[Firam]

I've been looking at http://www6.head-fi.org/forums/showthread.php?t=166545 and I know what I need to do but not what supplies to do it.

It is suggested that I need 2 caps being anywhere from 1uf-44uf. I have a limited understanding of which to pick. I would think that a 44x capacitance difference would make a difference. I think I can use either electrolyte or film right? Then there is the issue on what voltage, does it matter? Is this a important part of the amp and would it be best to buy a more expensive cap or will a cheaper one do just as well? There are just so many types, it makes my head hurt.

The resistor should be 100k. Does the type matter? What about the wattage?

Finally the wire. I want something like 22-24 awg right? Somthing like this? http://cgi.ebay.com/50-feet-stranded...QQcmdZViewItem

 

[dsavitsk]

If you look at my first post in that thread, it will point you to my page (http://www.ecp.cc/cap-notes.html) with information on how to decide what size cap to use. Voltage is not much of an issue as the cap won't see anything over 8V.

As for type, electrolytics are not appropriate unless they are something like blackgate N or NX series or Nichican ES. Otherwise you want film caps. The same page with information about how to choose cap size has some notes on inexpensive coupling caps.

For the resistor, 50K to 100K is fine. Generic metal film is a good choice, and wattage won't matter.

Wire is probably wire here. Use whatever fits.

 

[Firam]

Quote:

Originally Posted by dsavitsk If you look at my first post in that thread, it will point you to my page (http://www.ecp.cc/cap-notes.html) with information on how to decide what size cap to use. Voltage is not much of an issue as the cap won't see anything over 8V. As for type, electrolytics are not appropriate unless they are something like blackgate N or NX series or Nichican ES. Otherwise you want film caps. The same page with information about how to choose cap size has some notes on inexpensive coupling caps. For the resistor, 50K to 100K is fine. Generic metal film is a good choice, and wattage won't matter. Wire is probably wire here. Use whatever fits.

Thank you very much. I saw that link in the Samgotit thread but didn't know it applied to me. I don't really have enough information to solve F = 1/(2 * pi * C * R) do I? The Sprague 500P9042F6 is well liked on that page. I think I will order 2@5 µF. Plus I live in Nebraska so fast shipping.

 

[dsavitsk]

I like those spragues a lot. If you look at Nebraska's list of oil caps, there are lots of choices. i don't think the brand matters much, so just look for something in the 4 to 5 uF range for a reasonable price. The standard favorites are the Vitamin Q's, and while they list some I think they are actually out. Also, be sure that they are PCB free -- I think most are, but it is worth checking.

I should also note that those caps a physically very large (they are the gray ones), so be sure they will fit.

As for determining output size, you should have all the info you need.

F = 1/(2 * pi * C * R)

F is the 3dB point that you choose, C is the cap that you choose (i.e., try some different values and see what you get, or rearrange the equation to pick a frequency and see what capacitance you need.) For R, it is the resistance of the output resistor and the input impedence of the next stage in parallel. But, basically, use 4uF or larger and you should be safe.

 

[Firam]

That is pretty big. I will have to see them in person and move them around to see. I think by the picture they will fit in the back corner horizontally stacked.

 

[Firam]

I got 2 1% RN50D Metal Film Resistors and 2 Sprague 500P9042F6 from Surplus Sales of Nebraska. At least I think I did they didn't send a confirmation email. I also ordered some wire from navships. I can see why he is highly recommended. I accidentally sent a eCheck instead of a credit card or bank transfer. He is going to send it before my check clears. I was amazed by that. So I'm all set.

 

[Samgotit]

It's a great modification.

Please post your results.

 

[Firam]

I got my caps and resistors in today (Wire came on Thursday). Words can't describe how %@^@#% huge the caps are. I will post pictures later because I'm eager to get started.

 

[Firam]

Edit: Doesn't matter anymore.

 

[Firam]

Done. It was rocky at times. In my first trial I had no sound from the right channel. I had a bad solder on the RCA jack and got it fixed. The case was tricky getting back together. Some screws didn't line but right and it took a little adjusting to get it closed. I did manage to lose one screw which isn't too bad considering the number. I will search the floor, it couldn't have gone far


It was fun but tedious. Trial by fire and I won. No idea on improvements yet.




Fuzzy one-handed picture but you see the size of the Sprague 500P9042F6.

 

[Firam]

Now I've failed again. I opened it back up to make sure my caps weren't too close to the transformer and were getting too hot. Now when I try to turn it on the LED goes on, for a few seconds and dims, then turns off. Then there is a click from the transformer. I have no idea what I did to break it.

Edit: Fixed that problem. Turns out you can't turn the DAC off and on too quickly or it won't work.

 

[Firam]

Next problem there is a buzzing in the problematic left channel. Is that indicative of a bad solder joint?

 

[Firam]

The problem is back. It only presents itself with the lower impedance headphones as I found when I tried my HF-1. I just assumed it was a solder joint somewhere that was bad, either at the board, the two cap leads, RCA plug, or the ground. What else could cause it?

Edit: Found it bridging between the ground and signal at the RCA jack. Fixed and everything looks clear.