Updating Onkyo DX-706?

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I own a Onkyo Integra DX-706 wich I have updated with LCAudio LClock 2 and shifted all analog opamps to LM6172. The LClock made some major improvements, but the opamps not so much.
I would like to make some new analog stage, but I cant find any information, servicemanual with scematic or datasheet on SM5813AP (dig. filter) and SM5861AP (single bit DA converter).
I did read the thread "Anyone tweaked the Onyko DX7711 integra CD-player?" http://www.diyaudio.com/forums/showthread.php?threadid=4624&highlight=onkyo without any result.

Can any one help me on this one, please?
 
You will getsome advice.

Hey, Henrik

you will get some help
by our "digital professor experts"
Elso and them.
They will come around and find this thread.

Elso will read about the concurrent's Clock,
and peranders will jump into the OP-amplifier thing directly!
---------------------------

you can not expect as much better sound quality
just by changing OP amp. Not that you can hear,
and it will even be har to measure - in some cases.

This is when you exchange a good OP-amp with a SUPER-expensive.
But when you have a very old like OP741 and some other
bad OPamps - than you can probably notice a slight improvement in Sound.

It all depends on what the level is - that your changes are made.
If you already is beyond human hearing, with your changes,
then it will not change anything you are able to sense, with your 5 senses.
(Somebodies than take their imagination to help - to "get the change")

:cool: ;) but this is a not so in your case :confused: :cool: ;)

/halo - mostly with his feats on the ground - not on the stars
 
Henrik said:
I own a Onkyo Integra DX-706 wich I have updated with LCAudio LClock 2 and shifted all analog opamps to LM6172. The LClock made some major improvements, but the opamps not so much.
I would like to make some new analog stage, but I cant find any information, servicemanual with scematic or datasheet on SM5813AP (dig. filter) and SM5861AP (single bit DA converter).
I did read the thread "Anyone tweaked the Onyko DX7711 integra CD-player?" http://www.diyaudio.com/forums/showthread.php?threadid=4624&highlight=onkyo without any result.

Can any one help me on this one, please?

I have the service manual at home,I´ll scan it (as soon as I can) and mail it to you.
I think the digital filter is pin compatibel with Burr Brown´s DF1700.
If you use LM6172´s you should bypass the opamps better,thats one really weak point in the CDplayer...

Try the constant current source mod,you will not be disappointed.

Nicke
 
Good Henrik brought up the DX 706, I also own one and use it as my only front end so I'm very interest in this thread!!!

Nicke, you would also make a big favor to me if you can send a copy of those scaned schematics.

I bought this CD new when they were current, more than 10 years ago, made some mods like adding 2 new PSU's, htere is room at the back besides the original trafo so now I have the original trafo for the digital section another for the clock plus other digital components and the third for analog.

Also changed opamps to AD827 with some apreciated sonic advantage plus output caps to Axons 2 x 5.6u for each channel. Replaced many caps and resistors.

Whats realy bad on this CD is the number of opamps used at the analog portion, 3 doubles for each channel!!!

My unit uses same NPC SM5861AP Sigmas DAC's (no surprise, he) I tried to get the specs for this at NPC site but they no longer publish the data sheets for those, I email to them requesting information they answered asking for what I would need them but finally there was a blank from NPC side.

Henrik, we need to do something with that output analog "stage", and also maybe to change those old Dac's and that DF as Nicke suggest.

Otherwise the DX 706 is an excellent built CD can't find a newer one built like that except if I go to ML or Krell of course but....
 
A suggestion about modifications...

One of the things I did that made a big difference was changing the resistors and caps in the analog stage.
Perhaps because the analog stage is a dual differential stage which uses 5%(or 10%...don´t remember which..) tolerance for the components.Or is it just better quality ?
Don´t ask me why .


Another thing I would do if I used the CDP today would be to modify the voltage reference for the analog regulator´s(it is a version of the well known Sulzer type).Now it takes the 5 V reference from the output of the +5 V regulator for the DACs.I would replace it with a suitable voltage reference(National has several) fed from a constant current source.

Let us know about the result.

BTW I didn´t suggest that you should replace the digital filter,actually I think that it is the same as DF1700 but it is from NPC instead of Burr Brown.

Good luck.:)
You can read all about the mods I made here:Nicke´s mods
 
I have made already some modification, temporary on my DX7711.
But, I still have left some things to do (I do not have too much time).

What I did is many of Nicke's changes, mentioned in Onkyo DX7711 thread.
1. Changed resistors (Holco)
2. Changed capacitors (Elna Cerafine)
3. Eliminated mute transistors
etc.
Some differences:
1. The opamps, what I use is OPA627 (all together 8 pcs, not cheap...)
2. Additional toroid trasformer for analog stage
3. Clock mod. not implemented yet
4. Voltage regulator update is not implemented yet
5. Another output caps (Elna Cerafine)
6. Silver Mica feedback caps
7. Copper shileding tape on receiver and DACs

So, I have still left many things, and when I have time, I'll implement those also.

The sound has changed already a lot.
It is more soft, and the clearance is better. I like more this sound, the previous was a bit aggressive for me.
There is some pictures about modification.

BR, Milan
 

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mpopovics said:
I have made already some modification, temporary on my DX7711.
But, I still have left some things to do (I do not have too much time).

What I did is many of Nicke's changes, mentioned in Onkyo DX7711 thread.
1. Changed resistors (Holco)
2. Changed capacitors (Elna Cerafine)
3. Eliminated mute transistors
etc.
Some differences:
1. The opamps, what I use is OPA627 (all together 8 pcs, not cheap...)
.

BR, Milan

I did make some similar boards for the opamps myself.
But I used AD797.

Looks nice.

Nicke
 
Scanned files

Tanks Nicke for the scanned schematics I have already made some study there.

What I will try first of all is to take the output directly from Q405/406 and get rid of the deemphasis removing R439/443 and signal resistors R437, R441, R451 plus Q407 and think I already eliminated R457. Also since i'm driving a 50K pot at the preamp will lower also C463/470 from 10u to 2/5u.

if I'm not satisfied with the results will try driving directly from Q403 which will eliminate all opamps except the mentioned one.

Did you ever test this Nicke?
 
Hi apassgear and all!

Since I want balanced output to my XBOSOZ I will try to take the output direct from Q403 and Q404. I have simulated this and it should give about 3.5 V output singleended. If this could be done, I will change to better opamps an bias them to class A by the currentdiodes sugested by Nicke.
And I will go for outputcaps at 33uF wich gives -3dB at 0.5Hz into a load of 10K.
Unfortunately I am too buisy the next week, so it will take a little while before I can try it out.
 
BALANCED DX706

Good Henrik, try that and let me know of the results.

i also thought what you proposed, but since for the moment I don't have a balaced pre I'l have to wait for that one.

Have been to lazy to build the BOSOZ for which I have most all the parts but continue to play whith vacuum preamps which are way more interesting than SS.
 
I now have some idea of what to do.
I hope that someone will make some comments if I am wrong in my proposal.

To day I tried to connect the balanced nodes marked 2 in the original scematic to my headphone amp. unfortunately this one is not balanced, so I was only able to hear one channel at the time. First I tried singleended by connecting + and GND and then - and GND. At last I connected + and - to the RCA input at my headphone amp and this time it played louder as a sign on the balanced output.
The sound was very good indeed, all though it wasn´t stereo.
My next step is to drill some new balanced outputterminals at the back of the CD, and the just connect them to the balanced nodes at mark 2, and the listen to it more proberly.
If this test comes out well, I will replace Q403 and Q 404 with four handmade and descrete opamps like in the second atached scematic. This is just a first draw of the idea, I have to consider supplyvoltage, wich transistors to use, the current flow, ccs design and many other elements, but all based on this topology.
 

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