insanity

I didn't solder the big SOT223 tabs. Is it recommended to do that? Thought of easier removal in case of a problem. I agree that there might be a bit too much solder on the other SOT223 pins, but being small they are difficult to solder. Considering the general amount of solder used on the other joints, I was aiming to achieve "ok" joints as seen here: The iron is around 370c or 430c. Don't remember exacty. What is recommended? @Kevin For the HV lines, I use silverplated wire with teflon, they tin very easily and I doubt that this was the problem. When I removed the wires from the terminal blocks I did not have the impression of not tightened screws. But it's hard to exclude of course.

What brand is that? The ones I used are rated 400V. As discussed earlier in the forum there are no terminal block with higher voltage and the same size.

Looks like I have found the culprit today. There was some charring on the B- header of one amp board... See for yourself. To me it looked like there might have been a bit of flux from the B- pad to the trace adjacent to it. I cleaned all the board on the back side as well as possible, but how the f*** was I supposed to get that flux under the header? Do you guys always soak the boards on both sides? But even then, no brushing possible there. The good news is that the transformer is alright. Unloaded voltages are fine. The bad news is that the amp board is trash (I got two spare boards luckily). Unfortunately the two GRLV boards don't work properly anymore. I guess I will have to replace the amp board and replace all the active parts on the GRLV. I still have to check the other amp board. Hopefully there was no damage to it. The GRHV seem to work properly (without load). FYI the amp was used approx. 50h before this happend and ran about 15min on the day it happened. What should I do to prevent this from happening with a new board and the other board?

Ok then I think I have a bigger problem. I took out an LV board and tested it out of circuit without a load and it measured way above the 15v it should have... This sucks... Looks like a major investigation...

No I have not yet measured the transformer unloaded. I is too late in the evening to start working with live voltages... ;-) So far I have only removed the toroid and measured the windings. A preliminary visual inspection of the amp boards top sides, has not revealed anything. I will have to do that another day. Btw: do you happen to know if the GRLV boards need a minimal load to properly regulated the voltages?

I just suffered a pop and all the lights of the amp went out. Seconds later I cut power to it. Checked the fuses in the IEC, 2A fuses were intact. Then I suspected the toroid simply because all the lights were out, and not just HV or LV. Removed the Toroid and measured all the windings. Dual Primary measured 4.5ohms each. So 9ohms against 230V = 25A WTF. Probably wasn't long enough for the fuses? Secondary HV@330V measured around 55 to 52 ohms for the two windings = 6A... LV@18 measured 1.5 each = 12A... I didn't measured the resistance of the toroid before, but when I built the amp voltages were good. If I'm not totally brain dead this looks like a burnt through transformer. Confirm? Transformer specs from toroidy were: TS200VA PRI: 2x 117V SEC: > 2x 330V @ 250mA > 2x 18V @500mA > 16-0-16V@500mA forget this winding, it was not in use. Any ideas?

I am looking forward to seeing pictures of your build. Yes, onboard means heat sinks on board.

I though Birgir said it doesn't matter as long as it is positive and the stax amps do it too? But certainly interesting to hear if the servo has an influence.

Brexit No. 2. lol.

This is the first finished y3 I see on this forum. Can you elaborate a bit on the sound? How much is the approx. cost in parts? Some chips are around 20$ I think.

your welcome. Glad you could solve the problem yourself.

No problem. At least you now know where your problem originates.

From experience it is always good to have at least two headphones and two amps to compare, otherwise it is often impossible to say, if the problem originates from the headphones or the amp or even the source. Maybe you can borrow another headphone from someone? Another possibility to exclude the source as the problem is to switch the cables from the source to the amp. I dont know if its possible with the output of the srm007tii but if there is a cable from the stax jack to the board, you could switch channels there. If the problem remains on the same side, its the headphones, if it switches the side, its the amp.

What do you prefer? I also have the 007mk2.9 but an older 009. I prefer the sound of the 007.

I have the opto servo running. You have tot set offset to about 20V and when you engage to servo it will go to 0. ref:

I'm also giving the "new" 007 way more use than the 009 recently. I love it with the carbon too!

And how do you like them sofar? Do you still use the 007 more?

@mwl168 What kind of insulating washers are you using for the 10m90s? They look unfamiliar. What kind of heatsinks are you using? What is their thermal rating?

Yeah the bias is fun to touch... Happened to me once aswell. Btw: I love to see how others progress with their builds.

I just wanted to give a bit more insight into my running carbon. I am running at 400V and 20mA per line. Total consumption of the amp in my configuration is 93W during normal operation. In the first few seconds it is up to 190W and then drops. The transformer is almost dead silent during normal operation. If I go really close with one ear, I can hear a very slight hum, but nothing to care about. During turn on there is a short hum which fades as the current draw drops. I use a custom transformer from toroidy with has the following specs: TS200VA PRI: 2x 117V SEC: > 2x 330V @ 250mA > 2x 18V @500mA > 16-0-16V@500mA - flexible leads - 40 cm long The reason for the 2 LV secondaries was stated before. As discussed previously I added thermal paste to all interfaces, now including the angle bracket to heatsink interface. I think to longest continues run time was 2-3h and the heatsinks were still touchable by hand. The amp boards clearly produce more heat than the PSU boards (heat gradient from front to back of the heatsinks). I use a 3U case from modushop. I listened with the 007 and 009. After a week I still think that it suits both headphones very well, which is a surprise considering that the headphones are quite different. IMHO the 007 was better on the conventional KGSSHV while the 009 was better on the KGST. I think the conventional KGSSHV (450V, 4686) provided quite a large soundstage which is almost too large in combination with the 009 (which provides a huge soundstage by nature) while the treble is a bit too harsh as well. On the other hand, the KGST provides a smaller soundstage, a bit less detail and a bit a softer sound, which suit the 009 much better. With the 007 it was just the other way around as the phones are more mid pronounced and have a smaller soundstage by nature (btw I love their sound too). Therefore I think it is surprising to find that the Carbon fits both phones well, although I cannot give a direct comparison between all amps yet. Just to mention: I use the ressonessence invicta as a DAC which provides the possibility to switch between various filters. I did not change them for the two headphones. I just used my favorite one, I have also been using with the other 2 amps. I would love to hear what others think. Also if you agree with my impressions on the KGST/conv. KGSSHV/007/009 opinion.

Depending on how much listening time I get during the week, I could give some impressions on the weekend. @ johnwmclean: I know.. But there was no other option. I don't even know if I can keep the position of the powerswitch or if I need to move a bit more to the center. I'see when I design the front panel, which will probably be similar to the others, as I don't have any other ideas. I have a question to those who have experience in building amps with offboard heatsinks. So far I only used thermal paste between the transistors, ceramic pads and angle brackets. I haven't put any between the angle brackets and the heatsinks. Would you recommend it, or is it rather unnecessary?

yes they are the ones from the GB.

I changed the resistors and it works like a charm. Just listened a few minutes with the 007A. Am I the first one from the GB who has it running? I wonder if others need the change the resistors too. With 150ohms I could just reach +20V, but I think it wouldn't reach down to 0. So maybe for those who have not started yet, order some 150ohms and 120ohms resistors just in case.

I have assembled all the parts and it everything works but I have one problem. HV Voltages are fine 402V -402V. Offset was around 200V to start with for both channels, but I cannot get offset below 70 / 80V on both channels. The current sources are set to 1V across the 50ohm resistor. I cannot reach the +20 requires to engage the servo. What shall i do? I am thinking of replacing the 182ohms resistor with 150ohms.

Yes exactly. Do you have any experience/comments on that? I have been using it for my XLR interconnects.