You know,
Come to think of it... I would probably shoot anyone that wired my amp that way... really... really... stupid. Of course tiger penis wire with rhino horn insulation is all the rage. All this supreme quality, and they couldn't run seperate grounds for RCA connectors... crimony. I believe a "space frame" is a mechanical engineering thing; and it's loosely based on triangles and elements that can withstand stress in both tensile and compressive modes (rather than tensile alone).
Let's all go out and buy number 40! I wonder how many number 40's there will be before these guys move to the St. Martin.
Come to think of it... I would probably shoot anyone that wired my amp that way... really... really... stupid. Of course tiger penis wire with rhino horn insulation is all the rage. All this supreme quality, and they couldn't run seperate grounds for RCA connectors... crimony. I believe a "space frame" is a mechanical engineering thing; and it's loosely based on triangles and elements that can withstand stress in both tensile and compressive modes (rather than tensile alone).
Let's all go out and buy number 40! I wonder how many number 40's there will be before these guys move to the St. Martin.
Hi, Sy
I read your thread with a great attention... For my old eyes, input dual Jfets are only 2SJ109 & 2SK389 (perhaps from a special ordered batch... John used so many fparts from Toshiba that they can have done it for him... Perhaps ultra-tight matching or very upper end of scale V class... Or both !).
Second stage seem to be Fullpack Mosfets (IR ?)... And about the Holco resistors, Bob Crump said me that they were only 2 W... So, in my mental reversing of the Blowtorch, second stage current was pretty limited... But with 5W, really have to update my calculations...
The Teflon boards must have been dictated by hygroscopic reasons as much as all over capacitance... But Teflon is very hard to work with, specially for engraving them... Bob said me that theywere all CNC routed...
So, guys, like me, just dream of... Or drop me a line if you can CNC route (LOL !).
I read your thread with a great attention... For my old eyes, input dual Jfets are only 2SJ109 & 2SK389 (perhaps from a special ordered batch... John used so many fparts from Toshiba that they can have done it for him... Perhaps ultra-tight matching or very upper end of scale V class... Or both !).
Second stage seem to be Fullpack Mosfets (IR ?)... And about the Holco resistors, Bob Crump said me that they were only 2 W... So, in my mental reversing of the Blowtorch, second stage current was pretty limited... But with 5W, really have to update my calculations...
The Teflon boards must have been dictated by hygroscopic reasons as much as all over capacitance... But Teflon is very hard to work with, specially for engraving them... Bob said me that theywere all CNC routed...
So, guys, like me, just dream of... Or drop me a line if you can CNC route (LOL !).
jbaudiophile said:
Une ligne.
M'appelle le gourmand.
Pour un fanatique du bouffe Francaise avec une carte du Metro cash and carry Lomme Lez Lille est le plus proche, une visite quelque fois par annee est obligatoire.
Et j'adore plein le fromage frais de Carrefour.
Dans ma jeunesse j'ai appris a CNC, c'est plus facile de demander les relations, experimentee la fabrication des panneaux teflon depuis dix ans. Mon pere etait un client de DuPont.
Stuart,
i know it sounds ridiculous, but i'm allergic to cheese.
Only kiddy stuff for me, like soft cheeses and Italian ones.
A cheese hard die should try Formaggio Marcio, if you can stand the maggets.
The lines were meant for the French audiophile, i visit his town frequently, i better send a pm next time as not to upset others.
Twice as much cnc routing for less than a DarTZeel, there's economics for ya !
i know it sounds ridiculous, but i'm allergic to cheese.
Only kiddy stuff for me, like soft cheeses and Italian ones.
A cheese hard die should try Formaggio Marcio, if you can stand the maggets.
The lines were meant for the French audiophile, i visit his town frequently, i better send a pm next time as not to upset others.
Twice as much cnc routing for less than a DarTZeel, there's economics for ya !
Re: getting back to topic ...
Most of Borbely stuff is pretty high OLG, closed loop.
Quite complex at that.
The Blowtorch is all open loop and does look very simple.
So on the surface yes, but a bit deeper and
the differences are there.
I'd like to know the servo arrangement. They always
are a point of contention.
Terry
mlloyd1 said:
Most of Borbely stuff is pretty high OLG, closed loop.
Quite complex at that.
The Blowtorch is all open loop and does look very simple.
So on the surface yes, but a bit deeper and
the differences are there.
I'd like to know the servo arrangement. They always
are a point of contention.
Terry
Shaft Extendeds needed here
The front panel mount switches would benefit from the use of shaft extenders to move them to the rear of the chassis. That way the amount of wiring could be minimized.
But real nice chassis. If anyone a an unused chassis from one of these, I would GLADLY pay the postage.
George
The front panel mount switches would benefit from the use of shaft extenders to move them to the rear of the chassis. That way the amount of wiring could be minimized.
But real nice chassis. If anyone a an unused chassis from one of these, I would GLADLY pay the postage.
George
It looks to me like the 'blotorch' operation needed a fourth guy, one to tell the machine shop guy to stop the mill instead of cutting right through the real panel. I can hear the "Oh sh-t! How many did you make like that?" all the way from cali.
A fifth guy would have been helpful to come up with a better wiring scheme. Although from the looks of it it seems as though the lack of plan was the plan.
I like the idea of the hands-off servo that would interfere minimally with the audio signal, the problem I experienced with servos is when things do start to misbehave they tend to sweep the dirt under the rug instead of doing real cleanup.
All in all very "DIY"!
A fifth guy would have been helpful to come up with a better wiring scheme. Although from the looks of it it seems as though the lack of plan was the plan.
I like the idea of the hands-off servo that would interfere minimally with the audio signal, the problem I experienced with servos is when things do start to misbehave they tend to sweep the dirt under the rug instead of doing real cleanup.
All in all very "DIY"!
QUOTED
"The Blowtorch is all open loop and does look very simple.
I'd like to know the servo arrangement."
"They always are a point of contention."
"John indicated that it was a plain vanilla servo integrator with a one second time constant. The "trick" is to trim the circuit up to be inherently stable, then connect the servo and let it just do a bit of cleanup when things start moving around."
A point of contention : a DC servo is quite the contrary of an open loop, it's the highest feedback you can find.
~~~~~~ Forr
§§§
"The Blowtorch is all open loop and does look very simple.
I'd like to know the servo arrangement."
"They always are a point of contention."
"John indicated that it was a plain vanilla servo integrator with a one second time constant. The "trick" is to trim the circuit up to be inherently stable, then connect the servo and let it just do a bit of cleanup when things start moving around."
A point of contention : a DC servo is quite the contrary of an open loop, it's the highest feedback you can find.
~~~~~~ Forr
§§§
John Curl
"Well folks, I saw your comments. It is unfortunate that you criticize without understanding my reasons for using servos, etc. You have the right to make something 'better' but I have not seen it on diyaudio at any time."
It is very easy to think that there is no "better". Reasons of using servos are never been mysterious : they are intended to add gain loop at DC. Below are texts extracted from thread "To use DC servo or not?" which I have written about my knowledge and thinking about servos. They may not entirely apply to the Blowtorch preamp.
Post #19
Is servo or not servo is the real problem ?
DC feedback is to maintain the DC output of the amplifier at 0V. Two mechanisms affect this DC : the DC offset at the output of the input differential pair and the DC offset due the the following stages of the amplifier. To get the lowest and most stable distorsion from an input differential pair, it should always work with strictlly equal operating points currents in both its devices. Any DC difference due to DC feedback will affect this operating point. So capacitor or servo feedback do not make great changes. A capacitor is much easier, a bipolar type is recommmanded for ultimate performances.
A more logical way to control the offset at the output of the amplifier is a servo which will act after the input stage. See Perrot's patent US 5 635 874.
Another way would be to connect the input stage to the followingstages only at AC : an all new scheme bringing back coupling capacitors.
Post #24
I think the complementary differential input is fundamentally a wrong concept because, among other things, each input differential creates its own offset at its output and the two offsets of the upper and lower differentials can never be fully equal in value. Particularly in this case, a servo fed back to the Vas à la Perrot should do better than one fed back to the input.
Threads URLs :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64930&perpage=10&highlight=&pagenumber=2[/url]
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64930&perpage=10&highlight=&pagenumber=3[/url]
~~~~~~ Forr
§§§
"Well folks, I saw your comments. It is unfortunate that you criticize without understanding my reasons for using servos, etc. You have the right to make something 'better' but I have not seen it on diyaudio at any time."
It is very easy to think that there is no "better". Reasons of using servos are never been mysterious : they are intended to add gain loop at DC. Below are texts extracted from thread "To use DC servo or not?" which I have written about my knowledge and thinking about servos. They may not entirely apply to the Blowtorch preamp.
Post #19
Is servo or not servo is the real problem ?
DC feedback is to maintain the DC output of the amplifier at 0V. Two mechanisms affect this DC : the DC offset at the output of the input differential pair and the DC offset due the the following stages of the amplifier. To get the lowest and most stable distorsion from an input differential pair, it should always work with strictlly equal operating points currents in both its devices. Any DC difference due to DC feedback will affect this operating point. So capacitor or servo feedback do not make great changes. A capacitor is much easier, a bipolar type is recommmanded for ultimate performances.
A more logical way to control the offset at the output of the amplifier is a servo which will act after the input stage. See Perrot's patent US 5 635 874.
Another way would be to connect the input stage to the followingstages only at AC : an all new scheme bringing back coupling capacitors.
Post #24
I think the complementary differential input is fundamentally a wrong concept because, among other things, each input differential creates its own offset at its output and the two offsets of the upper and lower differentials can never be fully equal in value. Particularly in this case, a servo fed back to the Vas à la Perrot should do better than one fed back to the input.
Threads URLs :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64930&perpage=10&highlight=&pagenumber=2[/url]
http://www.diyaudio.com/forums/showthread.php?s=&threadid=64930&perpage=10&highlight=&pagenumber=3[/url]
~~~~~~ Forr
§§§
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