Laowei

^ Great tip. Works well.

Posting a FYI to those new to tubes. It helps SQ to clean the oxidation off of the pins. I use a stainless steel Dremel wheel and automotive Mass Air Flow cleaner (or 99% IPA) with Q tips to finish. Do not follow up with any audio fool stuff like Pro Gold, etc. Most cannot stand the heat and self destruct to a messy gooey crap that is near impossible to clean out of the socket later. Edit: this is for unplated pins like all 6S4As used with the KGST.

Well then you are a modestly grand chef, cooking with only the finest ingredients. Not to deminish in any way the debt owed to Birgir and Kevin. I would never had ventured into Staxland if not for the generosity of their work.

Very beautiful build Geoff. Eye catching aesthetics. Polished and modern look. I know it sounds great, asI have your boards. That heat sink is giving me ideas... Thanks for making your PCBs available to all. The KGST is spoiling me.

Beautiful work Kerry. Immense envy here.

I like your reasoning, JimL.

Thanks!

Great project JimL. Lots to think about. I was wondering how you arrived at the 100 ohm value for the grid stopper on the lower DN2545. I have used cascaded CCS's on tube plate loads in the past and most of the schematics used >1K. Thinking of adding a lower DN2545 cascade to the 10M90 CCS to my KGST. Wondering what value GS to use. Do you recommend the 100 ohm?

I've been running and monitoring the balance and offset of my KGST, and once set it seems to be very stable. It sounds great as is. I am thinking about just not using the DC servo at all. Is there a safety or other issue that I am unaware of if the servo is not used?

Impressive design and build Kerry.

Great info! Thanks all. When I was first assembling, the bushings wouldn't fit either the heatsink or 10M90S. So I wrongly chose the heatsink to drill out.

Thanks chiguy. I had the parts bass ackwards. It "worked" but not reliably. Will fix the other CCS bushings before they go too. The photos above were just thrown together to show the assembled parts. In the amp I used Arctic Silver thermal grease as you noted.

The photo is of the back side of the heat sink. The 10M90S was mounted on the front with a ceramic thermal isolator.

I looked into PEEK screws but jeez they are expensive and hard to get. Maybe it's time to pay up and do it that way.

While listening to my KGST last night, after an hour the fuse popped. Checking it out I found carbon tracks on the isolator bushing and heat sink on the output CCS to ground. Any ideas on why this happened, or preventive measures? With new parts, would assembly with a silcone dielectric grease at that interface help?

Very very nice buld chiguy! Where did you get the rear panel printing done?

I have cascaded plate loads on small signal tubes, and preferred the sonics to single device CCS, or resistor. I was planning on trying it on my KGST, but now my new 009s are imbalanced. Grrrrrrrrrr. Over on DIYaudio there are several threads about the 10M90S, and of particular interest was that cascading it with a DN2540 (not another 10M90S) gave best measured performance. I think that was from a Walt Jung article. Over at Gary Pimm's website he has some measured performance graphs of various CCS. http://pimmlabs.com/web/ccs_performance.htm Near the bottom are single device graphs. Locally he is a tech at Tektronics HQ (or was, haven't talked with him in years). He got me into CCS tube loads. Some of his later designs are more sophisicated.

Would cascading the output 10M90S's be on your idea list? Loving the KGST with my SR-009s (when the Stax are working right).

Yeah Spritzer, I suspect there may be something amiss with the diaphram, but just checking everything to be sure to isolate the cause. Listening again last night, the 009s twice developed a similar imbalance in the first hour. Shorting the jack pins with my fingertip again restored the left channel. Was then able to listen for several hours without a problem. We have had some drastic weather changes here -record cold with freezing rain and snow to record highs of 70+ degrees and dry within two weeks. Maybe that is a contributor, I don't know.... ATM, it does not seem catastrophic, the imbalance issue is only a nuisance.

That's an original way to boost the Black Friday sales stats......

Another data point..... After a half hour listening to my newish SR-009s last night, I started to get a channel imbalance. The left channel was slightly lower, maybe 2-3dB. I tried the Spritizer Thump, but that was unsuccessful in restoring. With the amp playing and the headphones on I pulled the cable jack out of my amp, touched the pins with my finger and reinserted. The left channel was now immediately restored. A while later I noticed a slight bit of static in the left channel that was not in the same place when repeating the track. I wiggled the tubes in their sockets and taking off the headphones, I cranked the volume control back and forth a few times. The cans played fine after that. I had not experienced either problem previously in the month and a half I have had the cans. Originally I broke in my KGST with an unmatched quad of Philips branded 6S4As, and only recently replaced with a matched quad of GEs and readjusted balance and offset. I'll try reswapping tubes and see if the problem repeats. Also, I'll clean all connections, and double check all solder joints.

Maybe the sticky side of a post it note? That's a fairly mild adhesive.

That's correct. The ones etched USA with grey plates are GE, and black plates are RCA. Those are often rebranded. There are also rare printed Japan manufactured 6S4As that have black plates. I am unaware of any European manufactured equivalents. Late edit: ECG Philips branded grey plates are a different internal contruction from the GE. The Sylvanias I've seen are rebranded Philips.

Very nice!

From the experience on my past tube amps, by habit on my KGST build, I tightly twisted all paired wires. The result is it is dead quiet operation. Now I am wondering how best to dress the wires between amp PCBs outputs to the Stax jack. Not sure what is best practice driving e-stats. Right now on my build they are twisted too, which would minimize capacitance in the pair. Scatter wired pairs would maximize capacitance. Maybe paralleled wires like the Stax cord would be the theoretical best?