Marantz CD63 & CD67 mods list - Page 497 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 5th December 2006, 07:59 AM   #4961
diyAudio Member
 
Fidelity Audio's Avatar
 
Join Date: Dec 2005
Location: Doncaster England
Those goldenjacks are a good price. His plugs look like the WBT types.

Brent
  Reply With Quote
Old 5th December 2006, 08:10 AM   #4962
Chivvyp is offline Chivvyp  United Kingdom
diyAudio Member
 
Join Date: Apr 2006
Location: London
Default Single op-amp

Hi,

A year or so ago I had my CD63KIS modified (new clock and output stage biased to class a). When it came back it sounded better and in the meantime I'd discovered this site so I made a few changes to voltage regs diodes etc. and left it. Bought a CD67 and started from scratch.

I decided to revisit the 63 and see if there were any more improvements that I could make with the benefit of (your) experience.

When I looked at the new output stage I found that the analogue output from the dac was taken to a new board sat on top of the hdam cans bipassing the normal filter and dual op-amps completely.

On the board is a new filter, transistors (one per channel, presumably to bias to class a) and a single op-amp per channel (LM6171).

Has anyone else tried replacing the dual op-amps with a single? From a technical viewpoint what would be the supposed benefit of doing this? What are the likely downsides.

Regards

Pete
  Reply With Quote
Old 5th December 2006, 08:23 AM   #4963
awpagan is offline awpagan  Australia
diyAudio Member
 
Join Date: Nov 2004
Location: sydney
no opamps.

passive filter then fet or transistor buffer.

I prefer the fet version

allan.

ps and no DAMH
__________________
Indecision makes the world gone round.
Maybe
  Reply With Quote
Old 5th December 2006, 08:26 AM   #4964
diyAudio Member
 
Fidelity Audio's Avatar
 
Join Date: Dec 2005
Location: Doncaster England
Chivvyp can you post some pics.

Brent
  Reply With Quote
Old 5th December 2006, 08:38 AM   #4965
poynton is offline poynton  United Kingdom
diyAudio Member
 
poynton's Avatar
 
Join Date: Mar 2005
Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
Default Re: Single op-amp

Quote:
Originally posted by Chivvyp


On the board is a new filter, transistors (one per channel, presumably to bias to class a) and a single op-amp per channel (LM6171).

Interesting.

You may be the first on this thread to have heard a 'class A' output.

Who did the mods ??
As Rowe said, can you post pictures of the top and bottom of the board and any values you can see?

Thanks

Andy
  Reply With Quote
Old 5th December 2006, 08:48 AM   #4966
awpagan is offline awpagan  Australia
diyAudio Member
 
Join Date: Nov 2004
Location: sydney
I think this was mentioned before
http://tangentsoft.net/audio/opamp-bias.html

allan
__________________
Indecision makes the world gone round.
Maybe
  Reply With Quote
Old 5th December 2006, 09:24 AM   #4967
Chivvyp is offline Chivvyp  United Kingdom
diyAudio Member
 
Join Date: Apr 2006
Location: London
Quote:
Originally posted by rowemeister
Chivvyp can you post some pics.

Brent

I'll try to get some photos tonight. Probably only the top as the board is soldered to the hdam cans and I don't want to remove it before I have some idea of what I'm going to do with it.

re the tangentsoft links - I just built a PPA headphone amp from them and biased the opamps in that (using a fet cascode rather than a single). To be honest I can't say that I noticed any difference before and after adding the class a bias but the basic amp was stunning and probably exceeded my hearing capability anyway.

Any comments on the general principle of using a single op-amp rather than a dual.

Regards

Pete
  Reply With Quote
Old 5th December 2006, 09:53 AM   #4968
Glenn2 is offline Glenn2  United Kingdom
diyAudio Member
 
Glenn2's Avatar
 
Join Date: Oct 2006
Location: London, UK
The LM6171 may be being used to perform differential to single-ended conversion and LPF duties (it is very well suited to this task) but then why not use half of the existing circuit? So this is unlikely unless they have a standard board they use in various players.

It may be that they took only LO/RO (or LON/RON) from the DAC (i.e., only single-ended), fed it through a passive filter and then used the op-amp as a buffer and/or to provide a bit of gain to make up for the drop in voltage of not using the differential output.

You can make an op-amp class a by attaching a resistor, CRD or cascoded JFET between the output and the supply rail with the worse (or is it better? can never remember!) PSRR.

A pic would be nice.

I've currently got the first half of the op-amp as normal, and fed to the HDAM which I've converted to be the 2nd stage of the LPF (like in the CD6000 but single-ended). So it is the same circuit as the dual op-amp in principle, though I have the Bessel filter slope. Mine's a 67SE.

I tried various combinations in A/B comparisons (leaving the 2nd half of the dual in circuit and connected to identical interconnects) and I always preferred the discrete op-amp (bass much better).

(HDAM - if you cut the feedback track you get O/P and -VE inputs and it's a fully-functional discrete op-amp - see CD6000 schematics.)
  Reply With Quote
Old 6th December 2006, 08:47 AM   #4969
Chivvyp is offline Chivvyp  United Kingdom
diyAudio Member
 
Join Date: Apr 2006
Location: London
Quote:
Originally posted by rowemeister
Chivvyp can you post some pics.

Brent

Well, I took some photos but the filesizes were too big to add in so I had to resize them! Hope they're viewable.
Attached Images
File Type: jpg cimg0137-1.jpg (80.7 KB, 309 views)
  Reply With Quote
Old 6th December 2006, 08:49 AM   #4970
Chivvyp is offline Chivvyp  United Kingdom
diyAudio Member
 
Join Date: Apr 2006
Location: London
The analog inputs are taken from R21 - R24 which are lifted at one end to disable the normal signal route.

Pete
Attached Images
File Type: jpg cimg0139-1.jpg (66.2 KB, 286 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 07:16 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2