Hafler P1500: how to make volume down to zero (∞db)? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 16th April 2011, 01:50 AM   #1
jackup is offline jackup  Viet Nam
diyAudio Member
 
Join Date: Jul 2007
Default Hafler P1500: how to make volume down to zero (∞db)?

Hi Alls,

I own a Hafler P1500. I dont know why the volume can come down only to -15db. My concern is, how to mod this amplifier to make volume down to zero (∞db)?

Thank you very much,
Jackup
  Reply With Quote
Old 16th April 2011, 02:11 AM   #2
Chartal is offline Chartal  Canada
diyAudio Member
 
Join Date: Nov 2004
Location: Montreal
Because it's an amplifier and not a integrated.
The knobs on the front are to fine-tune the gain.
You need a pre-amplifier for the volume control.
  Reply With Quote
Old 16th April 2011, 03:10 AM   #3
diyAudio Member
 
Join Date: Nov 2009
Location: Los Angeles
Quote:
Originally Posted by Chartal View Post
Because it's an amplifier and not a integrated.
The knobs on the front are to fine-tune the gain.
You need a pre-amplifier for the volume control.
What you say is true but modding for down to 0 is no big deal. There are fixed resistors on the electrical 'bottom' of the pot that when shunted with wires will expand the range to infinity. KEEP in mind that the input loading might drop a LOT. Many units will be OK with that but not all. If it was mine I'd try for a load of at least 5K and not more that 25K. This may require changing the pots to a higher value. Solid state sources would be fine with this but tube gear would not be happy. Since I don't use tubes, I don't mind.

G
  Reply With Quote
Old 16th April 2011, 05:36 AM   #4
jackup is offline jackup  Viet Nam
diyAudio Member
 
Join Date: Jul 2007
Quote:
Originally Posted by stratus46 View Post
What you say is true but modding for down to 0 is no big deal. There are fixed resistors on the electrical 'bottom' of the pot that when shunted with wires will expand the range to infinity. KEEP in mind that the input loading might drop a LOT. Many units will be OK with that but not all. If it was mine I'd try for a load of at least 5K and not more that 25K. This may require changing the pots to a higher value. Solid state sources would be fine with this but tube gear would not be happy. Since I don't use tubes, I don't mind.

G
Could you please specify which resistors need to be shunted with wires?
Please refer to this Parts list: http://www.hafler.com/techsupport/pd..._P3000_man.pdf
Thank you very much
Attached Images
File Type: png hafler.png (143.6 KB, 89 views)

Last edited by jackup; 16th April 2011 at 05:50 AM. Reason: add board layout
  Reply With Quote
Old 16th April 2011, 09:15 AM   #5
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
That is a common mode volume control, it may not go to 0 even after modification, there may be some very low level high frequency present (-60dB~-80dB down). R6 is the part you want to remove and/or short out.
__________________
Candidates for the Darwin Award should not read this author.

Last edited by djk; 16th April 2011 at 09:19 AM.
  Reply With Quote
Old 16th April 2011, 12:04 PM   #6
jackup is offline jackup  Viet Nam
diyAudio Member
 
Join Date: Jul 2007
Quote:
Originally Posted by djk View Post
That is a common mode volume control, it may not go to 0 even after modification, there may be some very low level high frequency present (-60dB~-80dB down). R6 is the part you want to remove and/or short out.
Thank you very much! I'll try and report later!
  Reply With Quote
Old 18th April 2011, 02:22 PM   #7
jackup is offline jackup  Viet Nam
diyAudio Member
 
Join Date: Jul 2007
Quote:
Originally Posted by stratus46 View Post
What you say is true but modding for down to 0 is no big deal. There are fixed resistors on the electrical 'bottom' of the pot that when shunted with wires will expand the range to infinity. KEEP in mind that the input loading might drop a LOT. Many units will be OK with that but not all. If it was mine I'd try for a load of at least 5K and not more that 25K. This may require changing the pots to a higher value. Solid state sources would be fine with this but tube gear would not be happy. Since I don't use tubes, I don't mind.

G
Quote:
Originally Posted by djk View Post
That is a common mode volume control, it may not go to 0 even after modification, there may be some very low level high frequency present (-60dB~-80dB down). R6 is the part you want to remove and/or short out.
Thank you all of you! Now the volume can down to zero with RCAs only. If i use XLRs, there is still low signal at speakers. I don't know why.

Last edited by jackup; 18th April 2011 at 02:48 PM.
  Reply With Quote
Old 18th April 2011, 09:28 PM   #8
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Because it is a common mode volume control.

Try adjusting R8 (CMRR) for a minimum with the volume control all the way down. Unfortunately, there is no adjustable capacitor for HF CMRR, just the pot for LF CMRR. You should be able to get -60dB~-80dB.
__________________
Candidates for the Darwin Award should not read this author.
  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
Audax PR170M0 100 dB or just *94 dB?? rick57 Multi-Way 44 22nd December 2013 12:50 AM
Hafler P3000 trans nova volume potentiometer... ladaniva Solid State 4 27th May 2011 06:29 PM
Hafler DH-101 Volume Pot David Baldwin Solid State 0 10th April 2010 06:12 PM
Hafler "Trans Nova" P1500 imix500 Solid State 25 5th May 2007 08:58 PM
Coverting dB/2.83w to dB/1w moving_electron Multi-Way 27 9th March 2004 02:47 PM


New To Site? Need Help?

All times are GMT. The time now is 10:37 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