sorenb Posted December 26, 2015 Report Posted December 26, 2015 41 minutes ago, kingofsnake said: Happy Holidays everyone.. Happy to report i have my CARBON up and running for some 6 hours now. I have set the current output to 17ma approx. I attached some digital thermometers to the Hottest part of the 2 heatsinks and monitored the temperature. 35 deg/c +/- 1 seems to be what they have settled at over the last couple of hours. I zeroed balance/offset to practically zero, the offset drifts a volt or two but much lower than any previous KGSSHV BUILDS. I have found that having 2 headphone outputs makes balance/offset adjustments easier. This amp drives my sr507/009's easily with plenty of range left on the volume control. Speaking of which i was thinking of a relay based volume control such as this http://diyclub.biz/catalog/product_info.php?cPath=1_248_85&products_id=410 does anyone have any experience with these? any advice on alternatives would be appreciated (i would rather something pre-assembled). I won't go into what it sounds like (i will leave that to those more capable than myself at explaining such things) But i will say i have put my other amps in the closet for now! this thing just sounds superb. As always many many thanks to KG and all those that make these projects possible. Any questions you have i shall do my best to answer them. Usual rules apply......If no Pictures.........Then it didn't happen!! So here you go. By the way i think i over-did it with the Heatsinks in the psu and could well have gotten away with a single heatsink for the HV +/-. Con grats Thats a tiny Carbon ;o)
kingofsnake Posted December 26, 2015 Report Posted December 26, 2015 Thank you sorenb. I could have put the amp pcb's in a smaller case but i thought i would need the extra heatsinks for when i turn the current up to 20ma. Also i have room to possibly accommodate a relay based attenuator or a nice Siemens or Elma based volume control.
chinsettawong Posted December 26, 2015 Report Posted December 26, 2015 That's beautiful. Congratulations!
kingofsnake Posted December 26, 2015 Report Posted December 26, 2015 Thanks Kerry. I contemplated cutting the front and Back panels in Half (vertically and i would still retain the same heat-sinking) and having the boards overlap each other (There is enough head-room i believe to keep things safe). This would make the front profile very small indeed!!
kingofsnake Posted December 26, 2015 Report Posted December 26, 2015 Thanks Chinsettawong and mwl168. The front panel that you see on the amp is one i made up myself (4mm thick). The Original is 8mm!! thick and has a nicely brushed finish. My drill would not be able to cut through it so will probably have to find a metal-shop that can cut out appropriate holes for me as i would surely make a mess of it. By the way did i mention the amp sounds Fab! can't drag myself away from it!
kingofsnake Posted December 26, 2015 Report Posted December 26, 2015 4 minutes ago, spritzer said: You need more Flukes... Ha ha..I actually have 2 more in the shed. I just couldn't be bothered to go get them for initial setup.
sorenb Posted December 26, 2015 Report Posted December 26, 2015 (edited) 7 minutes ago, spritzer said: You need more Flukes... hmm...I thought you recommend removing all Flukes before powering up? Edited December 26, 2015 by sorenb
headinclouds Posted December 27, 2015 Report Posted December 27, 2015 Great job. KoS, and I love the instrumentation. I am able to get on with my Carbon now and am looking forward to hearing it. I have high hopes for this as reports sound very positive.
kevin gilmore Posted December 27, 2015 Report Posted December 27, 2015 those diyclub attenuators are the same one Mikhail used. They work fine. Physically pretty gigantic.
kingofsnake Posted December 28, 2015 Report Posted December 28, 2015 13 hours ago, kevin gilmore said: those diyclub attenuators are the same one Mikhail used. They work fine. Physically pretty gigantic. Thanks KG. I found what looks like the same attenuator minus mounting hardware and small transformer.http://www.analogmetric.com/goods.php?id=2589 I have ordered a few items from them previously and they were just fine. Hopefully this will work ok. I just fancied a change from a stepped attenuator and as much as i would love an rk50 i don't think my builds are at the level to justify it. I shall report back once it arrives.
astrostar59 Posted January 3, 2016 Report Posted January 3, 2016 On 5 Dec 2015 at 3:02 AM, Pars said: Not that he was a reference on best practices, but Mike Elliot/Counterpoint used to do this kind of shit all the time on mods with 500V BlackGates and Cerafines, only they were just adhered to the board with clear silicone RTV. At least these look like they are secured with tie wraps. I don't really see a problem with that. With this case and amp, I wouldn't want the caps sticking out the top for aesthetic reasons. The input wiring and ac wiring with uninsulated spades should definitely be addressed though IMO. But you could get covers to drop over like tube covers? In black would look be fine.
mwl168 Posted January 3, 2016 Author Report Posted January 3, 2016 I have a few general operating questions (balance and offset) that apply to all KG ES amps and have not been able to find definitive answers on the threads. So pardon me if these topics have already been discussed before. Before I ask the questions, here are some baseline information from my own observations (all without servo engaged): after adjusting the balance and offset to below 1VDC when the amp is fully warmed up (after more than 60 minutes of powering on), from a cold start, I usually observe the balance to be around 10VDC and offset to be around 35 VDC. It then takes about 20 minutes for the balance and 60 minutes for the offset to settle to below 1VDC. They'll drift a bit afterwards. Here are the questions (for headphones operating at 580VDC bias): 1) what's the highest balance and offset voltage to safely operate the headphone without concern of damage? 2) what's the balance and offset voltage where the headphone's performance starts to be impaired? 3) relevant to question 1, is it advisable to keep the headphone plugged into the amp at all time including power-on and power-off or is it better to unplug the headphone from the amp during power-on and power-off? Thanks!
spritzer Posted January 3, 2016 Report Posted January 3, 2016 Hard to say when the phones will be damaged but let's not play them with the DC rails floating on the stators. Anything short of that and they should be fine. Stax says the amps should be below 20V when warmed up but I think it is far too conservative. Doesn't matter if they are there or not. The amp certainly doesn't care.
gepardcv Posted January 3, 2016 Report Posted January 3, 2016 I usually unplug my headphones when powering on the KGST, because I measured the offset at +/-350V (the DC rails, essentially) for the 1-2 seconds it takes for the heaters to kick in and the tubes to start working. It's probably unnecessary to do that, but I don't plan to conduct a controlled experiment to find out.
mypasswordis Posted January 3, 2016 Report Posted January 3, 2016 You could put in a timed relay, for example the 555 timer in the T2. 1
mwl168 Posted January 3, 2016 Author Report Posted January 3, 2016 5 hours ago, spritzer said: Hard to say when the phones will be damaged but let's not play them with the DC rails floating on the stators. Anything short of that and they should be fine. Stax says the amps should be below 20V when warmed up but I think it is far too conservative. Doesn't matter if they are there or not. The amp certainly doesn't care. Thanks Birgir! If I understand you correctly, the headphone should be safe to be plugged into the amp at all time as long as the amp is functioning properly. The exception would be the amps that use tubes as output devices and without a HV delay. The headphone should function properly as long as the offset is below 20 VDC which, in my observation, usually occurs after 15 minutes of power on.
kevin gilmore Posted January 4, 2016 Report Posted January 4, 2016 Actually it's ok for tube amps without a delay because the positive turn on bump subtracts from the bias
mwl168 Posted January 5, 2016 Author Report Posted January 5, 2016 Thanks Kevin! No sure if this is a sensible question to ask, but what are the likely amp operation scenarios that can damage a Stax headphone?
spritzer Posted January 5, 2016 Report Posted January 5, 2016 Full voltage swing with a high enough input signal from most of these amps will burn the diaphragm. An amplitude twice the bias voltage or higher on either stator would be very bad indeed.
kevin gilmore Posted January 5, 2016 Report Posted January 5, 2016 anything that forces the bias voltage above 600v is going to damage the headhpones. So a fet that is shorted Drain to Source, or a tube that is shorted plate to cathode. or massive amounts of negative dc on the input. 1
kevin gilmore Posted January 7, 2016 Report Posted January 7, 2016 here is something for you people to play with. emission labs 20b-x4 tube in the kgsshv-carbon-tube is a direct plugin. just cut the filament lines tying the 2 tubes together, there are already 2 connectors, one for each tube. 4 tubes about $2100. solves the center tap filament issue.
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