Denon DVD2900 tweaks

[Guido Tent]

Re: Re: Re: Clock upgrade....

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]

starting to do 2900 mods

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]

2900 Mod help please...

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]

Oops more thing...

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]

mods are working...

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]

oops...

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]

Capacitor for PSU

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.

 

[Htguy]

rubycon caps and other stuff...

Hi
Thanks for your input. I am wondering what ERS stands for (IE low esr caos?) I am pretty new at this and don't know a ton of terms.

Also, how does one tell if a dioide in soft recovery or not? (there are fast switch, fast recovery... and I can't tell which is soft recovery. What is the rating I should look for and what is a good range for a soft recovery diode for power supply rectifying? (IE, is a higher "trr" time mean soft recovery? (200ns instead of 35ns?) If not what is the abreviation of the rating I should look for?


Thanks

God bless...


Mark

 

[q1]

Hi all,

Nice to read all the new replies

Maybe it is a idea that everybody who is getting this messages post a list of all the modifications he made to his 2900 and what the results were?

I own 2 pieces of denon 2900. 1 for to play DVD+ SACD's and 1 for the pc room as cd/sacd player only (second hand for 575 euro)

What I did is nothing complicated:

- Removed the output capacitors - 1 piece both channels +/- 3 mv DC / 1 with one channel 50mv* DC. : --> Better soundstage and bass response.


- Removed the muting transistors: --> better soundstage.

- Silver wire and 70 ohm resister connected from op275 to output terminal. --> Better bass response.

- Disconnecting power and signal cable to video board improve sound as well (1 use one as music player only)
--> Better bass response.


Future plans:

- Improve powersupply with Black Gates?
- Replace op275 with 2 x opa627BP with a adapter. (order placed on ebay 4 for 20 usd!!)
- TentClock?

Does anyone know why there are 2 op-amps (op275gb) needed in the signal way? what would happen when we disable one half of the op275? I would not mind when sound would improve and output voltage would decrease.

Best regards,

Rene

* Maybe this will improve with other op-amps.

 

[WTS]

DOes anyone ever do any improvements for the video side of the dvd players.

 

[Htguy]

video improvements...

Hi,
So far the only video improvements I have seen is an SDI output. I would love to see some way of making video improvements, but I think it is a tough thing to do (that is apart from making the power supply better so teh video circuits perform better.

Has anyone tried hooking the sdi pins right to the mpeg chip rather than the video card ribbon connector? Does it make the video better?

 

[WTS]

Hi HTguy,

Thats what I was referring to though, was just improving the supply and maybe the clock for the video. Or does nobody here use the players for video, just audio. I've done enough pooging in audio, I'm now into getting a better signal for my 8" crt projector.

Anyone care to jump in, I know this is a audio forum, but it is a DVD player(s) we're talking about here.

Thanks

 

[A 8]

I've probably done more to the videosection then anywhere else in my unit.
When I first got it I thought the picture was way to soft and a little "nervous"so I got going on it.
I've changed all the decoupling caps to shielded oscons (in the component/PS signal path), replaced the video op amps, replaced the dc filtering caps to film types and increased the PS filtering (coils and caps) going on the board.

The picture is now rock solid, with a bit more details, much sharper and less noisy. The only issue I still have with it is a slight ringing which got marginally better after the mods but still not where I want it.

 

[WTS]

Hi A8,

That sounds great, so what opamps did you go with. What coil/cap(values) combo did you use. Did you anything to the clock circuit.

Thanks
Walter

 

[Htguy]

video upgrade...

Hi A8,

Do you have pics of the video mods? What opamps did you use? Where are the video opamps? Were all these mods done on the video board or on the main board? I am using SDI output, so I am guessing that most of these mods would not effect that data stream, right?

Thanks

God bless...

Mark

 

[A 8]

Hi Guys,
I am not the one to document stuff, I tend to focus on a issue at a time, figure out whats needed and get it done.

However browsing through my files I think I've used a MAX4216 opamp, 200Mhz, -75dB THD@5Mhz, not becouse its the best but becouse it was what I could get that would be a drop in replacement. Its still better then the TOKO 15420 originally mounted. Be aware though that these opamps are VERY, VERY sensitive to layout and decoupling. You can easiliy end up worse then you are.
If I really wanted the best I would try to change the layout and cut down to one opamp per feed, then use the MAX4108 single channel, 400Mhz, -93dB@5Mhz or the BB OPA843 with a similar spec.
I did this a few years back using a BB OPA620 on an Pioneer 717 with really stunning results.

When it comes to filtering and decoupling I don't have the specific values but there are many options on the video board not used to filter ps lines, use them with good coils (very high resonance freq) togeather with oscons and you'll lower the noisefloor significantly.
For the ps entering the board you can easily cut the cables, add coils directly on the cables with a set of high value, low esr caps to keep the overall esr down and at the same time lower incoming noise and smooth off any 50Hz residues.

I've done the clock curcuits by changing the decoupling on the clock curcuit(s) and basically all the digital processing that I found relevant to audio and video performance.

The video board is easy, its the first thing you see above the audio board and the DA is marked AD7300, the opamps are three in a row and marked 15420.
Hope it helps with your inspiration.

/Michael

 

[WTS]

Hi Michael,

Thanks for your input. I'm not modding a 2900, I was just looking for mods that have been done and what improvements where the result. I would think that reworking the clock would make just as big an improvement as it would to the audio side, do they use the same clock for both audio and video as a rule in most players.

Thanks