mwl168

fingers crossed

Thanks all for your response. I do plan on getting a DY294 in the near future.

Well, it cannot be officially a Mk3 really. Who knows what Stax might do next? So maybe a 007 Mk2.7 just to be safe?

More good news - I counted the boards and SeeedStudio actually sent me one additional set. I debated what to do with this extra set and here is my thinking right now: I'll keep the extra set as spare for now in case there are problems during the shipping to you all. When and if everyone receives their boards fine I'll then decide what to do with the extra set ( keep them or sell them). To make things easier and be fair to the GB participants, I'll deduct $1 USD from each set. Please let me know if you, the GB participants, feel this is a reasonable compromise between risk and benefit.

So I received two packages today and one of them is the 2SC4686A I bought on eBay from UTSOURCE. In the photo below are two 2SC4686A, one I bought from BDENT (on the right) and one from UTSOURCE (on the left). Can anyone spot any difference or discrepancies other than the batch code? All I have is a Fluke 112 multimeter. Is there some way I can test the two to see if the eBay ones are legit? Thanks!

Great news. The PCB boards arrived today. They look great. The picture below are the actual boards. I'll PM each of the GB participants with the remaining amount in the coming days and soon as I receive your PayPal payment I'll mail the boards out to you. This process will take a little longer for those overseas participants because I'll need to bring the actual package to the post office for them to determine the shipping cost. Please PM me if you have special request (shipping address change, custom declaration, etc.). Edit: actual board size: kgsshvampv16mini (amp): 182mm x 86mm kgsshvpsminifinalstn9360 (PSU): 176mm x 167mm Best!

Speaking of that, do we officially now have a 007Mk3?

Newbie question - does the sound of the electrostatic headphones go through a run-in period?

Hi Birgir: This is very encouraging to hear for me and very timely. I just received my SR-007 MKII yesterday, North America black version, serial # SZ3-19xx. First pair of Stax electrostatic can I own so I have no reference and no way to assess how it compares to the different versions of SR-007. This is my first foray into the electrostatic and I don't even have a proper amp to use - currently in the process of building a KGSSHV. All I have on hand is a SRD-7 (normal bias) hooked up to an old Quad 405. I'll be converting the SRD-7 to pro-bias (thanks again for your help) to serve as an interim solution. I eagerly await your findings.

Quick update; I received e-mail from SeeedStudio early this morning inform me that the PCBs have been shipped. The shipping tracking number does not work yet. Based on my experience last time the PCBs will arrive at US Custom first, once they clear custom, I will be able o track them. Stay tuned.

Thanks Birgir! To honor the overkill spirit, do you see concerns (or benefit) in using a separate, perhaps more elaborated regulator for the +/- 15V rails (bypassing the built in one on the PSU board)? I assume I will need to tie the ground of both PSUs together to make sure they are on the same potential. Just a thought.

I intend to use the ceramic pad together with the PPS shoulder washer Kevin suggested. This way, the transistor should be completely insulated from both the heatsink and the bolt used to secure the transistor to the heatsink. That being said, I am trying to locate sources for thicker ceramic insulators that do not require me to buy them in huge quantity. Better safe than sorry. Edit: Found AAVID aluminum oxide ceramic insulators at both Mouser and Digikey: 4170G: 19.3mm x 13.97mm x 1.57mm (L / W / Thickness), center hole is 3.68mm diameter 4171G: 16.51mm x 12.7mm x 1.778mm, center hole is 3.81mm diameter This should work well with either 7721-3PPSG or 7721-10PPSG shoulder washers. 3PPSG bushing is 3.18mm in length and 10PPSG is 2.41mm, both with 3.56mm outer diameter. Trouble may lie with the transistor's tab hole diameter which (based on data sheet of 10m90s and 01n0100d) can range from 3.53mm to 4.08mm.

Sorry, bought them off eBay - don't have part number. They are listed as TO220 insulator.

The ceramic insulators I bought are only 1mm thickness. Are they safe to use for the KGSSHV application?

Got it. Thanks!

I am sourcing the power transformer for the +/- 15V regulator for KGSSHV. Can I use a dual secondary transformer configured as a center-tapped transformer by joining one wire each from the two secondaries to form the center tap? Anyone sees concerns of doing so? Or better yet, anyone has a Mouser part number that you recommend for this part? Thanks!

It was the S5277G I was not sure about. Thanks!

S5277G and Z1100 diodes are both obsolete. Can someone recommend current production replacement? Preferably Mouser stocked parts - I am about to place a big order with Mouser for a KGSSHV build. Thanks!

Thanks Craig and all. This is very good to know. Kevin: Do you mean 7721-3PPSG as this one ? http://www.mouser.com/ProductDetail/Aavid-Thermalloy/7721-3PPSG/?qs=sGAEpiMZZMu6TJb8E8Cjry%252brZ0Ynb0Cb Mouser part number 532-7721-3PPS

Thanks Birgir!

So essentially move R104 to between C108 and the bias pin of the output jack?

Good point about the thread stripping. I assume the standoffs do not need to be peek material?

Apologize for the ignorant question; Does one need to use peek nuts with peek screws in this application? The only reason I ask is the cost - those peek nuts are expensive.

Thanks Birgir. I'll have to fabricate it on a perf board then. To confirm the right way to convert the SRD-7 to run on Pro bias (580V): 1. I disconnect the factory bias portion of the original circuit after the 150K resistor and neon bulb. 2. Construct the bias circuit of the SRD-7 Mk II in post #6 but skip C108 and change R104 to 4.7M. Thanks again for your help!

Thanks Birgir. Do you still have the custom PCB you made for this modification available? I checked your website but did not see it.