mwl168

I'll post a pic when I get home to show the heatsinks I am using - they are quite big but still not up to snuff. If you are running the multiamp around the same current setting I am, I suggest you consider larger heatsink than the one you mentioned in your post Another problem with large heatsink for the GR LV is that they may interfere with the terminal block for the AC wires. When I come to case the amp, I very likely will go with Kevin's suggestion and mount the transistors on the chassis.

Also consider the fact that the zeners voltage will rise as they get warm.

Thanks Kevin. I did not think of the variac idea, I'll give that a try. My toroid has 22v secondaris so the voltage drop on the pass resistor is quite high. I did test the PS without load and the heatsinks didn't even get warm.

Hi Kevin: How hot do the heatsinks on your GoldenReference PS get at this condition? I just tried running my SUSY Dynalo with the GR PS running on 18V rails and about 18mA per output mpswx6 devices (360mV voltage drop on the 20 ohm emitter resistors). I was using the same heatsinks as shown on your pic but they got too hot to the touch and I had to put much larger heatsinks on. I am a bit surprised.

For my own benefit - do those 680uf caps need to be 450VDC rated? Two each are in series so would 250VDC or 300VDC rated caps work? I recently changed my KGSSHV PSU to use 1200uf/250VDC caps in the 680uF pre-regulator positions. they are both much smaller in size and much lower cost. I am running 400V for my KGSSHV and the voltage after the STTH512 rectifiers is about 450VDC.

R5 and R6 set the current of the 4686 output devices. I have the off-board heatsink version and I use 100R in those positions which sets the current to about 10mA. With the on-board heatsink, the current needs to be reduced to prevent overheating.

you can use 71-RN60D1743F for the 174K positions. This part has proven to work for many and is in stock at Mouser.

Very nice! Did you specify the size to fit your layout? How do you plan to secure them in position? Also, what capacitors are you using for the .47uf/50V positions? Any partcular reason you pick them over the ceramic caps?

Thanks. Very good to know.

Thanks Kerry. Onto the headers and wire housing for the servos on Carbon V5 board; the Molex 22-11-2022 part in my previous Mouser project/BOM and jdineshk's Mouser project does not work for me for the position next to the 4N25 - it collides with the 6P DIP socket. I've updated my BOM and project to use 3M 961102-6404-AR which is also a 2.54mm pitch. Based on the data sheet this part should fit the board. I cannot be 100% sure without having the actual part on hand to try. Hope others can chime in.

Thanks Wink. I did not consider the toleance of the meter. I will check and see what range adjustment my meter offers. Any recommendation of meters that are more accurate and has more resolution without breaking the bank?

Yes, the missing knob is a long story. Basically the shaft of the knob just snapped when I went to turn it on one day. Probably exceeded the maximum turnning velocity and torque combination specified by the manufacture. So please treat your meter gently. Took it apart but no replacement part available from Fluke. I complainted and they were nice enough to offer me a new one with special discount. The meter still functions fine, so I got a Torx 27 socket and use it as the knob. Works really well and has the added benefit of preventing unauthorized use of the meter.

Double posting here but I had my GoldenReference LV Dual running which is built with board from the Carbon GB. The regulated output is rock steady and even though it shows +/-14.98VDC it's within the range of the LT1021-10 tolerance (0.5%).

Another GoldenReference LV Dual lives! This one is, obviously, built with the the board from the Carbon GB. Had it running for 30 minutes for testing and the regulated voltage was rock steady as kevin mentioned. I hand-matched the resistors that determine the output voltage so I am annoyed that I am getting +/- 14.99VDC. I blame it on the LT1021-10 reference. I got the 0.5% tolerance ones so the result is within range (why can it not error on the other side?). I'll decide later if to go through the trouble of desoldering the change the resistors to get to +/- 15VDC. The heatsink is more for show. I plan to use this one to supply the LV for the HV Carbon. I doubt it they'll get any warmer than room temperature. Thanks Kevin for the great creation. Edit: forgot to mention, I used 2.1V LEDs and smaller bridge rectifiers. Just happened to have these parts on hand and the under-sized rectifier's spec'ed output current works for my forseable applications.

Hi Pars and insanity: I chose the caps in the GR LV BOM for no particular reason other than personal preference. I always liked the Silmic caps. However, the longer life spec should be a major factor to consider as well. I have added the caps Pars listed in both the Mouser project and BOM as alternatives. Size wise, they all fit the board fine. The 220uf Silmic is a bit taller.

Hi George: I received my Mouser order today and you are right - the QYX1H474KTP is quite large in size. I am not sure if using film caps in these positions has any benefit over using the MLCC capacitors. I picked film caps because I generally prefer them over ceramic caps. For better fitment, I updated the BOM and Mouser project to use MLCC caps (Mouser part #594-K474K20X7RF5TH5). Hope others more knowledge about the circuit can chime in which caps are better for these positions and why.

I updated the BOM and Mouser project for the Carbon V5 to use Vishay RN60D 174K resistors for the two 175K positions. The correct part to use is Mouser part # 71-RN60D1743F. It's a mil-spec resistor that is actually 1/2W even though it's listed as 1/4W. The previously listed Xicon 174K resistors are rated 1/4W and not sufficient for these positions. Sorry for the oversight.

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.