huangyong 0 Report post Posted September 10, 2004 Modded my CDP 2 days ago. Throw in 2 x OPA627BP + Burn in for 12 hours = WOW!!! Backgroud: I bought a second hand CDP to learn how to mod. It's a German Made Denon-715, 8xoversampling, using PCM61 technology. After spending days of circuit analysis, the CDP deisgn is rather strange ; it uses direct PCM61's output as analog output, i found no opamp or buffer in the output stage. Headphone out section is very interesting though ( may be i am new to this ), the design is opamp + discrete output (nec4570c + 2sd2144), cool!! which means it might able to rival some of the low end headphone amp.... had a set of x-canv2 + x-psu paired with the cdp. However, I found out the sound was really sucks after comparing them with voxel's setup. His China made 8PR is really great. Later i found out that x-canV2 only improve the sound by a small margin compared to the headphone out of the cdp . Final decision: X-can V2, i m so sorry, i m looking for someone who can sing better...good try...but sorry...you have to go.... ----------------------------------------------------------------------------------------------- Mod phase I (low end mod): While waiting for some parts to arrive, I read lots of article about CDP mods. Got some tips, so i bought 4 schottky diodes from a guy in echoloft. Threw them in, wohoo.. it really does clean up the noise. Cool.... . I cant wait for the other parts to arrive anymore!! Got an idea pop up in my mind.. "why dont i mod the headphone out section to rival some good headamps".. Immediately, i desoldered the original lousy opamp and pop in a NE5332. Add a 100uF cap & by pass 0.47uF cap at the power rail of the discrete output. The result : The sound became smoother, non-fatigue, my ear felt good. Another improvement was the bass, when i listened to my favourite Titanic soundstrack, i could hear the low-bass, it's like headphone shaking.. the feeling was wonderful.. Soundstage improve slightly, but sound imaging (3D) was better compared to the prvious lousy opamp.. There's lot more rooms for improvement..... gonna take a break now.... high end mod review in the afternoon... professor coming..arrgggh..... Share this post Link to post Share on other sites
digi01 0 Report post Posted September 10, 2004 wonderful,have you modify the power supply parts?only add schottky diodes? Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 10, 2004 Cool ! Waiting more comments from you. If you got time, please show us some pictures I would be very helpfull to see the pictures Anyway, why didn't mod the X-CanV2? at least you already got cool casing Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 10, 2004 Mod phase II : Just received a package of caps 2 days ago. Those caps include Elna Cerafine, Elna Silmic, Panasonic, and Blackgates. Within an hour, i replaced the caps in the signal path and some power caps in the PSU region. I replaced Elna Silmic caps at the analog output while the headphone out with blackgate caps. After doing that, hmm... think not good enuough, so i threw in 2 OPA627BP. Now... listening test: The overall sound is not so impressive at first, so i decided to leave it on till next morning. In the morning, when I listened.... it sounds so real so natural... gosh!! someone plucking harp beside me?? It was Wide World Over: A 40 Year Celebration Track 12. It seems like the CDP loves string instrumental music, it really sings. All the details which i miss out earlier..it's there now.... I played violin sometimes back, so i am familiar with the imperfectness of string instrument, sometimes there's a slight "eehkk" while bowing... Now, I can hear that , it might be annoying to some of you, but it sounds real... I am not a good reviewer, that's what i can tell so far... Commed on OPA627: Money well spent. Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 11, 2004 Cool Mod! Do you mind to post the pics? Do you have to put cap in the audio line? Especially the headphone output? I think with the precission OPA627, you can at least take out the blackgate. No matter how good the cap is, it will be much better without it Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 11, 2004 (edited) Sorry, poor man like me don't have camera.. may i bring it to you to help me take picts.. now new idea coming up.. just read about this article. CDP mod and found the datasheet of PCM61P PCM61P After tracing the PCB track, The CDP's DAC uses PCM61P "Vout" as Analog Out, which only can output +/-3V ..... And i doubt the internal opamps of the PCM61P are good stuff... so i am thinking of ground the "Vout" and build a I/V converter either with discrete or tube circuit... What you guys think?? Edited September 11, 2004 by huangyong Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 11, 2004 may i bring it to you to help me take picts.. Sure no problem After tracing the PCB track, I did once tracing PCB track of my Technics CD player long time ago (about 9 years ago), until I brought it to sleep I think +/-3V is high enough for DAC / line output. But if you want to replace the internal Op-Amp, I suggest you better try a similar configuration with OPA627 replacing the internal Op-Amp (tap pin 10 and 13). Later you might experiment with discrete or tube. But I doubt that gonna be easy, because without the internal Op-Amp, you get I out not V out. Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 13, 2004 Yes, bripadi. I agree with you. Should try the opamp I/V converter first. I will try this configuration first. In order to do this, i have to remove a few resistors and caps on the PCB... hope it'll be alright trying this week... with a seperate power supply unit to power the DAC and opamp....hehe.. Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 13, 2004 Good luck Huangyong Sleep well, otherwise your hand will be shaky, not good doing the mod with shaky hand Anyway, I don't really like to see the low pass on your output (pin 13), you should try without it at first. When you hear metallic treble, then start to design active low pass which has better characteristic than the passive one. The active low pass offer a more stable impedance over the frequency compare to the passive low pass. Another alternative to low pass is to use slow slew rate Op-Amp. It might give better result than passive low pass. Try OPA2227 (or OPA227 for single), the slew rate is only 2.3 V/uS. I know that it is still high to perform effective low pass function, but it is cheap, why don't give it a try My suggestion: Disconnect only pin 10 and 11, leave the rest as it is. Build new board on top of the original board for your new circuit (use plastic spacer). Happy Modding ! Bram Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 13, 2004 Some reading stuff: I/V converter (discrete) Non-oversampling DAC I/V converter Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 13, 2004 Good stuff thanks! Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 14, 2004 WOOhoo.. Had done my PSU. A very simple regulated power supply using 15-0-15 transfomer and 79/7815. but now i have one Question. Can i just tap the AC source from the AC inlet to my new transformer? Share this post Link to post Share on other sites
bpribadi 0 Report post Posted September 14, 2004 Yes sure! but I would prefer to use fuse for protection. You can also buy the 3 pin AC socket with noise filter, so you will get a cleaner AC. SLT basement has a lot. Share this post Link to post Share on other sites
huangyong 0 Report post Posted September 14, 2004 (edited) Yes sure! but I would prefer to use fuse for protection. You can also buy the 3 pin AC socket with noise filter, so you will get a cleaner AC. SLT basement has a lot. I would like to, but i lack of proper DIY tools to cut the metal plate. Housing the 3 pin AC will be a BIG project for me. the CD player doesn't ground to earth. Is it ok if i ground the chasis to earth? Edited September 14, 2004 by huangyong Share this post Link to post Share on other sites
