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HAFLER P500 - DH500 difference

wingzam

wingzam

VIntage audio??
Picked up this Hafler amp, it's a bit rough but at 250wpc I couldn't tear myself away from it.

It powered up properly and I got 35mV on the Left channel and 4mV on the right
Information on this unit is slim to none. Mostly what comes up is DH500 with glowing reviews. Also can't find any comparisons between the two.

Anybody know anything about this amp and the difference between it and the DH500?

There's an outfit that does modifications to the DH500 that sound very attractive..I'll be contacting them about what's available for the P500 if anything.
 

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May just be the pro version with a rack mount front panel and level controls as the main differences.
 
Correct. It's the pro version of the DH-500. The Left/Right gain knobs, and the 1/4" headphone input jacks are the main differences.

We used a P500 where I used to work, in one of our audio studio's. The other studio used a Bryston 4B. The rest of the gear, even the speakers, were identical between the rooms. The 2 studios were the same size as well. We kept it that way, to make mix comparisons easier. So, to me, the Hafler was better than the Bryston. Warmer sounding, more musical. Less dry in the treble too. The high end on the Bryston was really dry, flat, with no air.

Oh yea, just recently read an old review for a DH-500. It bench tested at over 300 watts into 8 Ohms, 450 watts into 4 Ohms, and 390 watts into 2 Ohms. Short term peak output was 792 watts into 4 Ohms. Not too shabby.

http://www.hifi-classic.net/review/hafler-dh-500-287.html

One other thing. eBay seller qua-co, is a former Hafler employee/engineer. He sells spare parts and rebuild kits for Hafler gear. Good prices too. Worth looking at if you ever need to do a rebuild on the amp. I'll use him whenever I rebuild my DH-500. qua-co sells mod kits also, including newly designed driver boards. They seem to get good reviews. Another company doing mods is Musical Designs. They offer many different mods and upgrades. They've been offering their mods for years, and are well received.

http://www.musicaldesign.com/Haf_pwrmods.html
 
Thanks for that info - I am very excited about this amp and that there's good support for it!
Here's an owners review from Audio Review and his experience with Musical Concepts kits

[Mar 02, 2002]
dewmonster
Audio Enthusiast

Strength:
Having a solid enough basic design to have someone like Musical concepts take an interest in perfecting it.

Weakness:
yeah right LOL

What has prompted this review of my Dh500 is a recent upgarde done by musical concepts. I have owned this amp for 19 years so I am completely aquainted with the sound of it as a stock unit. It was definately a fine amp which is why I have kept it for this long but it was always a little strained and after some listening sessions at higher volume you felt the need to turn it off. I had literature from msical concepts from 1982 in a file and had never done any of the mods. on the amp, and I guess I just assumed musical concepts was long dead and buried until just a while back I saw someone refer to a hafler for auction on e-bay with the musical concepts mods and proceeded to list the website (www.musicalconcepts.com). Well I had long regretted not going through with this back in the 80''s so I decided to go ahead and get it modified. Here is the list of work it received: 1000 watt torroidal transformer with dual windings. 4 power reserve caps to replace the two originals and converted to a totally dual mono design with over twice the storage capacity of the original. Cardas copper binding post, gold rca jacks, a replaceable 3 prong power cord, a new sculpted aluminum faceplate and the middle grade 599.00 signature series front end modification with extensive use of black gate caps throughout. Grand total $1400.00. Now the question you are asking is how could he have spent twice as much as it was worth new on an upgrade? Well the answer is if you want to hear anything even Close to what has come out of Mr. Hillig''s workshop for the poultry $1400.00 I believe you will be spending upwords of 5 times that much. It is simply beyond description. If you own a hafler or have a chance to buy one, RUN, don''t walk to his website and get at least the front end upgrade if not any of the other ones I have had done. You will absolutely not be able to get the grin off your face after you hear the difference it is simply amazing. No it is SIMPLY MUSICAL.....PERIOD please do yourself a favor and get this done, it is the best!
 
The P/DH500 amps are great sounding as is. I'd get it and enjoy it for a while, before making changes. Then, you'll be more able to appreciate what the upgrade brings.
 
The is a difference between the P-500 and the DH-500. The pro version of the DH-500 is the P-505, which I never knew existed until I bought one about 6 months ago. If you go to the following webpages on www.hifiengine.com you can see the differences between the three amps:
https://www.hifiengine.com/manual_library/hafler/dh-500.shtml
https://www.hifiengine.com/manual_library/hafler/p505.shtml
https://www.hifiengine.com/manual_library/hafler/p500.shtml
The P-505 and DH-500 show the same exact "Semiconductors": 27 x transistors, 12 x MOSfet, 33 x diodes, 8 x zener diodes, 1 x IC, 1 x diode bridge
While the P-500 shows a difference in the "Semiconductors": 33 x transistors, 12 x MOSFet, 35 x diodes, 6 x zener diodes, 7 x IC, 6 x LED, 1 x diode bridge
 
I have a Hafler P500 that I've had for a year and I am absolutely love, except for the fan noise which is a bit much when playing at lower volumes. In fact, I love it so much that I recently bought a DH500 as well.

Much to my surprise the DH500 fan is substantially quieter, in fact you can barely hear it whereas the P500 fan is quite audible.

Does anyone know if this noted difference in fan noise is to be expected? I am now wondering if there is something that can be done to improve the fan noise on the P500.

I wasn't planning on keeping them both but they sound so incredible that if I can address the noise on the P500, I might just do so!
 
avionic said:
Replace it.At least give it a good cleaning and a drop or two of oil on the sleeve/ball bearings.
Click to expand...
Thanks, I think I'll go ahead and replace it. I thought it was as it was performing as it was supposed to be until I got the DH-500. Any recommendations on what fan to use to replace it?
 
EPICF said:
I have a Hafler P500 that I've had for a year and I am absolutely love, except for the fan noise which is a bit much when playing at lower volumes. In fact, I love it so much that I recently bought a DH500 as well.

Much to my surprise the DH500 fan is substantially quieter, in fact you can barely hear it whereas the P500 fan is quite audible.

Does anyone know if this noted difference in fan noise is to be expected? I am now wondering if there is something that can be done to improve the fan noise on the P500.

I wasn't planning on keeping them both but they sound so incredible that if I can address the noise on the P500, I might just do so!
Click to expand...

These 2 versions of the 500 are basically identical except the 'P' version has XLR Balanced Inputs, 1/4" unbalanced Inputs, Input Level controls & Status LED's & Status Indicator Processing PC-20 Bd. & a Stereo/Mono Switch. The heat difference may be because the Bias is set or has creeped up too high causing the Output MOSFET's to run hotter than they should & making the Fan Speed Thermal Switches engage sooner. Bias should be 350mA although some series of the stock Hitachi MOSFET's run a little hotter than others so you may need to back off the Bias a tad- maybe 10-20mA or so. At idle, with no signal, the MOSFET's should just be slightly warm to the touch when Biased properly. There are 3 Fan speed levels: Idle(slowest), Medium(50 deg C) & High(65 deg. C) that are controlled by Thermal Switches that short across (2) 300 Ohm 7W Resistors supplying more incoming 120V AC to the Fan motor. Cleaning & lubing the Fan will also help quiet it down. The stock fan blades get dirty over the years and can get out of balance making them noisier. Cleaning the blades will quiet them a bit. Just make sure that the fan in the cooler one is running properly(all 3 speeds activate) and hasn't had its Fan Speed circuitry 'modded' by a previous user. I have seen this before. Or maybe the DH is biased much lower than it should be. Hope this info helps.
 
A close friend of mine who couldn't afford a Mac 2250, bought and built a DH 500 back in the early 80 or late 70's to drive his Mac speakers. Davie O'Brien at. a Mac clinic said the 500 was probably the best amp Hafler even produced. It measured just as well as the Mac amps and had a very nice sound. I had Crown at the time and the Hafler even sounded nicer as Crown have a real rough time with highs above 10 Khz. They tend to be too dry like Brystons. I prefer Mac amps without autoformers, or at least my speakers do much preferring MC 7200 and my current MC 207's.
 
I built a studio in the 80s. Used one P500 in mono per side to power Fostex LS-3Bs. A nice combo. Got the 'kit' version, which took about half an hour each to assemble.
 
jsettecase said:
These 2 versions of the 500 are basically identical except the 'P' version has XLR Balanced Inputs, 1/4" unbalanced Inputs, Input Level controls & Status LED's & Status Indicator Processing PC-20 Bd. & a Stereo/Mono Switch. The heat difference may be because the Bias is set or has creeped up too high causing the Output MOSFET's to run hotter than they should & making the Fan Speed Thermal Switches engage sooner. Bias should be 350mA although some series of the stock Hitachi MOSFET's run a little hotter than others so you may need to back off the Bias a tad- maybe 10-20mA or so. At idle, with no signal, the MOSFET's should just be slightly warm to the touch when Biased properly. There are 3 Fan speed levels: Idle(slowest), Medium(50 deg C) & High(65 deg. C) that are controlled by Thermal Switches that short across (2) 300 Ohm 7W Resistors supplying more incoming 120V AC to the Fan motor. Cleaning & lubing the Fan will also help quiet it down. The stock fan blades get dirty over the years and can get out of balance making them noisier. Cleaning the blades will quiet them a bit. Just make sure that the fan in the cooler one is running properly(all 3 speeds activate) and hasn't had its Fan Speed circuitry 'modded' by a previous user. I have seen this before. Or maybe the DH is biased much lower than it should be. Hope this info helps.
Click to expand...
 
This is very helpful but way above my pay grade as it relates to actually checking the bias levels. Can anyone recommend a good tech in or near Indianapolis that I could have take a look?
 
I
EPICF said:
This is very helpful but way above my pay grade as it relates to actually checking the bias levels. Can anyone recommend a good tech in or near Indianapolis that I could have take a look?
Click to expand...

The P500's were often used in PA rigs so you may want to check with a local music shop tech. If you don't happen to find a local tech, I'm in Cleveland, Ohio. I don't market myself as a repair service since I typically install QUA-CO Audio's PC-1 upgrade kits in DH Series amps, but I routinely adjust these. It's not a job for an inexperienced individual as there are lethal voltages involved. The design engineer at QUA-CO, Ed Fantasia, was Hafler's Amplifier Project Manager for 25+ years, but he no longer does bench work. He has been mentoring me for the past 3 yrs.. I do all his install work. So I know these pretty well. If you get stuck, reach out to me. I usually have a waiting list for amp upgrades since I do this work on the side from my TV Engineering job, so you would have to get on my list. I know these are very heavy(50lbs.), but if double boxed & packed properly, they travel well via UPS ground. Average shipping costs are about $40-$70 each way. Suggestion: If you don't need the balanced Inputs or Input level controls of the P500, you may want to sell that one off and buy another DH500 especially for home use. Its a much simple circuit and more stable. There are LOTS of DH500's on eBay that can be had from $300-500. And if you want an upgraded 'High-end Audiophile' version, I'm your guy. I have lots of very positive testimonials. Hope this info helps.
 
I've been lucky enough have one of the p500s, since 95.

It's a beast. It's THE beast. The fan might make you want a DH, but you likely need to clean the blades, and the heat sink. My fan doesn't run unless I'm annoying my neighbors with the DQ10s. I can't really imagine not having the level controls...

So far I've replaced one resistor. Pretty sure they just got a bad batch in manufacturing, as it seems to be the leading cause of dead channels...

It will bump up your electric bill, but you will never need more power in a 2 channel Amp.
 
jsettecase said:
I

I’d like to have you take a look at the P500 for me. Interested in having you check it out and to get a quote for the audiophile upgrade. Waiting list is not a problem. How can I get in touch?

The P500's were often used in PA rigs so you may want to check with a local music shop tech. If you don't happen to find a local tech, I'm in Cleveland, Ohio. I don't market myself as a repair service since I typically install QUA-CO Audio's PC-1 upgrade kits in DH Series amps, but I routinely adjust these. It's not a job for an inexperienced individual as there are lethal voltages involved. The design engineer at QUA-CO, Ed Fantasia, was Hafler's Amplifier Project Manager for 25+ years, but he no longer does bench work. He has been mentoring me for the past 3 yrs.. I do all his install work. So I know these pretty well. If you get stuck, reach out to me. I usually have a waiting list for amp upgrades since I do this work on the side from my TV Engineering job, so you would have to get on my list. I know these are very heavy(50lbs.), but if double boxed & packed properly, they travel well via UPS ground. Average shipping costs are about $40-$70 each way. Suggestion: If you don't need the balanced Inputs or Input level controls of the P500, you may want to sell that one off and buy another DH500 especially for home use. Its a much simple circuit and more stable. There are LOTS of DH500's on eBay that can be had from $300-500. And if you want an upgraded 'High-end Audiophile' version, I'm your guy. I have lots of very positive testimonials. Hope this info helps.
Click to expand...
 
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