I recently reread this thread from the beginning (again), which left me with two thoughts.
First, while Mr. Curl hasn't given us detailed instructions on achieving the ultimate preamp, he certainly left enough breadcrumbs on the path that we can follow him if we are willing to put in a little thought and effort. He doesn't owe us any obligation to hold our hand at every step, in fact he owes us nothing at all. He didn't even start this thread, so any hints he may drop here should be counted as a generous gift.
Second, in post #178, Richard (JustCallMeDad) posted this schematic
PSU - Global
to which Mr. Curl responded:
I certainly learned a thing or two from this circuit as well and I understand how all the individual sections work, but I have been left guessing as to what Mr. Curl saw that he had not considered before. Care to elaborate, Mr. Curl?
First, while Mr. Curl hasn't given us detailed instructions on achieving the ultimate preamp, he certainly left enough breadcrumbs on the path that we can follow him if we are willing to put in a little thought and effort. He doesn't owe us any obligation to hold our hand at every step, in fact he owes us nothing at all. He didn't even start this thread, so any hints he may drop here should be counted as a generous gift.
Second, in post #178, Richard (JustCallMeDad) posted this schematic
PSU - Global
to which Mr. Curl responded:
I certainly learned a thing or two from this circuit as well and I understand how all the individual sections work, but I have been left guessing as to what Mr. Curl saw that he had not considered before. Care to elaborate, Mr. Curl?
John,
Let me first make clear that you owe me or anyone else nothing! It is apparent however that my normal critical note is interpreted by some as being hostile, sadly. I have nothing against you or anyone, so don't take it too personal.
My only remark is that you bring up a subject and when questions start coming to bring about a discussion, you sort of back off with, as I call it, an enigmatic remark.
The open-loop design discussion has now switched to audio design in general which is ok to me. I completely understand that you cannot disclose any information on your current/future project.
Many have proposed schematics for discussing open-loop, DC-servo and power-supply design in general, somehow related to but not specifically aimed at the BT as some do suggest. Those that have contributed to a large extend have put much time and effort in digesting your given answers and learn from them. But at some point the discussion stops and one is somehow left in the woods. Maybe I look at things quite different from many others, but I believe it is a good thing to be upfront.
Let me first make clear that you owe me or anyone else nothing! It is apparent however that my normal critical note is interpreted by some as being hostile, sadly. I have nothing against you or anyone, so don't take it too personal.
My only remark is that you bring up a subject and when questions start coming to bring about a discussion, you sort of back off with, as I call it, an enigmatic remark.
The open-loop design discussion has now switched to audio design in general which is ok to me. I completely understand that you cannot disclose any information on your current/future project.
Many have proposed schematics for discussing open-loop, DC-servo and power-supply design in general, somehow related to but not specifically aimed at the BT as some do suggest. Those that have contributed to a large extend have put much time and effort in digesting your given answers and learn from them. But at some point the discussion stops and one is somehow left in the woods. Maybe I look at things quite different from many others, but I believe it is a good thing to be upfront.
courage said:
Yeah, i know. Silly, isn't it ?
But i do think i've got a good blueprint of the CTC thanks to the many posts of Mr. Curl on this thread.
I've copied every relevant post of Mr Curl on parts, construction and operating points. That gives more than a global picture of the Blowtorch.
It's a good initiative to post a circuit of the linestage based on SY's description at the beginning of this thread, Courage.
I find it interesting to compare it to real circuits by Mr Hansen, Borbely and Pass that are available and comparable in parts and topology, such as the Pass UGS versions and figure out why Mr Curl made his linestage different and more simple.
The rest is probably as Poobah said: the big M.
Trying to force more out of this thread is aimed at copying the Blowtorch linestage, that is not showing gratitude to the designer for his willingness to explain his craftmanship.
Gone to the point where someone deduced that there must have been some resistors on the bottom of the boards... someone has the time and inclination to pour over a couple rough photos like that, and count resistors? That speaks for itself.
Keep in mind jacco, I meant Matching... component matching... when I said "M".
I suppose many thought I meant Money. It is ALWAYS about money... in all things. Money = Work = Time = Life
Tail wagging? Waiting for crumbs to fall... sure. The best teachers don't give the best answers... they ask the best questions. Some here bang the table under the veil of "learning", when in reality they would prefer to skip the learning and go directly to "knowing"... odd, but predictable.
Hello, Poobah
Not so sure that parts matching took such a time to John..
First of all, the dual input Jfets (2SJ109 & 2SK389) are already matched, and I guess that no special tweaking is to be done with them... But perhaps... In such a case, looking carefully to the bad pic we all refer to, I just can't see any resistors but two between the Jfets. They are setting the bias current, IMO...
But if any extra matching has been done and was by John (and that is the point you advocate), in order to "fine tune" all cross polarity Jfets discrepancies, some extra resistors have to be put somewhere in the sources connections... And here, Courage would be right about some extra resistors need...
But I think that I point why Courage suggested that... Simply because of JustCallMeDad DC offset correction that would need some "resistor spiltting" in order to have the DC offset correction applied... A trick that John used previously on Parasound stuff (and is perhaps still using here with the Blowtorch...).
Perhaps that he will tell us...
Pursuing on your point, I disagree that extra matching on the Blowtorch Line amplifier would be needed... On the boards, seems to be only Fulpack Mosfets around the Jfets path. Modern Mosfets don't really need any matching if they are taken from the same batch (here, just my experience with them...). And, as I suggested it previously, if theye a
Not so sure that parts matching took such a time to John..
First of all, the dual input Jfets (2SJ109 & 2SK389) are already matched, and I guess that no special tweaking is to be done with them... But perhaps... In such a case, looking carefully to the bad pic we all refer to, I just can't see any resistors but two between the Jfets. They are setting the bias current, IMO...
But if any extra matching has been done and was by John (and that is the point you advocate), in order to "fine tune" all cross polarity Jfets discrepancies, some extra resistors have to be put somewhere in the sources connections... And here, Courage would be right about some extra resistors need...
But I think that I point why Courage suggested that... Simply because of JustCallMeDad DC offset correction that would need some "resistor spiltting" in order to have the DC offset correction applied... A trick that John used previously on Parasound stuff (and is perhaps still using here with the Blowtorch...).
Perhaps that he will tell us...
Pursuing on your point, I disagree that extra matching on the Blowtorch Line amplifier would be needed... On the boards, seems to be only Fulpack Mosfets around the Jfets path. Modern Mosfets don't really need any matching if they are taken from the same batch (here, just my experience with them...). And, as I suggested it previously, if theye a
PMA said:
Upupa Epops said:I'm in fear, that some questions stay unanswered...
Are you guys a tag team operation or something
So we are talking recording gear,
_o_ that is very high quality and zero FB topology.
www.gordonaudio.com
http://www.gearslutz.com/board/showpost.php?p=547413&postcount=15
http://www.3daudioinc.com/3db/showpost.php?p=10039&postcount=6
http://www.3daudioinc.com/3db/showpost.php?p=10051&postcount=18
there's plenty more of the same but you get the picture, most of
these guys have used the best mic pre's available, and they don't
want colour, they have racks of Neves etc for that.
Get with the program guys!
Cheers,
Terry
Sorry, guys... A far too big finger hit the "send" key too soon...
If there is some matching degree, to an extent, must be Id vs Vgs, under the realistic conditions John's prototype degaged... Industrial grade parts just are a bit closer on those parameters...
Just wondering now if the 350 Khz bandwith is not due to those very effective Mosfets use (indeed, they have capacitances ways in excess 650 pF !!!) rather than Audio grade ones we discussed on the Forum... with some good entries in my audio data lines now...
And a separate question to John : is there any special gain to have used "six nine" silver under teflon jacket (as Bob said me... From Bear Labs, I am told...) instead of copper cable (your past practise for short runs...)... Perhaps that the answer is that copper oxide doesn't is highly resistive, but silver oxide is just as good as plain silver... Just puzzled with
jbaudiophile
If there is some matching degree, to an extent, must be Id vs Vgs, under the realistic conditions John's prototype degaged... Industrial grade parts just are a bit closer on those parameters...
Just wondering now if the 350 Khz bandwith is not due to those very effective Mosfets use (indeed, they have capacitances ways in excess 650 pF !!!) rather than Audio grade ones we discussed on the Forum... with some good entries in my audio data lines now...
And a separate question to John : is there any special gain to have used "six nine" silver under teflon jacket (as Bob said me... From Bear Labs, I am told...) instead of copper cable (your past practise for short runs...)... Perhaps that the answer is that copper oxide doesn't is highly resistive, but silver oxide is just as good as plain silver... Just puzzled with
jbaudiophile
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