[Andrea]

Well, it seems like eventually I've 'settled for less'.

Today I tried just substituting the standard opamps with AD823 for gain and AD8056 for buffer. Great!! Quite a bit better than the standard opamps to me.


The AD8056 is a double opamp capable of 60 mA output current per channel (and 110 mA 'short circuit current'), nearly twice that of the OPA2227. Only 'downside' is, it will run perfectly with 9 volts, optimally with 12 volts, but doesn't accept any higher (datasheet tells that 13.2V is 'absolute maximum'). The AD823 is a rail-to-rail double opamp, and as such it also works perfectly with a single 9V battery (obviously even better with 12V).

The result is a sound a little brighter than before, with powerful/deep/tight bass, and very clear&clean midrange and treble. Vocals are smooth. Guitars, violins, etc. sound excellent.


In short, I'm satisfied with this (so simple) upgrade enough to not want to experiment anymore. This "maxed out Zero amp" works great.

edit- I forgot that the mod has had a pleasant side-effect: the complete disappearing of any glitch at power on and off

 

[Andrea]

This thing rocks!

 

[Andrea]

7th post in a row! My record

 

[naughty#9]

i'm very pleased with mine still. i have not changed anything on it and don't really plan to.

i am now using mine w/ a set of akg k240s almost exclusively and i am really happy. i didn't care for the ms-1's i had, so i sold them and got the akg's, which i am very happy with. i also use it with a set of the studiophonic hearos (amazon deal a while back) and koss ksc-35's. overall, i'm really happy w/ the amp and the headphones i have purchased lately and i have no interest in buying another amp, as i think this is the best i can do for the price i am willing to spend.

my enthusiasm is not enough to warrant 7 posts in a row, but i'm still pretty damn happy with this amp

 

[skysaxon]

Quote:

Originally Posted by Andrea Today I tried just substituting the standard opamps with AD823 for gain and AD8056 for buffer. Great!! Quite a bit better than the standard opamps to me.

Excuse my ignorance on the subject of opamps but where do you purchase them? Looking at the Analog Devices site, I see there are many different versions of the AD823 and AD8056. Which ones to use for the Zero? Thanks!

 

[nerd1949]

sxr71,

You're right about the rail splitter. It's got a pretty limited current capacity and I bet it's getting pretty hot with 27 volts. The chips can handle the voltage though. It's not the voltage per se, I saw in another thread that the gain chip is biased into class a which further increases the current drain. Raise the voltage by 3 and you are raising the bias current by 3. Does any one know the value of the bias resistor (I'm assuming it's just a resistor), and you can calculate the current for 27 volts.

I like what I hear about this app though, maybe when payday comes...

 

[sxr71]

Quote:

Originally Posted by nerd1949 sxr71, You're right about the rail splitter. It's got a pretty limited current capacity and I bet it's getting pretty hot with 27 volts. The chips can handle the voltage though. It's not the voltage per se, I saw in another thread that the gain chip is biased into class a which further increases the current drain. Raise the voltage by 3 and you are raising the bias current by 3. Does any one know the value of the bias resistor (I'm assuming it's just a resistor), and you can calculate the current for 27 volts. I like what I hear about this app though, maybe when payday comes...

Surprisingly the rail splitter isn't really getting all that hot. On the other hand the OP-AMPs get pretty toasty. I really don't know the value of the bias resistor, but I suppose the amp eats up a lot of power in this 27v situation. The good thing is that it will still work while the batteries decline to as little as 3v per battery. Still the area under that portion of the curve must be pretty small if you understand what I'm saying.

I discovered something else (and people might think I'm crazy) but the amp sounds better with 3 General Purpose 9v batteries than with 3 9v Alkaline batteries. I don't know why other than to guess that it has to do with lower internal resistance (at least initially).

However, you raise a very pertinent point that basically once we calculate the current that my little mod generates, maybe we can just switch OP-AMPs to get the same result with 9v and keep the amp portable.

 

[nerd1949]

Quote:

Originally Posted by sxr71 Surprisingly the rail splitter isn't really getting all that hot. On the other hand the OP-AMPs get pretty toasty. I really don't know the value of the bias resistor, but I suppose the amp eats up a lot of power in this 27v situation. The good thing is that it will still work while the batteries decline to as little as 3v per battery. Still the area under that portion of the curve must be pretty small if you understand what I'm saying. I discovered something else (and people might think I'm crazy) but the amp sounds better with 3 General Purpose 9v batteries than with 3 9v Alkaline batteries. I don't know why other than to guess that it has to do with lower internal resistance (at least initially). However, you raise a very pertinent point that basically once we calculate the current that my little mod generates, maybe we can just switch OP-AMPs to get the same result with 9v and keep the amp portable.

I don't think you're crazy about the batteries. I have an amp that sounds better with 2 9v NiMH cells than with 16 AA Alkaline cells. I've found http://tangentsoft.net/audio/opamp-ps.html really helpful.

 

[sxr71]

Quote:

Originally Posted by nerd1949 I don't think you're crazy about the batteries. I have an amp that sounds better with 2 9v NiMH cells than with 16 AA Alkaline cells. I've found http://tangentsoft.net/audio/opamp-ps.html really helpful.

Try NiCd, they supposedly have the lowest internal resistance of any consumer battery chemistry. BTW, that is an awesome article.

 

[Andrea]

Quote:

Originally Posted by skysaxon Excuse my ignorance on the subject of opamps but where do you purchase them? Looking at the Analog Devices site, I see there are many different versions of the AD823 and AD8056. Which ones to use for the Zero? Thanks!

You need the "PDIP" version of both. You can have samples sent to you.

Expect a more forward/immediate sound than before, maybe a bit lighter (I still need to 'burn in' my amp anyway), yet the timbre (aside from balance) feels somewhat warmer, more like 'orange' and less like 'blue' to me, which is welcome here as I like warm colors better

 

[Andrea]

Quote:

Originally Posted by nerd1949 Does any one know the value of the bias resistor (I'm assuming it's just a resistor)

10K

 

[Andrea]

Forgot to say that since I switched opamps I've only used a 9V non-rechargeable battery to power the amp, as my only regulated PSU was temporarily elsewhere. Tomorrow I'll try it with better power and see.

 

[tortie]

Quote:

Originally Posted by ryangs I am wondering if this background hiss is a problem with the cmoy design, and if I should be looking at a MINT design instead?

No background hiss with my Cmoy....plus mine has a volume knob.

LOL

For pete's sake, sell that amp and replace it with an amp that has one. I cant imagine how you could live with an amp that doesnt have volume control.

 

[Andrea]

I'll repeat myself: this thing rocks!

As burn in has progress, the sound is gaining the final touch of smoothness and fullness needed for me to become confident that this is a "bang for the buck" sound for a $80 worth amplifier!

I might be once again victim of my weakness of doubling the things I'm more fond of: that is, I may soon buy my '2nd Zero'

 

[Andrea]

Another experiment -- out went the AD8056 and in went a second AD823.


I'm surprised. Sounds definitely better: that orange-ish tone went away, and left a more neutral timbre and significantly more refinement. But my surprise arises mostly from the greater bass impact and fullness. Wow, that's what my 595 needed. I really didn't fancy the AD823 having such a plucky character. I think I'll stop here (this time).