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Hafler DH-500 - bridge rectifier? recommendations?

mrhandlin

mrhandlin

New Member
Thanks in advance for your help. It's great to be part of a community of like-minded individuals.

I've recently recapped an old Hafler DH-500. It's a bit unusual in that it has the pc10a version of the boards which don't quite match the manual available online. Anyhow, I've recapped it and changed the input to rca terminals and installed better line input cables. The sound is much improved.

I would like to change the bridge rectifier. I've heard something about the "fred" type for this amp. I'm also willing to go with a board build if it's affordable and not too difficult with snubbers and newer diodes.

My question is..... Which bridge rectifier from mouser... digikey... And, if I go the other route - what parts should I order. In general, what would be the pros and cons? I'm learning, so I'm happy to go the more complicated route if it improves my skills.
 
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Whats the part number on the bridged rectifier thats installed ?
 
I do not have one to look at but it is probably a GBPC35 amp 200V or higher type. They are very reliable, I would not bother to change it imo.
As far as up grading did you not just invest in new big filter ecaps? If so using a new PS rectifier/filter adds a lot more $. I was just looking yesterday someone pointed me to Musical Concepts web site where they are selling PS upgrades. I see that they are using a IXYS FRED bridge diode type which Mouser sells. Strange that the package has no hole in it so it needs a holder if you are going to heatsink it to the chassis bottom plate.
 
I've heard it's a 30 amp. I found some pics old pics I took, but they don't show a model number.
The filter caps you see are new ones. I went with the same Uf value. At least one of the originals was pretty toast (although it still played okay. BTW, I have cleaned it since I took these pics and organized the wiring a bit more. It was pretty dirty inside.

What's the purpose of the component above the rectifier (between the posts)?

Hafler DH-500 Power Caps (new)

Hafler DH-500 Power Caps (new)

  • Media owner mrhandlin
  • Date added
Hafler DH-500

Hafler DH-500

  • Media owner mrhandlin
  • Date added
Bridge rectifier
 
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rcs16 said:
I do not have one to look at but it is probably a GBPC35 amp 200V or higher type. They are very reliable, I would not bother to change it imo.
As far as up grading did you not just invest in new big filter ecaps? If so using a new PS rectifier/filter adds a lot more $. I was just looking yesterday someone pointed me to Musical Concepts web site where they are selling PS upgrades. I see that they are using a IXYS FRED bridge diode type which Mouser sells. Strange that the package has no hole in it so it needs a holder if you are going to heatsink it to the chassis bottom plate.
Click to expand...

If I want to find it on mouser, do I just need to stick in 35A, 400v, and then search? Why, in your opinion, should I just leave it? Will it make much of a difference in the way the it sounds/functions?
 
This is what you need...

Replacing it will not likely improve sound. This is something to replace when replacing factory filter caps with new filter caps with a much higher uf rating. No harm in replacing it as part of a restoration though even if using 20Kuf caps.

1588225663043910212810.jpg
 
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mrhandlin said:
Thanks in advance for your help. It's great to be part of a community of like-minded individuals.

I've recently recapped an old Hafler DH-500. It's a bit unusual in that it has the pc10a version of the boards which don't quite match the manual available online. Anyhow, I've recapped it and changed the input to rca terminals and installed better line input cables. The sound is much improved.

I would like to change the bridge rectifier. I've heard something about the "fred" type for this amp. I'm also willing to go with a board build if it's affordable and not too difficult with snubbers and newer diodes.

My question is..... Which bridge rectifier from mouser... digikey... And, if I go the other route - what parts should I order. In general, what would be the pros and cons? I'm learning, so I'm happy to go the more complicated route if it improves my skills.
Click to expand...
There is plenty of room to build a HexFRED bridge that will be a little more "quiet". However the stock is a 25A so using a 35A standard bridge will be great if you plan on upping the main filter caps. That ceramic capacitor is to stop the rectifier diodes from "ringing". Using the HexFRED diodes eliminates the need for the ceramic snubber cap(s). The only thing you might gain, is a slight reduction in "hash noise" on quiet music passages at higher volumes. Otherwise there are no other "benefits". I stuck with the "stock type" in my own and never looked back.
 
I already went with the stock UF value for power caps. Could I simply add a third of equal value, in series, to the original without changing the rest of the power supply, or at that point would it be better to change the bridge to something higher? Part of this is a learning process for me and I would like to "hear" the differences. The upgrades in the caps and signal cables were quite obvious and audible. I don't want to spend money or time without audible improvements.

I figure this is a good amp to hear any differences as its design is pretty minimalistic and it's so easy to work on.
 
mrhandlin said:
I don't want to spend money or time without audible improvements.
Click to expand...

Then I would say you are going down the wrong rabbit hole.

Nothing in the way of filter caps and bridge diodes is going to make an audible difference unless you are talking about replacing a leaking cap or otherwise faulty cap with a new cap. But that just brings it back to stock.

If you want a significant boost in sound quality, then you need to replace the driver boards. 20Kuf for filter caps is plenty for this amp. Adding to that is not going to make it sound better.

If I were in your position, I would keep the filter caps as is, put in the bridge diode I mentioned and install Quaco boards. For $220 (chump change for what you get in return) you get a very noticeable improvement. Another option would be Musical Concepts....twice the money (at least) depending on options you choose.

I have no experience with Musical Concepts, but they get good reviews.

I have a lot of experience with Quaco. I have built 15 amps with the Quaco kits. Great product designed by David Hafler's right hand man Ed Fantasia, the engineer that oversaw the design of the DH200 and DH500. He improved it quite a bit and most would say that David Hafler would be jealous. I highly recommend if you really want a significant improvement. This playing around with filter caps and bridge diode will do nothing. This Quaco kit will put the amp into a whole other class. Great price for a great product.
 
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