Leve
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Posts posted by Leve
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28 minutes ago, chinsettawong said:28 minutes ago, chinsettawong said:
Your amp looks really nice. Please show us the underside as well.
About the volume, it might have something to do with your source putting out too soft sound too. Please check.
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:
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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.
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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/
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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).
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31 minutes ago, HemiSam said:
Just got back from an event where I got to test out my new setup. The first day was a bit painful....some teething pains and it hailed after only two passes. We worked through those and I managed some clean passes the second track day which was cool and sunny.
This pass we pushed the boost ramp and found the track's limits. It was a colorful pass for a couple of reasons...
I've got some adjustments to make like rear gear and tune tweaks, but it's close to being in a good place.
HS
Very impressive !
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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
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1 hour ago, kevin gilmore said:
washers near the tubes are too close, use smaller washers
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.
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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.
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Megatron Electrostatic Headphone Amplifier
in Do It Yourself
Posted
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.