Quote:
Originally Posted by Kruemelix
- CAP - Monolithic Ceramic, 0.33uf, ??V ---> are the P4669-ND @ digikey ok?
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It is my opinion that 0.33µF is excessive capacitance as rectifier snubbers. I personally used 100
pF monolithic ceramic 100V axial lead caps on my build (Digikey 399-1812-1-ND or Mouser 80-C410C101J1G). This is the same as what Tangent specifies for the STEPS supply. Btw there is nothing magical about 100pF. Anything in the 100pF to 680pF are common for snubber applications.
Quote:
- 0.1uF 50V ceramic Z5U radial |
If you're referring to those on the PSU board, I actually used 0.1µF 50V X7R monolithic ceramic axial lead caps (Digikey 399-4484-1-ND or Mouser 80-C412C104K5R). The X7R ceramics are slightly superior to the Z5U grade, and the axial leaded version fit the board nicely.
Quote:
- how much (or less) gain can a Dynamight handle? 1,5? 2? |
I wouldn't go below 5, and even at a gain of 5 you should change the 33pF compensation capacitor to a 47pF to ensure stability. See
this post on headwize.com. Also keep in mind that for a dyna
might in balanced configuration, the effective gain is twice that of the amplifier gain, so if you set the gain to 5 on each amp, the real gain as seen by the headphones is 10.
Quote:
- 10k or 25k attenuator for a Dynamight? |
You can use anything between 10K and 50K. The "10KΩ" resistor going to ground at each input should be increased to at least 10x the value of the pot or stepped attnuator, so if you use a 10KΩ pot/attenuator, that resistor should be at least 100KΩ. I used a 50KΩ Alps Black Beauty RK40 pot, and a 1MΩ resistor at the input to ground.
For a dynamight you will need a four-gang pot/attenuator to control all four amps simultaneously.
Also, I recommend that you add a series resistor between the output of the pot and the input terminal of the amp. I used a 475Ω resistor but up to 1KΩ is also fine. This resistor provides a little buffer to prevent the input FET's gate from shorting directly to ground at minimum volume, and also provides a small buffer between the driving source and the input FET when the volume is set to maximum. Without this resistor the amp may misbehave. See the schematic diagram of the dynahi and psu with all part values
as I built it (including wiring):
My dynahi page
Amp schematic
PSU schematic
Edit: There are also dynahi-specific build discussion threads at headwize.com that you should peruse:
dynahi amp thread
dynahi psu thread