Marantz CD63 & CD67 mods list

[6h5c]

And now for something completely different....

What's the status of our custom tranny project?

Is it just me, or has everybody's enthousiasm regarding this idea cooled down a bit?
Or am I just being impatient ? I'd really like this thing to go through.

Michael, you were going for a quote on a 50VA, any news yet?

Regards,

Ray.

[poynton]

Hi Folks.

After a short delay ( I broke my soldering station ! ).....

It's going and sounds excellent.
Really good bass, mid and top a bit recessed - need to play around with the filter caps a bit - I used slightly different (higher) values to Thorsten's. Also the amp is on long leads from the cd-p - 12" or so and it's only in mono.

I used 12k anode resistors not dual cascode but I will try later and see if it makes any difference.

NOTE THE VOLTAGE BEING USED !!!!!!!!!!!! 50v

I have taken the B+ down to 20v.
The output drops and distortion starts at this point but from 25v up i cannot hear any difference.

I will post a circuit when I have drawn it.

Andy

[poynton]

quick sketch - most will be familiar already

[6h5c]

Excellent dude!

The tubes are starting to be common practice in this thread .
I'm about to order some parts for it and build the passive filter part on the players PCB.
Wow, 50 volts is low! This can be done with a standard 2x24V tranny. I did notice the circuit goes on for a long time when I switch-off my power supply. What tubes did you use?
Do you have a (too) high output signal?
Lose the 2k2 resistors and try the CCS FET in the tail. It will bring balance in the circuit, cuz the resistor is not much of a constant current.

Regards,

Ray.

[poynton]

Wow, 50 volts is low! This can be done with a standard 2x24V tranny. I did notice the circuit goes on for a long time when I switch-off my power supply.

Yes, it is low. It does not make an audible difference if I increase it to 100v so I am redesigning the psu to use a 20-0-20 tx I have. ( Maybe the redundant windings on the existing Tx ?? )It should fit on the board with the amp.
I am putting all the stuff on the board and using links to the Marantz PCB ( DAC output ).

What tubes did you use?

I've used E88CC and ECC88. I will try the small valves soon! (single 6.3v heater )

Do you have a (too) high output signal?

Yep. It does seem on the high side. It overloaded the radio input to the small amp I first tried it out with but was ok (low) on the tape. (it's an old Armstrong of early '70s)

Lose the 2k2 resistors and try the CCS FET in the tail. It will bring balance in the circuit, cuz the resistor is not much of a constant current.

Balance is not bad according to my meter but it's on the list for trying tomorrow.



Now that it has been running for some hours, it seems to have 'run in' and now sounds better.
'She who must be obeyed' says it sounds really good! I realised that the lack of prescence etc was due to the fact that it is MONO!!! and 1 channel only !!!!

I have just bought a Marantz cd53 ( no HDAM to remove ) for future experiments!!!

Andy

[6h5c]

Originally posted by poynton
'She who must be obeyed'

Wow, do you have your mother-in-law living with you ?

Cool!
When I receive my parts i'm going to try it on 50V too. I have two PCC88's here that I can use. It has a bit high mu for this application, but it is better suited for low-voltage use.

I'm curious how the small valves will do.
Did you measure any noise residue at the output that I experienced earlier?

Ray.

[awpagan]

low voltage for tubes
this may give some ideas
http://headwize.com/ubb/showpage.php...d=5395&fpage=2

allan


post 17

[poynton]

Originally posted by 6h5c


............ I have two PCC88's here that I can use. It has a bit high mu for this application, but it is better suited for low-voltage use.....................

Different heater voltage but should work (see awpagan's post). An attenuator may need to be used (!!!!) if the stage gain is too high . Try ECC82/81 , I have loads - want some? I am also going to try some new Russian tubes, 6N3P. The pin layout is good for pcb making.

I'm curious how the small valves will do.

Me too. I note on the site below that using JAN6111WA pencil tubes is mentioned.

Did you measure any noise residue at the output that I experienced earlier?Ray.

Not yet. The amp I'm using puts out loads of hiss anyway but using the cd-p did not seem to increase it any.

Originally posted by awpagan
low voltage for tubes
this may give some ideas
http://headwize.com/ubb/showpage.php...d=5395&fpage=2

allan


post 17

Thanks. I had already looked at Headwize for some ideas - very useful.


Andy

[6h5c]

Hi Allan,

Thanks for the link! I didn't think of the headphone-guys. They are used to using tubes at low voltages for a long time .

Your earlier remark about the HDAM circuit got me thinking (again...).
Maybe it can be changed as you said, into a discrete buffer without any feedback, to buffer Thorstens filter circuit. I'm going to look into that and do some experiments.

I got some inspiration when I found this circuit again at Ultranalog.
The differential input stage and current source are already there in the HDAM.

Regards,

Ray.

[poynton]

Originally posted by 6h5c
...............Lose the 2k2 resistors and try the CCS FET in the tail. It will bring balance in the circuit, cuz the resistor is not much of a constant current............

Ray.

Did you use a 2SK170 for the CCS and did you have to select it for the 4mA? I have a lot of 2N5484 - I suppose i can use them?

Andy