Denon PMA-2000IVR concern

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Jockos
Jockos Posts: 310
edited April 2007 in Electronics
Just recieved the Denon PMA integrated amp from russman. Amp looks new. Happy to find it undamaged on it's long journey in only it's original box. First listening is that it's clear, maybe a tad bright. The only concern I have is that I tested the DC offset and the R channel is 12.5mv and the left is 2.5mv. The right seems abit high for a fairly late model amp. Wonder if I should get it checked by a shop. I'll try to download the owners manual but I doubt they have the service manual available. Is 12.5mv ok. for the right channel? When you purchase a new amp will the DCoffset be low, say 1-5mv?

Thanks Jockos
Post edited by Jockos on

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  • Jockos
    Jockos Posts: 310
    edited April 2007
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    Marker,

    I believe in a earlier thread that you have one. Have you ever tried measuring your DC offset?

    Thanks Jockos
  • Systems
    Systems Posts: 14,873
    edited April 2007
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    12mv should be no cause for concern.Some amps have as much as 50mv -100mv at their outputs. It is normal to have the two channels of an amp to have different levels of DC offset because it depends on how closely matched the transistors and voltages of the power supply are.Many amps also have a pot that can be adjusted to null the offset.Also the relative levels will change as the amp warms up.
    Testing
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    Testing
  • Jockos
    Jockos Posts: 310
    edited April 2007
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    Maybe I'll try to contact denon to find a service manual and see if it is adjustable. My adcom 5500 measures 2.5mv and 1.8mv. If anyone else is familiar with this amp please chime in.
  • Jockos
    Jockos Posts: 310
    edited April 2007
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  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited April 2007
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    GV#27 wrote: »
    Many amps also have a pot that can be adjusted to null the offset.Also the relative levels will change as the amp warms up.


    Ed Zachry. Dana, keep me in the loop - I'll admit to not checking DC offset, I never have before. It drove the VR4's and sounded GREAT.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • heiney9
    heiney9 Posts: 25,109
    edited April 2007
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    12mV is very respectable and no cause for concern. When did you measure the DC offset? Typically it should be measured after about 30-60 minutes of power up after the trannys stabilize. No need to have both channels exact, as has been stated the matching of the output stage namely the trannys is what can cause slightly mis-matched DC offset. 12mV is well within normal operating for any amplifier.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • Jockos
    Jockos Posts: 310
    edited April 2007
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    Numbers and specs have always bothered me. I did let the amp warm up for around 2 hrs. Thanks for chiming in and putting me at ease. It sounds good especially the phono section is much better then my 20 yr old yamaha. I'd still like to get that right down to 5mv.....................
  • Jockos
    Jockos Posts: 310
    edited April 2007
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    Sorry to revive this thread but does anyone have any knowledge of the PMA2000, specifically if there is a pot to tweak the dc. I know after reading the threads on audiokarma that many older amps are adjustable.

    Thanks Jockos
  • heiney9
    heiney9 Posts: 25,109
    edited April 2007
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    Jockos wrote: »
    Sorry to revive this thread but does anyone have any knowledge of the PMA2000, specifically if there is a pot to tweak the dc. I know after reading the threads on audiokarma that many older amps are adjustable.

    Thanks Jockos

    Check www.diyaudio.com. Don't mess with things if you don't know what you are doing, in the end you'll have more problems then when you started. I've read about it 1000 times where someone gets it in their head they know what they are doing or want to do just a small tweak here or there and then they either ruin something or have a large repair bill.

    Of course if you have experience fixing and measuring electronics and have a schematic and proper equipment then you might be alright. Why is it so difficult for you to understand that the dc offset you are measuring is very good and well within normal OP for an amp of that age and design? How do you even know the adjustable pots are for dc and not for bias setting?

    Good luck

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • Systems
    Systems Posts: 14,873
    edited April 2007
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    heiney9 wrote: »
    How do you even know the adjustable pots are for dc and not for bias setting?



    Good luck

    H9
    Although not wise or neccessary considering the little amount of measured offset,if he really wants to mess around inside, the pot MAY;) be appropriately labelled offset on the PCB .Otherwise don't touch it.
    Testing
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  • heiney9
    heiney9 Posts: 25,109
    edited April 2007
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    GV#27 wrote: »
    Although not wise or neccessary considering the little amount of measured offset,if he really wants to mess around inside, the pot MAY;) be appropriately labelled offset on the PCB .Otherwise don't touch it.

    That may be, but no good ever comes of just blindly adjusting something inside an amp. ;) It's his to do with whatever he wants, I'm not trying to be preachy but just trying to give him some solid advice. When I was much younger in middle/high school I used to tear electronics apart and try to fix them, most times it was a disaster and in high school I took 4 years of electronics classes as electives. Even with that experience I'm not too eager to jump into my own stuff and I have great book knowledge on electronic circuits, just very little hands on in the last 15-20 years. :).

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • Systems
    Systems Posts: 14,873
    edited April 2007
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    Read my post,Im NOT recommending that he does it,only giving him a tip if he really feels the need to tinker.
    Testing
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  • Jockos
    Jockos Posts: 310
    edited April 2007
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    heiney9,

    I know exactly what you are trying to say. I did the same in my childhood days and ended up with problaby breaking more than fixing things. Anyway it's my own ecentricity(wrong spelling) that I'm pursuing this.There is a couple of threads from the AK thread, that echowars mentions that below 10mv is where you get the least distortion. So in my crazy mind it would be nice to get the R below 10mv.
    If a member where to come forth and say "Ya I did mine here's what to do and it's fairly easy" and back it up with a schematic then I would follow thru. I would not go poking inside without some solid advice. I did take a basic electronics course around 35 years ago, of course I can't remember anything.
    Anyway I value your opinion because you have responded and given excellent advice, suggestions before. I apologize if I offended you in anyway.
    This will be my last post on this matter unless someone else chimes in with good direction.
    Thanks Jockos
    Thanks GV
  • heiney9
    heiney9 Posts: 25,109
    edited April 2007
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    Jockos wrote: »
    heiney9,

    I know exactly what you are trying to say. I did the same in my childhood days and ended up with problaby breaking more than fixing things. Anyway it's my own ecentricity(wrong spelling) that I'm pursuing this.There is a couple of threads from the AK thread, that echowars mentions that below 10mv is where you get the least distortion. So in my crazy mind it would be nice to get the R below 10mv.
    If a member where to come forth and say "Ya I did mine here's what to do and it's fairly easy" and back it up with a schematic then I would follow thru. I would not go poking inside without some solid advice. I did take a basic electronics course around 35 years ago, of course I can't remember anything.
    Anyway I value your opinion because you have responded and given excellent advice, suggestions before. I apologize if I offended you in anyway.
    This will be my last post on this matter unless someone else chimes in with good direction.
    Thanks Jockos
    Thanks GV


    Not offended in any way at all. That thread of Echowars is very informative, but it is a bit broad. At the very least check out www.diyaudio.com those guys over there are very good as most who post alot are current or former techs and they have the hands on experience to guide you. I've learned a lot just reading and picking their brains.

    Have fun

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • turbochrgd1
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    The Aux1 Input on my Denon PMA-2000IVR Integrated Amp quit, so I switched my audio TV input to Aux2. Now the Aux2 input "channels" (switches from left to right channel out) and the LED on the front panel works intermittently. Any ideas for a fix?
  • Emlyn
    Emlyn Posts: 4,427
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    Do any of the other inputs work correctly?
  • skrol
    skrol Posts: 3,345
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    Could be bad solder joints on the PC board or dirty switches. I've seen this with Denon and others.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601