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Old 21st December 2007, 01:28 AM   #1
RFENG is offline RFENG  United States
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Question Hafler P505

Hi,

Has anyone come across Hafler P505? I looked at the Hafler's webpage but didn't find any manual. Not much talk on the internet about it as well. I am wondering if anyone here knows about this amplifier. Claims to have same power specs as DH-500. It has quarter inch inputs on the back and level controls. I think they are balanced inputs. Any help would be greatly appreciated.

This is my first post at DIY Audio, so if I have posted this at a wrong place please let me know.

Thanks,
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Old 21st December 2007, 04:16 AM   #2
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The circuitry seem identical...of course the 505 was marketed to the pro market with the 1/4 inputs, level pots and I think extra fuse protection, not absolutely sure about the latter.
The P505 manual list it as being net 48lbs. vs 45 for the DH500. Also channel separation: 65dB vs 60. @1Khz.
I have one, but haven't played it in quite some time...I do remember that it didn't sound as clean as the DH500.
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Old 21st December 2007, 05:38 AM   #3
RFENG is offline RFENG  United States
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Thanks a lot for your reply. You mentioned P505 not being as clean as DH-500. I am about to acquire one for just purr stereo listening at home. Do you think this is a good choice? I ask because you mentioned having one. Also do you have the manual for it, would it be possible for you to share it?

Thanks again...
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Old 21st December 2007, 09:21 AM   #4
djk is offline djk
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The main amp boards are identical to the DH500.

You can bypass all the extra stuff and it will sound the same.

Download the DH500 schematic from Hafler and take a look, I'm sure you will be able to figure it out.
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Old 21st December 2007, 11:20 AM   #5
d3imlay is offline d3imlay  United States
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As I recall the pro stuff had a bunch of opamps for balanced inputs etc. that may account for differences in sound.
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Old 21st December 2007, 08:51 PM   #6
RFENG is offline RFENG  United States
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Thanks guys...

I will be picking it up tomorrow, will keep you guys posted. It seems like everyone is very helpful here. I am glad I found this place.

Happy holidays...
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Old 22nd December 2007, 08:53 PM   #7
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I could send you the page or two that is different from those included in the DH500 manual. BUt it is so minor, dealing with the wiring of the balanced 1/4 jacks.
Good luck, hope the amp you are picking up is in good condition.
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Old 28th December 2007, 04:45 AM   #8
RFENG is offline RFENG  United States
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Hi,

Hope everyone had a wonderful Christmas.

Well I picked up the P505. I also bought a DH-110 from ebay.

(1) Connected speakers to the amplifier, turned on and there is a audible hum (more from tweeter and midrange than woofer). The amplifier has a three prong plug with the ground prong chopped off. There is a switch on the back, one side says "float" the other side says "chassis". The switch is currently on "chassis" side. I tried the "float" side but it did not help with the hum, I also flipped the ac chord but that didn't help either.

(2) Second I connected the preamp to the amplifier, the hum remains at the same level. But when I turn the "tone" switch on the DH-110, the hum gets amplified. I also noticed when I turn the volume to maximum the noise shifts from one side to other side (some kind of phase shifting) the hum level doesn't rise a whole lot.

Does anyone has any ideas? The 1/4" connectors are screwed on a fiber washer so they don't make contact with the chassis. There is a level control on the back which is essentially a potentiometer blocking the incoming signal. No circuit, op amp etc.

Please help me in getting rid of this noise. To make things worse the fan is a loud one as well... I don't know what to do with the fan either. Help is greatly appreciated. I will be looking into it more, will try to post some pictures if that helps.

Thanks,
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Old 28th December 2007, 04:45 AM   #9
RFENG is offline RFENG  United States
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Quote:
Originally posted by AcidJazz
I could send you the page or two that is different from those included in the DH500 manual. BUt it is so minor, dealing with the wiring of the balanced 1/4 jacks.
Good luck, hope the amp you are picking up is in good condition.

AcidJazz,

Thank you very much for your offer, I am still trying to understand the very basics of this amp. I posted the problems with the amp, as you will read. Amplifier looks good, just a hum as I mentioned in my post...

Thanks,
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Old 28th December 2007, 05:12 AM   #10
d3imlay is offline d3imlay  United States
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One channel or two? are there level controls? If so do they make any difference?
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