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Discussion Starter #1
So I've recently become a Hafler fan. (mostly b/c i need clean cheap amps while my main 2 amps are being refurbished ETA 2 months!!!)

My XL280 sounds really good to me. Warm, good low end grunt, not as loud as I wanted so I picked up a relatively inexpensive DH 500. (I know you get what you pay for :)

The potential issue I am exploring is the amp just doesn't seem to put our 255 wpc. The low end bass is not there either compared to the XL280. The amp doesn't sound terrible but I think something is amiss or maybe the difference in the amps is just that they are different amps?

So my "sophisticated" test is I have a pair of Martin Logan Montage speakers rated at 150 watts and 5ohms. So I would expect this DH 500 to blow them apart if turned all the way up. It doesn't. I can crank the DH500 up all the way and the speakers sound fine ... no distortion ... okay sound. It's loud just not as loud as I would guess it should be. Any thoughts?

I wouldn't mind putting a few bucks into this but not going crazy.

Thanks for the assistance and recommendations!
 

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I have always felt the older Hafler amps sounded a little "soft" in the bass region. Going from an XL280 to a DH500 is not much of an increase, however; it's less than 2 dB power increase at 8 ohms, so you would hardly (I would say you would not) notice the power difference. It is possible expectations exceed reality in this case. It happens.

IMO - Don
 

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Thanks Don ... that makes sense. I've always heard that "watts" doesn't really mean much and when I heard a 6 watt fisher tube amp I believed it! That thing rocked hard.
 

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NP. Might want to check out an SPL calculator to see about how much power you are using/need: http://myhometheater.homestead.com/splcalculator.html

As for as power, the scale is logarithmic and loosely correlates to how we hear:


  • 1 dB increase in barely detectable by most of us and takes 1.26x the power
  • 3 dB is about what we do when we "turn the volume up just a little" and takes 2x the power
  • 10 dB is twice as loud and takes 10x the power

HTH - Don
 

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Discussion Starter #5
NP. Might want to check out an SPL calculator to see about how much power you are using/need: http://myhometheater.homestead.com/splcalculator.html

As for as power, the scale is logarithmic and loosely correlates to how we hear:


  • 1 dB increase in barely detectable by most of us and takes 1.26x the power
  • 3 dB is about what we do when we "turn the volume up just a little" and takes 2x the power
  • 10 dB is twice as loud and takes 10x the power

HTH - Don
cool nice little tool!

thanks
 

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I recently sold that model Hafler amp on E-bay to some guy out west that refurbished them for resale. Purchased it new back about 82. Beat the heck out of that thing as a kid when I was growing... Never had a problem,built like a tank. That 3 speed fan was on "high" many, a many time back in the day... thanks for the memories.... LOL
 
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I was using my Hafler DH200 for driving my subwoofers for several years. One day just for fun I connected my subs to unused channels on my Kenwood KM-X1. Wow! The subs sounded so much better using the Kenwood amp! I was surprised and have not gone back to the Hafler for sub duty.
 

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Discussion Starter #9 (Edited)

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My best guess as to why the DH500 sounds anemic is that you are not giving it a high enough signal level from your source device.

Looking at both the Heos and the AVC 1800...

Neither has a specification for their output voltage. The AVC-1800 looks more like a preamp, and will probably have a higher output than the Heos, which looks more like a source device.

Looking at the HCA-855 amp, which was the partner to the AVC-1800, it only wants to see 1.2v for full (85W) output, so, who knows.


Try the AVC-1800 and report back.

--

Now I see the Heos has a fixed output at 2v, but no spec for the variable output, and does call itself a preamp.

Oh well...
 

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Discussion Starter #11
My best guess as to why the DH500 sounds anemic is that you are not giving it a high enough signal level from your source device.

Looking at both the Heos and the AVC 1800...

Neither has a specification for their output voltage. The AVC-1800 looks more like a preamp, and will probably have a higher output than the Heos, which looks more like a source device.

Looking at the HCA-855 amp, which was the partner to the AVC-1800, it only wants to see 1.2v for full (85W) output, so, who knows.


Try the AVC-1800 and report back.

--

Now I see the Heos has a fixed output at 2v, but no spec for the variable output, and does call itself a preamp.

Oh well...

Thanks you bring up an important point that most of us newbies probably are not tuned into when trying separates ... I've never considered the output voltage to input voltage of the preamp/amp combo.

I will try the Parasound and also if I feel really ambitious may try my Onkyo sr 805 .... its just a pain since that is well buried into my HT set up...

Will report back tomorrow or so...

Thanks again.
 

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Reporting back!!!

wow I mean wow what a difference the preamp makes ...

I set up the DH 500 with the Parasound AVC 1800 and its pushing my Martin Logan reQuests ... bass a little sloppy, highs a little tinny but what do you want for a few hundred bucks and a 30 year old amp!!!!

I learned a lot so far from just 2 posts on this forum ... thanks gents.

To summarize: I guess the XL280 was a little more sensitive and the HEOS is really just a toy but that combination sounded good to me. The DH 500 needs more voltage from the preamp ... if i got that right :)
 

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Seems that way, yes.

Good catch, RayDunzl.
Thank you, Don

---

My pre says it will output 7V unbalanced or 14v balanced

The three amplifiers in the series I have want to see 2.53/2.87/3.71Vrms and all have a gain of 26.4 dB.

I looked at Crown, got various results, but it looks like the newer gear that is (somewhat) aimed at the home (theater) market has settled on 1.4v despite the ultimate power level, so the gain (which isn't always listed) must vary in the series.

Somewhere, I think it was a Lamm (who has one of those?) would swing 27V.

So, it's a consideration, if trying to drive a power amp with whatever you find to plug into it.
 

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Thank you, Don

---

My pre says it will output 7V unbalanced or 14v balanced

The three amplifiers in the series I have want to see 2.53/2.87/3.71Vrms and all have a gain of 26.4 dB.

I looked at Crown, got various results, but it looks like the newer gear that is (somewhat) aimed at the home (theater) market has settled on 1.4v despite the ultimate power level, so the gain (which isn't always listed) must vary in the series.

Somewhere, I think it was a Lamm (who has one of those?) would swing 27V.

So, it's a consideration, if trying to drive a power amp with whatever you find to plug into it.

Yes thank you RayDunzl you made my whole night :)

I have the DH 500 hooked up to my Kef 104.2 (not easy to drive) and they are singing nicely ... now I feel that 255 wpc! I can't believe you can pick these Haflers up for a few hundred bucks ...

I may keep it when I get my Denons back ..

Just curious what pre are you using?

I think I may plug the HEOS into my Parasound but then I'll need another pre ... Ive seen Anthem AVM20s and BK Ref 50s on ebay for what seems like a good deal ... maybe I'll invest in another pre ... I really like being able to plug the HEOS into the USB and control it via smart phone ...
 

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Yes thank you RayDunzl you made my whole night :)

I have the DH 500 hooked up to my Kef 104.2 (not easy to drive) and they are singing nicely ... now I feel that 255 wpc! I can't believe you can pick these Haflers up for a few hundred bucks ...

I may keep it when I get my Denons back ..

Just curious what pre are you using?

I think I may plug the HEOS into my Parasound but then I'll need another pre ... Ive seen Anthem AVM20s and BK Ref 50s on ebay for what seems like a good deal ... maybe I'll invest in another pre ... I really like being able to plug the HEOS into the USB and control it via smart phone ...


Pre is a Krell KCT.



links in sig below.
 
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