Zen 4 resistors - 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 23rd September 2002, 06:45 PM   #1
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Default Zen 4 resistors

From Nelsons partlist:
R0, R14, R15: 0,47R metaloxid, 3 watt.
R1: 1R metaloxid, 3 watt.
R10: 100R metaloxid, 3 watt.
R20: 22R metaloxid, 3 watt.

I was planning to use:
R0, R14, R15: 1R metalfilm, 3 watt, in parallel.
R1: 1R metalfilm, 3 watt.
R10: 100R metalfilm, 3 watt.
R20: 27R metalfilm, 3 watt.

What will happen if R0, R14, R15 are 0,5R and R20 is 27R?
A couple of watts output decrease?

Thanks
/Jan
  Reply With Quote
Old 23rd September 2002, 09:20 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
R14 and 15 are already .5 ohm (well .47 actually),
so this is just fine.

If R0 is .5 ohm, then the bias is about 1.3 amps, which
is enough for 30 watts into 8 ohms. Adding 1 ohm parallel
to that (R1) gives .33 ohms, which with a circuit that sets the
voltage across these at .66 volts, makes 2 amps bias.

This runs the amp hotter, but also allows 30 watts into 4 ohms.

  Reply With Quote
Old 23rd September 2002, 10:38 PM   #3
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Thanks Nelson, I'll stick to R0 0,5R and leave out R1 for my Zen. My heatsinks are on the small side already.
30 watt/8 ohm will be a fine amp for my speakers, no doubt.
Should R16 be 1K if R1 is left out?

Could I put a few additional parts questions here:

1. The CL-60 thermistor would it prevent my 10A fuses in my old apartment to blow at turn-on? I use one 800VA, 20A, 36volt trafo for both sides. Or does this part perform some kind of thermal protection and closes down the amp, if it gets to hot?
I was thinking to place a softstart relay circuit before the trafo, but if the thermistor does the job, then I don't need it, do I...?

2. I use a 20K trim pot instead of the recommended 25K. Would that be fine?

3. What would be the best distance from the pcb to the heatsinks, i.e. how much room does the FETS need?
8 mm OK?

regards
Jan
  Reply With Quote
Old 24th September 2002, 12:29 AM   #4
Account Disabled
 
Join Date: Aug 2002
Location: Near to the Pacific Ocean
[list=1][*][*]The 20k pot is OK. I could replace it even with a set of 10k pot + 5k resistor in series, which provides us with better possibility for precise adjustment.[*]If your PCB likes summer season, then as close as possible. If likes winter season, then as far as possible. If doesn’t mind the season, the distance doesn’t matter.[/list=1]
  Reply With Quote
Old 24th September 2002, 01:20 AM   #5
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Basically keep the FETs as close to the PCB as possible so that you can keep all the leads short and hence minimize their effect. As far as heat goes, as long as the PCB doesnt touch the FET's casing, thermal effects wont be too bad, just keep the PCB about an inch away from the cases and heatsink.
  Reply With Quote
Old 24th September 2002, 09:04 AM   #6
miguel2 is offline miguel2  Portugal
diyAudio Member
 
Join Date: Jun 2002
Location: Portugal
Hi

Is there any advantadge of increasing the voltage on the regulated PSU instead of increasing current? I got a 750VA 45-0-45 transformer which will give about 54V unregulated. Should I use about 45V regulated or is it better to just burn it on the pass transistor?

Miguel
  Reply With Quote
Old 24th September 2002, 11:09 PM   #7
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
I would bump up the regulated supply a few volts. It
will sound slightly better, as the Mosfets do like some
voltage.

  Reply With Quote
Old 25th September 2002, 08:31 AM   #8
miguel2 is offline miguel2  Portugal
diyAudio Member
 
Join Date: Jun 2002
Location: Portugal
Thanks Nelson.

I will use an additional zener to raise it some 4-5 volts, all other things remain equal.

I got this transformer used by 10 Euros, including two 35A / 400V bridges, 8 x 1000microF/250V caps and a lot of TIP3055's which I don't know what to do with.

Yesterday I was testing the transformer and with anything connected it powered up OK, but when I used the test leads of the multimeter on it (in voltage mode) the switchboard went down several times! Any ideas why?

I just guess that the 8000 microF will not be enough but I am going to experiment with those before I can get my hands on some more caps... I will just have some more ripple - Microcap simulation gave around 10V on unregulated and 0.01V on regulated.

  Reply With Quote
Old 13th October 2002, 01:52 PM   #9
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Default Power down

I will use my Zen 4 (not build yet) also for cinema and background music listening.

I've started to worry a bit about my electricity bill and was thinking of making some sort of power down switch to lower BIAS.

My idea was the following. In both positions I leave out R1 cause my sinks are already on the small side.

Normal power:
0.5R at R0

Low power:
1R at R0 (or more?)

It's OK for me that output power drops from say 25 watt to 10 watts when I watch a movie.

Do I get what I want if I make such a resistor switch?
Did anyone try such a power down facility?
  Reply With Quote
Old 15th October 2002, 09:01 AM   #10
Warp Engineer
On Holiday
 
AudioFreak's Avatar
 
Join Date: Oct 2001
Location: Queensland, Australia
Probably the easiest and safest way to achieve that would be to use 2 parallel resistors for full bias and then switch 1 of them out of the circuit when you want the low bias setting.
  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
5 Watt Resistors on Aleph 4 and Holco Resistors nicharis Pass Labs 16 8th February 2012 07:50 AM
FS: Resistors, LM3886, speaker terminal, variable resistors, switches and rectifiers chris-man Swap Meet 1 28th May 2009 11:47 AM
Ptc Resistors Ziggy Solid State 4 13th January 2009 01:31 AM
Inductive resistors for source resistors bbakota2000 Pass Labs 12 25th March 2005 11:33 AM
Weird Resistors, anyone know anything about resistors priscared Parts 1 19th March 2004 11:59 AM


New To Site? Need Help?

All times are GMT. The time now is 04:40 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