mwl168

Very interesting! Looks like these new headphones are expected to be officially on the market in Japan by end of October.

Updated BOM and Mouser projects: For GR HV Dual - replaced the Fairchild uninsulated 7815/7915 with CJR insulated ones per wokstarr26 For HV Carbon V5 - replaced 182ohm offset pot tail resistor with 100ohm to get to 20mA current per Kevin

If you are talking about the GR HV Dual BOM, the P/N you listed is what's currently in the BOM. I do remember I first started the BOM using mica caps and later changed it. Sorry about that. The mica caps are larger in size and more expensive and I don't know if it offers meaningful advantage in this particular application.

No worries. Please do continue to report errors in the BOM and suggest more appropriate or better parts to use. Especially those capacitors, the size and lead spacing can be tricky and I am never quite sure what material of capacitor to use for some of the positions.

Checked the board today. 80-C320C104J5R (two needed) is for the servo position. 667-ECQ-E2105FK (one needed) on the BOM is for the 1uF/50V position on the board. It's 1.5mm lead spacing and rated 250V.

I purposely picked the 1.7V LED because that's what I built the KGSSHV with. If you read the original KGSS article Kevin published in HeadWize, the first and second stage LEDs will even each out regardless of 1.7V or 2.1V LED used. However, higher voltage LED on the output stage will bias the amp to run at higher current I believe. Hope Kevin, Burger or others can chime in.

I like to keep it simple. You cannot "flip the wrong switch" so to speak since the secondaries are not energize unless the main switch is on. The worst thing can happen is no delay to the B+ supply - everything is energized all at the same time. I've grown very used to this power on sequence - it's employed on the OTL speaker amps I've used for almost 10 years.

I am looking for on/off switch for 325vac secondaries on power transformer for KGST, SRX etc.. Anyone knows where I can source them? The highest voltage rating switches I can find on Mouser seems to be 250v. I think I need 350vac rating or higher. 1A or 0.5A should be sufficient for current rating. My plan is to have two power switches on my power supply. The main switch controls the primary windings of the transformer(s) and energizes the low voltage power supply/regulator and the tube heater supply. I then flip on the second switch after 30 seconds or so which connects the secondary windings for the HV supply/regulator. A simple, poor-man's delayed B+ control if you will.

Out of town at the moment so cannot check the board. But I believe these caps (80-C320C104J5R) are for the servo. There is another 1uf cap (ECQ-E2105KF) listed in the BOM for the 1uF position. Will double check when I return home.

Would it be better to keep the XLR and the signal wires as far away from the toroid as possible?

Does it matter what forward voltage LED to use so long as D2/D8 and D1/D9 match?

Thanks Birgir. I measured the footprint of the 100uf/25V caps on the GR HV Dual board and it can accomodate up to about 7.5mm diameter caps. So either should work. The one I included in my Mouser project and BOM is 6.3mm.

Thanks Insanity, Birgir and Pars for your help. I took a close measure and I believe Birgir is correct that the lead spacing for the 100uf/25V caps is indeed 2.5 mm. I changed the Mouser project and BOM to use Panasonic Low ESR caps with 2.5mm lead spacing and 5000 hours rating. hope this is the last time I am making correction to this part If anyone has stuffed the board please chime in and verify.

According to Vishay data sheet, RN60D and RN60C are the same power rating and same physical size. C is 50ppm and D is 100ppm. Both are rated at 1/4W @ 70C and 1/8W @ 125C. Not sure why Mouser lists RN60D as 1/4W and RN60C as 1/8W. 3N254 is listed in both the Mouser project and BOM for GR HV Dual. Will confirm the lead spacing of the 100uf caps in the morning and correct if necessary. EDIT: Thanks to jdineshk for catching this error. The 100uf/25V caps on GR HV Dual need to be 3.5mm lead spacing. I've corrected both the Mouser project and the BOM. I picked a different cap, 647-UTT1E101MPD for its low ESR rating. It's not listed as an Audio grade capacitor like 647-UFG1E101MPM which is a Nichicon's Muse series. Both caps will work. Also, 10M90S is back in stock at Mouser.

Thanks JimL for your detailed and thorough insight. This is really great information to have.

No particular reason from my own perspective. I've always used Vishay RN60D in the past and started using KOA Speer for the first time when I built my KGSSHV. From everything I read both should work fine. I do go for the better 50ppm spec whenever I can but I don't get hang over it. I do like the KOA Speer's blue color better although RN60D is much easier to use for me - I don't have the color coding scheme memorized. Just my 2 cents worth. I am also very interested in hearing others' thoughts of this matter.

Hi JimL: I came across this discussion at diyAudio while searching for information on tube heater power supply wiring. http://www.diyaudio.com/forums/tubes-valves/211731-heater-wiring-good-bad-ugly.html. It offers some observations about AC vs DC heater supply among other things. It also discussed the effect of reducing heater voltage and quoted a study done by RCA in post #27. I am very interested in hearing your thoughts and comments.

Thanks Kerry! For 400v secondary, the pre-regulator filter capacitors will need to be rated for at least 600VDC. I would also pay attention to the heat generated by the pass transistors.

I am looking for the drop-out voltage - the smallest possible difference between the input voltage and output voltage to remain inside the GR HV regulator's intended operating range. 360vac for 450VDC works out to be 50V difference. That seems very high to me.

What is the drop-out voltage of the GoldenReference HV PS? I remember one of the advantages of the GR HV PS over the KGSSHV PS is the lower drop-out voltage. This information will help to spec the proper transformer for the HV Carbon build.

I just checked and looks like 3N254 which is marked on the silkscreen on the GR HV dual board is too large correct for the GR HV Dual board but too small for the GR LV board. I will check the actual boards when I get home tonight and make necessary corrections. Thanks for catching this. EDIT: Also see Kevin's post below. 3N254 is correct size for GR HV Dual board. For GR LV Dual board, RS402L is one of the bridge rectifiers with the correct physical size. It's rated 4A/100V, Mouser part #: 583-RS402L. These observations are made by fitting the actual parts onto the boards.

I am whining but I am in US and just placed a large order with Mouser ($300 +) and I have to pay shipping. I guess that beats having to worry about VAT Also, Mouser does not carry LT1021, the 10M90S and C2M1000170D are back-ordered, and the aluminum oxide insulator 4171G for TO220 is not in stock at the moment. These are all available at Digikey.

Many thanks Todd!

All boards have been shipped as of today. Please let me know when you receive them. Happy building! EDIT 9/12: It's ironic, the padded envelopes I ordered from USPS showed up yesterday, same day I finished shipping all packages

Another batch of packages posted today (Wednesday 9/9), all US destined packages have been sent. More packages will be posted tomorrow. On track to have all packages posted by end of this week.