this current amplifier, so offset is low and stability improves.

 

[Mad Max]

Quote:

Originally Posted by diditmyself /img/forum/go_quote.gif Pin 5 on AD744 is a compensation pin. You're supposed to connect a capacitor from this pin to ground or one of the supply rails. The exact value depends on the circuit and what bandwidth you're after... but this pin is a direct output from the voltage amplification stage and can be used to bypass the internal output stage and use an external output stage instead. Since the VAS in AD744 is single end it can't operate in anything but class A. There's no need for further Class A biasing when used as described above. A resistor from neg rail to pin 5 does nothing but mock up the circuit. In general ClassA biasing of opamps might be theoretically appealing, but I don't think it holds up in a blind test. The resistor (or better a constant current source) is choosen to class A bias the output stage to a point where you're certain it will operate in single end class A at all levels.

So Class A biasing doesn't yield any sonic benefit? Just makes the opamp run a little hotter then, from what I've read. I decided to ask since AD744 and TLE2141A are recommended (744 in the past) for the iBasso D10, either with output bypass and Class A. I haven't tried any of this though, just the opamps as stock.

[rant]Man, I looove AD744's midrange. Something about it sounds sooo right compared to all the others, but I can't put my finger on it.[/rant]

 

[kuben]

Is there a big SQ difference between AD797 ANZ and AR?

 

[kumaiti]

Double post, sorry.

 

[kumaiti]

OMG, 157 pages.


Would any kind soul recommend an opamp with a "bassy" sound signature that is compatible with the Essence STX/ST?
I have a bass-light headphone and I am considering to get some opamps for the Essence to make up for that.

Or at least a more "newbie-friedly" article about these things? This thread is almost like greek to me...


Thanks!