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Hafler DH-200 Stereo Amplifier - RESTORED - $400 (Monument)

Hafler DH-200 Stereo Amplifier - RESTORED 1 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 2 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 3 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 4 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 5 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 6 thumbnailHafler DH-200 Stereo Amplifier - RESTORED 7 thumbnail
condition: good
make / manufacturer: Hafler
model name / number: DH-200
For sale, a restored and upgraded vintage Hafler DH-200 MOSFET class AB audio power amplifier.

I restore and upgrade vintage Hafler power amplifiers as a hobby, this is my latest completed project.

Restoration includes replacement of all electrolytic capacitors with Nichicon audio grade, and non-electrolytics with polypropylene film or ceramic types and replacing broken or worn parts. Also installation of new insulators and thermal compound on all output transistors. DC offset is checked and if it's greater than 10mV then I replace the input stage Darlington pair matched transistors to get the offset to where it should be. Output transistor bias was also set to factory spec of 250mA.

Upgrades include replacing input and output jacks with gold plated jacks, larger power supply capacitors and installation of an inrush current limiter.

This amplifier is rated for 100 watts per channel into 8 ohms, however I measured almost 145 watts per channel into 8 ohms! Hafler MOSFET amps are known for their smooth sound and this amp sounds great! The case shows wear and tear and isn't pretty, but it's what's inside that is really fantastic! Hafler doesn't spec this amp at 4 ohms, however I measured about 210 watts per channel into 4 ohms.

This amp is one of the later models (circa 1985) with the rounded heatsinks, older models have sharp-edged heatsinks.
I do have a rack-mount faceplate for it for an additional $75.

Here is the work that has been done to this particular amplifier:

Replaced both speaker fuse holders
Installed insulated gold RCA jacks with 2.2ohm ground resistors on both channels
Installed insulated gold binding posts
Replaced power switch
Replaced power cable
Installed new 20,000uF 100V Kemet power supply filter caps, original were 10,000uF 75V
All TO-3 MOSFET output transistors repasted with new mica insulators
CL-40 Inrush current limiter installed
Recapped both PC-6 circuit boards with Nichicon kit from fantasiaaudio on eBay
Replaced Darlington pair transistors with matched set on both channels
Replaced bias trimmer potentiometer
Replaced feedback resistors with 1% tolerance resistors
Left channel DC offset measures 9.1mV after 30 minute warmup (see photo with voltmeter measurement)
Right channel DC offset measures 3.2 mV after 30 minute warmup(see photo with voltmeter measurement)
Left channel power output measured at 143 watts into 8 ohm dummy load (see photo with oscilloscope measurement)
Right channel power output measured at 144 watts into 8 ohm dummy load (see photo with oscilloscope measurement)

post id: 7755734107

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