F5 power amplifier - Page 513 - diyAudio
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 8th October 2009, 07:33 PM   #5121
cviller is offline cviller  Denmark
diyAudio Member
 
cviller's Avatar
 
Join Date: Dec 2005
Location: Copenhagen
Blog Entries: 2
Hi dave,

Sounds like a nice big project to keep you busy and warm during the winter!
If I were you I think I would build 6 channels in three boxes - then you can use them for other purposes later.
The 45VAC doesn't sound perfect for this you need to get your rails down to ~2x23V.
  Reply With Quote
Old 8th October 2009, 08:23 PM   #5122
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by scranton View Post

I reversed channels and disconnected signal and output and the transformer still buzzed after warmup.

Ok, though it was aimed at the humming speaker. Did you check that

8-10 mv around zero (Is negative DC offset an issue?)

Nothing wrong there

I adjusted slightly to keep offset above zero.

?

I do think I have two problems: instability due to earlier mistakes and a transformer.

Maybe not. Did you check your signal wires, and ensured that they are away from supply lines. I think it has been suggested to use only shielded signal wire

You may have missed it, but it was suggested to try and decouple transformer mechanically by using rubbers. I may be enough to make the buzzing inaudible, and its cheap


Last edited by tinitus; 8th October 2009 at 08:29 PM.
  Reply With Quote
Old 9th October 2009, 12:13 AM   #5123
alazira is offline alazira  United States
diyAudio Member
 
alazira's Avatar
 
Join Date: Jun 2007
Location: Las Vegas
Blog Entries: 1
Default N&P channel mismatch

Quote:
Nelson Pass from Post 169 FirstWatt J2 thread:

The IR P channel parts have higher distortion. You could use
the Fairchilds, or take a look at Toshiba or Harris (if you can
find them).

The N vs P channel mismatch is a small source of distortion
down around a watt or so, which is why you want to be
able to trim the Mosfet Source resistors values a bit (if you
have the analyzer handy). Also, it is effective to use a
couple hundred ohm pot, wiper grounded, connected across
the Sources of the input JFETs and trim for least distortion at
1 watt.
Hi Mr. Pass,
This was on the J2 thread but thought I'd ask here for the sake of relevance. Were you referring to trimming R11/R12? As for the 2nd part is my sketch correct? Not that I have anything to analyze with but perhaps I'll look for something on eBay if it seems worthwhile.
Attached Images
File Type: jpg sketch.jpg (14.6 KB, 820 views)
  Reply With Quote
Old 9th October 2009, 01:29 AM   #5124
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I meant the 3 watt resistors on the Sources of the power
Mosfets going to the supply rails.

And yes, your drawing would be correct.

Either approach works - the pot is more convenient.

  Reply With Quote
Old 9th October 2009, 03:33 PM   #5125
diyAudio Member
 
Join Date: Jun 2005
Location: Massachusetts
Ok, though it was aimed at the humming speaker. Did you check that? No I didin't. But good tip.

? and Nothing wrong there What I mean here is I raised the offset since, if set to zero, it would cycle between +4mv and -4mv. Raise it to 8 or 10 and it stays zero or above. As a novice, I take things literal.

Maybe not. Did you check your signal wires, and ensured that they are away from supply lines.Yes. And shielded.

RubbersDidn't have any. Used speaker dampening stuff. And loosened it. Did reduce the amplification of the buzzing but it still buzzed.

Have all the resistors in a new board. Add the rest of the parts tonight. Test tomorrow to see if I had one problem. Thanks for all your input.
Q: Is transformer buzzing alright if I can isolate it and make it inaudible?
  Reply With Quote
Old 9th October 2009, 03:36 PM   #5126
Tea-Bag is offline Tea-Bag  United States
not politcally affiliated
diyAudio Member
 
Tea-Bag's Avatar
 
Join Date: Feb 2006
Location: Kennebunk
Blog Entries: 7
Quote:
Originally Posted by scranton View Post
Ok, though it was aimed at the humming speaker. Did you check that? No I didin't. But good tip.

? and Nothing wrong there What I mean here is I raised the offset since, if set to zero, it would cycle between +4mv and -4mv. Raise it to 8 or 10 and it stays zero or above. As a novice, I take things literal.

Maybe not. Did you check your signal wires, and ensured that they are away from supply lines.Yes. And shielded.

RubbersDidn't have any. Used speaker dampening stuff. And loosened it. Did reduce the amplification of the buzzing but it still buzzed.

Have all the resistors in a new board. Add the rest of the parts tonight. Test tomorrow to see if I had one problem. Thanks for all your input.
Q: Is transformer buzzing alright if I can isolate it and make it inaudible?
Scranton, My F5 trannies have a tiny buzz to them, but it's not audible through the speakers, only if your standing a foot or so away from it.
__________________
Salas Boards 2014 #2 On order |F5TC board and power supplies available PM | Hot-Rod DCB1 boards and kits available PM |Mesmerize kits available (no boards)
  Reply With Quote
Old 9th October 2009, 05:07 PM   #5127
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
transformer hum can be worse if excessive AC non symmetric waveform are passed (=AC + DC).
This can be alleviated by fitting a DC blocking filter to the mains fed primary circuit.
__________________
regards Andrew T.
  Reply With Quote
Old 9th October 2009, 08:18 PM   #5128
alazira is offline alazira  United States
diyAudio Member
 
alazira's Avatar
 
Join Date: Jun 2007
Location: Las Vegas
Blog Entries: 1
Default adjustments

Quote:
Originally Posted by Nelson Pass View Post
I meant the 3 watt resistors on the Sources of the power
Mosfets going to the supply rails.

And yes, your drawing would be correct.

Either approach works - the pot is more convenient.

Hi Mr. Pass,

Thanks for the reply.

Just to confirm, you are referring to R11&R12=0.47ohm 3watt source resistors, right? It does seem that it would be difficult to adjust this value.

While on this subject, on the last page of the F5 manual it says:

"If you have the equipment to see it, you may find that different gain devices will give you a small peak somewhere just below 1MHz. I have found that you can trim this by playing with the values of R13 and R14, but as both values approach 0 ohms, you are likely to see parasitic oscillations."

Is this also doing the same thing as the afore mentioned adjustments? It continues:

"You can additionally limit frequency response with an input capacitor across R10, and also in the feedback loop with capacitance across R5 and/or R8."

Approximately what value caps are we talking here? I've read this whole thread and I don't recall anyone mentioning that they did this. If anyone has, please comment. The only thing said about adjustments was Than1971 in a post about fiddling with R1 & R2 to increase/decrease 2nd/3rd harmonic.

Garrett
  Reply With Quote
Old 9th October 2009, 10:43 PM   #5129
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
If you have a scope and/or distortion analyzer, then you
can play with this. Try different values, starting with values
close to the stock values and see what you get.

  Reply With Quote
Old 9th October 2009, 11:10 PM   #5130
diyAudio Member
 
Join Date: Sep 2008
Location: Minneapolis, MN
Quote:
Originally Posted by AndrewT View Post
transformer hum can be worse if excessive AC non symmetric waveform are passed (=AC + DC).
This can be alleviated by fitting a DC blocking filter to the mains fed primary circuit.
my Naim amps did this quite frequently.

i placed an order for a 18+18 500VA TX from SumR. the other TX i have from Richard is dead quiet. not terribly expensive at $98 either. the PS will be in a separate chassis a la Naim for possible future Pass recipes. i've opted not to go down the bridged amp route for now - it's time i started playing around with FR drivers.

heatsinks arrived today too!
  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 10:00 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