jokerman777

Hi, back with a load of dummy questions in the midst of building it 🙂 (Again I got the boards and chassis from GeorgeP which I believe are same as Kevin's original design). PSU Front Panel Power Indicator: There is a circular cutout in the center of the PSU front panel, I measured and diameter is roughly 19mm, any recommendation on what part to use here? I suppose it will be a switched light, although the IEC inlet is already switched? I think I found some push button with LED on parts express that should fit. Grounding: If I'm understanding the layout correctly, I believe mains earth/XLR input ground/Amp chassis are connected together as chassis ground, and can be connected to the circuit ground via the on board switch. It seems like the PSU chassis is not grounded? Also there are two GND output pads (electrically connected on board) on the PSU board and multiple GND pads on the AMP board, is it recommended to or not to pass both GND output points from PSU to the amp? don't how much it matters but passing both sounds like ground loop to me. Transistors Mounting: With AAVID 4171G thermaloy can I get away with not applying thermal grease? Anyone has the success of using nylon screws for mounting the transistors? I got a bunch of them and thought they will give me a peace of mind when it comes to insulation but second thought they are not as mechanically stable as metal ones. Components placement: On the amp board I figured these are probably better to be soldered on the back of the board (facing top): LEDs, power resistors, trimmers and test points, are there any other components that might run warm which are better to be soldered on the back? Thanks in advance for your opinions!

Thanks for the info! Yes I used Toroid Inc once a few years back and I think it was very pricy for what I asked for - I think their one-off pricing is based on designing and making initial prototypes for businesses, which is understandable. I been using Antek whenever something off-the-shelf fits the need, unfortunately just not for a T2. Guess I will reach out to toroidy and mueller-rondo in EU for a quote then. Tricky part is I already got the chassis and I think Kevin designed them for the SumR ones originally where the diameter of each trafo can't really exceed 3.6", probably pretty marginal for their ratings and I'd need to spec that too, this might further reduce my options. (no lundahl, EI, C core etc..) btw I contacted Toroidy once for something else and I got the impression that they don't have 115V or dual primary winding trafos in stock in general.

That's unfortunate.. I been planning on getting a set of power transformers for T2 build from SumR. Any recommendation on other good winders within North America who'd do custom one-off toroids? Other alternatives I heard mostly are from EU, prefer not to get heavy irons from overseas unless running out of options....

🙂Got the amp finished and running fine for more than a week by now, finally got to experience some ES setup. Many thanks for all the helpful advices I received here and there on the forum, thanks to KG for the great design and also Birgir who spent extra time clarifying a lot of my confusions in addition to supplying the partial kit. For offset I ended up paralleling a couple of 10K resistors on the back of the board to the R in series with the trimmer, and with that I'm able to trim the offset down around 0. For the currently back-ordered parts: I used STP8NK80ZFP instead of FQP8N80C, and 5027 instead of 5026MOS and it has been working fine. 5027 has higher capacitance but I suppose it matters less when it's only used in the PS regulator here.

Thanks, it shows back-ordered again on the UK site now, back to living with 5027s

Tried to order some but seems like they don't deliver to US address 😑

I finally gotten it put together and powered it on for adjustment, high and low supply voltages are fine and all LEDs lights up. I observe the following however: -The balance adjustment I can get it drift around 0V but likely only down to the accuracy of +-0.XV at best -The offset adjustment I can only trim the pot all the way down and get +25V and +35V on each channel, it won’t go lower and seems to be slowly drifting upwards over time. -Bias TP measures 600V instead of 580V (I can maybe try other zeners to adjust this) I built it with A1968 CCS, testing is done without headphone plugged in nor is servo connected, unit was on for about 30mins when doing measurement. I suppose at least this DC offset suggests I'm doing something wrong here? I cannot trim it around zero and nowhere near. Also before any adjustment I checked that all the pots are in middle position, when I turn the amp on the first time DC offsets are as high as 150V - was that an extreme value for the offset pot? Edit: msged Birgir and was told changing the resistor value in series with the offset pot should do it and rest is fine, sorry for dumb questions bombing

Thanks! I will give them a try and report back, tho won't be able to find out till after a good while. 😀

Hi, I'm slowly sourcing parts for a T2 build and wondering if 2SA1627 will be a fine replacement for the 2SA1486s that are not mounting to the heatsinks (those I will just use KSA1156)? Seems to have mostly the same ratings other than only 1W of maximum dissipation, would make my life easier if it works comparing to using the SMD STN9360... Thanks! 🙂

I was doing a little bit of layout planning on my KGSSHV build and have this newbie question about grounding.. I will be building it out of the partial kit from Mjolnir audio, the on-board heatsink version with 450V rails, other than the original PCB set I think I'm also going to make a small breakout board to distribute power from the PSU board to the two amp boards. I have the following 2 grounding configurations in mind and wonder which one is better? Config A both the input signal ground from the XLR jacks immediately return to earth ground, then they meet again on the breakout board. Config B the input signal grounds keep separated until they met on the breakout board then return to earth ground from there. In my mind config A has the shortest ground loop between the source and the amp; Config B however is more of what star grounding is like? Any input or suggestion much appreciated 🙂 Grounding A: Grounding B:

Very helpful info, thanks Simmconn! I was searching for high voltage depletion mode MOSFET and IXTP01N100D indeed came to the map. I kinda do want to get the amp running before the of expected shipping date of those transistors which takes months. Been sitting on a pair of X9000s that I can't listen to without an amp for a good while now. I don't know if I'm doing this correctly I took a rough guess of the current running thru the 10m90s based on its datasheet. And seems to use IXTP01N100D for replacement I should find the Vgs that gives the same Id and then get the Rk value from Vgs/Id? Tho the figure in the datasheet doesn't have the resolution for this application 😵

Thanks, looking at the datasheet I think the KSC5027 jamesmking suggested might be a better fit and pretty legit replacement for KSC5026M? the specs looks like they are the same thing other than the 5027 can handle more dissipation (I only know how to read numbers so I can be dead wrong). TO-220 should fit into the TO-126 footprint, base and emitter pin are swapped so just need to flip it when soldering it in? I'm also curious what makes the 10M90S special to be a current regulator IC? The datasheet label the pins as G/A/K (gate, anode, cathode?), is it basically a MOSFET?

ohh my bad I mean the pads for the 4CP-601 not the 2500. But cutting your 4 gang board is a good idea too, thanks!

Hi Pars, wonder what pad size do you use for the 4CP? I'm going to make a board for 2CP. Thanks! 🙂

Thanks for the advice! My mouser updates tell me that (which is probably not new info): STN9360 a batch of production is done and is on the way to warehouse now so I guess they will be back in stock soonish. 10M90S says production in process so despite long wait time probably will come back. KSC5026M it says "Production Issues Reported - Delivery Unknown" which doesn't look good 😅 I wonder if I can do 2SC3840 instead? it's in the PSU and for no reason and understanding I thought I need to either use 2SC3840/2SA1486 or KSC5026M/KSA1156 in complimentary pairs... but since 2SC3840/KSA1156 is what I can get realistically... btw I think I'm going to use STP8NK80ZFP instead of the obsolete FQPF8N80C, at a glance the specs looks very similar other than a different Id rating and speed.

New to ES headphones and am currently waiting on these back ordered parts to build a KGSSHV, trying my luck here in case if someone knows any reliable source having them in stock or has spare ones to get rid of. 4 x STN9360 3 x IXCP10M90S (TO220) 4 x KSC5026M

My ignorance but I'm curious what's the purpose of C14, C15 and R11 at the output of the power amp in this configuration?