Free Shipping on All Orders 1-866-764-1801

Vist our Online Store
+ Reply to Thread
Results 1 to 18 of 18
  1. #1

    Member Sales Rating: (43)

    Join Date
    Nov 2006
    Location
    CT
    Posts
    15,931

    Default How do you measure the DC offset of an amp

    I need to know how to measure the DC offset of an Adcom Amplifier (GFA-585).
    Thanks Ben

  2. #2

    Member Sales Rating: (6)

    Join Date
    Feb 2002
    Location
    Rockledge, Florida
    Posts
    11,588

    Default

    I don't think an end user or consumer needs to be worried about that. An offset is measured in mv at a point between the output transistors, so this point can be before any final filtering circuit which to output terminals are connected to. If you suspect trouble woofer being pushed in or out with amp on, the amp needs service and I would do this ASAP before speaker damage.

    Speakers
    Carver Amazing Fronts
    CS400i Center
    RT800i's Rears
    Sub Paradigm Servo 15

    Electronics
    Conrad Johnson PV-5 pre-amp
    Parasound Halo A23
    Pioneer 84TXSi AVR
    Pioneer 79Avi DVD
    Sony CX400 CD changer
    Panasonic 42-PX60U Plasma
    WMC Win7 32bit HD DVR



  3. #3

    Member Sales Rating: (1)

    Join Date
    Dec 2003
    Location
    Sooner Country
    Posts
    3,811

    Default

    Here is the best discussion I have found on the subject................http://audiokarma.org/forums/showthread.php?t=5634

  4. #4

    Member Sales Rating: (43)

    Join Date
    Nov 2006
    Location
    CT
    Posts
    15,931

    Default

    Thanks for the link I am on it
    Ben

  5. #5

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    Never would have thought you could let an amp sit for ten minutes not hooked up.
    humpty dumpty was pushed

  6. #6

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    Is this a record? Diggin up bones.
    humpty dumpty was pushed

  7. #7

    Member Sales Rating: (13)

    Join Date
    Mar 2002
    Location
    The Mars Hotel
    Posts
    30,464

    Default

    You can let a SS amp sit powered up without a load all day and twice on Sunday. Do NOT try it with a tube amp.
    'Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

  8. #8

    Member Sales Rating: (0)

    Join Date
    Jan 2010
    Posts
    563

    Default

    To check dc offset, do this:
    a) Turn on amp and let it warm up (half hour will do it)
    b) disconnect all inputs and speakers.
    c) Connect a multimeter (DC mv range) in the speaker terminals (+ - )
    d) it should read very low (10 mv or lower) the lower the better.
    I would consider a good and healthy reading in the 5 mv range, My diy amplifier is spot on the "0" mv.
    it will be a good idea to check the bias too, but this will need more steady hands and knowledge of what you are doing.

    PS: Every time you fix or upgrade an amplifier (change capacitors, resistors, transistors etc), you should check bias and dc offset.
    Make it simple...Make it better!

  9. #9

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    Bought a carver tfm35 yesterday, along with a ct-3, think i will check dc offset after first auditioning with my speaks.

    If this blows up, i will haunt you guys in the afterlife.
    humpty dumpty was pushed

  10. #10

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    just checked the tfm 35, nothin, the needle moves slightly as the probes touch the terminals,.
    humpty dumpty was pushed

  11. #11

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    after 45 minutes, i get 1mv on one channel, and 2mv on the other.
    humpty dumpty was pushed

  12. #12

    Member Sales Rating: (0)

    Join Date
    Aug 2013
    Location
    Abbotsford BC
    Posts
    1,462

    Default

    Analog meter or DVOM ?
    Living Room Evolved
    Onkyo TX-NR717
    Parasound HCA-1200II > Polk Audio RTi A7 Black Front
    Polk Audio RTi A3 Black Rear
    Polk Audio CSiA6 Center
    Tannoy TS2.12 Sub
    Marantz CD6004
    Apple Mac Mini
    Apple TV 3rd Gen
    Sony PS3 160Gb/Microsoft XBox 360
    Insignia 55 inch 120Hz TV

    Bedroom
    Harman Kardon HK 3490/HK 3375
    A:Onkyo SKF-4800 Towers Black
    B:Polk Monitor (Model) 5 with Peerless Tweets
    Polk PSW108
    PS3 320Gb
    Insignia 39 inch 60Hz TV

  13. #13

    Member Sales Rating: (0)

    Join Date
    May 2012
    Location
    New York
    Posts
    238

    Default

    Quote Originally Posted by scottyboy76 View Post
    Bought a carver tfm35 yesterday, along with a ct-3, think i will check dc offset after first auditioning with my speaks.
    It should be the other way around. Whenever I acquire a used/vintage amp, I always check the DC offset first before hooking up to speakers, and an expendable pair at that. If the amp has a major problem, I don't want it hooked up to my good speakers.
    Main system: Denon DP-59L | Audio-Technica AT33EV | Marantz Reference Series SA-11S2 | Classé CP-50, modified | Classé CA-300, modified | Classé DR-10, modified | Classé RC-1 | PSB Stratus Gold i's | DIY Balanced AC Power Conditioner with surge/spike suppression | Acoustic Zen and NeoTech cables | Oyaide and Furutech AC power connectors and receptacles | Hi-Fi Tuning Supreme fuses | Dedicated 20A IG AC line

  14. #14

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    just hooked it up to some **** speaks, and didnt push them.

    Other question, it was an analog meter.
    humpty dumpty was pushed

  15. #15
    Audiophile
    Member Sales Rating: (30)

    Join Date
    Mar 2006
    Location
    Seattle
    Posts
    11,112

    Default

    I also measure DC offset of amps that are new to me, and it's saved me more than once on 80's amps that had +200mv offset!

  16. #16

    Member Sales Rating: (0)

    Join Date
    Mar 2003
    Location
    Maryland
    Posts
    2,102

    Default

    The DC offset is the first thing I check on a new to me amp. I looked at a Hafler amp a few years ago that had a way high DC offset in one channel.

    Oh yeah, use a good DMM like a Fluke. Cheap DMM's can be trusted at such low levels.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade)
    Parasound: C/PT-600, HCA-800II; Denon: DVD-2910, DRM-800A; Monster HTS3600-MKII, Grado SR-225i

    HT:
    Denon AVR-888, Polk: RM7, PSW10, Marantz UD5005, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, DRA-825R, DCD-660, DRM-700A, DRR-780; Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S8, Monitor 5A, TSi100; Pioneer CT-6R, PL-530; Onkyo CP-1046F; Ortofon OM5E, Marantz PM5004, CD5004

  17. #17

    Member Sales Rating: (0)

    Join Date
    Dec 2009
    Location
    north georgia mountains
    Posts
    2,063

    Default

    Quote Originally Posted by skrol View Post
    The DC offset is the first thing I check on a new to me amp. I looked at a Hafler amp a few years ago that had a way high DC offset in one channel.

    Oh yeah, use a good DMM like a Fluke. Cheap DMM's can be trusted at such low levels.
    Did you mean to type "cant" be trusted at such low levels?

    If so i will borrow a better meter, im using a cheap sperry from home depot i have always used to do home wiring projects.
    humpty dumpty was pushed

  18. #18

    Member Sales Rating: (0)

    Join Date
    Jan 2010
    Posts
    563

    Default

    Quote Originally Posted by scottyboy76 View Post
    Did you mean to type "cant" be trusted at such low levels?

    If so i will borrow a better meter, im using a cheap sperry from home depot i have always used to do home wiring projects.
    You can always trust Fluke multimeters. They are the best multimeters your money can buy!. in my book, under 5mv dc offset is very good and 0mv is ideal!!!!
    Make it simple...Make it better!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

     

Similar Threads

  1. Measure twice, cut once
    By tuffgong in forum Vintage Speakers
    Replies: 3
    Last Post: 05-15-2006, 08:02 PM
  2. Is there a way to measure polyfill accurately?
    By VR3 in forum DIY, Mods & Tweaks
    Replies: 5
    Last Post: 11-03-2005, 09:06 PM
  3. How do you measure a cable?
    By Kevinvb11 in forum 2 Channel Audio
    Replies: 34
    Last Post: 04-07-2005, 06:28 PM
  4. amp is shutting down Offset LED lit
    By sirogenous in forum Car Audio & Electronics
    Replies: 33
    Last Post: 08-21-2003, 03:40 PM
  5. Test Measure and Diagnostics
    By HBombToo in forum Electronics
    Replies: 18
    Last Post: 05-14-2003, 01:55 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts