Output filter Caps

Gs5556: I mean no disrespect, but your figures and assumptions are way out in left field on this one. The amp already has two 22,000 uF caps in it from the factory for a total of 44,000 uF's. Why would anyone want to reduce total capacitance by a very measurable amount ( 44,000 uF's down to appr 30,000 uF's ) ? Surely, Hafler & crew did not produce a product that was severely underdesigned to the point of smoking the transformer under normal use conditions.

Besides that, the Hafler DH-500 does not "double down" or act like a voltage source as impedance is halved. As far as i can recall, it is not even remotely close to doing so. This tells me that the amplifier is of a current limited design and can use all of the "reserve" or "buffer" in the power supply that it can get.

I think that Linc wanted to install more ADDITIONAL capacitance to what was already there. As such, he can simply drop the caps into the circuit and wire them in parallel. As mentioned, the major draw on the transformer will come when first powering up the unit. After that, it is simply "topping off" or "refreshing" the charge that originally took place upon firing it up.

Having said all of that, i do agree that using multiple smaller caps ( two 15,000 uF's ) would be better than using one 30,000 uF cap. This could be broken down further into using a combo of multiple sized caps ( 470, 1000, 2200, 4700, etc... ) to achieve the same appr value. Only problem with doing so is that the wiring can become a mess. That is, unless one fabricates some type of sub-board with a wiring harness / adapter to compensate for such.

For the record, i have six preamps* that came with 1000 ( one thousand ) uF's of capacitance from the factory. They now have 42,000+ uF's of capacitance in them using the aforementioned "staggered value" approach. While the stock transformer would give out if it had to deal with in-rush current that would be required to refill this quantity of capacitance if asked to do so on a regular basis, i avoid this by never turning the preamp off. In fact, these preamps do not even come with power switches from the factory.

I also have another preamp that came from the factory with 44,000+ uF's of capacitance in it. While this unit has a very "beefy" ( for a preamp ) transformer, it is WAY below what one would find in an amp the size / power rating of a Hafler DH-500. As such, i would not hesitate to increase the amount of filter capacitance / power supply reserve. Nor would i fear problems from doing so as long as the precautions that i mentioned earlier were attended to. Sean
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* If you are wondering why i have so many identical preamps, I like this preamp and it is no longer available. As such, i have purchased several of them and performed similar modifications to each. Some of these have different factory options though, such as different gain levels in the phono stage, factory upgraded / redesigned output stages, etc...

Sean: no disrespect taken whatsoever...my mistake - I did not make it clear that my off-the-back-of-the-matchbook calcs were for EACH channel; not the total. Again, I make no claim that I can "re-design" the power supply better than the designers, just trying qualify what MIGHT happen should filter caps be added to a PS with regard to the xfmr.

Gs5556, Sdcampbell and especially you Sean, THANKS for taking the time to respond to my post. By the way Sean, I found output caps on SoundValves websight http://www.soundvalves.com/updatesheet_2.html
Im not sure if these are what you would consider cheap or even decently priced for that matter, they are within my budget though (still outta work). So, from what I gathered from all your posts, if I purchase 4 of the newer 22,000 caps and wire them in phase, I will be performing a decent little upgrade for my amp. Or perhaps multiple smaller rated caps for quickness. Either way..... Its gonna make a difference and not tax the xfmr too much. Am I correct?

Lincoln: Thanks for posting your source. Sound Valves used to have some other caps a while back that i was interested in. As it turns out, just as i was going to purchase some from them, they sold out. Glad to see that they "stumbled" across some new stock.

While i can't recall the overall height / internal layout of the DH-500 or the voltage that it runs at, i would give Sound Valves a call and see if they could help you. If at all possible, i would opt for running four of the 75V / 15,000 uF caps rather than two of the 22,000 uF caps. While this will set you back the same amount of money, you'll have picked up an additional 16,000 uF's of capacitance in the process. I just don't know if there is enough room in the chassis to do this.

Whatever you do decide to go with, i would add a few bypass caps across the top of these. As i mentioned, the more caps that you can run at various values, the better off you'll be. The "capacitance bank" that i built for the aforementioned preamps consist of four 10,000 uF caps topped with twelve 100 uf caps and these are bypassed with four .01 uF caps. I picked these values based on low ESR, lifespan, price and availability to me.

If i had my "druthers", i'd "druther" have chosen values that were not evenly divisible by each other. None the less, i have NO doubt in my mind that this set-up is FAR superior to what the factory installed. By shopping around and buying in bulk*, i was able to build this "sub assembly" for under $20 total. Not bad for 40,000+ uF's of high grade capacitance in a package that fits where the two original 500 uF caps originally resided. Sean
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* I purchased enough to do 8 identical capacitor banks as i had my 6 preamps to do and one each for my Dad and Brother. By some "strange coincidence", they too run the same preamps : )