Modding Hafler Amps?

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!

I had John Hillig mod my DH-500, did the dual mono upgrade and signature level mods plus a few other tweaks. It was a pricey leap in the dark, based on stuff I read on this forum and elsewhere online. I have to say I am very impressed and very happy with the sound. I have listened to the same CD on some really pricey systems (McIntosh, Krell, etc.) and to my ear my system sounds a good or better. Huge sound stage and depth, a really "live" sound, great bass and clarity, very musical. Don't know about Van A, but to correct an earlier post I believe Hillig worked with Hafler, and his redesigned circuit boards are much more than a passive swap-out of parts. In any case, whether you go Van A or JH, you are buying the guy's ear... I only know JH's and I like it - a lot! That's my two cents.

If you're going to mod your DH-500 yourself, I highly recommend The POOGE Chronicles. They outline modding in general, and the DH-200 specifically, along with a number of other pieces. The principles they use could be applied to anything you were modding, and cover both the theory and the implementation. I bought my copy here:

http://www.audioxpress.com/bksprods/books/bkaa25.htm

Well worth the price.

David