One of my local clients inquired if I would be willing to upgrade an old pair of Hafler 220s for him.
I informed him I would be very happy to. I used to build a few of these, back in the day. I had a rather built up DH-500 to power a pair of Infinity RS2.5s about 20 odd years ago.
He had ordered some parts form John Hillig of Musical Concepts.
This is NOT just a "mod". It is a complete teardown and rebuild of the amp. The only thing left stock is the chassis and output devices.
Each stereo amp was turned into a mono-block. The output devices were wired to double the stock amount per channel. The stock transformer (480 VA for two channels) was replaced with a toroidal (625 VA for one channel). The rectifier was replaced with a HexFRED bridge. Filter capacitors were changed from 20,000 uFd of 20 year old Sagamo for two channels to 40,000 uFd of Jensen four poles for each channel. The captive AC cable was replaced with an IEC connector.
Input RCA was changed to Cardas. Input cable was made from solid silver Summit. All of the AC and DC wiring was done in 14 awg Nitro. Output connectors are WBT NextGen.
The stock driver circuit board was replaced with the Musical Concepts PA-3E Signature board with BlackGates and PRP silver resistors in the signal path.
I biased the amps a bit more into Class A and they do run a little bit warmer then stock. The sound they produce is simply astounding for the price! I have heard $6,000.00 amps that can't compete with these.
If you happen to have an old Halfer amp sitting around, I can't urge you enough to get those thing rebuild into a pair of these. Simply amazing!
Here are some pictures of the rebuild process.
Stock amp
Starting over
Transformer and PS caps installed
Finished channel
BTW, each amp now measures 150 watts into 8 ohms. Stock was rated 110. aa
If anyone has a project or mod on almost any product, I would be very willing to talk it over with them. I'm open to mod just about anything.
