Marantz CD63 & CD67 mods list

[6h5c]

Hi Andy,

No, I didn't use a 2SK170. I have 2N5457, but they gave only 2.7mA. So I tried J309/310, which I have from building the Kwak-clock, but they gave too much. So I put a resistor in the source to adjust the current.

2N5484 looks o.k. These FET's have so much tolerance in spec's, I just put it in and raised the B+ voltage slowly and see what happened.

There is the risk that your FET will not have enough voltage to work on. Since you use 50V, the kathodevoltage will also be lower, because the tube will need less Ugk at 50V for this current. You can get around this by using a negative voltage (-12V from the player?) to tie the FET to, instead of ground.
You need some voltage headroom on the kathodes for the signal.

Ray.

[poynton]

Originally posted by 6h5c
...........You can get around this by using a negative voltage (-12V from the player?) to tie the FET to, instead of ground.

Ray.

HI. Thanks for the info.

Thats what I was planning to do with the redundant i/c psu. I have a circuit for a tube op-amp which uses +-24v.

Andy

[awpagan]

Originally posted by 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.

I hoped it my help

ps I built the headphone amp with 6922's and 40v does sound very good

seems the higher to B+ the less distortion
but maybe distortion is less of a problem in this application?

allan

[Franz G]

quick sketch - most will be familiar already

poynton has attached this image:
Click the thumbnail to see the original image.

Poynton: I lost track. Could you please point me to "Thorstens Circuit", mentioned in your sketch?

Kind regards
Franz

[poynton]

http://www.fortunecity.com/rivendell...da/vasfda.html

[float]

A question for the tube guys

We all seem to agree that good things have come from the removal of unnecessary parts (output caps, muting trannies, Hdams). Does the addition of a tube stage effectively take a step backwards?
It can't add transparency, which as far as I can tell is the goal of higher-end gear. I accept tubes add a 'flavour' that can benefit a system, but is this not done better at the preamp stage where you have more room to play with to allow better layouts and circuits?

[awpagan]

6h5c

"buffer Thorstens filter circuit"

I like the look of that circuit and it should be fet'able plus or i do have a heap of bc550/bc560's doing nothing at present (all C's)

and yes i don't like the opamps "just me" but the HDAM ciruit looks promising

will have to investigate further

also
"The differential input stage and current source are already there in the HDAM"

I made the CC-CCS-X-BOSOZ preamp and it is very good
and "balanced and/or single ended in and/or balanced and/single ended out"
But diff pair / cs got me thinking.


ps
has anyone got a picture of the pcb track layout? "cd67"

thinking of using unwanted circuit's as extra earth's

also help in using HDAM layout

allan

just to ad more confusion

[awpagan]

Originally posted by float
A question for the tube guys

We all seem to agree that good things have come from the removal of unnecessary parts (output caps, muting trannies, Hdams). Does the addition of a tube stage effectively take a step backwards?
It can't add transparency, which as far as I can tell is the goal of higher-end gear. I accept tubes add a 'flavour' that can benefit a system, but is this not done better at the preamp stage where you have more room to play with to allow better layouts and circuits?

I personally am not overly interested in tube stages.
but some people may like them.

what i prefer is discrete out

ie loose opamps

allan

[poynton]

Hi,

Originally posted by float
A question for the tube guys

We all seem to agree that good things have come from the removal of unnecessary parts (output caps, muting trannies, Hdams). Does the addition of a tube stage effectively take a step backwards?
It can't add transparency, which as far as I can tell is the goal of higher-end gear. I accept tubes add a 'flavour' that can benefit a system, but is this not done better at the preamp stage where you have more room to play with to allow better layouts and circuits?

Why is a tube stage a backward step? Don't forget that the ' i/v ' conversion is performed in the DAC. What is output from the DAC is PWM. Anything after the DAC is a filter and buffer, something which can easily be performed by tube or transistor. I think that it has been shown that the original circuit was lacking in many respects and can be upgraded by replacing with different parts or indeed removing 'superfluous parts' eg the HDAM. The main objection to using tubes is the B+ voltage but as I have found, that need not be as high as expected!

Originally posted by awpagan
6h5c

"buffer Thorstens filter circuit"

I like the look of that circuit and it should be fet'able plus or i do have a heap of bc550/bc560's doing nothing at present (all C's)

and yes i don't like the opamps "just me" but the HDAM ciruit looks promising

will have to investigate further

also
"The differential input stage and current source are already there in the HDAM"

I made the CC-CCS-X-BOSOZ preamp and it is very good
and "balanced and/or single ended in and/or balanced and/single ended out"
But diff pair / cs got me thinking.


ps
has anyone got a picture of the pcb track layout? "cd67"

thinking of using unwanted circuit's as extra earth's

also help in using HDAM layout

allan

just to ad more confusion

Agreed - opamps are a bit of an overkill solution and simpler discrete versions are available.

What's a CC-CCS-X-BOSOZ??

Originally posted by awpagan


I personally am not overly interested in tube stages.
but some people may like them.

what i prefer is discrete out

ie loose opamps

allan

Each to his own!

Since trying the tube output stage, however, I am going this route.

Anyone want to buy some opa627's??

Andy

[6h5c]

Originally posted by float
A question for the tube guys

We all seem to agree that good things have come from the removal of unnecessary parts (output caps, muting trannies, Hdams). Does the addition of a tube stage effectively take a step backwards?
It can't add transparency, which as far as I can tell is the goal of higher-end gear. I accept tubes add a 'flavour' that can benefit a system, but is this not done better at the preamp stage where you have more room to play with to allow better layouts and circuits?

Hm, this is a classic case of tube-misunderstanding i'm afraid. If a tube stage is designed properly, it will not add any 'flavour' to a system. The flavour that many people are used to these days is that of huge amounts of feedback in almost any system.

The goal is to get rid of the opamps that have an open-loop gain that's sky-high, and that needs to be restrained with lots of feedback to keep things stable. The nice thing of a simple discrete solid state OR tube stage is that no feedback is needed to get things working properly. It is in my opinion the feedback that kills the transparency in most circuits. When feedback was invented in the old days, it was seen as the great all purpose medicine to make an amp 'better'. But the concept is stupid actually. You take the (distorted) signal from the output and subtract that from the input signal, so that gets distorted too, and use that to feed the amp .

So i'm trying not simply to add a tubestage, i'm trying to replace the nasty opamps by a tubestage, or a transformer, or a discrete SS stage.

Ray.