Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 6th November 2012, 05:19 PM   #2011
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Quote:
Originally Posted by linuxguru View Post
There were several until Hollywood released 'Sideways' and screwed my happiness. Now the total number of US-imported cases of French Pinot Noir is 100x the official numbers of *all* production of Pinot Noir in France.
Do the math, most of the stuff is likely to be Syrah-Merlot rebadged as Pinot Noir - most sheeple can't tell the difference. Real Pinot Noir has a distinctive steely edge in the finish - a bit like licking antique ironware.

The 2-buck *real* Pinot Noir, but grown in Coastal CA or OR, was Nathanson Creek, available at Safeway. That's one of several inexpensive gems from the US that I miss in Bangalore; Ghirardelli chocolates are another.
But Sideways did make many fine Merlots more affordable No effect on top-notch Pomerol or Saint-Emilion however.
  Reply With Quote
Old 6th November 2012, 06:31 PM   #2012
diyAudio Member
 
Join Date: Sep 2007
Send a message via Yahoo to linuxguru
Quote:
Originally Posted by bcarso View Post
No effect on top-notch Pomerol or Saint-Emilion however.
Yup, the great Bordeauxs were never sold as Merlots or even listed their varietals on the label. Not that it would have mattered, a great vintage is a great vintage, regardless of the varietals. 'Sideways' probably killed the lesser California Merlots, and made some better ones affordable.
  Reply With Quote
Old 6th November 2012, 06:44 PM   #2013
diyAudio Member
 
Kindhornman's Avatar
 
Join Date: Aug 2012
Location: Los Angeles, California
Glad you all love your red wines, me personally I get sick from any red wine, sulfate intolerance on my part. Guess that means I will never purchase any of those expensive bottles, just give me a nice white or blush and at least it won't make me sick.
  Reply With Quote
Old 6th November 2012, 07:31 PM   #2014
diyAudio Member
 
myhrrhleine's Avatar
 
Join Date: Jan 2006
Location: Avalon Island
Quote:
Originally Posted by kgrlee View Post
Sonitus, will you oblige us with your LTspice file so us wannabe SPICE gurus can have a play? Also your Rush-Rush version?

On 2nd thoughts, 210mA peak may be a bit too stringent. c2240/a970 & bc556/546 are only 100mA. 4401/3 are OK but I was trying to get a series of tests for the contenders which didn't need too many special devices in special places. Special i/ps are unavoidable.

Got a link or sketch of Cordell's output stage accessible to beach bums?

Low loads aren't a problem if you are prepared to use medium power devices like the original 990 or even just 4401/3.

Scott, did you get your breadboard up & running?

My contention about offsets is that you may need tweak pots to avoid Volts of offset rather than mVs even with loadsa device matching. But this is just from SPICE so the breadboard man has the last (??) say.
Bob is a regular contributor here.
He might even be reading along in this thread.
But his amp is at http://www.cordellaudio.com/papers/MOSFET_Power_Amp.pdf
Hope this helps
__________________
Just because you can't hear it doesn't mean no one can.
  Reply With Quote
Old 6th November 2012, 09:08 PM   #2015
diyAudio Member
 
scott wurcer's Avatar
 
Join Date: Jan 2004
Location: cambridge ma
Back to circuits. Just fired up the output stage only, I want to measure its open loop THD, etc. That's from the two transitors whose bases connect to the VAS to the output. No matching, 4401/4403's right out of the bag 1% RN55's and no bias trim for now. I built my board with no thermal considerations yet either.

On +-15 fired up at 27mA and crept up to 28mA this will come down with trim. The offset was only -0.0021V. I will be doing the measurements over the next few days. I will be looking for the openloop distortion with and without a large source resistor.
__________________
“The earth's rotation will slow within days and stop for several days just prior to the pole shift. This is when you and your loved ones should be situated at your safe location.”
  Reply With Quote
Old 6th November 2012, 09:45 PM   #2016
diyAudio Member
 
Joshua_G's Avatar
 
Join Date: Nov 2008
Location: Small village, Israel
Quote:
Originally Posted by scott wurcer View Post
Back to circuits. Just fired up the output stage only, I want to measure its open loop THD, etc. That's from the two transitors whose bases connect to the VAS to the output. No matching, 4401/4403's right out of the bag 1% RN55's and no bias trim for now. I built my board with no thermal considerations yet either.

On +-15 fired up at 27mA and crept up to 28mA this will come down with trim. The offset was only -0.0021V. I will be doing the measurements over the next few days. I will be looking for the openloop distortion with and without a large source resistor.
Hi Scott,
Thumb up.
  Reply With Quote
Old 7th November 2012, 01:10 AM   #2017
fas42 is online now fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 9
Also, for kgrlee and anyone else, just to say I'm still working on the "more accurate" spice model of BF862; the curves for drain current vs. both gate-source and drain-source, typical case look pretty reasonable; requires a subcircuit definition to work at the moment.

And, plugging it into SW-OPA on a first attempt causes barely a ripple: yes, the quiescent currents were thrown out of kilter, but after adjusting the appropriate R's to close enough, the 2nd and 3rd harmonics for 20KHz, 10Vp-p, 100x gain had changed by less than 1/2 db ...

Frank
  Reply With Quote
Old 7th November 2012, 04:30 AM   #2018
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
Originally Posted by scott wurcer View Post
Back to circuits. Just fired up the output stage only, I want to measure its open loop THD, etc. That's from the two transitors whose bases connect to the VAS to the output. No matching, 4401/4403's right out of the bag 1% RN55's and no bias trim for now. I built my board with no thermal considerations yet either.

On +-15 fired up at 27mA and crept up to 28mA this will come down with trim. The offset was only -0.0021V. I will be doing the measurements over the next few days. I will be looking for the openloop distortion with and without a large source resistor.
what is your choice for test equipment that you will use? Thx-RNM
  Reply With Quote
Old 7th November 2012, 05:37 AM   #2019
diyAudio Member
 
Join Date: Nov 2011
Location: Cooktown, Oz
Quote:
Originally Posted by scott wurcer View Post
The offset was only -0.0021V.
After initial excitement on your advice to twiddle the 20Rs in the output stage, I found that this didn't help things at all.

Twiddling the 250R for offset as you recommend is definitely less twitchy than twiddling the 30R source resistor. But still more twitchy than twiddling the current mirror in a 990 type circuit.

I think it will be wise for anyone doing PCBs to make provisions for a twiddle pot on the 250. Don't think we can match FETs accurately enough.

Frank, can you post your models?

So far I've been impressed by LTspice. It seems to at least qualitatively behave as I expect real life even if I don't take the numbers as Gospel. But I don't believe the input stage at all as swapping between all the models I have for BF862, J305, J111, 2sk170 doesn't seem to make any difference on these amps.

myhrrhleine, thanks for the link to Bob's stuff.

sonitus, thanks for your SPICE files

Brad, Scott & co., I don't see how yus guys can keep good wine for so long. Surely you can find an excuse to broach a bottle.

lee sipping his meths in Cooktown ...
  Reply With Quote
Old 7th November 2012, 08:49 AM   #2020
fas42 is online now fas42  Australia
diyAudio Member
 
fas42's Avatar
 
Join Date: Jun 2012
Location: NSW, Australia
Blog Entries: 9
Quote:
Originally Posted by kgrlee View Post
Frank, can you post your models?

So far I've been impressed by LTspice. It seems to at least qualitatively behave as I expect real life even if I don't take the numbers as Gospel. But I don't believe the input stage at all as swapping between all the models I have for BF862, J305, J111, 2sk170 doesn't seem to make any difference on these amps.
Can do, but be warned this has only had a rough first check - no guarantees in other words!

Note that this is a subcircuit - even though the icon is the same you need to replace the JFETs with this identically shaped item; give us a yell if problems ...

The results of modelling are only as good as the accuracy of the models; the more you add all the little parasitics and what have you the more real info you get from the exercise.

Cheers,
Frank
Attached Files
File Type: txt BF862alt.asc.txt (496 Bytes, 37 views)
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Discrete OPAMP audio-gd Vendor's Bazaar 27 20th September 2012 04:02 PM
discrete opamp help blackpowderaudio Parts 0 16th December 2009 03:46 PM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 12:52 PM


New To Site? Need Help?

All times are GMT. The time now is 09:53 AM.


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