mwl168

That's what I intended. I thought it would keep things simple. Kevin can clarify, but I figure the whole purpose of the V5 is so we can obsolete V2 and V3 boards. I personally will be very surprised if someone would want the V2 or V3 board instead of the V5 but I don't feel right to not give the participants the option. Please do keep in mind, smaller quantity of boards will drive the per board cost high. To avoid further confusion, I like to stick to what I proposed - "No action is needed from you if you agree with this proposal - I will switch your order to the V5 board. Please respond to this thread if you prefer to stay with either the V2 or V3 board."

With the new development of the KGSSHV Carbon V5 board, I like to propose that the GB switch to use the V5 board and obsolete the V2 and V3 boards. V5 board basically allows the builder to choose between the original or new servo using the same board. For more details please read Kevin's posting #4970 and subsequent discussions over at the KGSSHV main thread. This will effectively drive down the amp board cost for both the V2 and V3 boards but definitely more so for the V2 boards. No action is needed from you if you agree with this proposal - I will switch your order to the V5 board. Please respond to this thread if you prefer to stay with either the V2 or V3 board. I will be posting the details of the quotes I obtained for the various boards soon. It's been a busy weekend for me and I need to make sure my calculation is correct.

I asked Kevin the same question when inspecting the board. Here is Kevin's response: "the 10 ohm thing is the krell way of earth ground to power supply ground. very few if any will ever use it. but its there just in case." Nice build IKong. What voltage and current do you have running with the PS and what's the temperature of the MJW21193?

As promised, I want to share the two responses I received from EMB PCB after I notified them of the PCB quality issues that were reported to me (see posting # 12). For space reason, I did not post my complaint to EMB but it's basically a copy-and-paste of posting 12 for the most part. While I don't expect a manufacturer to be perfect, I do expect a manufacturer to be sincere and proactive in addressing issues arise. I do not plan to request quotes from this manufacture for the HV Carbon GB based on our collective experience. Please feel free to share your thoughts. Thanks! "Hi Michael, Here are our responses to your questions: 1. The reason of solder came off from the board while de-soldering could be the overheated soldering iron or repeatedly soldering. 2. Please advise which holes you mentioned are too-small or over-plated, we manufacture boards based on your gerber files, and the through hole tolerance is +-0.08mm, so if your hole designed exactly 100% fit to the parts, the tolerance might cause the problem. 3. & 4. The friction between boards during production or packing might cause the visible copper on the boards, as well as the silkscreen smudged. But as long as these issues don't bring any malfunction to the boards, we'll count as qualified boards. 5. Please clarify which holes you need are NPTH but not PTH. The default of manufacture is PTH, unless you have specially mentioned (either in the gerber files or emails) which holes you need them to be NPTH, the holes will be all plated. Please refer to the attached file of our trading terms which I have send to you in my first email. About your question #3&4, please see item 13; also, please kindly read item 14-15, we have certain time restricted toward the customer complain. We checked the record that your package was received on 5/27, but now it's already 7/15, almost one and half month passed, so now we could only help and solve your doubts, to prevent any possible caused misunderstanding maybe in next business. Thanks," "Dear Michael, We believe the professional skills that your person have, but there are still some possible reasons caused that solder came off during the soldering and de-soldering process, I know our quality would become the first suspect you have, however, the SMT line we have is also using the boards we made, and this kind of question never happened before. Also, other customers' boards which we manufacture at the same time(same production line) as yours are all fine, we didn't receive any complain letter about this issue. As to the holes, please help to provide photos showing exactly which holes on which boards are not made base on your gerber designed, and you can attach pictures showing parts that solder came off as well . Otherwise we cannot understand clearly the questions you have now. We'll do our best to help you clarify where the problems come from, even though this order is already passed the warranty time. We have faith in our quality and price, but I know sometimes there might be some mistake during the production, that's why we didn't escape from your first complain email. We're sorry to hear that these boards didn't fit to your expectation. But now all we can do is to examine the photos and try our best to trace back and clarify all these problems. Thanks,"

Stax is believed to have altered the 007 Mk2 driver sometime last year which significantly improved the sound. Check Birgir's posting# 9573 and subsequent discussions.

Attached spreadsheet of final order entries and total board count in the first post. For the single PS boards, quantity of 2 indicates the participant will receive 1 left and 1 right boards (or 1 plus and 1 minus for the LV).

Soniccraft carries the Mundorf HV+ caps: http://www.soniccraft.com/index.php/mundorf-mlytic-hv-c-23_318_362?osCsid=20df84e13rd2696naqengmbio1 Not sure if there are other US distributors.

This GB is officially closed as of 7/12/2015. Due to the changes Kevin made to the PS boards today, it'll take a few more days for these boards to be checked before I officially request quotes from the fab houses. I hope to have information on the cost of the various boards to share in a week or so. I will post an image of the spreadsheet here for all to review.

While I do like Mundorf's film capacitors (no experience with their electrolytic caps), my vote is to let builders have more freedom to use capacitors of their choices and not be limited to a single choice.

Indeed the V2 and V3 board numbers have changed drastically in the last week or so. I won't know the cost difference until I get the new quotes based on the updated quantities. That's very interesting and good to know. At the end what we really do care is the quality in relation to cost. Wonder which china fab house PCBNET uses?

The list of GB participants and number of boards seem to have stabilized. I like to finalize the counts in the next few days and request new quotes from the fab houses. Please double check and confirm or make any final updates to your record on the spreadsheet by end of day Saturday, July 11. On Sunday, July 12, I will officially close the GB, lock down the counts of the various boards, post a snap shot of the spreadsheet on this thread for your review and proceed to request final quotes from the fab houses. Once I receive the quotes, I’ll make a decision which fab house to go with and provide the cost of each individual board and calculate the total for each participant. Cost for each board will account for contribution to Kevin’s boards and cost for packaging materials (not shipping cost). Given the number of boards, I expect this to amount to around 25 cents per board. I very much appreciate Sorenb’s and all your kind offers to pay for my boards. Respectfully, I like to decline and pay for my boards. A few words about the fab houses; I requested quotes from one US fab house (PCBNET) and three overseas. PCBNET quote is, not surprisingly, quite a bit higher than two of the overseas quotes ( I have not used PCBNET in the past but they come highly recommended. My interaction with them so far has been encouraging.). The margin of difference in cost does narrow as the volume goes up. Surprisingly, one of the quotes from China is actually about 60% higher than that of the PCBNET. The cost difference will amount to a few dollars per board for the larger volume boards but can be substantial for the small volume boards. Please do feel free to share your thoughts and/or preference in this matter by responding to this posting. Please let me know if I missed something. More to come. Thanks!

This is the Kemet ALC cap I used for my KGSSHV PS, 450V/680uf. They are 8cm tall. two pin snap in. http://www.mouser.com/Search/ProductDetail.aspx?R=ALC10A681DL450virtualkey64620000virtualkey80-ALC10A681DL450 Cannot speak to the 550V caps though.

Thanks for the kind offering. I appreciate it. No need to cover my sets but I don't feel right charging Kevin for the boards myself. I second the proposal that we cover Kevin's boards. It's voluntary of course so please PM me if you don't want to take part. The numbers of boards have changed quite a bit so I need to get new quotes from the fab houses. I am going to wait a few days for all the participants to have the chance to update their numbers. Once the dusts are settled so to speak, I'll get new quotes and post the information here. To be clear and consistent, please use number of boards as the unit NOT SET. For one pair of the amp boards, please put down 2 as the quantity. Same applies to the single PS boards.

Many thanks to sorenb for doing this. I have not found time to figure out how it works. It's a great help.

Updated first post to include Golden Reference LV and Bias board options and GB details accordingly. New participants please read the first post in detail and be specific with your request. Thanks!

Ouch!

I'll add Golden Reference LV options to the GB, both the dual (goldenreferce3.zip) and singles (goldenrefernceplus4.zip and goldenreferenceminus4.zip). Help will be needed to trace these boards, I may not have time to trace them all before placing the order. Again, keep in mind that board cost will be high if volume is low. I'll also add the NB board option but I don't think Kevin has posted the Gerber file yet. It's a stand alone board that provides both pro and normal bias.

Updated the GB participants details in my first post, added one column for the Carbon V3 amp board and updated the numbers based on the recent posts. Please check and let me know if correction is needed. Quotes continues to come in and I have some ball park figures for the board cost but they will change because of the fluctuations of numbers. I traced the single fat boards today but not the skinny ones yet. Again, I cannot guarantee there are no issues in any of the boards included in this GB, any help with tracing the boards will help identify potential issues so Kevin can correct them before we have the boards fabricated. Thanks!

The only difference between the V2 and V3 board is the addition of the opto server for the V3. The rest of the circuit is identical between V2 and V3. I'll add a column to the table on my first post to track those that opt for the V3 boards. I had asked for quotes on small quantity of the V3 boards in anticipation of this. I have a few caculations to do yet but at a quick glance and given the volumes we currently have, the V3 board will likely be 2x the cost of the V2 board. This is more due to the massive quantity ( > 120 ) we have on the V2 boards. Same will likely apply to the single skinny PS which we have much lower volume than the other 2 PS options.

I have posted the GB participant details as of July 2 in my first post of this thread. Please check and make sure I got your information correct. Sorenb has asked for the GoldenReference LV boards and separate Bias boards. Are there others that are interested in these boards? Also, I have one inquiry on using the V3 Carbon board. I have visually traced both the latest Carbon V2 and V3 boards that Kevin posted on 6/30 (someone(s) else really need to trace them, including the PS boards, to make sure I did not miss something). However, we know the V2 circuit has been tested but not the new servo on the V3. I am inclined to use the V2 board for the GB but am open to make V3 boards for those daring J Please bear in mind that the cost of the board is in direct correlation with the number of boards ordered. I am working on getting quotes from fab houses and hope to provide updates soon.

Congrats JimL!

On my Atmasphere OTL amp, there are two power switches. One powers the first stage tubes (6SN7) fully and only the filament of the output section tubes (6AS7). The second one supplies the B+ to the output section 6AS7. The procedure is to turn on the first switch and wait at least 60 seconds before turning on the second switch. The switches are wired such that the second switch is only effective when the first switch is on. Turning off the first switch cuts off the power to the second switch. Seems very similar to what JimL described about the T1. It was implemented this way to preserve/extend the life of the 6AS7. It's manual but it works very well for me.

What did you not like about the box? I am contempating getting a smaller one for my Carbon build.

that's a great idea!

I have been informed of a few PCB issues from a few GB participants in the last few weeks and want to bring this information to your attention. Please do let me know if you run into similar issues or other issues which you believe are related to the PCB. I like to file a complaint with the manufacture with a summary of the issues and get their response. This manufacture (EMB PCB) was recommended to me by a forum member and this is the first time I’ve used them. I should also note that my order with EMB PCB includes other PCBs other than the KGST ones. Here is a summary of the issues that have been reported to me but they are not specific to the KGST boards: 1. One report of an entire island of solder came off during de-soldering with solder wick 2. Two reports where a few through holes were either too small or over-plated making inserting the parts difficult 3. One report of a couple of spots on the PCB where the copper is visible through the solder-mask maybe the solder-mask didn't take properly 4. One report where one corner of the silkscreen appears smudged 5. One report where 2 through holes were completely plated an need to be drilled open. For issue #2, I tried inserting parts in the same spots on the board I have and did not encounter problem. So this appears to be a QA consistency issue. I should also mention that sorenb who encountered the problem with the solder island coming off has built a working KGST amp with the boards he got from this GB. However, the solder island should not have come off so easily. Again, please let me know if you run into issues or if I have missed issues that you have reported to me. I apologize for these problems and will share with you what response I receive from the manufacture when I file the complaint. Thanks!