My amp is current running in "enhanced HD mode" 
I added a 680K nested feedback resistor across C7 as discussed earlier.
Initial impressions are slighlty reduced upper mids and treble... the music sounds like it's a bt further away. Prior to this I did find the amp a tiny bit "spotlit" in the upper mids, now it might be a touch the other way. What is noticeable is an improved resolution of upper mid percussion etc. I need to do some 'serious' listening when the family is out to get a better handle on this, but intial impressions are that this is indeed a significant improvement.
I added a 680K nested feedback resistor across C7 as discussed earlier.
Initial impressions are slighlty reduced upper mids and treble... the music sounds like it's a bt further away. Prior to this I did find the amp a tiny bit "spotlit" in the upper mids, now it might be a touch the other way. What is noticeable is an improved resolution of upper mid percussion etc. I need to do some 'serious' listening when the family is out to get a better handle on this, but intial impressions are that this is indeed a significant improvement.
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Hello zman01,
Please see attachment. I have highlighted in yellow the parts which I checked/replaced .
There were a few errors
Please use caution and recheck again, I am a human too and prone to mistakes
.regards
Prasi
edit: C1 and C3 need to be audio grade, I have changed them.
Also 0.22 ohm resistors need to be non-inductive.
See if you can find 220uF 63V caps in 5mm pitch 13 mm dia, smaller package is better.
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My amp is current running in "enhanced HD mode"
Hello Dave,
That's a very smart way to name it
. Although I read the post before, just now it struck me what you mean by enhanced HD mode.I am most interested to hear your impressions after your serious listening tests that you are planning to do.
regards
Prasi
HD = Hugh Dean? Harmonic Distortion? High Definition?
Aptly said about HD . it's true.
Thanks!, Here you go sir!
regards
Prasi
Hello all,
As an addition to the post, I wanted to share following info with potential builders using manufactured PCBs.
The PCB has planes duplicated on top so it will be manufactured as double sided PCB with pads on top layer too.
The mounting hole for MOSFETs has 6.3mm dia on the PCB and the holes are 81.3 mm apart.
After fitting the mosfets (with legs bent) to heatsink, insert the populated PCB from top and then adjust the mounting hole standoffs accordingly. solder the legs carefully from top.
Corner Mounting hole pitch in horizontal direction: 92mm.
Corner Mounting hole pitch in vertical direction: 83mm.
The drill template is attached for convenience, do confirm the above dimensions once, as I used online gerber to pdf converter.
Hope this helps in your build planning.
regards
prasi
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One issue with this topology is the resolution. So if the change is toward better resolution, it is very probably an improvement.
Another issue is the tonality. Not really a problem because most people do not even know what the right tonality is. But if you care, you may want to see if there is improvement in this department.
But changing the compensation may change how you feel in the long run and Mooly's design is already proven by time, at least to him, so beware of that.
To know right from wrong, independence of speaker tonality, you can compare with the source/input.
All cfp amps that i know of have 'wrong' tonality. I don't know the reason so i don't know how to fix it. Best guess is the low damping.
AD823 is an opamp with cfp output. It has a lot of things for enjoyment. But the output current is too low too. I use buffer at its output, enclosed inside the feedback loop. I use AD845 so not to change what i want to retain. This is all for high frequency channel only.
So, I don't really care much for tonality except for cfp amps.
How do you do this?
I can sympathise with this view but I think it's dangerous to generalise.
Many years ago I built an amp with a similar o/p stage to the MMAMFM. It sounded dull. It put me off this topology. However the MMAMFM is anything but dull. Looks like my bias was wrong.