CD63 Transistor Output Stage
No more opamps!!!
I managed to put this long weekend to good use by putting together Ray’s excellent transistor output stage…on the 63 PCB itself. It did take me three days, and no, it didn’t work the first time around,
but as with many complex DIY projects that was to be expected . I slept on the problem on Saturday night, and lo and behold, I found a missing jumper on the PCB… was wondering why I was getting +12V of DC on the output when I turned on the CD player prior to installing the high-pass filter 
To be honest, I was quite relieved that it worked…a real tribute to Ray’s excellent diagrams and instructional pictures (I did have to improvise stuffing the parts onto the 63 HDAM board as the pictures of the 67 HDAM board are a bit different - but the part numbering is mostly the same).
As Brent said, I too had difficulty sourcing 2SK170BL FETs for a FET stage, so I decided on the BC550C transistors. I did use the 2 170BLs from the original HDAM in position T4, so my transistor stage is a bit of a “hybrid” (BC550Cs for T1/T2, 2SC2240 for T3, 2SK170BL – from original HDAM – for T4). I also matched the HFe of the BC550’s to closely matched pairs. For the passive filter, I used 0.1% Welwyn resistors (Ray confirmed that 2K21 and 2K37 could be used in positions R3/R4 and R1/R2 respectively, instead of 2K2 and 2K4 – I couldn’t get these values in 0.1% tolerance). For all the other resistors in the transistor stage, I got 1% metal films, since these were the easiest to get my hands on and most cost effective as well.
If anyone’s going to build this on the CD player’s PCB, one will quickly realise that part size, for the passive filter, becomes a major issue when stuffing these parts in. It pays to get the smallest size high quality parts you can find.
Stuffing the CD63 PCB for the passive filter is very straight forward (the parts fall into place as per the placement list – the only exception is I had to run a separate ground for (I think) R3/R4. The transistor stage was a bit more challenging for me, but if you could follow the schematic, along with the parts placement list, you can easily figure out how to connect these components on the standard PCB. The key is to follow each junction on the schematic and double check this on the PCB with a DMM for connection (as I learned the hard way by leaving out a jumper).
I have used a very generic 3.3 uF metalised polyester “green cap” for C5,
until I can get my hands on a pair of Mundorf Supreme polyprops very soon.
So how does it sound??
To put this in perspective, before I ripped out the player (again!!), I was running LM6172 opamps (PSU bypassed with XR7 ceramics on the IC), tweaked the active filter for constant group delay and had the stock HDAM as a buffer (with the output stage capacitors C651/C652/C653/C654 removed). In this state, I thought my CD63 (along with the other plethora of mods) sounded pretty good… great bass weight, a “decent” midrange and extended highs.
Keep in mind that the transistor output is still running in (with some horrible coupling caps in there at the moment)… and these observations are based on a 4 hr running in period: Never have I felt a greater need to upgrade the rest of my equipment than I do now!!
Compared to the Opamps, the “mostly” transistor stage (I’m using FETS in the T4 position) simply blows it away in terms of “rightness”. Yes, there’s perceptibly deeper bass and the midrange is even more neutral… but it’s simply more REAL. The sound is BIG and bold… and really really smooth. It reminds me of my broken Sony XA7ES… even though the CD63 (tweaked) now sounds as good or better than the Sony, it never had that smoothness….until now! So much so that it’s starting to show flaws in the rest of my system, especially in the midrange. To really see if this was the CD player or the other equipment in the chain (amp/speakers), I plugged in my HD600 headphones into my preamp and listened…. WOW. I mean, the midrange out of the CD63 is to die for . It confirms that there’s a certain mid-band peak out of my speakers that disjoints the whole presentation. Somehow the transistor stage highlights this. I never noticed this before.
Ray, this passive output stage and transistor stage that you’ve put together turns the humble CD63 into a giant killer!!! Many many thanks for posting these schematics and supporting us (and me especially offline) through this build. I’ve done a lot of mods on my CD63, but this has made the single biggest difference to the sound of the player to date, and has helped all the other mods to simply “gel”…..and the best part is….it’s still running in!!! What will it sound like after 200 hrs, I wonder
If anyone’s interested, I can post the RS Components part numbers I ordered for the output stage and some of the notes I took (and a couple of pics) in adopting the CD67 placement list for the CD63 PCB. I even managed to put back the standard CD63 copper HDAM covers, for lower EMI.
Once again, Thanks Raymond!!
A very highly recommended mod! 
Champi (Counting the minutes to get back home and see how much the output stage has "run in")
No more opamps!!!
I managed to put this long weekend to good use by putting together Ray’s excellent transistor output stage…on the 63 PCB itself. It did take me three days, and no, it didn’t work the first time around,
but as with many complex DIY projects that was to be expected . I slept on the problem on Saturday night, and lo and behold, I found a missing jumper on the PCB… was wondering why I was getting +12V of DC on the output when I turned on the CD player prior to installing the high-pass filter To be honest, I was quite relieved that it worked…a real tribute to Ray’s excellent diagrams and instructional pictures (I did have to improvise stuffing the parts onto the 63 HDAM board as the pictures of the 67 HDAM board are a bit different - but the part numbering is mostly the same).
As Brent said, I too had difficulty sourcing 2SK170BL FETs for a FET stage, so I decided on the BC550C transistors. I did use the 2 170BLs from the original HDAM in position T4, so my transistor stage is a bit of a “hybrid” (BC550Cs for T1/T2, 2SC2240 for T3, 2SK170BL – from original HDAM – for T4). I also matched the HFe of the BC550’s to closely matched pairs. For the passive filter, I used 0.1% Welwyn resistors (Ray confirmed that 2K21 and 2K37 could be used in positions R3/R4 and R1/R2 respectively, instead of 2K2 and 2K4 – I couldn’t get these values in 0.1% tolerance). For all the other resistors in the transistor stage, I got 1% metal films, since these were the easiest to get my hands on and most cost effective as well.
If anyone’s going to build this on the CD player’s PCB, one will quickly realise that part size, for the passive filter, becomes a major issue when stuffing these parts in. It pays to get the smallest size high quality parts you can find.
Stuffing the CD63 PCB for the passive filter is very straight forward (the parts fall into place as per the placement list – the only exception is I had to run a separate ground for (I think) R3/R4. The transistor stage was a bit more challenging for me, but if you could follow the schematic, along with the parts placement list, you can easily figure out how to connect these components on the standard PCB. The key is to follow each junction on the schematic and double check this on the PCB with a DMM for connection (as I learned the hard way by leaving out a jumper).
I have used a very generic 3.3 uF metalised polyester “green cap” for C5,
until I can get my hands on a pair of Mundorf Supreme polyprops very soon. So how does it sound??
To put this in perspective, before I ripped out the player (again!!), I was running LM6172 opamps (PSU bypassed with XR7 ceramics on the IC), tweaked the active filter for constant group delay and had the stock HDAM as a buffer (with the output stage capacitors C651/C652/C653/C654 removed). In this state, I thought my CD63 (along with the other plethora of mods) sounded pretty good… great bass weight, a “decent” midrange and extended highs.
Keep in mind that the transistor output is still running in (with some horrible coupling caps in there at the moment)… and these observations are based on a 4 hr running in period: Never have I felt a greater need to upgrade the rest of my equipment than I do now!!
Compared to the Opamps, the “mostly” transistor stage (I’m using FETS in the T4 position) simply blows it away in terms of “rightness”
. Yes, there’s perceptibly deeper bass and the midrange is even more neutral… but it’s simply more REAL. The sound is BIG and bold… and really really smooth. It reminds me of my broken Sony XA7ES… even though the CD63 (tweaked) now sounds as good or better than the Sony, it never had that smoothness….until now! So much so that it’s starting to show flaws in the rest of my system, especially in the midrange. To really see if this was the CD player or the other equipment in the chain (amp/speakers), I plugged in my HD600 headphones into my preamp and listened…. WOW. I mean, the midrange out of the CD63 is to die for . It confirms that there’s a certain mid-band peak out of my speakers that disjoints the whole presentation. Somehow the transistor stage highlights this. I never noticed this before.Ray, this passive output stage and transistor stage that you’ve put together turns the humble CD63 into a giant killer!!!
Many many thanks for posting these schematics and supporting us (and me especially offline) through this build. I’ve done a lot of mods on my CD63, but this has made the single biggest difference to the sound of the player to date, and has helped all the other mods to simply “gel”…..and the best part is….it’s still running in!!! What will it sound like after 200 hrs, I wonder If anyone’s interested, I can post the RS Components part numbers I ordered for the output stage and some of the notes I took (and a couple of pics) in adopting the CD67 placement list for the CD63 PCB. I even managed to put back the standard CD63 copper HDAM covers, for lower EMI.
Once again, Thanks Raymond!!
A very highly recommended mod! Champi (Counting the minutes to get back home and see how much the output stage has "run in")
Re: CD63 Transistor Output Stage
Hi Champi,
No thanks, you're welcome! Excellent post, you've made a nice 'how to ...' guide. I'm glad you like the results
.
The reason this stage makes such a big difference in sound at the moment is also caused by the fact you didn't have the HDAM circuit jumpered yet, double impact.
Regards,
Ray.
pantera6 said:No more opamps!!!
...
Once again, Thanks Raymond!!
Champi (Counting the minutes to get back home and see how much the output stage has "run in")
Hi Champi,
No thanks, you're welcome! Excellent post, you've made a nice 'how to ...' guide. I'm glad you like the results
.The reason this stage makes such a big difference in sound at the moment is also caused by the fact you didn't have the HDAM circuit jumpered yet, double impact
.Regards,
Ray.
6h5c said:
I was recommended these by Simon, he uses them in xovers.
http://www.maplin.co.uk/Search.aspx...rue&Stock=28&MinPrice=0&MaxPrice=9999&SD=true
I use the AMPOHM ones from RS but these were too big
Brent
Re: CD63 Transistor Output Stage
Excellent mate can't wait to fit mine
Brent
pantera6 said:No more opamps!!!
So how does it sound??
To put this in perspective, before I ripped out the player (again!!), I was running LM6172 opamps (PSU bypassed with XR7 ceramics on the IC), tweaked the active filter for constant group delay and had the stock HDAM as a buffer (with the output stage capacitors C651/C652/C653/C654 removed). In this state, I thought my CD63 (along with the other plethora of mods) sounded pretty good… great bass weight, a “decent” midrange and extended highs.
Keep in mind that the transistor output is still running in (with some horrible coupling caps in there at the moment)… and these observations are based on a 4 hr running in period: Never have I felt a greater need to upgrade the rest of my equipment than I do now!!
Compared to the Opamps, the “mostly” transistor stage (I’m using FETS in the T4 position) simply blows it away in terms of “rightness”
Ray, this passive output stage and transistor stage that you’ve put together turns the humble CD63 into a giant killer!!!
If anyone’s interested, I can post the RS Components part numbers I ordered for the output stage and some of the notes I took (and a couple of pics) in adopting the CD67 placement list for the CD63 PCB. I even managed to put back the standard CD63 copper HDAM covers, for lower EMI.
Once again, Thanks Raymond!!
Champi (Counting the minutes to get back home and see how much the output stage has "run in")
Excellent mate can't wait to fit mine
Brent
rowemeister said:
brent
This might help
http://www.diyaudio.com/forums/showthread.php?threadid=23954
allan
ps i'am about to read it too
rowemeister said:
Just been reading some of the links to audioasylum in that thread
discussions from some and helpful ideas from Elso Kwak and John Curl.
I have some 2sk368's and 109's sitting around here
I'll try them for a fet stage.
allan
ps
That from page one
I should read the rest of it
I have looked up the difference between BL and GR too.
Drain current specification is the difference among the classes of these FETs. According to Toshiba Idss classification for the GR is 2.6 ~ 6.5ma, BL is 6.0 - 12.0 ma, V is 10-20 ma.
And looking at other threads the GR is the one to go for in the 170's.
Brent
Drain current specification is the difference among the classes of these FETs. According to Toshiba Idss classification for the GR is 2.6 ~ 6.5ma, BL is 6.0 - 12.0 ma, V is 10-20 ma.
And looking at other threads the GR is the one to go for in the 170's.
Brent
rowemeister said:
Brent,
In my quest for 2SK170BLs, I came across this link....and actually ordered some samples...if they ever turn up, I'll substitute these samples for the BC550Cs that are in the output stage now:
www.linearsystems.com/datasheets/LSK170.pdf
These appear to be "improved" low noise 2SK170s.
Cheers mate,
Champi
Coupling Caps
I found this link that talks about coupling caps and how they sound.... may be of interest to anyone considering building Ray's FET output stage:
http://www.humblehomemadehifi.com/Cap.html
Champi
I found this link that talks about coupling caps and how they sound.... may be of interest to anyone considering building Ray's FET output stage:
http://www.humblehomemadehifi.com/Cap.html
Champi
Re: Re: Coupling Caps
Erm, have you seen how much those things cost?!?!
http://www.partsconnexion.com/catalog/CapacitorsFilm_files/sheet005.html
click on DUELUND at the bottom (page redirects - can't link directly)
Simon
rowemeister said:
Erm, have you seen how much those things cost?!?!
http://www.partsconnexion.com/catalog/CapacitorsFilm_files/sheet005.html
click on DUELUND at the bottom (page redirects - can't link directly)
Simon