[Strut]

I know there is probably already a thread dedicated to this subject, but as I am new to the group and as such unworthy of employing the search feature you'll have to bear with me.  I've recently pulled a vintage kit-built Hafler DH 200 out of storage.  It's never been exposed to heat or moisture and still seems to sound as good as the day I finished building it (of course my ears have deteriorated in that time), but I know that with an update it would sound so much better.  I've read plenty of reviews arguing for either the QUA-CO OR the Musical Concepts boards, but have yet to hear anything from someone who has actually heard both and can render a reasoned rather than an emotional opinion.  Is that person out there??? 

[Blackmore]

I can't offer comparisons, but I've been to John Hillig's house many times (Musical Concepts) and his upgrades are excellent.  If you're unsure about what direction to go, start by replacing those big blue capacitors first.  They are very reasonable, or John can suggest his mod to the power supply caps and that will improve things too.  Keep posting and you'll gain access to the search functions soon.

Mark

[Saturn94]

Ah, I have fond memories of the DH 200.   I had two of them, one I built from the kit, and another I bought used.  Sometimes I wish hadn’t sold them.

Doesn’t Van Alstine have experience updating Hafler amps?

[Strut]

I can't offer comparisons, but I've been to John Hillig's house many times (Musical Concepts) and his upgrades are excellent.  If you're unsure about what direction to go, start by replacing those big blue capacitors first.  They are very reasonable, or John can suggest his mod to the power supply caps and that will improve things too.  Keep posting and you'll gain access to the search functions soon.

Mark

Thanks!  I've been to John's house as well.  He rebuilt my DH 110 about a year ago and I've been very happy with the result.  I'm really interested in his dual power supply modification, but not sure I can afford that and the boards as well. 

[Strut]

Thanks!  I've been to John's house as well.  He rebuilt my DH 110 about a year ago and I've been very happy with the result.  I'm really interested in his dual power supply modification, but not sure I can afford that and the boards as well.

They used to, but don't list that service on their website any longer.  Kind'a glad or I'd have to pick from three options! 

[Rusty Jefferson]

Dual mono still available for Hafler.
http://www.musicaldesign.com/Haf_pwrmods.html
Link near the bottom of the page.

[dB Cooper]

They used to, but don't list that service on their website any longer.  Kind'a glad or I'd have to pick from three options! 

Not so fast....
https://avahifi.com/collections/dyna-and-hafler-rebuilds/products/dyna-and-hafler-solid-state-amplifier-rebuilds?variant=5835821645854

[Strut]

Not so fast....
https://avahifi.com/collections/dyna-and-hafler-rebuilds/products/dyna-and-hafler-solid-state-amplifier-rebuilds?variant=5835821645854

My bad!  Didn't dig deep enough.  So much for limiting the options!

[Francois G]

I know there is probably already a thread dedicated to this subject, but as I am new to the group and as such unworthy of employing the search feature you'll have to bear with me.  ..... I've read plenty of reviews arguing for either the QUA-CO OR the Musical Concepts boards, but have yet to hear anything from someone who has actually heard both

I’m in the same boat re. searching. Could you post a link to the QUA-CO modification, please. My general searches are coming up blank. Have you decided which mod to get yet?

[Strut]

Yes, and no.  I had a DH200 modified with the QUA-CO boards a while back and have been extremely impressed.  Its much smoother than most solid state amps I've compared it to and works quite well with my LS 50s.  The work was done by Jim Settecase (7houses on Ebay) if you're looking to have the work done for you... but be prepared to wait.  Right now I have a DH500 in the queue for the same QUA-CO boards with Jim (for another system) but am also considering having John Hillig (Musical Concepts) modify another DH200 I've come across with his new PA-7 boards and a dual mono power supply.  The dual mono power supply option intrigues me.  If and when I move forward with that I'll be able to render an opinion between the two, but for the $s I suspect the QUA-CO will be hard to beat.

[jakeni]

Here's the  musical concepts dual mono kit and pa-3 boards.  Very nice sounding.

[milanomike]

I thought of these upgrades also, but at the end I took my DH 200 and simply replaced the big caps with ones a bit larger (Qua Co offers these, but Mouser and others have them) and also replaced all the electrolytics on each board. 

I also bought like 10 or 20 of each semiconductor that controls the DC offset and matched/replaced them to get the DC below 15 uV. 

These upgrades to the standard boards made a nice improvement in sound, at least compared to 30 year old components. 

I also learned a lot by doing the project.  I'm pretty satisfied with the sound, maybe someday I'll take the board upgrade path, but for now am quite happy.  Worth thinking about in my opinion..