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.
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.
6h5c said:
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
6h5c said:
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
Poynton: I lost track. Could you please point me to "Thorstens Circuit", mentioned in your sketch?
Kind regards
Franz
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?
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?
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
"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
float said:
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
Hi,
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!
Agreed - opamps are a bit of an overkill solution and simpler discrete versions are available.
What's a CC-CCS-X-BOSOZ??
Each to his own!
Since trying the tube output stage, however, I am going this route.
Anyone want to buy some opa627's??
Andy
float said:
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!
awpagan said: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??
awpagan said:
Each to his own!
Since trying the tube output stage, however, I am going this route.
Anyone want to buy some opa627's??
Andy
float said:
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.
6h5c said:
Well, I KNEW that was gonna happen
I'm guilty of misunderstanding as well; I assumed the tube was an extra buffer stage and not a replacement for the filter/I-V opamps.
I tend to skim past the tube posts due to a lack of real interest/understanding so I missed your true intentions. I would agree that in this case the tube would be a valid and possibly better alternative than the op627 solution, although I'm very happy with mine.
6h5c said:
Hi.
Yes, Float, you may have stirred things up.
But isn't it nice that this thread has not degenerated into name calling and backbiting as so often seems to happen on this forum, especially from some members whose thoughts and ideas are well respected.
And we may have a concrete outcome in the form of working circuits and a custom Tx.
Andy
poynton said:
It sure is.
We all want the same thing (better sound ); although we'll never all agree what it is, or how best to get there 🙂
Reading Thorstens page now....
poynton said:
Hey, we may be going for a record? 655 messages and no moderator had to jump in! I like it too 😀.
Ray.
awpagan said:
Hi Allan,
When you mentioned it, it struck me. Maybe the HDAM can be useful after all!
I have the service manual of the CD67, but I have to get my old scanner working to get you a print of the layout. I will try it tonight, and post it here if I succeed.
Regards,
Ray.
6h5c said:
Hi Ray,
Connected the cathodes and kept the 2.2k to ground. With a B+ of 50v, the cathode is at 1.7v with the grids at 1.5v. So You may be right, not enough for a CCD.
Anyway, it sounds the same which is great!!!! Plenty of air and space, deep bass. It's good on 'modern' stuff like Madonna 'Music' and excellent on vocals - Sade etc. Acoustic guitar like Gypsy Kings - you can hear the fingers clearly. So I'm satisfied.
So now to the small valves and stereo !!
I am thinking of getting some pcb's made - anyone onterested?
Andy
poynton said:
Perhaps not worth making this point but if it makes Madonna Music sound good it may not be giving the full picture. This album sounds dreadful. If it doesn't there's colouration or not enough resolving power. IMHO.
edit - maybe that's a moot point in the context of a mod only affecting one small part of the chain.
SimontY said:
Err........I meant artificially extended bass lines
I had to put a large paper bag over the cd-p when playing this - only way to make Madonna LOOK good!
poynton said:
hehe, she can drink all the bottled water she likes but age WILL catch up eventually!!
I just wonder if that hyped up super compressed sound will ever go out of fashion with these producers... what a painful mess.
And I bet it sounds dreadful through her B&W Nautilus speakers...
ed: oh yeh, looks like that was post 1000, time for a little celebration
