Hafler DH-500 Opinions

[rmaiers]

I have a Hafler DH-500 amplifier powering 2 RTA-12B speakers and I am consistently blowing the 3/4 amp fuses that protect the tweeters when I play at high volume but less than 12:00 (1/2 power) set at the preamp (Hafler DH-110).

Other threads have suggested the Hafler is underpowered for the speakers playing at high volumes, but my understanding is the DH-500 is one of the more powerful vintage amplifiers out there. The RTA-12Bs are rated to handle 500 watts.

My Hafler was was checked out by a Hafler knowledgeable technician and he said it met or exceeded all specs (255 watts/channel into 8 ohms).

I would welcome any suggestions/opinions.

[GV#27]

Your Hafler is definately not underpowered and it sounds like the fuses are doing exactly what they are supposed to.Use a bigger fuse or listen at lower levels.

[WilliamM2]

The fuses are blowing because you are clipping the amp. 12:00 is not 1/2 volume, it's closer to max output.

[GV#27]

it's closer to max output.

It can be but not necessarily.It is highly dependant on the source material,preamp gain etc.And the fuse is blowing because level is to high for the fuse rating, amp clipping or not.

[Fongolio]

I believe those RTA-12B's are 4 ohm speakers. The Hafler although capable has to work pretty hard to drive them. Expecially at high volume. If you want ear bleed volume perhaps a more 4 ohm friendly amp is in order.

[ESavinon]

The dh-500 is stable to 2 ohms.

[rmaiers]

Thanks for the responses. I tend to believe the Hafler is not underpowered and the fuse blowing is not due to clipping.

I don't get to listen at high volumes that often but when I do it is annoying that the fuses tend to go.

Does going to a 1 amp fast blow fuse seem reasonable or am I risking blowing the tweeters? They are the highly thought of Peerless tweeters and I don't think you can get direct replacements for those so I don't want to take any undo risks.

As others have suggested, I may just have to be content with lower volume settings.

[jinjuku]

Do you know anyone with a comparable amp that you could try?

[rmaiers]

Not really. I do have a vintage Nikko NR-1019 receiver that is rated at 75 watts/channel into 8 ohms and is supposed to be capable of driving 4 ohm loads, but I am afarid of getting into clipping if I try it on the Polks.

[Fongolio]

The dh-500 is stable to 2 ohms.

I stand corrected. As someone earlier suggested perhaps it's a source/gain issue. Have you tried different sources and/or pre-amps? I would be very hesitant to swap the tweeter fuses for higher values though. I do agree on one thing said above...you are probably near full output power at the 12 o'clock mark on the pre. With my Carver amp (soon to be back from the tech!!) and Carver pre anything past 12 o'clock has very little effect on the output on the meters. I have a Hafler DH-220 so if as a last resort you want to just send me those 12B's I'll be happy to test them on my Hafler. :)

[debussyj]

Boy does that bring back memories. I had the Hafler back in the 80's. Used it to drive my Acoustat electrostatic speakers. Man that baby got so hot you could fry an egg on the top of it! Anyway, I realized this was not a good match for my system so I sold it and got two Adcom GFA-555's (original design) (biamped) and still have (love) them to this day. Don't get me wrong, the Hafler is a great classic piece, it's just I was expecting too much of it in my system. Best of luck. DJ

[ohskigod]

barring freak circumstance its not the amp. is your treble fully cranked on the pre? if you do that, and listen at high volumes on what is a pretty beefy amp, you might just be sending way too much volume to that peerless tweet, again espescially if you like things on the bright side

I reccomend trying either dropping the treble a skosh (i used to be a serious high treble listener until i broke myself out of the habit) or maybe another preamp is in order (I've definitly gone that route)?

The Hafler is a beast of an amp and is more than enough for RTA12's. it should handle that load like it's a cakewalk, but any amp if used wrong can distort/clip and cause problems. Given the particulars here I'm going with that being the case here, hate to sound like I'm bagging on you but I;ve owned both the Hafler and the RTA 12 and I gotta go with my gut on this.

this might come down to having to correct something (like treble setting)

[rmaiers]

Thanks for all the great feed back. I run the preamp (Hafler DH-110) in neutral positions. The volume is pretty crazy loud when I am playing at high volume settings (near 12:00 or mid volume, but my wife complains she has to straighten all the pictures after one of my sessions).

The one complaint I have with the Hafler is it does not have power meters. Any body know of good add ons?