steefdebruijn

No suggestion (because no experience) but will investigate if these can somehow be fitted: https://www.intertechnik.com/Shop/Cross-over-parts/Capacitors/Audyn-True-Copper-Cap/_-ATC022630_1768,en,6559,53292 https://www.intertechnik.com/Shop/Cross-over-parts/Capacitors/Audyn-Cap-True-Silver/_-ATS0221000_1768,en,6226,123941

Thanks again, I rephrased my quote. Will not receive answer before next week with High End Munich going on this weekend.

Thanks! Asked for a quote on separate 350vac 300ma and four 6.3vac 3a trafos. All with two windings and specs per winding. Will parallel the secondaries on two of them for the center tubes. What secondary is best suitable for the LV if we use 12vdc output? I would guess 12vac would be enough but maybe it does not provide enough headroom. Also no other mods necessary to the LV than using 78(79)12 instead of the *15 ones? (I think remembering from GRLV discussion that also zeners had to be lowered but maybe that is not applicable here) thanks for all your input and feedback! Steef On sockets. Will these do? http://www.jakeband.it/sockets.html

I think this n00b is beginning to understand. So one of the large caps (the one connected to the rectifiers) should be a large 600V+ one and for the other one a standard 550V will do. So only two expensive caps then for the PS (trying to avoid expensive audio-grade caps on the Megatron board) :-)

Just to be sure: 25va 15v is plenty for the LV (regarding the filament current of 600mA)? And: if the two 4A 6VAC secondaries from the AS-4T360 - 400VA 360V are enough for the center tubes (equals 2A per tube), 25va 6v (2.1A per tube) should also be enough for the outer tubes? Or is it better to give the trafo for these outer tubes more headroom? Regarding the caps: so we should look for better caps then presuming we cannot lower the HV trafo secondary and/or the +-VDC to the Megatron board... I hope these are overkill (wo'nt fit to board also) with needing four of them... :-) http://nl.rs-online.com/web/p/aluminium-capacitors/8707188/ Maybe easier (and cheaper) to lower the PSU to +-400VDC (using 320VAC secondaries) and use normally available 680uF/550V caps? Or is that simply not enough for this amp...

About the PS... In the GB we are supplied with the GRHV boards originating from the Carbon. It can be configured for +-450V by changing 2 resistors from 390K to 442K right? Somewhere in this thread it is stated that we need a 360VAC secondary on the trafo. Is this correct? We need 12VDC filament supply for the little tubes on the GB megatron board. Can we lower the LV supply on the GRHV board to +-12VDC by just changing the 7815 and 7915 to 7812/7912 ones or should we lower the 15VAC too? And, can we just use the -12VDC for the -15VDC connection on the megatron board (I trust trying +12 and -15 from this one supply is a stupid idea)? If so, I would like to try to keep this in one (large...) box with the following trafos: One http://www.antekinc.com/as-4t360-400va-360v-transformer/ This gives me two windings with 360VAC and two with 6VAC for the filaments of the center power tubes. Two http://www.antekinc.com/an-0206-25va-6v-transformer/ This gives me two times two 6VAC windings for the outer power tubes. One http://www.antekinc.com/an-0215-25va-15v-transformer/ This gives me two parallel windings for the LV supply Will this do it? Any thoughts or corrections welcome. Steef

Hi, I already created one. Please check and advise. Does NOT contain the 2SA1968 (ordered from bdent) the C1815 tube sockets Also does NOT YET contain terminal blocks. http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=87e75194b6 Steef

Hi spritzer and others, I am investigating tube options and have a question about the compatibility of the KT77. First of all I am a tube n00b but trying to understand all this. The megatron is designed for 6CA7 tubes. From what I read these are also called EL34 tubes. So these are the same. If I compare the info on the tube directory (http://www.audiomatica.com/tubes/el34.htm vs http://www.audiomatica.com/tubes/kt77.htm) I see no difference in specs and max ratings. The connections are slightly different but the effect is zero (pins 1(g3) and 8(c) are separate on the EL34 but connected on the board, the KT77 has internal connection between g3 and c on pin 8 with pin 1 not connected to anything). The measurements differ slightly however (from my eyes). Is this difference in measurements the culprit why the KT77 cannot be used in the Megatron? Steef

Hi, I joined the just closed GB too for this amp so I thought I should shoot some n00b questions to this thread. This first one is about tube matching. It is asked on this thread before a while ago but I did not understand the answer given at that time. So the question is: for matched *pairs* see the following arrangement options: For the small tubes we should obviously match black to black and grey to grey, but what about the el34/6ca7 ones? green-yellow pairs? red-purple pairs? blue pairs? And if I can obtain matches quads: Same question.. green-yellow quads? red-purple quads? blue-grey quads? left quad and right quad (not color-coded in the picture) Thanks! Steef

thanks a lot Kevin!

Thanks spritzer, Any chance we can also get access to the schematics for the boards that were posted in these threads but all linked to Kevin's site? I mean for example the GRLV schematic at http://gilmore.chem.northwestern.edu/goldenreference.pdf which is no longer accessible. Thanks! Steef