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 5th February 2009, 01:38 AM   #2691
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> you can try with them , but these have fairly low xconductance comparing to verticals ;and you need gain in F5 output stage ...... you'll have lower open loop gain , so less feedback ;

True. But you can lower the source resistor from 0R47 to 0R22 to compensate for that, as the source resistor is actually dominating in the original circuit.

> second - they also have pretty smaller Ugs , so drain resistors in first stage must be smaller , further decreasing that stage gain ...... further decreasing OLG

Not true. You can keep the drain resistor values by lowering the first stage bias by say 2mA or so. No problems for the JFETs.

> don't think that you're first with these thoughts

Of course not. Been there before, umteen pages back.
Jackinnj also have a layout with Hitachi laterals.




Patrick

  Reply With Quote
Old 5th February 2009, 01:49 AM   #2692
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally posted by EUVL
>.....

Not true. You can keep the drain resistor values by lowering the first stage bias by say 2mA or so. No problems for the JFETs.

.......

Patrick


true ...... but even in stock F5 current through first (Jfet) stage is already on lowish side ........

I know that Jackinnj tried them ( and like them ) ...... but 2mA is sooo low ..... and that wasn't F5 anymore ;

you can do that , Jack too ..... but not everyone , knowing what's needed to make it work .
__________________
my Papa is smarter than your Nelson !
tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb ; Papatreasure
  Reply With Quote
Old 5th February 2009, 01:59 AM   #2693
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> but 2mA is sooo low .....

I said, "You can keep the drain resistor values by lowering the first stage bias by say 2mA or so."

8mA - 2mA = 6mA, not 2mA, Sir.


Patrick
  Reply With Quote
Old 5th February 2009, 02:01 AM   #2694
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally posted by EUVL
> but 2mA is sooo low .....

I said, "You can keep the drain resistor values by lowering the first stage bias by say 2mA or so."

8mA - 2mA = 6mA, not 2mA, Sir.


Patrick

thank you , Sir .

__________________
my Papa is smarter than your Nelson !
tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb ; Papatreasure
  Reply With Quote
Old 5th February 2009, 02:05 AM   #2695
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
You're welcome.


Patrick
  Reply With Quote
Old 5th February 2009, 02:32 AM   #2696
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Any particular reason that feedback resistors are listed as 3W, they seem to run rather cool?
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 5th February 2009, 02:36 AM   #2697
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> Any particular reason that feedback resistors are listed as 3W, they seem to run rather cool?

The theoretical max swing is say -4V from rail.
Even in my balanced version, that would be 12V. Which means 10V across the feedback resistor.

10*10/50/2 = 1W. Safety factor 3 -> 3W.

I actually use 4x PRP 1W in parallel.

Actual signal level is of course normally much lower.
So in theory you might get away with 0.5W or so.




Patrick
  Reply With Quote
Old 5th February 2009, 03:01 AM   #2698
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Oh man, I am in trouble now.

I am using 4 F5's -- with Fairchild devices driving these Pioneer (TAD) S-1eX spxrs. I have a bunch of the Renesas (Hitachi) devices but haven't used them since last year.

On the bench is an NP/aX design from the AX article -- and we are are gonna look at the THD% figures for various combinations of JFET with Idss all over the lot. I know that THD% is not the ne plus ultra stat for the definition of quality, but it's the onlu completely reliable and reproducible stat that I can produce.
  Reply With Quote
Old 5th February 2009, 02:27 PM   #2699
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
Something odd is going on with my F5. When I push the volume a bit I get lots of breakup distortion.

Need to investigate this.....


Fran
  Reply With Quote
Old 5th February 2009, 03:17 PM   #2700
udailey is offline udailey  United States
diyAudio Member
 
Join Date: Mar 2008
Fran,
Try a new pot and also reflow your solder connections to the pot on the board and on the pot. If that doesnt do it then try reflowing the rest of your soldering. I find that usually when I have crackling due to change in volume that there is a screwed up solder joint somewhere and I have also had that happen with junk pots or nice pots with bad solder joints. Never know, if you are using a stepped pot you could have a nasty joint somewhere on there as well.
Uriah
__________________
purchase LDRs anytime Also try my Resistor Replacers or LDR based Input Selector Email me. diyldr@gmail.com
  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
Rockford Fosgate Power 20001 bd amplifier power rating?? pachoorion Car Audio 8 8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option? destroyer X Solid State 38 9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard johnnyrt Solid State 2 23rd August 2007 10:22 PM
Output power for a power amplifier Progg70 Solid State 33 10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 06:20 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