John Curl's Blowtorch preamplifier part II - Page 1801 - diyAudio
Go Back   Home > Forums > Member Areas > The Lounge

The Lounge A place to talk about almost anything but politics and religion.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 16th November 2011, 11:34 PM   #18001
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Too many series unbiased series caps in the Korg.
  Reply With Quote
Old 16th November 2011, 11:50 PM   #18002
diyAudio Member
 
Chris Hornbeck's Avatar
 
Join Date: May 2011
Location: Little Rock
Quote:
Originally Posted by gurevise View Post
Can you elaborate about "ground contamination caused by the (series) power supply regulators" ? Is it a rectifier diode switching noise or something else?
Sorry, wasn't well explained. Nakamichi used a pair of FETs as source followers to supply DC (and ground) to the *other* polarity's local zener diodes, gates connected to ground. True clean grounds in consumer electronics are made of unicorn horn, so this element at least kept dirty currents away from local ground. Folks enamoured of "shunt" supply regulators need to think about grounds just as much as anybody, maybe more.

Thanks,
Chris
  Reply With Quote
Old 16th November 2011, 11:53 PM   #18003
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by john curl View Post
Too many series unbiased series caps in the Korg.
The pure PWM output doesn't bother you? Feed it right into your power MOSFET's and your done (perfect sound forever, finally?)
__________________
Silence is so accurate.
  Reply With Quote
Old 16th November 2011, 11:58 PM   #18004
diyAudio Member
 
john curl's Avatar
 
Join Date: Jul 2003
Location: berkeley ca
Isn't that nice!
  Reply With Quote
Old 17th November 2011, 12:35 AM   #18005
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
I use a Kork MR-1000 with a pair of Microtech Gefell ORTF mics straight into the box. It sounds pretty damn good. When i make down sampled CDs from the master the main difference is in the bass. The master sounds a bit fuller, warmer and spacious.
  Reply With Quote
Old 17th November 2011, 12:54 AM   #18006
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by Joachim Gerhard View Post
the main difference is in the bass.
Of course.
__________________
Silence is so accurate.
  Reply With Quote
Old 17th November 2011, 01:06 AM   #18007
diyAudio Member
 
Joachim Gerhard's Avatar
 
Join Date: Mar 2009
Yes, that is really strange but i hear nothing over 16kHz. Martina Schoener of Garrard-Loricraft hears much better in the treble then me though. Just today she was complaining about a preamp i build her. With the volume control in a certain position she could hear a crackling noise when i moved the control back and forth. Me with the ear at the tweeter heard ( you guest it ) .... nothing
  Reply With Quote
Old 17th November 2011, 01:28 AM   #18008
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Quote:
Originally Posted by Joachim Gerhard View Post
.... nothing
Monty Python . Spot the Looney - YouTube
__________________
Silence is so accurate.
  Reply With Quote
Old 17th November 2011, 02:03 AM   #18009
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Scott,
The Nak 1000ZXL machines could really do a good job. Getting rid of the felt pressure pad on step one (no more FM scrape noise). They really did understand analog electronics very well. Some of their CD players used similar methods, and not just the reference ground measures. I still have an OMS-7 (14 bit) that sounds great. I'd love to route the RF signal into a modern chip set and PCM-1702 or better.

Did the Nak analog guys mention anything else of interest? Doing service for many brands, Nakamichi was one of those that I was eager to see new designs from. Most other brands later on were pretty much more of the same inexpensive stuff. Ho-hum.

Hi Chris (Hornbeck),
A lot of the following is for people not familiar with the concepts that Nakamichi used.

Nakamichi also did the same thing with BJTs. Use the ground as a reference and pass the actual operating current to the other supply. To explain this better, a normal regulator sends it's own operating current into the ground it uses as a reference. Nakamichi did two things that were important to this idea. The first was that these regulators were local to the circuit, right at the point of use. They used ground for a reference only, and passed their operating current (with it's fluctuations and input noise) off to the opposite rail before the complimentary regulator. The other related concept was that the absolute voltage was not important. What was important was that the voltage drifted very slowly and did a good job of blocking any noise on the supply. One example of engineering trade-offs made to optimize what was most important.

Now, what noise would there be on the supply rails? After all, these supplies are already regulated. Just as there is a finite impedance in what you call "ground", there is also in the power supply wires and foil. That leads to minute voltage variations due to the demands of anything else sharing that supply (I*R), and also what can make it through the first stage of regulation. These power supplies can also pick up radiated noise along the way inside the chassis. Whatever you want to call this collection of noise, you'd best get rid of it before feeding a high gain stage - like a tape head EQ amp, or maybe the analog stages immediately following a D/A converter. You can make the same argument for the clocks in a CD player, and the I/V converter that processes the signals from the photo-diodes.

There is more than one way to "skin a cat", and this method is pretty powerful if used with the same detail as the rest of the circuits involved.

I would have absolutely loved to have seen a Studer 24 track that utilized Nakamichi designed electronics. That would have been totally amazing! Only a Studer transport would make this worthwhile in my view.

-Chris
__________________
"Just because you can, doesn't mean you should" my Wife
  Reply With Quote
Old 17th November 2011, 02:32 AM   #18010
diyAudio Member
 
Join Date: Mar 2002
> Feed it right into your power MOSFET's and your done

Assuming no xover issue nor shoot thru ..........
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 02:36 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2