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Here you will find useful information, tweaking tips and other useful information. Is there a topic you would like to see on this page? Let us know! Some of these are simply e-mails we have answered. Sometimes the answers are made separate from the question and others are integrated into the text in bold to add context to the answer.

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John:

What do you set the bias at on the DH 220's.  I have 2 "factory" values of 250 and 275ma and will set it to the lower one without further direction? --------You can even set this at 400ma. Of course, you will pay a penalty in heat, electricity and very slightly reduced lifespan. You will gain a smoother sound with greater naturalness.  They have the DH500's at 350ma but I'm going to use your value of 330ma - much safer. ---------I see your logic, but I doubt that you will find it safer. At some point, as you raise the current, your fan will kick into the second speed and this degrades the sound if you are anywhere near the fan. Thanks,

Eric
 
Good Listening
 
John Hillig

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sirs, I've been reading your website, I had a Hafler DH500 amp.  A few
questions, you mention sonicly superior SOLDER?  I always thaought
solder is just melted metal holding the components in place..., how can
it have a soudn quality?  --------We will soon publish more information on this subject in a new newsletter to be posted on our website. This will be a detailed description of solder properties as we believe they relate to sound quality. In the meantime, I think you will agree that most people believe that solder is either solid or liquid. Not so! Most solders actually solidify over a range of temperature. Also you mention in replacing power supply
caps, with superior sounding ones you supply, again, can you please
explain how capacitors have their own sound qualitys? --------------Do you believe that all flutes, violins and guitars sound the same? Then why would a musician pay hundreds of thousands of dollars for a Stradivarius violin? For that matter, are all cars the same, telephones, baseball bats, ice creams? If so, then you should buy the cheapest thing that will do a certain job. Pardon me for answering your question with questions, but understand that a capacitor is actually a complex device, appearing simple, with different resistance/impedance, inductance and dielectric noise problems. Things such as the methods of attaching the internal foils to the electrodes have an effect. The dielectrics and separators are issues that are the subject of ongoing, constant research. Unfortunately, not all of man's technical problems have been solved and will not be solved in our lifetime or that of our children.    Lastly, in your
circuit boards description, you mention teh superiorty of yours versues
Hafler's, eliminating "bounce effect".  i can't find that spec anywhere,
can you explain.  --------Here I was mainly referring to the profile of the foils we use on the circuit board. Circuit boards are as imperfect as many other of the materials that we work with. Our civilization is in it's technical infancy and we have to find ways to design around these burdens. Energy from the signal traveling on the board material is, to some degree, absorbed by the circuit board and over a period of time it is re-released back into the foil from which it came and the other foils in proximity. We use thin width, but thick foils to minimize the amount of this energy leaked into the board material.  your add on are a bit pricey..a new Hafler model 9505
has a 7 year warranty, for the similar wattage, Hafler has an excellent
reputation.  Why should I buy your kits over a new Hafler.  I'm trying
to come to a conclusion in my search.  ---------If you believe that power and warranty are the only things to consider in your decision then you can easily find the warranty and power for even less money. The price of a used Hafler XL-280 or DH-500 would be under $400, maybe less. Adding our basic kit for $299 would provide you with an amp of considerable sonic prowess, well beyond that of any production Hafler. I should know, we were technical consultants on the original Hafler 9500 series. Many of them are outfitted with Musical Concepts capacitors.
 
If you seek further information and views on our mods, you can bypass magazines and such and go directly to the people who buy these kits and form their own opinions, some are found on our web site under "Customer Testimonials" and others at the web site www.audioasylum.com . Do a search for "Musical Concepts" on that site. 
 
Regards Carl 

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I’ve another unrelated question: I’m selling an older Denon A/V receiver which used two "shorting pins" to bridge main out and front in preamp RCA jacks. I’ve lost the "pins" and ask if you have any suggestions on where I could get replacements. The local Radio Shack had NO idea what I was talking about...

Thanks, John

My answer: "A very short loop of interconnect comes to mind. I imagine getting the parts from Denon with shipping is expensive, but worth a check. A lot of audio dealers may have these in their "parts bin". A bent piece of 10GA bus wire might do."

JH

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Mr. Hillig:

I own a Hafler XL600, 1990. Is there any reasonable method to eliminate the fan? If not, do you know a method to quiet it, yet sufficiently cool the amp? A high S / N ratio isn’t worth much if the noise floor is somewhat high from a cooling fan. If the amp is place in or near cabinets, the fan noise gets even worse. I’ve reduced it some by creating a muffled air way with scraps of carpet. But this fault alone makes me think about selling it. ————Is it quiet when you first turn on the amp? It should be whisper quiet until the amp begins to warm up. Do you believe it to be operating at a ‘normal’ speed? Are your speakers unusually inefficient? Do you play loud? At the lowest speed it should be very quiet even after a long "no sound" warm-up.

There were several iterations of this product. Initial units were very unstable with reactive loads. Later "improvements" were aimed at taming the mercurial nature of the beast. Some versions would oscillate with little provocation. If you are playing your amp at low volumes or it is idling and you have a high fan speed + very warm air exhaust it might be oscillating or inappropriately adjusted. If you are not the original owner perhaps that person adjusted the idle current for more Class-A operation which results in a much hotter running design with high fan speed.

I haven’t seen reviews on your mods for this unit in particular? What exactly is of marginal design / quality in my original amp which would I get noticeable improvement from replacing?

Hope you have a good suggestion. ——————Every amp we have modified including ARC, Krell, Spectral, Levinson etc. has parts that we consider to be second-rate in certain sonic aspects. From a reliability and technical specification standpoint I suppose you might say that few of these parts are of poor merit, but that’s not what audio reproduction is about. Every part has it’s own sonic signature and we have spent years separating the poor and the outstanding. Our level of dedication to our ‘art’ is uncompromising. If you would like to get the opinions of other customers, you can read a great deal about us at www.audioasylum.com by doing a search for "Musical Concepts".

Thanks in advance, KP

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