Hafler 500 Power Amplifier: Vintage Audio Review Episode

[@parttime9070]

I feel it was one of best I've ever owned. It had a commanding low end , the high and mid was sweet sounding. When it died there was no one around any more to repair it .. Sadly it ended up in the land fill back in the 90's , wish I would of kept it..

[@jozeilersic7620]

Super! Please upgraded version TOO!

[@vintageaudioreview]

Yes, I will do the upgraded version- probably a few months down the road. Thanks!

[@bblimediamostlyspeakers]

I aquired 3 of the Pro version (P500) several years ago that I pulled from a small local theater. These were installed new in 1985 and ran daily till 2020, powering Klipsch Lascala LCR, Heresy surrounds and a pair of dual 15" Klipsch MWM horn subs. I love the sound of the amps, very warm but clear, and in my opinion some of the tightest bass Ive ever heard. A Crown macrotech powered the subs briefly and sounded sloppy in comparison. The subs I discovered were also accidentally wired in parallel internally and were running one amp channel, which means the Hafler was feeding probably 1 ohm or less and had zero problems! The only problem I have with the Pro versions is the circuit that drives the signal LED's leaks noise onto the audio path and makes a static/ crackling sound when the LEDs are lit. Now I have one powering a pair of Fisher towers used as subs and I don't hear the noise! If it weren't for the noise problem I'd be using another one on my Electrovoice Sentry IVs, but for now have an AB International running them.

[@vintageaudioreview]

Wow, that is quite a tale! What is the LCR mean? Interesting about the LED's causing some noise. Thanks for the commentary!

[@bblimediamostlyspeakers]

Left, center, right- speaker arrangement. Someday ill teach myself how to repair the noisy circuit

[@artysanmobile]

@@bblimediamostlyspeakers Well, that’s not very PRO of them is it? Quick fix, cut the feed. Who needs LEDs?

[@artysanmobile]

Hafler amplifiers enjoy lots of fans in the recording studio market for a number of important reasons. I have one surround 5.1 and one stereo system of Hafler monitor speakers that I chose after long comparison of five different brands and I think the amplifiers within were a lot of my reason. In addition to meeting a high spec, their high damping made them easy to apply to a wide variety of very critical speakers. Studios need a LOT of amplifiers and they must have balanced inputs. Long ago, that was not nearly as common as it is today. A typical room would need 6 stereo amps back in the stereo days. Once surround became normal, there were excellent choices in active speakers, replacing some of the need for discrete amps.

[@vintageaudioreview]

Thanks for sharing the info. I am not sure if the non pro versions had balanced inputs- I don't think they did. This is my 1st Hafler gear review and they seem to be about as popular as Carver gear. You certainly have a lot of Hafler amps!

[@artysanmobile]

@@vintageaudioreview The monitoring systems I mentioned are all active speakers. I have no discrete amps but I recall their near ubiquity in South Florida studios. You’d see them on the way in to the control room and think “all’s good.”

[@artysanmobile]

@@vintageaudioreview Thank you for an excellent test review. I’m surprised how cheaply they are selling.

[@vintageaudioreview]

@@artysanmobile I was not aware they were used in control rooms- probably on the version with balanced inputs.

[@vintageaudioreview]

@@artysanmobile I appreciate all your commentary! I am excited to test the "upgraded version" version in the future, and thankx for the compliment!

[@TriAmpHiFi]

I certainly remember the Haflers................. Can't remember if we sold them or hated them at Tech Hifi. Didn't matter, I couldn't afford them or the Crowns I really wanted at Daddy's Junkie anyway. So it was Peavey amps for the big EV cabinets & horns. Couldn't afford JBL drivers either. Lol, besides the one horn cap, I ran no crossovers at all. Heck I didn't know any better. Sounded kick-ass to me and I made a pretty fair dollar DJing with that rig. Thanks! Acid Jazz, Funk & Brass 🔈🔉🔊

[@vintageaudioreview]

Always appreciate your taking some time to share your experiences. Your Dj system sounded like it would work ok, and you could use it for playing a guitar, I suppose. I was lucky to be able to buy LaScalas for my DJ/home speakers 😁

[@artysanmobile]

The MOSFET output devices were a large part of their appeal. Their speed and low ON resistance made the Haflers studio regulars. MOSFETs are in even greater use today and there are new even better devices that will certainly work. They are not going to be plug and play, requiring some mods in the driver circuit, and obviously they will all need replacement. Let google be your friend.

[@vintageaudioreview]

Nothing is planned on being done to the amp in this review- it is not mine. I will be getting an "upgraded" 500 shortly to test and review/compare before too long. I have seen some upgrade kits for these that look promising were you to go that route. Thanks again for taking the time to comment

[@basspig]

Excellent amplifiers. I own five of them and I still maintain them after all these years. A major upgrade would be increasing the size of the filter capacitors. Another upgrade is to add an input buffer to make the amplifier more stable. When running and it's normal stereo mode it can tend to become unstable depending on the grounding resistance of the output stage to the chassis. I find the best way to run them is in Bridge mono because the cancellation of power supply common mode affects occurs. With the boosted capacitor size and the bridge mono the amplifiers can produce closer to 1800 watts for 300 milliseconds until the power supply voltage starts to sag.

[@vintageaudioreview]

That is quite a lot of power for a brief period of time. You are the 2nd person to comment about increasing the filter caps. It is not my amp and don't think the owner will want to do anything since he has an upgraded one- neither of which he is using now. Will do a review on the upgraded one (by a company that does that kind thing) at some point. Thanks for sharing!

[@basspig]

@@vintageaudioreview The power supplies on these units are spongy, hence they benefit greatly from larger energy storage to lengthen the period which they can deliver short term higher power. A decade ago, I had one go into oscillation in the middle of a listening session. It seems to be an issue with varying resistance from the speaker common lead and chassis. There is a 10 ohm resistor connecting these two points. If you overdrive them with asymmetrical audio in stereo, they will trip protection because the power supply rails will become unbalanced under that kind of load. Running them bridged solves this. I have a couple of XL600 Haflers driving my front mains, bridged, and modded. They will deliver just over 130 Vrms into an 8 ohm load for short durations, yielding an incredible 2200W of short term headroom. Bridging also cancels common mode noise.

[@vintageaudioreview]

@@basspig You sure know a lot of the Haflers! Running in Mono is always nice if you can live with the increased noise level from the increased gain- might not be a problem depending on your speakers

[@bblimediamostlyspeakers]

Five? I only have 3 😆

[@basspig]

@@vintageaudioreview running bridged actually eliminated the residual hum, which was a real problem with me running 112dB efficient subwoofers.

[@davidstevens7809]

I didnt explain well. Rockford fosgate purchased hafler in late 87 I think.. we made a home amp under the rockford fosgate badge. RF2000 .it was also sold with hafler badge JF2000. There was a 3rd version rfp2000 that had xlr balanced inputs..I cant remember if any hafler versions had the balanced inputs..but I urge everyone reading this try to find one..I was told only 50 were made. Not sure if that includes all 3 versions or if that was how many rf2000 were sold..either way its awesome amp and did double rated power straight from the factory

[@vintageaudioreview]

Thanks for the extra info! I have not run across any Rockford amps (other than for cars) Did not see an option for balanced inputs for the 500. Will be on the lookout for rfp2000s.

[@glenncurry3041]

I have one with one bad output channel. Hope they're not unobtaniums! They do not have a 4 ohm rating and I found they were not happy with my low efficiency 4 ohm Maggies. I even added some active ventilation, moving more air thru the tunnel and venting the case. Switched to my ADCOM GFA555. Let my son use this on his AR 91. Came back one bad channel.

[@vintageaudioreview]

AR9's, according to my buddy Ian, are amp killers except for the most robust amps. I posted in an earlier comment that you can rebuild the DH500 for $265 for the parts/kit if you wanted. Thanks for sharing!

[@glenncurry3041]

@@vintageaudioreview Another of my son's has AR9. This one has AR91. The 9's do require some power, but far from as bad as my Maggies! He's been powering them with a pair of Audio Purist LO-7M's.

[@vintageaudioreview]

@@glenncurry3041 Am not familiar with the AR91's nor the Audio Purist gear. Hope to do the review of the upgraded hafler 500 in a few months. Never been a big fan of the maggies that I have heard

[@EddyTeetree]

Hey doc. this has similar to the Marantz 240 power amp. from 1974 Im currently (haha) using!

[@vintageaudioreview]

Are you sure- I am not sure there were many amps using power FETs then..?

[@HillsWorkbench]

Makes me wonder how bias (idle current) is set. Clipping indicators can be easily added.

[@bblimediamostlyspeakers]

The Pro versions have clip indicators

[@vintageaudioreview]

I did not see any bias adjustments. One could figure out what the Pro versions did for the clipping indicators and adapt, I suppose

[@TheBerdaguer]

Which one is better the Hafler DH-500 or the Soundcraftsmen PCR800 ? Both mosfet amps, almost same specs. Regulated power supply for the PCR800, more power for the Hafler

[@vintageaudioreview]

Thanks so much for the question- particularly on items that I have actually reviewed! I often get questions about gear I have never heard of, so this is a pleasant change. Depending on your speakers and listening material, the PCR should be plenty of power. The Hafler is a bit better on the measurement side, though my loads and testing methodology have improved since the PCR800 was reviewed, but I am not sure you would actually hear any measurement differences. If bridged in mono, the PCR can put out 600w/8ohms, and I am guessing the same could be said of the Hafler if bridged- both had bridge kits for them. Both have two speed fans that can be loud when in the high speed mode. The Hafler's fan did not return to normal speed once it cooled down- until it was powered off (not sure if that was a defect or not). The PCR is narrower which could be handy, plus it has clipping indicators, which means I would vote for it.

[@basspig]

Two other modifications I like to do to these amplifiers is to replace the Twisted wires for the input with coax. The second modification is to save the power switch from the inrush current. The Rocker switches on these amplifiers notoriously fail. I use a triac to turn the amplifier on and on so the power switch never sees more than 1 milliamp of current as it is used to operate the Gate of the triac.

[@vintageaudioreview]

The twisted wires being replaced with coax sounds good, but am not sure it really would make a difference as we are talking audio frequencies and they are twisted, but an easy thing to do, A triac is a creative thing to do, but I would use a switched power control center like the Monster HTS3600 and have the preamp coming on trigger the Hafler

[@basspig]

@@vintageaudioreview assuming line voltage were 0% THD, that would be true, but it's full of harmonic hash from power supplies and light dimmers. A $3 power strip is a way to save the internal switch too, but I wanted a more elegant solution.

[@vintageaudioreview]

@@basspig Just a few weeks ago I plugged a 15amp hoover vacuum into the same outlet as I had a power cord with open ends on one end and did not see any noise on the ac line when looking at it with my scope when I turned on the hoover. I was mainly looking for something else, but found that surprising. A triac is definitely more elegant.

[@basspig]

@@vintageaudioreview you'll not likely see this on a scope. The spikes are tiny. But you can hear the light dimmer at 50% as a buzz in the tweeters.

[@vintageaudioreview]

@@basspig I don't have light dimmers in rooms where my stereos are (not on purpose, just the way it worked out). I would like to do a test one day if I can find a cheap dimmer switch where I see if I can see the effect on some different devices....I certainly remember hearing noise from them many years ago.

[@fisherhutchens9452]

What was the condition of the amp you tested? Bone stock? Re-capped? Something in between?

[@vintageaudioreview]

It looked pretty much stock- thanks for the question.

[@johnstone7697]

According to the literature, THD spec at full power is .025%, not .002

[@vintageaudioreview]

Thanks for bringing this up- according to the service manual, the typical thd at 255w @1khz is 0.002%, but less than the 0.025% at any frequency in the band at 255w (8ohms)

[@TriAmpHiFi]

Oh Hey.................. May I have a free professional opinion please? I'd appreciate it. Is it OK/Safe to plug-in wall power to my power amps this following way? I have a dedicated 120v 20amp circuit with a non-traditional (to me) outlet for the window AC nearby. I found the proper adapter ( 20A AC Power Plug to 15A T-Blade Adapter Cable, 6-20P to 5-20R,6-20P to 6-15R,6-20P to 5-15R, 4 in 1 AC Adapter,12AWG Heavy Duty Extension Cable for Air Conditioner Etc.). So question is, can I plug-in my 115 volt power amp into this circuit all right? Thanks, Pal.

[@vintageaudioreview]

Thanks for the question and I am by no means an electrician, so a lot of what you are saying about the electrical outlets is greek to me. My Crown SA-2 (see the video I did on it) had a 20A power cord connector that required an adapter to fit the standard 120v socket, and it worked fine. That is about all the information I can provide.

[@jasonk5979]

Be careful buying a used example. The output transistors are no longer made . And they quit making substitutes as far as I am aware. I have an example that got shorted years ago. Ask me how I know.

[@vintageaudioreview]

Thanks for the advice and I will have to ask how you know. You can get a full rebuild kit for the dh500 on ebay for $265 w/out the filter caps, that includes the fets. But you have to build it...

[@jasonk5979]

@@vintageaudioreview Interesting. The Hitachi originals haven't been made in a long time. I heard those were the best sounding. People used to have the originals on eBay for reasonable prices. But now they are in the 15-20 apiece range. If you can find them. Exicon used to make a replacement but have discontinued the TO3 production. I'll have to check out the eBay kit.

[@vintageaudioreview]

@@jasonk5979 I think the Ebay kit used Toshiba Fets. I am someone who would challenge a person about hearing the difference between different FETS as long as they measured similarly. FANTASIA AUDIO sells the kit on ebay

[@davidstevens7809]

Wish you had a hafler jf2000 or a rf2000.they are same amp..I helped make them..Im confused about your 1988 comment..I worked there in 1988 and they made the new line after ces jan 88..

[@vintageaudioreview]

I have a modified DH500 that will be tested/reviewed at some point. I try to be as accurate as I can on the date I give for some of the products, using old Audio/Stereo Review buyer's guides which could be off a year.