Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 11th December 2006, 07:33 PM   #11
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally posted by flg
I believe in ZV8 & 9, Nelson uses a gate to GND R in the circuits without feedback. Then when he adds feedback he takes them out...
They are still there because the output is attached to ground
via resistance, and so a ground reference is still there through
the feedback resistor

  Reply With Quote
Old 11th December 2006, 07:54 PM   #12
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
So, could it be that the warm humming sound I heard when adding a 221K to ground at the buffer gate of my ZV7 was a ground loop hum? Did I attach the buffer correctly?

John

ooh, sorry for hijacking your thread, flg
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 11th December 2006, 10:23 PM   #13
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Hi jack away dude. I wish I had a good answer for your ZV7-T with a buffer. The reason I don't is cuase I thought about that already a few months ago in the GSOZ-T thread I started and it becomes difficult to use feedback with the output at an absolute value of 23V or somethinig... You are then not really using the ZV4 buffer in the spirit it was originally used?
If I wasn't so busy with the "parental units" and my own ZEN variant, I might have some answers or ideas...
In your case, you have a voltage divider to ground from the output, in addition to the feedback requirement. A cap in the feedback line might be an answer but, that could also be a problem??? I need a cap in my output also but, a really big one... Gotta go for now...
  Reply With Quote
Old 11th December 2006, 10:29 PM   #14
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
I solved the problem. At least, I think I did. I'll post a little schematic on my little ZV7-T thread describing pictorially what transpired.

Long story short, I doubled the resistor value from the output. It was 221k, now it's 442K. What a difference! I could actually turn down the gain knob on my electronic X-over. Happy days!

Thanks for thinking of me, flg.

John
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 15th December 2006, 02:20 AM   #15
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Well, it works I lit up my prototype ZV9 with an inductor load tonight Worked great! I'll post a pic of what I built with the exact values below. Except for the inductor. I really have no idea what it is Well, I have some idea I suppose. It's just that from all the reading I've been doing, and experimentation by others, and myself, I just figured what the hey, I'll just use the biggest thing I got up here. Especially if I have two of 'em. The inductor is actually an AC power Xfmr for 115VAC 60Hz input. Gotta weigh in at a good 15-20 lbs. The laminated core is 3" W x 4.5" H x 5.25" L. The secondaries are open. The Rdc measured about .2 ohms and it dosent even get warm at 2.5 Amps...
Some initial voltage measurements are on the pic. In addition, the -3db on the low end is about 10Hz! And, it's nice and flat up to at least 10K. It's starting to clip(on the positive side) at about 13.5 Vrms into my 7.5 ohm load resistor.
Attached Images
File Type: png l loaded zv9.png (18.4 KB, 289 views)
  Reply With Quote
Old 15th December 2006, 05:04 AM   #16
Paper mache horn fabricator
diyAudio Member
 
carpenter's Avatar
 
Join Date: Mar 2002
Location: Oregon City, Oregon
Great Scott! What does it sound like?

John
__________________
I enjoy audio so much that I constructed a web site. I share my ideas at: www.inlowsound.com
  Reply With Quote
Old 15th December 2006, 12:48 PM   #17
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Sound Haven't tried anything like that yet... After a little more bench test I suppose I will. I don't really have any speakers worthy of critical listening at the moment though. That would be the next project
  Reply With Quote
Old 15th December 2006, 03:48 PM   #18
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
I just had to try another Load. I plugged in an Avel 800VA Toriod in the 115V connection. I guess that would be rated at about 7 Amps rms. I believe I previously measured this thing at about 275mH of inductance I was still running the Iq at 2-2.5A.
So it did not look as good Square waves seem to tell some kinda story here... The square waves have an overshoot worse than the laminated xfmr or at least at the same freq. This response seems to worsen at lower frquencies compared to the laminated guy. The -3db seemed to be more like 80Hz with much more extreme peaks on the rising edges... Hmmmm... Saturation
The high frequency response seemed to maintain a better looking square wave higher though. Also the -3db at the high end seemed to be more like 100KHz.
Now it would be interesting to try an air core device... Hmmm
  Reply With Quote
Old 15th December 2006, 04:08 PM   #19
Formerly "jh6you". R.I.P.
 
Babowana's Avatar
 
Join Date: Jul 2006
Quote:
Originally posted by flg


The square waves have an overshoot worse than the laminated xfmr

It says, "Large overshoots are indicative of peaking or excess phase shifts in the high frequency response of the device under test."

And, "Well-behaved devices will have smooth overshoot, symmetrical on both positive and negative peaks."

  Reply With Quote
Old 15th December 2006, 04:16 PM   #20
Fuling is offline Fuling  Sweden
diyAudio Member
 
Join Date: Aug 2001
Location: Sweden (Mora)
Toroids (usually) have no airgap in the core, so they tend to saturate very quickly in a situation where DC flows through the windings.
  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
Choke loaded LTP jane Tubes / Valves 6 8th November 2008 02:25 PM
ccs-loaded sziklai ionomolo Solid State 132 30th June 2008 06:39 AM
Slot loaded PR DAMIC Multi-Way 0 17th April 2008 06:48 AM
Front loaded and back loaded horn DrWoofer.com Subwoofers 0 3rd August 2007 06:55 PM
Loaded Question dr._sleep Tubes / Valves 2 23rd November 2005 09:23 PM


New To Site? Need Help?

All times are GMT. The time now is 08:33 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