peteg%sequent.uucp@RELAY.CS.NET (Pete Gibson) (11/16/90)
About 8 years ago I built a Hafler DH100 power amp from the kit. Throughout
the years, it has suited my needs admirably. 'til now. I am getting
increasing hum and hiss in both channels, and I assume it's due to aging
of important components and/or solder joints. I would ideally like to
replace the Hafler with a better unit, but at this point my budget
(and wife ;-) won't allow it.
I've heard of good modification kits for the DH100, and would like to hear
from those who have experience, good or bad, with any of them. Your help
is greatly appreciated.
Thanks,
Pete
peteg@sequent.sequent.com
..{uunet,ogicse,tektronix}!sequent!petegroger@spool.mu.edu (Roger Abrahams) (11/27/90)
In article <7696@uwm.edu> you write: > >About 8 years ago I built a Hafler DH100 power amp from the kit. Throughout >the years, it has suited my needs admirably. 'til now. I am getting >increasing hum and hiss in both channels, and I assume it's due to aging >of important components and/or solder joints. I would ideally like to >replace the Hafler with a better unit, but at this point my budget >(and wife ;-) won't allow it. > >I've heard of good modification kits for the DH100, and would like to hear >from those who have experience, good or bad, with any of them. Your help >is greatly appreciated. Unfortunately, Hafler used some pretty inexpensive transistors in the front end of these, and it was well before the point where they tried to keep electrolytics out of the signal path. It is important to note if the increasing noise is equally apparent in BOTH channels. If it is, it most likely is a problem with increasing series resistance in the power supply capacitors, if the problem lies with the amp at all. It also could be caused by aging corrosion of the interconnects, etc. A good high-quality cleaning and general "tune-up" might just be indicated. - Roger
jdhill@BBN.COM (Jack D. Hill) (12/05/90)
In article <7696@uwm.edu> you write: > >About 8 years ago I built a Hafler DH100 power amp from the kit. Throughout >the years, it has suited my needs admirably. 'til now. I am getting >increasing hum and hiss in both channels, and I assume it's due to aging >of important components and/or solder joints. I would ideally like to >replace the Hafler with a better unit, but at this point my budget >(and wife ;-) won't allow it. > >I've heard of good modification kits for the DH100, and would like to hear >from those who have experience, good or bad, with any of them. Your help >is greatly appreciated. A year ago I purchased an upgrade kit for the DH100 direct from Hafler. It costs under $20 and includes better op-amps and a few resistors and capacitors. The upgrade involves replacing the socketed op-amps and soldering in the rest. It turned out to be a nice upgrade. The biggest difference I heard was that the high end wasn't nearly as grainy and harsh like it used to be. It sounds like you might have problems in your power supply. Try repacing the diodes and electrolytics. Jack
pmr@drutx.ATT.COM (RastocnyPM) (12/10/90)
In article <8094@uwm.edu>, jdhill@BBN.COM (Jack D. Hill) writes: > > In article <7696@uwm.edu> you write: > > > >About 8 years ago I built a Hafler DH100 power amp from the kit. > > ... I am getting > >increasing hum and hiss in both channels, and I assume it's due to aging > >of important components and/or solder joints. > ... > A year ago I purchased an upgrade kit for the DH100 direct from Hafler. It > costs under $20 and includes better op-amps and a few resistors and capacitors. > The upgrade involves replacing the socketed op-amps and soldering in the rest. > It turned out to be a nice upgrade. The biggest difference I heard was that the > high end wasn't nearly as grainy and harsh like it used to be. It sounds like > you might have problems in your power supply. Try repacing the diodes and > electrolytics. The latter part of this last sentence is probably the culprit. Electrolytic caps age and have a life (brand dependent) of from 5 to 10 years. Audiblility of this aging process usually comes in the form of hummmmmmm, graininess, edginess, no bass punch, loss of inner detailing, poor imaging, and loss of transient response. There are two uses for electrolytics: power supply filtering and DC-blocking. Failures in the latter cause severe signal degredation and failure in the former causes hum/noise and transient-related signal degredation. If you can find replacement values and matching or greater voltage ratings of non-electrolytic type capacitors (such one of the mylar varieties), a simple one-for-one replacement will greatly improve the sound of the unit. When replacements are not possible because of large values, better quality (high frequency) electrolytics should be used. Another thing to check are the screw connections on the power supply capacitors themselves. On my amp, I have to go in about twice a year and crank down on the screws (they back out from normal thermal changes). Yours for higher fidelity, Phil Rastocny