Hafler DH-220 Power Amplifier

Hafler DH-220 Exposed Front

The Hafler DH-220 is a two channel audio power amplifier designed to the very highest performance standards. It is available either as a kit, or fully assembled. Its 115 watt per channel power rating is sufficient for driving all loudspeakers in home applications, and its design assures extremely low distortion of all types. A combination of high performance, dependability, reliability, and moderate price is in the Hafler tradition of using the very latest technology to provide outstanding value.
— Hafler DH-220 Manual

I grew up with this model amp, so to speak, as my father had purchased it for use in the basement to practice the drums to music without headphones. So he needed power and an 8 ohm capability to drive the PA speakers. Over the years, we’ve blown fuses often on this amp by trying to drive the wrong-speakers during various band practices. I think eventually the amp just couldn’t take it anymore and one of the channels permanently failed. We definitely abused it.

I decided to look into it recently when the need came up to power some monitors for writing music on the computer. I did some research into power-amps for this use, and basically most stuff out on the market is pretty much garbage with a lot of bad reviews. I would have had to spend nearly $1,200.00 to get close to the quality of this Hafler amp. While a standard stereo would have been more affordable it would have been overkill involving more transformation & distortion of the music I was working on; I wanted a direct output from the computer to the speakers without additional EQ and other effects and stereo-gimmicks involved. I did a quick Google search and was happy to find people speaking highly of this amp by today’s standards. So, after a quick search on eBay, I found one for buy-it-now for $150.00 and made the purchase.

Hafler DH-220 Exposed Top
Hafler DH-220 Exposed Top

Specifications

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Power Rating: Less than 0.02% total harmonic distortion at any power level up to 115 watts continuous average power per channel into 8 ohms at any frequency between 20 Hz and 20 kHz with both channels driven.

IM Distortion (SMPTE): Less than 0.005’%, from 1 watt to 1 15 watts into 8 ohms.

Typical THD at 115 watts into 8 ohms:
1 kHz – 0 0025%
10 kHz – 0.007%
20 kHz – 0.012’/‘

Frequency Response into 8 ohms:
-3 dB. 2 Hz to 160 kHz at 1 watt
+O, -0.5 dB, 6 Hz to 60 kHz at 1 15 watts

Typical Channel Separation:
20 Hz:>75 dB
1 kHz:>85 dB
20 kHz:>65 dB

Signal to Noise Ratio, unweighted:
Better than 100 dB at 115 watts into 8 ohms.
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Input Impedance: 47,OOO ohms.
Input Sensitivity: 1.55 volts rms for 1 15 watts into 8 ohms.

Damping Factor:
300 to 1 kHz into 8 ohms
60 to 10 kHz into 8 ohms

Rise Time: 10 kHz. 60 volts peak to peak square wave, 10% to 90% 2.5 us.
Slew Rate: 10 kHz. 60 volts peak to peak square wave: 30 VI’,~ s.

Semiconductor Complement: 26 transistors. 8 power Mosfets, 29 diodes, 4 zener diodes. 1 diode bridge.

Power Consumption: 1 15 watts into 8 ohms: 840 VA;

Quiescent: 125 VA.

Size: 5-1/8” high. 16” wide, 10-l/2” deep.
Net Weight: 26 Lbs.
Shipping Weight: 30 Lbs.

[button link="http://www.hafler.com/techsupport/pdf/DH-220_amp_man.pdf" style="medium red rounded" target="_blank"]Hafler DH-200 Manual[/button]

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Hafler DH-220 Front
Hafler DH-220 Front

Upgrades

Hafler DH-220 Modified by Musical Concepts
Hafler DH-220 Modified by Musical Concepts

There are plenty of upgrade paths for the Hafler DH-220.
Hafler DH-220 Upgrade from Musical Concepts.com
Hafler DH-220 Rebuild from Audio by Van Alstine
Hafler DH-200/220 Mods on diyAudio.com forum