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Hafler DH-100 - what should this should this sound like?

I have never heard a perfect example of one of these so I no idea what the target is here.  I have a DH-100 that i completely recapped and replaced all the OP-AMPS, JFETs, Regulators, diodes, etc.  I more or less replaced everything except the resistors and the pots.  I have tested it and it has exaggerated bass and sounds a bit muffled to me.  However, it is totally quiet;  with no inputs, I can run it into my 75 watt amp (Speakercraft BB275) all the way up and there is no noise at all.  The phono section will pickup the 60 cycle transformer hum but connecting a TT with a ground makes that go away, too.  I've been thinking there is something wrong but I can't find anything.  I have even checked all the resistors and found them to be in spec.  I have run my amp through the "record" output and the heavy bottom muffled sound goes away.  I do like the less than perfect "fat" sound but I have to run this with the bass backed off most the way to make it listenable and I normally bump the bass up a touch on other devices. What should this thing sound like?  
wgh64
corelli
977 posts
 
Neutral sound. Do you think the problem might be in the tone control section which I believe is bypassed the record output?  Try Deoxit spray on the pots, look for an out of spec component in the tone control section.
wgh64 OP
28 posts
 
I have deoxit’d all the pots already but I was thinking the same thing regarding a possible tone circuit issue.  You are right about the record output bypassing the tone pots and it also bypasses the pre-amp amplifier circuit (volume and balance pots).  I looked at the schematics and I can jumper the tone section out completely, pull the JFETs on the muting circuit and then the amplifier circuit will be isolated. That should at least pin-point which circuit that is have trouble. Thank you all for the input; it has really helped me a lot.
wgh64 OP
28 posts
 
DH-100 Update: I isolated the amplifier and still had the problem.  I re-inspected the amplifier circuit and discovered I put .047 mf caps in the  op-amp circuit that should have been 47 pf caps ( I think that's 100x less f).  They were the only caps that didn't come in the re-cap kit I bought (my bad; oops).  All it took was a quick trip to the electronics shop and a couple of minutes with the soldering iron, if you don't count the 1,000,000 hours I spent troubleshooting and test listening.  I just finished testing it and it sounds awesome: is "stage" when you hear different instruments in different spots? if it is that it's got great staging.   The bass is a bit understated and the highs can be too forward with pop/rock, but nothing that gentle twists of the tone control knobs won't hide.  I'm so relieved to get this right; it was close to becoming an anchor.   I could have never limped through this without the input I got here on Audiogon.  Thanks!

 
deadhead1000's avatar
deadhead1000
714 posts
 
Enjoy it! I did for many years. In some ways I miss it still. Damn, now I gotta play some blues to cheer me up. Take care. 
normansizemore
601 posts
 
Everything David Halfler made sounded good.  Somethings wrong.
Hafler amps are clean, quite and smooth.  
I hope you get it sorted out.  It’s a nice one.

N 
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