irribeo, thank you for the response , I desoldered the capacitor from the second board to check the ratings on it and its 1 uf , soldered it on this board to check if it works and its working alright.I am planing on replacing the Capacitors and inductors on theses boards so will purchase 22pF and 1uF caps.
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The master chip controls the switching of the slave chip through r13-c33. TI datasheet values 10k-1nF do not function, the slavechip is in an uncontrolled switching mode with lots of distortions. The EVM manual and TI support give you 4k7-47pF values that do function. The 10k-1uF you have found will filter at 15Hz lol, signal for synch is around 100kHz, so 100% certainly completely absent just like with the TI datasheet values. 100kHz must be able to pass the r13-c33 filter reasonably easy or you have non functioning synchronisation, while the gainsettingresistors do set one of the chips to slave. You have to consider what other parts have random values on these boards, but have fun.
If C33 is removed already ! Very good. Not needed. Causes heatup in right channel inductor when C33 is present. I have done some extensive mod with this board & to my ears it clearly sounds better than Allo Volt + D that i own too. If you need details on my mod, will be happy to share.
pixelgarden, You are absolutely correct the right inductor was slightly warmer than the left and overtime it reached 55C, I removed the C33 1uf capacitor on both boards and the inductors are slightly above ambient. I was perhaps paranoid and didn't bother checking the unit in its current state, I have two so naturally thought one is missing and the other has it so went through all the trouble of finding a spare board and doing some cap extraction and solder. I am planning on replacing the inductors with better quality ones and also replacing the caps with Nichicon FW series. What kind of mods have you performed on this board?
This is going to be enclosed in a custom case i have made very soon ! The mods as you can see has been implemented at the positions which would give most returns. The Input coupling capacitor (ceramics) have been removed & sorted. The potentiometer has been removed & those points have been used to further mount Bevenbi MKPA E 2.2 uF capacitors which will act as input capacitors. I have tried a plethora of caps in this position, Jantzen Standard, Dayton, Bevenbi MKPA E, C, S, Elna, Nichicon ES & lots of others. Bevenbi MKPA E simply synergises the best with my other gears. Also it is bypassed with Vishay MKP 1837 0.022 uF. In front the four caps are Nichicon FW 1000 uF. I have tried different caps in this position as well (mostly nichicon), Kemet A750 polymer caps, Pana FM, FR etc. Kemet A750 was a huge dissappointment, I wish i had bought Pana SEPF instead. C33 is removed. The four black caps you see very close to heatsink is Nichicon 330uF 25V. Those are mounted on top of the four ceramic caps that are mostly responsible for fast response of HF. In my entire list of mods this gave the most returns, a bit more than the change in input caps (Bevenbi E). The sound after Nichicon KZ was detailed, energetic & very lively, engazing, kind of 3d like. If there is only two mod i would do it will be these four KZ caps & Bevenbi E at input position. I have tried other caps to at this position but KZ was clearly the best to my ear (i do prefer its presentation as opposed to ELNA which are good as well but soft). Next up the coils has been changed to Coilcraft Inductors 33uH. I removed the schottky diode & replaced it with wire to avoid any potential drop across it. On the backside the bootstrap mod is done. Vishay MKT370 caps (1uF in total) are output caps with Bevenbi 330pF & 10ohm resistors acting as bootstrap. Though i later i realized the bootstrap is already available in this board. The tiny caps & resistors that you see in between coils are exactly those. But i prefered keeping it since i felt i liked the sound with it. Overall the board is very much like Ti EVM layout-wise.
This is my third MH 190 board as i have used previous two boards to carry out a lot of modifications. The board thin tracing cant withstand this much soldering & desoldering. Even if i promised I wont carry out experiments on my 3rd board & only will implement the changes that i have verified to be positive on previous two boards. I still fall for it & have damaged many soldering points & so you see the condition of it !!
Nonetheless, in my subjective view it sounds better than Allo Volt + D. Is very dynamic, lively & doesn't distort even at full volume. The only thing is that may be due to my capacitor choices (Nichicon KZ closest to chip & Bevenbi E in input coupling position), i feel that the fullness in sound is lacking a bit. Everything sounds very very good , bass is very punchy but the low end feels a bit weak. I am using an ultra cheap tube preamp with all caps changed to Nichicon, Panasonic & Kemet in tested spots with Voskhod tubes. It certainly helped making the sound fuller with slight loss of dynamics & slightly making HF less sharp. I am using heavily modded Aiyima A7 for couple of month now & really do like it for the power it can put in the speakers effortlessly. The sound is very good & bass is effortless. But still not a single day goes when i dont use my XH M190 just to compare how my Aiyima A7 mod is shaping up in terms of SQ wrt it.
This is my third MH 190 board as i have used previous two boards to carry out a lot of modifications. The board thin tracing cant withstand this much soldering & desoldering. Even if i promised I wont carry out experiments on my 3rd board & only will implement the changes that i have verified to be positive on previous two boards. I still fall for it & have damaged many soldering points & so you see the condition of it !!
Nonetheless, in my subjective view it sounds better than Allo Volt + D. Is very dynamic, lively & doesn't distort even at full volume. The only thing is that may be due to my capacitor choices (Nichicon KZ closest to chip & Bevenbi E in input coupling position), i feel that the fullness in sound is lacking a bit. Everything sounds very very good , bass is very punchy but the low end feels a bit weak. I am using an ultra cheap tube preamp with all caps changed to Nichicon, Panasonic & Kemet in tested spots with Voskhod tubes. It certainly helped making the sound fuller with slight loss of dynamics & slightly making HF less sharp. I am using heavily modded Aiyima A7 for couple of month now & really do like it for the power it can put in the speakers effortlessly. The sound is very good & bass is effortless. But still not a single day goes when i dont use my XH M190 just to compare how my Aiyima A7 mod is shaping up in terms of SQ wrt it.
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