Currently looking around for the parts for the two F4 amps that I have on my mind. With the active devices already purchased, the choice is now narrowing for the remainder of the passives. I have elected to purchased 4x PSU PCB from Brian at Chip Amp as it allows a fairly straight forward build. I have use his kits in the past, quality and service is very good. The main question is how much to budget for this build. With the use of high quality resistors and capacitors, the passives alone for a 4 channel build will be close to the US$1,000 mark. The thought of diminishing returns start to play a part here.
- Rectifiers - The specified ones from Brian are the MUR1560, which are 600V 15A ultra fast diodes. The schematic in the F4 manual states of 35A 200V bridge. The other option is an IXYS HiPerFRED Epitaxial diode DSEP 12-12A. The IXYS seems more favourable as it can handle higher voltages at 1200V and has a faster recovering time at 40 nS. Looking at Mouser, I also found IR 15EYX06, 30ETH06 and 15ETH06 interesting as their recovering times are 18, 28 and 22 nS respectively. This will require more research.
- Capacitors - I can find three main choices; Panasonic TSHA, Mundorf SI and Nichicon KG Snap in.
- Filter Resistors - This can either be a parallel group of 0R47 5W resistors, or a low value inductor. For the resistor option, Mills MRA-5 and the Caddock MP915 15W seems to be the most sensible options. But only the Mills is available in the 0R47, and that from Parts Connexion... This is important as it also is the resistor on the source (?) of the MOSFET and I would like to get them in bulk, since there will be so many, 14x4 = 48 in total. The use of a very low mH range inductor here as an alternative may be as much an economical one, as a design choice. the Hammond 159ZJ 10mh/5A or the 159ZL 2.5mH/10A are around US$26 each, where as Caddock resistors will be in the range of US$20 and Mills around US$10. The question is, will a choke be a better design choice.
- Transformer - Amplimo makes a suitable 500VA range. That should be more than adequate for 1 channel. But at Euro 94.96, it ain't cheap. Even moving down to the 300VA range, is still Euro 70.45 each. I will need 4 such transformers.
- Resistors - For the source resistors, see above. The gate resistors and other signal resistors will be something like a Tantalum, Carbon composition or Charcroft type. The other supporting resistors will be high quality Takman, Kiwame, Amtrans or similar.
- Capacitors C1, C2 - Appear to be signal coupling capacitors, connecting directly to the gate resistors. Something more special needs to go in this place, possibly an electrolytic with a high quality film bypass. Nichicon ES Muse may be a starting point. Maybe a Mundorf Bipolar as an option. The board only has minimal space for the coupling capacitor, a Mundorf Tin or a small value copper in paper oil maybe possible. Given the feedback about Teflon capacitors and this design, I want to stay away from this combo, and keep towards a metal foil type.
- Capacitors C3, C4 - Seem to be power supply only, nevertheless, something like a high end Nichicon KZ or a Sanyo Os-con will do nicely.