John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Jump to Latest
john curl

john curl

Member
Joined 2003
Why don't you check out Walt Jung's ADI book, you know, the chapter on op amp history? There is supporting info on this.
Now, let me remind you that you personally know and have worked with Walt Jung, for years. That you work for the company that published his book, and that this section is about op amp history, something of which you might be interested in.
Unfortunately, last night, when I checked Walt's Website to make sure and to give further directions to the information challenged, it was temporarily out-of-service at the ADI website. Surely, you can wait till the site is fixed, or just look up this schematic in your own copy of Walt Jung's book, either in hardcopy or on your computer.
Thanks PMA for putting the schematic up on this thread. I tried to get SY to do it, yesterday, but he is out of the country at the moment.
 
Last edited:
B

Bob Cordell

Member
Joined 2006
cordellaudio.com
john curl said:
Why don't you check out Walt Jung's ADI book, you know, the chapter on op amp history? There is supporting info on this.
Now, let me remind you that you personally know and have worked with Walt Jung, for years. That you work for the company that published his book, and that this section is about op amp history, something of which you might be interested in.
Unfortunately, last night, when I checked Walt's Website to make sure and to give further directions to the information challenged, it was temporarily out-of-service at the ADI website. Surely, you can wait till the site is fixed, or just look up this schematic in your own copy of Walt Jung's book, either in hardcopy or on your computer.
Thanks PMA for putting the schematic up on this thread. I tried to get SY to do it, yesterday, but he is out of the country at the moment.
Click to expand...

Hi John,

Walt's book you mention is a great book. I wrote the book review of it that appeared in the JAES a few years back. In the process, I read it thoroughly, and don't recall seeing a design that was any closer to my IPS-VAS than the conventional one posted by PMA.

Cheers,
Bob
 
john curl

john curl

Member
Joined 2003
I do see problem with the Burwin circuit, that I did not initially see. There is an extra ground lead in the schematic that I, for one would not have put in there. I guess I next have to attribute the true current mirror second stage to the Marantz 14-15 power amp, hopefully that would be Sid Smith.
 
B

Bob Cordell

Member
Joined 2006
cordellaudio.com
john curl said:
Conventional, in 1966? Can you please give me an earlier reference with the same circuit topology?
Click to expand...

Hi John,

I did not mean to imply that the Burwen circuit was conventional in 1966. I referred to it as conventional because it has been well known for many years. In contrast, my design was unconventional in that it used the differential current source load.

BTW, I beleive Bob Widkar invented the current mirror. Not sure when he did it, but it might have been seen first in ICs after 1966.

Cheers,
Bob
 
B

Bob Cordell

Member
Joined 2006
cordellaudio.com
john curl said:
I do see problem with the Burwin circuit, that I did not initially see. There is an extra ground lead in the schematic that I, for one would not have put in there. I guess I next have to attribute the true current mirror second stage to the Marantz 14-15 power amp, hopefully that would be Sid Smith.
Click to expand...

I stand corrected. If that schematic is correct, that circuit does not have a current mirror and does not have even a complementary VAS. The ground serves as a return for the unused collector of the VAS differential pair and as the positive voltage source for what is merely a constant current source at the bottom.

Cheers,
Bob
 
john curl

john curl

Member
Joined 2003
Now, what were we talking about before? Oh yes, capacitors. Perhaps we can return to that path. In truth, the BLOWTORCH has surprisingly few capacitors, and most of these are in the power supply. No caps are in the audio path, and only the best caps that we can find are used for direct power supply bypassing. We find this to be very important, and one of the first things that we do to improve a design is to look at the bypass caps on the power supply voltages.
 
C

Curly Woods

Banned
Joined 2005
Joshua_G said:
Caps in the PSU are supposed to affect the sound as well.
Click to expand...

I have always been told this Joshua, but never realy experimented with them. I just use motor run oil filled ASC capacitors as a rule with a film bypass cap. As i said, never really experimented with anything else as this seemed to be a good combination, but I would think that a single large film capacitor would be the cats meow.
 
Joshua_G

Joshua_G

Member
Joined 2008
gomeh.com/
Curly Woods said:
I have always been told this Joshua, but never realy experimented with them. I just use motor run oil filled ASC capacitors as a rule with a film bypass cap. As i said, never really experimented with anything else as this seemed to be a good combination, but I would think that a single large film capacitor would be the cats meow.
Click to expand...

It looks like the time to do some experiments.
I also intend to do such experiments with tubes PSUs.
 
Status
Not open for further replies.
Top Bottom