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Hafler XL-600.....The Eviction Notice Amp

Discussion in 'Solid State' started by Son-of-Vere, Nov 10, 2018 at 8:25 PM.

  1. Son-of-Vere

    Son-of-Vere Super Member

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    Just got one of these off the 'bay. Price was right, and in both mechanically and cosmetically good condition, still has the protective wrapper on the faceplate. Went thru the normal checks before hooking it up to my speakers. DC offset is high, as in 48mV L, 75mV R. Well, that's not good. I've also reset the bias, it made the offset slightly worse.
    The amp has no adjustments for offset, so I went poking around the web, in AK, and on the 'bay again. Truth is, there isn't a whole lot of info on this amp. It probably isn't the best choice for high fidelity, it's more of a PA amp with RCA inputs and some exotic "Excelinear" circuitry, best left for a pro to fiddle with.

    But it's a monster, I've always wanted to own something like this, and this opportunity came along. Bad news is it sounds kinda rough around the edges, and I know it could be better once I get the offset somewhere more reasonable.

    This is where my quandary lies. Do I rebuild the current driver boards and hope I get it right (differential pair, I know) or do I go with the PC-1 boards offered by QUA-CO which have an offset adjustment built into them? Here's the real bad news, the PC-1 boards while fitting numerous Hafler amps were never designed for the XL-600, but can be "shoehorned" in.

    Either way is risky, what is the better choice?

    I'll throw some pics up next time I have the cover off.
     
    Last edited: Nov 11, 2018 at 7:18 AM

     

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  2. avionic

    avionic " Black Knights " Subscriber

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    Millivolts
     
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  3. avionic

    avionic " Black Knights " Subscriber

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    [​IMG]
     
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  4. Son-of-Vere

    Son-of-Vere Super Member

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    Well, that was helpful..........
     
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  5. Dropthatbass

    Dropthatbass New Member

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    ive got the hafler 500 im still waiting
     
  6. Binkman

    Binkman AK Subscriber Subscriber

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  7. Son-of-Vere

    Son-of-Vere Super Member

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    index-1.jpg
    Hmmm, that's interesting. This doesn't seem to follow Echowars theory on offset. Is it the high output of the amp that allows such high offset? Did they figure no one would care? Considering the fact that someone went out of their way to create new driver boards to address this issue, somebody didn't think it was right.
     
  8. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    Obviously we'd like the offset to be 0 but I've seen specs on plenty of amps saying it's ok at 100mV and a few even higher.

    I doubt the offset is what's making the amp sound the way you describe. I've heard amps with 200+mV and after proper adjustment sounded the same on my test speakers. With that low an offset I doubt you'll hear any difference at all between what you've got and 0. Something else is going on or you just don't like the sound of the amp.
     
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  9. Binkman

    Binkman AK Subscriber Subscriber

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    Very true. I've read and regularly read a lot SM's. 'OMGcat's observations are very accurate. And reading all those sms the number of units that have dc offset adjust are a fraction of millions of units made without offset adjustment. You may consider the age of components. In that link I posted? the guy wasn't happy with 10mv and wanted zero?? Like 100mv is 1/10th of a volt.

    You could post pics of age.. consider looking at the components like transistors and look for soldering. Good cosmetics doesn't mean the caps are not aged etc.

    (In addition.. my sta-2300 takes an hour before it really sounds good and I haven't replaced one cap...low hours. I'm the orig. owner so i know.}
    So .... How many hours do you have on it.. since you just got it? Everybody here with some time will agree that caps can reform a couple hours on and off low vol.. I play rock with a good beat at low vol. as electrons get aligned.. and after some running time you may see that dc offset balance out. Same as bias can drift but eventually gets stable.. thats why we monitor it after replacing transistors and caps etc.
     
    Last edited: Nov 11, 2018 at 11:09 AM
  10. Son-of-Vere

    Son-of-Vere Super Member

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    I don't think the cover has ever been off this amp before. It looks all original and untouched inside, Judging by the amount of dirt accrued on the fan, it has not seen a lot of hours. While it could probably have a recap done to it, I'm just going to use it for a while. It's not going to blow anything up.
    This is why I came here, if I'm chasin' the dragon for no good reason, I want someone to say so.

    I've had another problem crop up, I'm coming down w/a cold. While I didn't feel the first effects of it until after I tried the amp, it may have affected my hearing. My right ear popped yesterday and the sound field shifted to the right. Being I was hearing the most harshness on the right channel, the one one with the most offset, I figured that was the problem, it may have been that my ear was just plugged up.
     
  11. Elliot Thompson

    Elliot Thompson Well-Known Member

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    Hi.

    The Hafler XL 600 was expensive when it was in production which, is why you won't find a lot of information regarding this amplifier. Hafler was synonymous with Home Hi-Fi however, dabbled in the Pro Audio market.

    Best Regards, Hafler XL 600 Specifications.jpg
     

     

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  12. damacman

    damacman Blown and Injected Subscriber

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    GM Delco (and many other) OEM high power car stereos have 5VDC present on the outputs ...
     
  13. avionic

    avionic " Black Knights " Subscriber

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    This aint no Bowtie..:biggrin:
     
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  14. Binkman

    Binkman AK Subscriber Subscriber

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    I'm very susceptible to barametric change. I lose a lot of hz till e.g. a storm moves on out. really frustrating as I'm continually having to ask what was said or crank up the audio.
     
  15. llwhtt

    llwhtt Super Member

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    This weekend I ran across my Bose 1800/1801 Service manual, they only ask the DC offset to be less than 250mv, not very picky to say the least. The rest of the test measurements aren't very critical either.

    Craig
     

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