WHAT I DO KNOW
- The 3321 resistors measured 3.3Kohm.
- The 4531 resistors measured 4.5Kohm.
- All the components are repeated somewhat on the underside with another 33078 that seems to be in parallel with this one, however both opamps share the larger 47uF caps, there is one for ea +/-input & low signals present. I think they may be DC blockers, does this seem right? The output lead from C47 goes through R12 (and then another 4.5Kohm on the underside I believe) then through R22 for a total of 12.3Kohms of measured resistance before the +input on pin 3.
- The interior leads of R32 and R22 are connected to the interior leads of the small caps above them and also to a + or - input pin.
- All the caps on the right side (C17-C20) have one lead tied to ground.
Correction on point 3:
All the components are repeated somewhat on the underside with another 33078 that seems to be in parallel with this one, however both opamps share the 4 larger 47uF caps, there is 1 for ea op amps +input & low signals present. I think they may be DC blockers, does this seem right? ex: the output lead from C47 goes through R12 (and then another 4.5Kohm on the underside I believe) then through R22 for a total of 12.3Kohms of measured resistance before the +input on pin 3.
ALSO:
All the components are repeated somewhat on the underside with another 33078 that seems to be in parallel with this one, however both opamps share the 4 larger 47uF caps, there is 1 for ea op amps +input & low signals present. I think they may be DC blockers, does this seem right? ex: the output lead from C47 goes through R12 (and then another 4.5Kohm on the underside I believe) then through R22 for a total of 12.3Kohms of measured resistance before the +input on pin 3.
ALSO:
- Supply rails are +/- 15.1V
- On the board just outside of the pic are 2 little 22uF (35V) caps, one lead of each is ground and the others are tied to the +or- 15V supply rails which power every op amp. So these help supply at least (10) 33078s.
The 22 ufd caps are decoupling caps. They do not ring and have low high impedance at high frequencies. There are also (most likely) some ceramic caps rail to rail.
I like to attach a small leaded cap rail to rail on each opamp. The MC33078 are not fussy about decoupling. But too much does not hurt anything.
I like to attach a small leaded cap rail to rail on each opamp. The MC33078 are not fussy about decoupling. But too much does not hurt anything.
So I followed the advice of a few of you and did not swap these op amps. abraxalito has been a fantastic help through PMs, and with his guidance, I improved the power supply as I much as I could within my abilities. I added 2000uF of Nichicon HZs to the DAC analog supply and the rails of these op amps. The couplers after the DACs were swapped to ClarityCap ESA.
I also rolled the output buffer op amps from the Muses 8920Ds to the Burson Vivid V6s and they really did bring out the dynamics. The Bursons are the real deal and I would highly recommend them. I also added the same additional decouplers to these op amps per abraxalito's instructions. A .1uF MKP cap was also put across the rails as Burson recommends.
The results were quite dramatic. Sounds fantastic... just a huge sound! I wanted to swap the couplers first and see what that did by itself but, due to space, I had to add the analog DAC decouplers at the same time. The first thing I noticed is the brightness the Bursons brought had been warmed up a bit but still razor sharp treble... nice! So I added the op amp decouplers and started listening to stuff. What was immediately noticeable was all the detail in the background. Lush, airy reverb trails around transients, even discovered a few things (not supposed to be there) in some recordings I've listened to my whole life that I've never heard before. Super dynamics and puts life into any decent recording but dynamic recordings are just a sonic assault! I think the only downside is that if there is something a bit too forward in the mix it will tend to really take over, whereas the stock sound is very nice but more compressed and tends to homogenize all material.
Thanks to everyone for their input, but especially abraxalito, who spent hours responding to my endless noob questions. It was quite a daunting task without a schematic and I'm sure I could not have got it to this level without his help. I'm discovering a lifetime of recordings all over again.
If anyone wants to mod one of these units please PM, I'd be happy to point you to the locations of everything.
I also rolled the output buffer op amps from the Muses 8920Ds to the Burson Vivid V6s and they really did bring out the dynamics. The Bursons are the real deal and I would highly recommend them. I also added the same additional decouplers to these op amps per abraxalito's instructions. A .1uF MKP cap was also put across the rails as Burson recommends.
The results were quite dramatic. Sounds fantastic... just a huge sound! I wanted to swap the couplers first and see what that did by itself but, due to space, I had to add the analog DAC decouplers at the same time. The first thing I noticed is the brightness the Bursons brought had been warmed up a bit but still razor sharp treble... nice! So I added the op amp decouplers and started listening to stuff. What was immediately noticeable was all the detail in the background. Lush, airy reverb trails around transients, even discovered a few things (not supposed to be there) in some recordings I've listened to my whole life that I've never heard before. Super dynamics and puts life into any decent recording but dynamic recordings are just a sonic assault! I think the only downside is that if there is something a bit too forward in the mix it will tend to really take over, whereas the stock sound is very nice but more compressed and tends to homogenize all material.
Thanks to everyone for their input, but especially abraxalito, who spent hours responding to my endless noob questions. It was quite a daunting task without a schematic and I'm sure I could not have got it to this level without his help. I'm discovering a lifetime of recordings all over again.
If anyone wants to mod one of these units please PM, I'd be happy to point you to the locations of everything.
That is what I did with a KRK Ergo. Improving the decoupling and snubbing the regulators made a dramatic improvement. The MC33079 are fine opamps.
