RiStaR

Congrats Emooze I'm using 35v caps and I have headinclouds to thank for that. He posted earlier in the thread about the 25v caps being run at close to its limit and I did the calculation and thought I'd do 35v just in case also.

I intend to use them in place of the 12AU7s. Ok, from reading it seemed I just had to make sure I could supply the heater current (which I have gobs of with the LT1083). So do let me know what I need to swap around to test them [While I got a tube amp up and running, I'm still pretty much clueless on tubes apart from looking at pinouts/gain and the bh7s looked just like a straight drop-in replacement]. I know Birgir talks about the ECC99 a fair bit as well. Let me know what you'd recommend? Cheers Jon Almost there! http://www.ebay.com/itm/SL9155A-10-DIY-FULL-Aluminum-Audio-chassis-Audio-Amplifier-Chassis-Enclosure-/261050882766?pt=US_Pro_Audio_Parts_Accessories&hash=item3cc7d85ace It's in champagne... tried stripping it but didn't go too well... so ended up spray painting it with Metallic paint - it's darker than the other chassis, but it's good enough for me. Edit: Link didn't show for some reason.

Have finished my PS unit, but only just realised Mouser didn't pack one item for my connector so I can't actually use them. It's been about 2 months since that order, hopefully Mouser does good on it. Still waiting on some wood so I can finish my amp chassis. In any case, to test the HV delay I connected directly to the terminal blocks using wire. The good news is it works properly and I spent another 8 hours on it. The HV comes on about 66 secs after power on. The issue I had previously with the DC offset going to 450v momentarily doesn't happen anymore - so the delay did the trick there Further impressions, the bass on the Megatron is perfectly fine - it may even be tighter than my KGSSHV. There is more volume in the bass with the KGSSHV so the impact is stronger there, but the Megatron with the big bottles has enough bass to please. On the upsides: There's definitely more clarity with the Megatron - I picked up on stuff I didn't notice with the KGSSHV. Going back to the KGSSHV, I can hear them, but the Megatron just made it more obvious. You just tap more to the music with the Megatron and things just seem more 3D. I changed my 12ax7 from EH to Tungsol and now there's less reverb - not negative just different. Where the Megatron really is enjoyable are with tracks with strings (Kotaro never sounded better) and drums with cymbals. I have some 12bh7s coming soon, so hopefully I can get everything else up before they arrive. Now I can't wait to finish this thing and listen to it more. Edit: oh the temperature on the valves vary a fair bit depending on tube... some are at 105c while some are at 130c. My transformer is running at 41c and really quiet. The amp's top surface approaches 42c. The sinks on the KGSSHV PS is about 61-66c still. The amp is definitely hot.

Ouch! I see wut u did 'dere [sic]

I agree heh. While I haven't heard the original, I'd say this is improved. Considering how hot this thing can run - especially if you go crazy with the bias - I don't understand how the originals could last so long without heatsinks?

Finally had time to finish drilling the chassis for the Squarewave. Here it is stacked on top of the DAC that I'm working on - waiting for a prototyping board to finish my Arduino shield, not enough pins to plug the LCD, encoder and DAC board together. Also waiting on a multichannel DSD USB interface to be released (USBPAL has been "soon" for 6 months now...) Still a fairly tight fit. Wires still need to be neatened up, but everything is working right now and I'm listening to it right now. Yes, I'm still using the wrong size sinks but I'll wait for Kevin to post up proposed tweaks to the KGSSHV ps before doing another order. I googled images of the old Squarewave and I'm quite amazed how Mikhail managed to fit everything in such a tiny chassis (albeit with an external ps brick).

Ume, do share your impressions between the two versions, too. You're probably one of a handful who have built both an IXYS and A1968 version. The PCBs really do draw you in somewhat haha!

I agree! Congrats ume! Do share your impressions when you get some time with them

I'm using a Toroidy that hasn't given me any problems, but its only been just under a year of daily use. Got it from a fellow forum member here.

May be hard to spot, depending if you have the onboard or offboard - but maybe check the 25 ohm resistors? This is the resistor that burnt out for me on the amp board (it took out an LED along the way or the other way round?) when I initially got it up. It's hard to spot/access between heatsinks for the onboard version Mine has been running fine daily since replacing those. Good luck!

Congrats 'pantsless' What do you mean by 270 and 307 on the rail? - this is your 300v line? I guess we should list down the tubes for the sound impressions - I'm using a matched octet of 'cheapish' EH 6ca7s because of a great contact from Victor. The 12ax7 and au7s are also EH. While I only listened to it for 4-5 hours, I do think the KGSSHV has just as much detail and separation. Which headphone were you using for the comparison? While I enjoyed both the 007mk1 and SR-202 with the Megatron, I do think the SR-202 got more out of that pairing - I didn't think I got much more out of the SR-202 from the KGSSHV versus the SRM-252 and I thought it was just because the SR-202 doesn't improve much with better amplification. I guess I'm wrong on that front. Agree on bass impact being better on the KGSSHV versus the Megatron, but it also seems that the Megatron does that more naturally? Waiting on parts to increase the height of my casing so I will update on this when I get more time with both. End of it all, it looks like I may be keeping both amps afterall. I just need to think of an excuse to justify that to the "finance minister"

The local Electronics shop where I "invest" a fair amount of my money just loaned me this (http://www.ston.com.tw/spec/H3Y-2.pdf) to try out. I intend to use that in front of the HV transformer. Is there value in putting the soft-start circuit after this? Or should i leave the soft-start just for the filaments. Open to suggestions since it's my first tube amp and there's just so much contradicting info about HT delays ><

Probably be a while for that to happen - typically takes 3-4 weeks for stuff to reach me and I haven't ordered the delay, yet. I'm also not sure I want to finalize the layout until I know what I'm getting for the tube delay. The components inside my PS are going to be: KGSSHV PS Soft-start circuit HV Time-delay circuit / relay LT1083-based LV PS set at 6.3v (though I'm contemplating dropping this down to 5.5v and using it for the delay relay as well?) HV trans 9V trans

Thanks Kevin; just making sure cause I saw you mentioning 10 big ones earlier in the thread. Spritzer: I've measured only in Celsius... All in this post () this is all running outside a chassis and in an air con room set at 25c. It's definitely a heater ;p Sorry for the late responses.. Busy with chassis work at the moment. Almost finished the one for the square wave. Will complete that by next weekend. I'm trying to find some way to increase the height of my megatron amp chassis to fit my filament transformers under it... So will take longer with this - same with the time delay circuit. For others who are still building, here is a list of things I used that are different from the BOM. Hopefully it helps some folks? 1k cathode resistors instead of 1.5k 10R instead of 15R for PSU I tried 2222As instead of 3904s but I still run into problems here so they are removed (waiting for Kevin's proposed workaround while I get everything else in order) 1.7v LEDs instead of the 2.1v (may have remembered this value wrong, but it wasn't the 1.7v ones used in the KGSSHV) 330uF instead of 220uF capacitors - I wanted better caps but the shop only had this value closest to it. From what I read it shouldn't make a big difference; maybe just a tad more bass?

Yep, this is it. I bought mine from aliexpress with the option to customize - you just don't get the accessories then. (http://www.aliexpress.com/item/Aluminum-Case-of-HIFI-Tube-Amplifier-Sandblasting-Silver-Process-HIFI-DIY-Cutting-Holes-on-Upper-Cover/1302491615.html) Kevin I only have eight 1k cathode resistors. I hope I didn't miss any? Also, thanks for the schematic!

Joamat, I bought it. I'll pm you the link tomorrow that said I underestimated the size of my transformer... Going to try to mod the case by adding maybe some wood trim (?) to the base. Cheers Kerry! Got it Kevin, I'll look into getting a time delay.. Right now I'm just using a soft-start circuit. I'm not sure why but the DC offset of my right channel goes up to 450v momentarily but the left is fine... Maybe the time-delay will help there? I'm going to miss it (took it all apart) while I try to get everything housed - weekend just isn't long enough ;p Time for my rest... Been a long fruitful day - thanks to all for the support when I ran into issues! I'm also almost caving in and getting the rk27.... Having a pain in the butt moment trying to mount my own rotary attenuator. ><

Thanks guys for all the help! Especially Kevin for the recent Squarewave and now this For the record I did listen to music it seems smoother compared to my kgsshv. It also seems a tad bigger as i get a sense more reverb in some of the tracks, too. I'm also using 10ohm resistors instead of 15. Instead of 1.5k on the amp boards I'm using 1k. Thats possibly why the current pull is so high. The 2.5inch heatsinks on the kgsshv ps are between a very toasty 61-66c. My 400VA transformer hits up to 40c, while the EL34s are at 99c. It's stabilized quite well. Only thing is on power-on the offset momentarily goes to almost 450v before settling at those voltages. Want to see if I can do something about that because I want to leave a headphone plugged in. Edit: sorry missed your request Kevin. Voltage across my 10R resistor is around 0.77v and still rising - just really, really slowly. Spent 4 hours listening to it Now to fit the amp inside the case:

Took out the 2222a... Offset is down to 5v Stupidly... Right channel balance keeps climbing up... It's at 8 now... I'll do some research on an even higher substitute than the 2222a (I did put it the right way around)... Dang.. I thought 3x the capacity of the 3904s would be enough

Thanks for inputs Spritzer... Changed the 1968s and I'm still at -100v for offset. Will continue tomorrow ;p Edit: ok just measured the voltage from the plus line... It has dropped to 150v... Probably the reason why. I'm using a 22k resistor to drop the 450v line to 300v... Will check again to see what's causing the problems... Looks to be my PS... May need to remove my 2222A and have no current limiter?

I must have measured things wrongly late last night. Balance is around 3v but I'm getting -120v offset. Any ideas Spritzer? I think it may be my 1968s (the ones I'm not certain about). The led besides it turns on and off while the tubes warm up. Will swap those out and see.

Thanks Joamat You're still the first to build it! Really looking forward to heading home and testing it tonight. palchiu: It's the KGSSHV PS board... the BOM for that is also on that site.

Cheers Wachara and Eggil I can't wait to go back and hook it up to a source and it's only mid-day here Hopefully everything works fine then I can focus on all the other parts (so much more to go!)

Have you looked at Lil Knight's site? http://tee8tee4388.blogspot.sg/ I didn't follow all of them but it's a good starting base?

Cheers! Good luck to you when you power yours on over the weekend, too!

Just did a power-on test with everything on the floor. It powers up nicely! Left it running for about 10 mins... no sparks and all... pretty stoked! Late over here now... will do the sound test tomorrow - going to have trouble focusing tomorrow! Offset/bias didn't go above 3.5V for the time I had it up running. Some night pictures: