Sean, I would estimate that the current in each j-fet was about 2ma. This is practical with this design, as well as the JC-1 and JC-2 from Parasound. This is because the INPUT stage does NOT set the peak current of the second stage.
The Blowtorch line stage uses much more idle current, perhaps 12-14ma. As much as I can get. This is because the output current is the same as the input current, so the input current must be high to get max class A output current.
The Blowtorch line stage uses much more idle current, perhaps 12-14ma. As much as I can get. This is because the output current is the same as the input current, so the input current must be high to get max class A output current.
Hi John,
I was particularly interested in your recent comments about PCB materials and platings/coatings.
Some years ago I replicated a low-level circuit (MC head amp) using Rogers Duroid 5880, and it sonically outperformed the same circuit built up on an SRBP (?) board. This was before FR4 was so widely in use, and your illuminating comments and references in this thread go a long way towards explaining why.
Is my understanding correct that your latest preference is to avoid all electro-plating and merely clean the bare copper traces and apply the low DA conformal coating directly to this?
The lowest-dielectric conformal I have so far found in a spray can (Mil spec acrylic) has a claimed DC of 2.5. Is this as good as it gets, or should I keep on searching for something better?
Do you see any harm in firstly populating the PCB, then thoroughly cleaning it and afterwards applying such material, which would then cover all of the exposed surface, including the soldered joints? The conformal coating I have in mind can be 'soldered through' (as Grey suggests), but it might be easier/possibly better to cover everything after any soldering, and this might give better long-term protection to the solder joints, themselves.
Thanks for your advice.
Regards,
I was particularly interested in your recent comments about PCB materials and platings/coatings.
Some years ago I replicated a low-level circuit (MC head amp) using Rogers Duroid 5880, and it sonically outperformed the same circuit built up on an SRBP (?) board. This was before FR4 was so widely in use, and your illuminating comments and references in this thread go a long way towards explaining why.
Is my understanding correct that your latest preference is to avoid all electro-plating and merely clean the bare copper traces and apply the low DA conformal coating directly to this?
The lowest-dielectric conformal I have so far found in a spray can (Mil spec acrylic) has a claimed DC of 2.5. Is this as good as it gets, or should I keep on searching for something better?
Do you see any harm in firstly populating the PCB, then thoroughly cleaning it and afterwards applying such material, which would then cover all of the exposed surface, including the soldered joints? The conformal coating I have in mind can be 'soldered through' (as Grey suggests), but it might be easier/possibly better to cover everything after any soldering, and this might give better long-term protection to the solder joints, themselves.
Thanks for your advice.
Regards,
Yup, Sam beats himself up repeatedly about not buying a Blowtorch in that article.
Also goes on about how great the Parasounds are including the new preamp. Mentions that they are a bargain.
Also Charles Hansen , who pops in here every now and then got
"2007 Product of the year" for his MX-R amp.
I have to say John, next Blowtorch type product that you do should have the case made by the guys that do Charles' stuff!
However you feel about Stereophile, it is great to see these guys get some (more) recognition!
Also goes on about how great the Parasounds are including the new preamp. Mentions that they are a bargain.
Also Charles Hansen , who pops in here every now and then got
"2007 Product of the year" for his MX-R amp.
I have to say John, next Blowtorch type product that you do should have the case made by the guys that do Charles' stuff!
However you feel about Stereophile, it is great to see these guys get some (more) recognition!
Congratulations to Charles Hansen for getting 'Product of the year' This is the playing field that Charles and I compete. It should inform others that we are taken seriously in the audio world, even if our ideas may sometimes seem 'exotic' or extreme.
Negative feedback, or lack of it, is a BIG reason that Charles won this year.
Negative feedback, or lack of it, is a BIG reason that Charles won this year.
john curl said:
It took me a number of years to arrive at the conclusion that negative feedback carried more baggage than commonly acknowledged. I've been steadily decreasing the amount of feedback I use with each circuit--and each piece sounds better than its predecessor. There is a learning curve, however. It's easier and faster to simply apply feedback as a band-aid in an attempt to fix whatever is wrong and many choose that path.
On the "would resistors cancel inductance if mounted vertically" front, my contact at Caddock suggests not, primarily for the geometry reason; that the wire lead cannot cancel the residual field of the resistor body--most of the field is too far away. His suggestion was to use surface mount resistors if inductance is a problem.
Grey
Tico, WHY would you want to build junk? Why not just buy it at the discount store? That's what I do, when I am not needing anything special. Our customers require us to make nice boxes, as well as audio quality. You can make your preamp in a coffee can, if you wish.
Still, I would not waste my time making what I can easily buy from a mail order catalog.
Still, I would not waste my time making what I can easily buy from a mail order catalog.
QSerraTico_Tico,
So who, here, has asked you to buy a preamp? Any preamp? Point to the post, please.
As you correctly point out, this is a DIY site. As such, the question is not whether you can or should or would spend a particular sum of money buying any particular preamp, the question is whether you can build something that approaches it in performance.
I know that if I were into building cars, I'd rather shoot for the performance of a Ferrari or Maserati than aim low and attempt to equal a Ford (you've got to know how much I despise Detroit for the full import and contempt of my comparison to become apparent). The Ford's performance may be easier to achieve. The Ford's parts may be more readily available. The parts to build a Ford-like car would certainly be cheaper. But why on Earth would anyone with any pride want to emulate something from a lowest-common-denominator manufacturer like Ford?
That's like a gourmet chef trying to cook a McDonald's clone hamburger, grease and all. If it's not illegal, it ought to be.
Aim higher and quit whining. There are enough hints given in this thread that you should be able to build a pretty decent preamp if you put your mind to it. Don't want to build John's transconductance circuit? No problem. Hang a follower output on it. Still not happy? Build one of Nelson's circuits. That doesn't float your boat? Snag a schematic from the Tube Forum. Not your cup of tea? Take a look at any of a hundred other threads here that propose other sorts of circuits.
Unless, of course, you'd rather have a Ford. I'm sure that Wal-Mart has something on special this week. Think of all the time and money you'll save.
Some people are just happier criticizing, I guess.
Grey
So who, here, has asked you to buy a preamp? Any preamp? Point to the post, please.
As you correctly point out, this is a DIY site. As such, the question is not whether you can or should or would spend a particular sum of money buying any particular preamp, the question is whether you can build something that approaches it in performance.
I know that if I were into building cars, I'd rather shoot for the performance of a Ferrari or Maserati than aim low and attempt to equal a Ford (you've got to know how much I despise Detroit for the full import and contempt of my comparison to become apparent). The Ford's performance may be easier to achieve. The Ford's parts may be more readily available. The parts to build a Ford-like car would certainly be cheaper. But why on Earth would anyone with any pride want to emulate something from a lowest-common-denominator manufacturer like Ford?
That's like a gourmet chef trying to cook a McDonald's clone hamburger, grease and all. If it's not illegal, it ought to be.
Aim higher and quit whining. There are enough hints given in this thread that you should be able to build a pretty decent preamp if you put your mind to it. Don't want to build John's transconductance circuit? No problem. Hang a follower output on it. Still not happy? Build one of Nelson's circuits. That doesn't float your boat? Snag a schematic from the Tube Forum. Not your cup of tea? Take a look at any of a hundred other threads here that propose other sorts of circuits.
Unless, of course, you'd rather have a Ford. I'm sure that Wal-Mart has something on special this week. Think of all the time and money you'll save.
Some people are just happier criticizing, I guess.
Grey
Hi QSerraTico_Tico,
I have to agree with Grey and John here. This is DIY, and we are here to learn. You can't learn buy looking at so-so quality stuff, that is unless you want to learn what not to do.
John, it's nice that you and Charles compete. The real test is competing against yourself. Getting better each time. You indicated that you and Charles compete on a certain level of "stage", and then point out that winners and losers are those things depending on mostly what amounts to electronic fashion. Hmmmmmm.....
Hey! It's only audio! It's not even close to life and death. However it's great to learn from "the masters".
I'm not belittling anyones accomplishments here. Just pointing out that we are in the entertainment business.
-Chris
I have to agree with Grey and John here. This is DIY, and we are here to learn. You can't learn buy looking at so-so quality stuff, that is unless you want to learn what not to do.
John, it's nice that you and Charles compete. The real test is competing against yourself. Getting better each time. You indicated that you and Charles compete on a certain level of "stage", and then point out that winners and losers are those things depending on mostly what amounts to electronic fashion. Hmmmmmm.....
Hey! It's only audio! It's not even close to life and death. However it's great to learn from "the masters".
I'm not belittling anyones accomplishments here. Just pointing out that we are in the entertainment business.
-Chris
I view Stereophile "Best of.." awards the same way I view Absolute Sound "Golden Ears." They're nice, I guess, in the sense that they give you bragging rights until the next round comes out, but then I've had some pretty good wines that hadn't won Wine Spectator's "Best" award, too. At least Wine Advocate doesn't do a big do-dah issue with their best-of wines.
I still maintain that the proper way to use audio reviews is the same as with movie reviews--use them to winnow out the obvious losers, then go listen to the most likely candidates yourself.
Huh...I've won exactly one award in my alternate life as an author...and the story that won was several notches down from what I consider my best writing. Good? Okay, yeah, maybe. But best? No. And the stories that the Russians liked well enough to pirate? One was the same one that won the award. The other...no way...unh, uh. Sorry. Not my best writing. It was a successful story in that it sold, but it's not one that I would pull out if someone asked to read one of my stories and I wanted to make a good impression. One of those "your mileage may vary" things, obviously.
One of the things I find problematic with annual best-of awards is that they are always rating "this year's" product. What if last year's is still king of the hill? Ooops! Too bad. It had the misfortune to be on the wrong side of the calendar flip. As a result, I prefer the kind of rating wherein a piece stays on top for as long as the reviewer thinks it's best, even if that lasts a year or two or three...
Charles, this in no way means that your amp doesn't sound good. Although I haven't heard it, I suspect it would be on my short list of things to hear if I were in the market for an amp, if for no other reason than because you and I seem to share similar goals, sonically. My complaint is with the structure of the awards system, not you or your amp. Here's hoping that it gets on someone's non-annual best-of list and remains there for a while.
Grey
I still maintain that the proper way to use audio reviews is the same as with movie reviews--use them to winnow out the obvious losers, then go listen to the most likely candidates yourself.
Huh...I've won exactly one award in my alternate life as an author...and the story that won was several notches down from what I consider my best writing. Good? Okay, yeah, maybe. But best? No. And the stories that the Russians liked well enough to pirate? One was the same one that won the award. The other...no way...unh, uh. Sorry. Not my best writing. It was a successful story in that it sold, but it's not one that I would pull out if someone asked to read one of my stories and I wanted to make a good impression. One of those "your mileage may vary" things, obviously.
One of the things I find problematic with annual best-of awards is that they are always rating "this year's" product. What if last year's is still king of the hill? Ooops! Too bad. It had the misfortune to be on the wrong side of the calendar flip. As a result, I prefer the kind of rating wherein a piece stays on top for as long as the reviewer thinks it's best, even if that lasts a year or two or three...
Charles, this in no way means that your amp doesn't sound good. Although I haven't heard it, I suspect it would be on my short list of things to hear if I were in the market for an amp, if for no other reason than because you and I seem to share similar goals, sonically. My complaint is with the structure of the awards system, not you or your amp. Here's hoping that it gets on someone's non-annual best-of list and remains there for a while.
Grey
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