Modding Hafler Amps?

let me transform your DH500, 200, 220 etc. you will not be disappointed.
I can send you a modified one to listen too and you can
decide for yourself. There are many levels to mod too.

My major mod takes you way beyond pooging and passive part
replacement. I can explain all the mods if you care to
listen. The major requirement is a solid running amp
to start with!!! I can also repair if necessary.

Please feel free to ask questions I will try to explain.

Ralph

I guess i was "thinking inside the box" on that one. I agree with the others. That is, there are GOBS of info available about modifying these amps. Much of what either of these guys would do and charge a high hourly labor rate, you can do yourself. That is, it is simply a matter of unsoldering one part and replacing and resoldering with another higher grade part. That part could be capacitors, resistors, wiring, etc... There's nothing hard about doing something like this, but it can seem VERY scary at first. Just take your time and make notes along the way. Having a schematic and then looking at how the schematic equates to the actual parts layout on the board can help you with signal flow and what parts play key roles. Sean
>

Something I should have mentioned in my original post. If they are not soldered in, VERY CAREFULLY remove each mosfet and clean the pins. Of all the things I did to improve the sound of my old DH 200, I don't think anything I did made as big a difference. I got that advice from some post on a Hafler user group site. P.S. I was satisfied with my Hafler until I got an original Son of Ampzilla. The Ampzilla is better in everyway.

Hi Aggielaw -

The previous responses here have provided a lot of good information about upgrading your Hafler amp, but have not addressed the question of bi-amping with your DNA-0.5 Rev A. Whether this can be made to work well (or at all) depends on what you have in mind. If you are thinking of "passive bi-amlification" (using the speaker's own internal crossover networks), this works best with a matched pair of amps. It can be made to work with 2 different amps, but this is far more difficult and rarely works well unless the crossover point is very low - around 100Hz. Even then you will need some way to independently adjust the input level to the amp with higher sensitivity - almost certainly the DNA-0.5 in this instance.

Some of the problems I have mentioned can be overcome by using an adjustable electronic crossover, but this introduces a whole new set of issues, some of which are technically difficult.

So, the "mix-and-match" approach to bi-amping is rather problematic, in my estimation. On the other hand, it can work very well indeed with a matched amplifier pair. You may want to consider moving in this direction in the long run. Another DNA-0.5 or Hafler can be arranged to match what you have now, and I believe this will give you the most flexibility and best performance. In addition, the DNA amps can be converted to true balance monoblock operation, delivering over 400 Watts per into 8 ohms. That should satisfy your taste for more power ;-)

Please give me a call if you would like to go over the various options.

Happy holidays,

Steve McCormack
www.SMcAudio.com

Great info - thanks all!

Short term I will mod the Hafler. Then in January '06 when I get my bonus from Uncle Sam I'll use some of that to match a pair of your DNA amps and have my RLD-1 upgraded, Steve. That'll probably be they last sum of money I spend on amps and preamps...ever. :)

Happy holidays, all!