Denon DVD2900 tweaks

[Guido Tent]

Originally posted by BerntR


Guido,


I would appreciate more than hints on this subject. What will work??

best regards,

Bernt

Hi

A clean power supply to start with. Get rid of al LM / LT / TL or whatever based circuits. Think in clean current souyrces and discrete shunts, or use voltage followers together with clean references (like buried zeners or LEDs)

Bandgaps are prcise references, but not clean

THEN use decent caps where they are used for: To suppress RF voltage variations caused by the load, rather than trying to flatten the noise gennerated by the supply

cheers

[A 8]

Guido is of course right, however it is really not practical for the mainboard in a player like this. I think it has more then 15 individual regulators. It would be a huge redesign of the powersupply and unless you are really on top of each and every IC and find space for it you are very likely to fail.
The only place I would consider it would be the Audio Board which only needs 4 regulated supplies. I would build a separate supply and get a low noise regulator as Guido suggests.

The main board has a lot of L-C, R-C powersupply filtering built in for most of the IC's so adding HQ Low ESR Caps after the filtering will help to reduce noise on the ps and if you increase the caps values you'll also get better low freq filtering.

I've done it and it sure makes a difference.

/Michael

[Htguy]

Hi,

I just bought a dvd 2900 to replace my dvd 3800. So far I have been unimpressed by the audio output of this player for everything but sacd(which sounds great). The 3800 sounds more lively, focused and forward w/o being bright. It seems like the power supply might be a good place to start. Does anyone have a design that might help me make this happen? (Pics, schematics etc? (I am pretty new at this stuff, so please be patient)

Thanks

God bless...


Mark

[machinow]

You need a resistor after the OP Amp's output, otherwise it may oscillate. You can keep it's value as low as 30..80 ohms though to minimize the effects of the interconects. Lowering this output resistance usually betters the sound quality of the player even when the mute-transistors are left in place.

PS: In my similar circiuts I put it as close as possible to the OPamp chip to prevent additional parasitic capacitance of the traces which may decrease the phase margin of the circuit. I usually work with SMD parts - SO, 1206 and mostly 0805 passives.

[Htguy]

Hi,
I am looking into upgrading my dvd 2900 for audio output and am pretty new w/electronic upgrades like this, so I could use some help.

1) to remove the mute transistors on the analoge outs I remove tr221-228 and replace them with a resistor between the outer solder points? (What value resistor would be best?)

-what about the tr207-214? What do they do? do they get removes as well?
-What about replacing them with relays to stop the poping, but keep the signal clean? (Could run mini relays off their own power supply and use the middle solder point and a transistor to switch the external power to the coil of the relay? Good idea or waste of time?)


2) Upgrading the coupling capicitors replace the radial caps (C361-364) with 10uf black gates? (How much base will I loose?)
-What should I put in place of the blue caps (C371-374)? A black gate alternative? Which one, or better alternative?

3) Are there any other caps that I should replace with Black Gates to make a big difference on the analoge or coax digital output to make them sound better, cleaner, more dynamic, better?

4) is it worth it to upgrade the caps on the main powersupply board to Black gate caps or are Phillips LL caps good enough as long as I up the capacitance? (I am thinking of using 2 caps of the same rating in place of each power filter cap in the power supply I.E. replae one 100uf 16v cap w/2 100uf 16v cap. Reason: two smaller caps recover faster and give better transient power than one larger cap. -->Does this logic hold up in the audio/video realm or not? ??Increased resistance negates effect??

Thanks for your help.


God bless...

Mark

[Htguy]

Hi,

I forgot a few things.

1) I want to replace the diodes in the power supply with FRED type.
what ratings should I look for? Anyone have a part number and brand to suggest?

2) anyone have suggestions/ pictures/schematics for upgrading the opamps to better ones? What is the best opamp for this player? (I know the Burr/Brown need an adapter to put 2 to replace the one on the player. what is the best Burr/Brown Part # )

Thanks for your help.

God bless...

Mark

[Htguy]

Hi,
Well the SDI mod is working great and the diode replacement really made a difference in the audio performance of the unit. (I just replaced the 4 that make up the bridge rectifier for ac)



Does anyone know if the Burr Brown ops 627 can be soldered in as a pin for pin replacement of the stock opamps?

Thanks


GOd bless...


Mark

[A 8]

Does anyone know if the Burr Brown ops 627 can be soldered in as a pin for pin replacement of the stock opamps?

Unfortunatly not, the ones in the 2900 are dual channel OP275GP for buffering, NJM2068 for I/V and some BA15218 for hf filtering. Any other SMD dual channel op will fit though.

is it worth it to upgrade the caps on the main powersupply board to Black gate caps or are Phillips LL caps good enough as long as I up the capacitance? (I am thinking of using 2 caps of the same rating in place of each power filter cap in the power supply I.E. replae one 100uf 16v cap w/2 100uf 16v cap. Reason: two smaller caps recover faster and give better transient power than one larger cap. -->Does this logic hold up in the audio/video realm or not? ??Increased resistance negates effect??

For the main board you absolutly need to stick with SMD's, partly becouse shorter lead lengts and less ESL but also becouse the critical ones are under the transport where there is not space for anything else. Dunno much about the caps you're referring to but I would suggest Sanyo Oscons, an SMD variant called SVP. I would not double up any caps, the caps I am referring to is as "fast" as you could expect.

Upgrading the coupling capicitors replace the radial caps (C361-364) with 10uf black gates? (How much base will I loose?)

If you remove the mute transistors I would suggest you just short the dc blocking output caps.

[Htguy]

Hi

I made a mistake describing the caps I want to replace. They are the ones on the power supply board not the main board. WOuld it be worth the Black gates for that board? Which ones ar worth the trouble and expense of replacing on that board?


Thanks

God bless...

Mark

[machinow]

You'd better use low-ESR caps, as Rubycon ZL series or Panasonic FC. I'm also pretty amazed how good ordinary Rubycon YK behaves in Switched mode PSUs - so I would prefer Rubycon ZL s.
But what are the stock ones??? They should be similar. To filter the supply better you may only need to enlarge the capacitors after the filter inductors at each Vout.