Leve

No. The input goes directly to the pot and from the pot directly to the board. At full volume I measure about 0.5 ohms between input and output. The pot is Khozmo's new relay based design.

Thank you chinsettawong. The source is a Yamaha SACD player (CD-S2100) so it's a balanced 2v output. Here's the underside with board not yet fully mounted and transformers not yet hooked up:

Finally - another Megatron is alive.. all the voltages came in within a couple of volts, and it really is a great sounding amp. I still have a bit of mounting and case work to do before it's finished, but listening is a constant distraction. The only issue I have is that I find I'm mostly up into the last 10% of the pot, and I'm wondering if I have something wrong, or is it just because the Mk 1 007 headphones are that hungry ? Any advice would be appreciated.

These are showing as out-of-stock at RS, but I have some here I can send you if you want to drop me a pm with your details: http://au.rs-online.com/web/p/ceramic-single-layer-capacitors/7214975/ Update.. they have several options in stock, but still happy to send you some if you prefer: http://au.rs-online.com/web/p/ceramic-single-layer-capacitors/7214966/ http://au.rs-online.com/web/p/ceramic-single-layer-capacitors/8313036/

Bravi.. the 3900pf capacitors listed in the BOM here: https://docs.google.com/spreadsheets/d/1tQvwqsARXGge6Tw6edqicCDti6Mite2F24T5YddyEEc/edit#gid=0 are available from Mouser, and are a film type. RS have several options listed for the 1000pf if you can't find them at Mouser.. the problem you have to watch going to a different type is that there's not a lot of room where these go on the board, so check the size and lead spacing. Glad to see another Megatron going together "down under".. mine is just about ready for it's initial start up (fingers all crossed here).

Very impressive !

Hopefully this will be useful to someone: Genuine 2SA1486 from BDent (right in both pics) vs fake from SWL Electronics - Ebay (left in both pics). V(BR) for genuine around 750.. fakes around 350. The most obvious feature is the back-plate.

Thanks VPI and HemiSam. I've been running these things for 30 odd years now, as has the driver of the car. It's our aim to ship the car to the US and run there for a while before we retire The big league and the rules are a little different, so a new challenge for us. We're doing a pass against Daniel Ricciardo in his F1 in 3 weeks.. something a bit different. There's a video about it here: Perth Speed Fest

They're just sitting loose in there Kevin.. I was using them as stands when I started the board. I'll take care when it goes in an enclosure.

This is probably a little different to the cars that most here are interested in, but someone did ask for pics so I thought I'd add it because it's a cool shot. Tuning this is my day job. It runs in Top Alcohol Funny Car in Australia. Has run a best elapsed time of 5.410 @ 267 mph:

Hi everyone and thank you all for the wealth of information here. My electronics knowledge is average, but I'm trying to build myself a nice Megatron using a board from Birgir and would welcome all advice and criticism. I do have someone a lot smarter than me giving a bit of advice. I'm using the KGSSHV power supply, even though I know it's not the number 1 choice anymore.. simply because I had a board and a lot of the parts already. It'll be 450v with offboard heat sinking. So the questions: The board uses 12vdc for the front end, so I planned on switching the 7815 to a 7812 and increasing the 16-0-16 output of the transformer to 750mA (for a bit of headroom above the 600mA required for heaters). Is that a logical approach ? Secondly, the main transformer.. the BOM says use 420v secondaries for 450v, but someone here suggested that was too high for a Megatron build. My buddy has suggested that in order to ease the work and heat from the FQPF8N80Cs, I could probably get away with 380v secondaries. Mains voltage where I live (Western Australia) is 250+, so his suggestion was a custom transformer with Primary: 230v/250v. Secondaries: 2 x 380v/200mA, 16-0-16v/750mA. Thanks in advance for any input, and thanks again for the great forum.. especially Kevin and Birgir for all their efforts in helping dummies like me build themselves a decent amp.

Welding up 'o' ring grooves ?