Hafler 500 Upgrade

machone

Last night I upgraded the driver boards on my Hafler DH-500 to Musical Concepts PA-6 Elite.
Powered it up, set the bias and DC offset. All good!
I plan to put it back in the rack tonight and start the burn in process.
These boards are supposed to be quite an improvement as they are more transparent without adding brightness or etching.
We shall see...

motorhead43026

I am wanting to have this done to my XL600. Looking forward to your review.

machone

I was not expecting much the first night I turned it on but wow.
Silent background and huge soundfield with effortless power.
Got the radio playing continuously to help burn in.

SCompRacer

Nice work! Long live DIY!

machone

Just a quick update on the burn in process:

24 hrs = not good
48 hrs = not good
72 hrs = beginning to change
96 hrs = now we are talking

The thing I don't get is why it sounded good at power up but at 24 hrs it did not impress and at a level that I was wondering about my decision to upgrade?

Unknown

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motorhead43026

I always felt large Hafler amps to be something special, and dependable too.

msg

Nice! Curious to hear your impressions as you get more time on it. That does seem kinda weird that it got worse for a bit before sounding good. Is that normal with these kinds of upgrades?

I have a Hafler Trans Nova 9300 THX that I've been considering recapping. Anyone have any experience with this model?

DaveHo

Sucks. All the killer piece from back when, that I had no hope of buying, are well past their prime now. I envy those who have managed to find a clean unit and had them restored. No small feat, or price. Bravo!

machone

Got enought hours on the new boards to start showing their stuff.
Hearing vocals and instruments never heard before. Things like brushes on a snare or the crash of a cymbal out the blackness. It's dead quiet at any volume. More transparent than ever but very natural without any harshness. The dynamics are explosive and contolled.
This amp seems invisible. I am impressed!

machone

Over 400 hours of burn-in. It's bordering on spectacular. Very impressed!

motorhead43026

Did you assemble the boards, or did you purchase already assembled?

machone

The boards come stuffed and are tested with both the bias and offset preset. The kit includes wire, solder and gold played RCAs, etc. Excellent instructions.

oldrocker

Cool story.
Glad it's meeting your expectations so well.

I got a 220 sitting in a box somewhere.

motorhead43026

Looks like you replaced the power supply caps as well? Which ones did you opt for?

machone

LC500's for the caps. Also it was recommended to replace the heat sink over-temp sensors located under the power module. With age they have been seeing them going bad.
Call John. He will set you up with what ever you need.

motorhead43026

Thanks, I really want to get the XL600 freshened up. I love these big Haflers.

machone

Just a quick update on the DH-500.
It's great. Slowly but surely it just keeps getting better. Smoother with no fatigue; so natural!

pkquat

How is the DH-500 noise with the fan? I've heard mixed impressions whether people hear it. Now that it is burning in, how is the richness compared to original Haflers?

machone

Like night and day compared to original Haflers.
My fan only runs on low. With everything else in the room turned off I can hear the fan but only if I listen for it. FWIW it does not register on my DB meter.

pkquat

TY I've been debating on doing an upgrade, but some really nice used amps are less expensive. Plus I only have a DH-220. I've found much of my stuff does benefit from amps in the 200W range.

machone

pkquat wrote: »

TY I've been debating on doing an upgrade, but some really nice used amps are less expensive. Plus I only have a DH-220. I've found much of my stuff does benefit from amps in the 200W range.

I get it.

The Musical Concepts stuff is not cheap. I bought my DH-500 back in the 80s, it finally stopped working so rather than change out a few parts to get it going I decided to have them rebuild it using their PA4 driver boards. Since then I have been slowly upgrading binding posts, IEC inlet, power cord, Dynamat and things like that. This time I upgraded again to their PA6 driver boards AND they just came out with a new power supply upgrade using Jensen 4 pole caps and their CRC design. This upgrade sets you up for their dual toroid transformers.

Sky's the limit

I does sound great though

machone

I see your point.
It's like a B52 with new engines and avionics.

machone

Latest upgrade:

Original 650 watt transformer.


New dual 500 watt toroidal transformers.


Got rid of the mechanical t-former hum and sets me up to go with a dual mono power supply in the near future.

Also upgraded all of the primary power wiring.

machone

The toroidal transformers have a little over 100 hours on them and I must say that I am very happy with the amps performance.

I expected mechanical t-former hum to be reduced and it has been reduced to a level that is not noticeable unless I am right next to the amp.

I expected the bottom end to be more dynamic and it is.

I did not expect the whole sound stage to open up x,y & z. Separation of instruments and voices are more precise and the overall image is just spectacular.

Everything is more natural drawing me into the music. Background "noises" in certain songs are now separated and understood. For instance, Muse is one band that uses some weird synthesized notes that sounded like noise but are now understood even I don't know why they would choose such bizarre notes.

I could go on and on but I guess my learn from this upgrade is power wiring and power supply hardware made a huge difference in this amp. And yes, don't forget the power cord............

machone

OK, I got the upgrade bug again.

I plan to change out the two existing power capacitors (39,000uF 100Vdc each) and the original rectifier with a dual mono capacitor/rectifier kit. There is one capacitor board and one hyperFRED soft recovery rectifier for each channel and they will be fed by dedicated toroidal transformers (installed earlier this year). Each board holds four snap in style capacitors. I can order the boards and stuff them with my choice of capacitor.

I am looking at eight Mundorf MLytic AG caps (15000uF 100Vdc each).

Does anybody have experience with these caps in a power supply?

Thanks............

machone

So nobody here has experience with Mundorf MLytic AG capacitors?

oldrocker

Certainly not me but nice work!!!

machone

I just ordered the capacitors, board and components for the dual mono power supply upgrade.

machone

The capacitors are here



Waiting on the circuit board kit.

pitdogg2

Purrty