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Posts posted by RiStaR

  1. Even with the max volume,imbalance still happen. About the tube, i try my best to swap them,i don`t think they are bad.    Based on what you say,measure will be done tomorrow(maybe).


    Anyway,thanks RiStaR.


    Not sure I'm helping... just suggesting some stuff :) Just to be clear, I meant to swap left channel tubes to right channel tubes as a check instead of swapping all of them.

  2. Not sure I understand your question, but those circled headers are the right ones if you don't use the RK27. If you used an RK27 and it's mounted then yes, because they are connected to those headers the mounted attenuator will affect it. 


    Even with the RK27 fully open (max volume) you're still getting channel imbalance? [you should be able to measure the attenuator with a DMM to see if it's bad - at max volume setting especially] I assume you also tried to swap the tubes around to make sure it isn't the tubes?

  3. Is there a reason why you're still using the ceramic insulators? The fqpf8n80c are insulated... so they actually reduce thermal conductivity. With regard to your balance issue are your tubes matched? Also check your attenuator (I had an issue once where the relays weren't working properly on my attenuator).


    Also, how do you like the sound? ;) 

  4. Thank everyone.


    i will order some 10Ohm Resistors and large sinks.


    But during the Chinese New Year, almost all the shop will be closed. :-[ 


    I have to delay the project.


    I'd really recommend going offboard sinks... with the right size heatsinks for the KGSSHV board, the temps are still a toasty 90C after 15 mins. This had the side effect of "killing" my LT1021s (it always made the voltage to +430V over time until I offboarded the cooling) when cased up.


    It's been close to a year and the whole setup still runs well.


    EDIT: just realized I listed the wrong IC and double quoted heh

  5. Had a few requests for this...


    In terms of a drilling template for the Megatron. I don't have CAD or anything, but this is the jpeg I did out for the drilling of my chassis. I'm not sure if it's useful to the rest of you but it's the closest I have. For the rest who have already built one, if you have something much more accurate, please share it.  :)




  6. Hi~ guys


    Is it work to mod the bias supply in KGSSHV PSU board to 300V for Megatron 300V PSU? And, how to mod?


    I think changing the Zener diodes to 300V, is that correct?


    Hi Peleus,


    What would you be doing for bias voltage for your amp? Just something to think about... If you're sharing it with that 300v line, you may want to be careful with using the right heatsink for the 10m90s. From memory, all my input tubes draw about 20+W. The max for the 10m90s is about 40W i think.


    Since you haven't started, if you're living in a place that has a high ambient temperature (in the tropics it's normal to be about 30+C), you may also want to consider off-boarding the fqpf8n80c instead of the onboard heatsinks... I was eating through the LT1021s on the + line (they would no longer keep the voltage consistent but drop them an extra +-30v after some random intervals) from the heat when the PSU was closed up with just vent holes at the top.


    I've since used a larger offboard sink for the fqpf8n80cs and added vents (those used in aircraft cabins for the aircon) to the side of the PS casing to bring the temps way down. 

  7. Hi Leonjo,


    You can use either if you're using the larger version of the PSU board. The insulated version is needed for the smaller board because the distance between the diodes are very close (it's like almost 2mm). If you use the 1210Ds on the newer smaller boards, you'd have to figure a way to insulate them. As to your insulator tubes for the transistor, there isn't any rating so it's hard for anyone to tell you if it'll work.


    I hope that helps :)

  8. Yes, 6c33 is just awesome in what Andy is doing.  Using 6P3S-E in a 900V amp is just untold amounts of stupid.  Just because some idiot on the net claims this tube is similar to the EL34 doesn't make it so.  It's a lower spec version of the 6L6 and is not compatible.

    Hi spritzer,

    Not disputing the conservative ratings on the mil tubes - I did know that going in. I thank you for caring enough to speak up about it though, even if its abrasive.


  9. one chicken on each of the 4 x 6c33's


    That sounds interesting - just googled the tubes and they look nice too :D


    On my megatron I think i found my tubes that work best for me... TS 12ax7; sylvania 12bh7 (it just sounded better than all the au7s i tried); Russian 6P3S-E (they also put out less heat than the EH 6ca7s). Bass is as much as the KGSSHV and the decay sounds perfect for me... now i'm wondering if I should take a gamble and a large box of unmatched ones or pay the premium for the matched quads for backups.

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