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DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: January 23rd, 2018, 3:34 am
by franjam
Ok I'd just like to share and talk about this latest mod. First of all I'd like to say that I'm essentially, (or was), a vinyl junkie, started my collection at aged 13 etc etc. So I invested heavily, for me at least, in my TT : new arm, new motor, new cartridge, different stylus tip etc. also in a decent pre-amp with a good phono stage.

I only recently turned my attention to my cd player, a Marantz CD63 SE which my brother had given me, as I do have a decent cd collection aswell, (he's gone 100% digital :roll: ). This is a classic tweakable unit and i did just that : complete re-cap plus several things outlined at TNT audio including a chandge of op-amps, ferrite chokes etc. This transformed the player from banal sounding to pretty good actually and I thought I was done.

As I'm currently awaiting pcb's for the kDCX project I had time to surf a bit and I came across a 10 year old archive site by a polish cd nut called Lampizator. Totally chaotic site but great fun and it convinced me to replace the output analogue stage ,(which I had just renewed :lol: ) with a low gain valve output buffer stage, (I do like valves :D ). For this I'm now awaiting the transformer with 115/12V secondaries and other sundry parts but I aready have 50% of what is needed including the 12AU7 valves. So that will be something to talk about when I have all the bits, however there is an intermediate stage which I found more than interesting from an audio point of view.

This guy also recomended an intermediate stage which consists of finding the analogue outputs on the dac, (I have a voltage DAC which makes it easier otherwise you should use leg 1 or 2 of the sequential op-amp for a current DAC) and wiring them directly to the RCA outputs via 2 coupling caps. He argues that this is the cleanest signal and that everything intermediate is unnecessary and simply helps to muddy the signal.

As it is all totally reversible and I had a couple of Jentzen 2.2uF's hanging around I thought i'd give it a try :).
The sound was definitely better, not mind blowing but yes definite impression of more clarity, space etc. So I left it in.

The next day, still looking for something to pass the time, I decided to put a proper ground connection in the Marantz in preparation for the valve mod which needs careful grounding. I had previously installed an IEC socket with mains filter on the unit but the pcb was still grounded via the RCA output sockets and there was still no earth wire connected from the mains cable.

I'd like to add at this point that I'd read a lot at one point on earthing, ground loops etc. and I have installed a dedicated mains supply for the HiFi, direct from the mains input to the house along with a seperate large diameter earth wire and a seperate 1.5m copper earth rod. Every chassis is independantly grounded to the same point behind the HIFI as well as through their various shielded mains supply cables to this copper rod.

The Marantz pcb has a common ground plane making it easy to scrape off the veneer and solder a large diameter wire from this point to the chassis. I also removed the old RCA sockets and replaced them with nice, heavier gauge, insulated, gold plated ones. I connected the RCA grounds to the chassis, I then connected an earth wire from the IEC SKT to the chassis via a spade and pcb screw. I put it all back together and plugged it all back into the system.

WOW!! :shock: :shock: :shock: There it was, the transformation of the sound to another level that the Lampizator guy had said would happen. It was totally unexpected as i hadn't thought I was making any significant changes : crystalline clarity, depth, detail and lovely musicality :D . Needless to say i was into my cd collection into the early hours, (it doesn't prevent my boys from sleeping they been raised on this ;-) ).

If I have any criticisms there is still a little digital hardness on certain voices and the higher frequencies so I can't wait to add the valves to see what happens to this. But what this experience has hammered home to me is the importance of good grounding in HiFi ; you can have the best caps and filtering in the world but if it isn't being conducted away properly the sound is going to suffer and not just a little.

here is a photo :-) :
Marantz CD63 DAC Mod.jpg

(yes that is a 10000uF cap on +ve of the 5v regulator which supplies the DAC, it was knocking around so I thought why not? ; I'm going to start another topic on cap choices, the right ones...;-) )
The player is also awaiting the AMB clock and voltage regulator ;) .

An obvious question : why bother with analogue ouput stage, op-amps, discrete amplifiers etc? I now have a sound I never dreamed could come from a cd, the only thing I have lost is the muting transistors so I need to turn the volume down before switching the CD player on or off or I get an ugly "scrape", but I can live with that.

This also raises another topic " Relative costs and return in terms of sound quality, CD vs Vinyl " I'm awaiting the return from The Expert Stylus Company of my Denon DL103R with a new paratrace diamond, My current thinking is that one needs to invest more in the vinyl front end than in the CD front end for the same quality of sound, even though I love vinyl and won't abandon it.What does any body else think?

I'll post the valve mod with the wiring diagram when the parts arrive :) .

Re: DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: February 7th, 2018, 4:24 am
by franjam
Now that the kDCX project is nearing its completion I' am starting to turn my attention back to this valve output project. I am also awaiting a Marantz CD40 with the famous TDA1541A DAC chip, which i picked up cheap and which I am also going to modify and compare with the CD63SE.
In both these cases there is only one 5V regulator to supply all the chips / DAC and transport . My intention is to add an o78 which will be exclusive to the DAC and o1 clock which I will also add. The existing 5v regulator will be relieved of these duties and can concentrate on what's left. Does this seem like a coherent plan? Others have added an 7805 chip to each end-user, adding up to 5 ; I don't intend to go this far.
on the CD63 I have found the 5V jumper which feeds the DAC and op-amps/ output stage. My intention is to remove the jumper and op-amps,( as the output stage is already by-passed), and connect the o78 5V output to the jumper input. I intend to feed the o78 input from a point just before the existing 5V regulator input which is 10.45V from memory. where do you think would be the best place be to put the ground? Also from the existing regulator or closer to the DAC , one of the caps next to it for example?


Re: DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: February 7th, 2018, 10:52 am
by amb
Placing the regulator ground needs some careful attention, because the ground currents need to be managed to minimize current loops and to prevent one circuit section's ground to be modulated by another. This is already difficult on a PCB with large copper ground planes, requiring careful component placement to achieve the desired result. When you're adding regulators offboard, the issues become even harder to manage. As a general rule, though, if you are going for local regulation of small circuit sections, then the regulator ground should be connected to the ground plane nearest the circuit portion being powered, and keep the regulator ground pin connection to the board very, very short (direct-solder if possible, not using any wires). This way, you'll at least not make the situation worse than before.

Re: DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: February 7th, 2018, 12:09 pm
by franjam
Great thanks, I take it this is the same principle for the o1 clock ie. to use the ground of the original crystal?

Re: DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: February 7th, 2018, 12:36 pm
by amb
Not quite the same. The circuit being powered on the ο1 (oscillator, etc) is on the same small PCB as its LDO super low noise regulator. It’s important that you use the U.FL cable and its ground to carry the oscillator output directly to where the clock is needed. But the input power supply source is not as critical in this case. Use the following post as your guide to installing the ο1 in the DCX2496:


Re: DAC Analogue output bypass + valves on Marantz CD63 SE

PostPosted: May 11th, 2019, 6:53 am
by Susnick
Hello Franjam new member here on AMB..... saw your writeup here and wondered if you ever installed tube output stage?
Did you like and may I ask what circuit you used for output stage?
Regards, Susnick