Laowei Posted July 10, 2014 Report Posted July 10, 2014 Sadly, I am that old too. So I have only built "normal tube amps". The KGST is my first amp for electrostatics. Going to learn a lot.......
spritzer Posted July 11, 2014 Report Posted July 11, 2014 This really isn't your typical tube amp, that's for sure. The tubes are used in the same way as you'd use a transistor. Just as a heads up, prototype boards for the KGDT have been ordered so things are moving forward there as well.
kevin gilmore Posted July 11, 2014 Author Report Posted July 11, 2014 npn transistors are always used in the same way as triodes dual gate mosfets (there are very few left) are used in the same way as tetrodes
kevin gilmore Posted July 13, 2014 Author Report Posted July 13, 2014 this will be the power supply people should use for the kgst and kgdt heavy modifications by 3 people from the original kgbh power supply. http://gilmore.chem.northwestern.edu/kgbhultramini.jpg 5.3 x 4.37 inches original was 6.6 x 5.5 inches
UFN Posted July 13, 2014 Report Posted July 13, 2014 Looks very good - only annoying thing is that I already ordered a couple of boards of the older version and the KGST amps I can see the amp board has been upgraded to v0.51 as well, can I ask what was changed? Oh, one minor error in the silkscreen by the way - one of the big caps is marked as 50V, not 500V. //UFN
kevin gilmore Posted July 13, 2014 Author Report Posted July 13, 2014 (edited) the stax mafia believes in continuous improvement I wasn't even going to do this, then it happened anyway. Very minor parts placement issues. silkscreen error fixed http://gilmore.chem.northwestern.edu/boards/kgbhultraminipsV2.zip Edited July 13, 2014 by kevin gilmore
headinclouds Posted July 13, 2014 Report Posted July 13, 2014 Group buy announcement! See why I said there would be a short pause? As soon as these two gentlemen commit to a final for production for the group I will do the group buy. Hopefully in the next few days. I will pm all people who have put their names down for confirmation and payment. The total requests for amps was around 80 boards and PS 50. 1
spritzer Posted July 13, 2014 Report Posted July 13, 2014 Just so it is clear, this PSU is exactly the same as the other one I did. Kevin just wanted to move it to the same layout architecture we use for all other boards so we drew it. Ohh and everything changes for us. There is nothing set in stone so constant improvements. I've lost count of how many revisions there are of the KGSSHV boards, at least 60 minor ones and almost 20 major ones.
headinclouds Posted July 14, 2014 Report Posted July 14, 2014 Thanks Birgir and Kevin, I have the files and am getting final price. I will pm all the people who requested boards and ask for you to confirm and do the paypal business. 1
headinclouds Posted July 15, 2014 Report Posted July 15, 2014 Group buy pcbs; I have just pm'ed everyone who asked for boards. If anyone else wants KGST amp or PS boards - shout now because the order will go in a few days. Confirm the number you want and I'll tell you how much to paypal me. Cheers
biosonar Posted July 16, 2014 Report Posted July 16, 2014 Thanks to the great work by everyone, this should be a excellent newbie project. Is it possible to still order 2 KGST amp boards and 1 PS board?
Sherwood Posted July 16, 2014 Report Posted July 16, 2014 They're not yet made up, so just get in touch with Geoff. The more, the merrier.
charlo89 Posted July 16, 2014 Report Posted July 16, 2014 Thanks for the GB you can add me, I take 2 set (mini PSU and last KGST )
meeskees Posted July 16, 2014 Report Posted July 16, 2014 Group buy pcbs; I have just pm'ed everyone who asked for boards. If anyone else wants KGST amp or PS boards - shout now because the order will go in a few days. Confirm the number you want and I'll tell you how much to paypal me. Cheers Is there still a possibility tot order a set of boards?
headinclouds Posted July 17, 2014 Report Posted July 17, 2014 (edited) Is there still a possibility tot order a set of boards? Yes - for a day or two. LAST CALL FOR KGST Edited July 18, 2014 by headinclouds
insanity Posted July 20, 2014 Report Posted July 20, 2014 (edited) Since this will me my first amp built with tubes, I have two questions. 1. Which tube sockets should I get? Are these the right ones and ok? http://www.ebay.com/itm/4pcs-GOLD-9pin-PCB-Ceramic-vacuum-tube-sockets-valve-base-12AX7-12AU7-ECC83-6N11-/231285734941?pt=Vintage_Electronics_R2&hash=item35d9b43e1d 2. Which 6s4a tubes should I get. Can I use other types of tubes? If I understand correctly I need at least matched pairs, better matched quads. Which tubes are a good choice for the KGST? Help is really appreciated, thanks! Edited July 20, 2014 by insanity
spritzer Posted July 20, 2014 Report Posted July 20, 2014 That socket should fit but these are the most common ones and what I used/designed for: http://www.ebay.com/itm/10-9pin-Ceramic-Tube-Socket-PCB-B9A-6DJ8-12AX7-ECC83-ECC82-12AU7-6922-6N11-Valve-/131242710847?pt=Vintage_Electronics_R2&hash=item1e8eacd73f Available from pretty much everywhere. The board also takes the teflon sockets such as this one: http://www.ebay.com/itm/NEXUS-MUSIC-Premium-9-PIN-9P-Gold-Plated-Teflon-Tube-Socket-12AU7-ECC83-2PCS-/181469359862?pt=Vintage_Electronics_R2&hash=item2a406aaef6 For tubes its the 6S4A that works and nothing else. There are really no tubes like it though some are similar but with incompatible pinouts. I got some 6973's on Friday which are a beam pentode and in current production which might work on a modified ST board triode strapped. As soon as I get my new board then I'll try it. As for matching, you need matched pairs for each channel but a matched quad doesn't hurt. Matched build is also what I'd go for so all of them RCA or GE, the actual branding doesn't matter. A note about the voltage though. After running my tiny 400V for some time now I would advice people stick to +/350V rail voltages as 400V runs too hot for comfort. It's the first amp I've ever had to use a fully vented cover for...
insanity Posted July 20, 2014 Report Posted July 20, 2014 (edited) Thank you for your reply. If I go for 350V rail voltage, what are the transformer specs I need? 0-6.3V 1.4A (2x) -18-0-18V ??A 300v? ??A I think the Zenerstring would need to be 150 100 100V, right? Anything else that needs to be adapted? What about the bias voltage? That socket should fit but these are the most common ones and what I used/designed for: http://www.ebay.com/itm/10-9pin-Ceramic-Tube-Socket-PCB-B9A-6DJ8-12AX7-ECC83-ECC82-12AU7-6922-6N11-Valve-/131242710847?pt=Vintage_Electronics_R2&hash=item1e8eacd73f Available from pretty much everywhere. The board also takes the teflon sockets such as this one: http://www.ebay.com/itm/NEXUS-MUSIC-Premium-9-PIN-9P-Gold-Plated-Teflon-Tube-Socket-12AU7-ECC83-2PCS-/181469359862?pt=Vintage_Electronics_R2&hash=item2a406aaef6 For tubes its the 6S4A that works and nothing else. There are really no tubes like it though some are similar but with incompatible pinouts. I got some 6973's on Friday which are a beam pentode and in current production which might work on a modified ST board triode strapped. As soon as I get my new board then I'll try it. As for matching, you need matched pairs for each channel but a matched quad doesn't hurt. Matched build is also what I'd go for so all of them RCA or GE, the actual branding doesn't matter. A note about the voltage though. After running my tiny 400V for some time now I would advice people stick to +/350V rail voltages as 400V runs too hot for comfort. It's the first amp I've ever had to use a fully vented cover for... Edited July 20, 2014 by insanity
UFN Posted July 20, 2014 Report Posted July 20, 2014 I believe it should be 280V and around 140-150mA, so complete min. specs for a custom wound would be: Pri: Whatever voltage(s) you need, power = 120VA or higher. Sec. 1: 280V/min. 40VA Sec. 2: 280V/min. 40VA Sec. 3: 15V/min. 10VA Sec. 4: 15V/min. 10VA Sec. 5: 6.3V/min. 10VA Sec. 6: 6.3V/min. 10VA You can go higher power if you want of course. The 15V windings can be higher voltage (16-18V) if you want but it should not be necessary given the dropout voltage of the LM78xx/79xx regulators. It can also be 15-0-15 center-tapped instead of two discrete secondaries if you prefer. //UFN
spritzer Posted July 20, 2014 Report Posted July 20, 2014 Two 280VAC windings are perfect for +/-350V.
Mangler Posted July 20, 2014 Report Posted July 20, 2014 Since this will me my first amp built with tubes, I have two questions. 1. Which tube sockets should I get? Are these the right ones and ok? http://www.ebay.com/itm/4pcs-GOLD-9pin-PCB-Ceramic-vacuum-tube-sockets-valve-base-12AX7-12AU7-ECC83-6N11-/231285734941?pt=Vintage_Electronics_R2&hash=item35d9b43e1d 2. Which 6s4a tubes should I get. Can I use other types of tubes? If I understand correctly I need at least matched pairs, better matched quads. Which tubes are a good choice for the KGST? Help is really appreciated, thanks! If it helps at all, I was able to get a matched quad of 6s4a for $32 from http://vacuumtubes.net. They seem to be one of the few places with a large enough stock to do any matching Sent from my iPhone using Tapatalk
Mangler Posted July 20, 2014 Report Posted July 20, 2014 Are there any non-custom transformers that would work, maybe something from Antek? Or is custom the way to go? Also, is there any reason not to mount the tubes on top of the amp with chassis mount sockets (aside from the extra work)? Sent from my iPhone using Tapatalk
insanity Posted July 20, 2014 Report Posted July 20, 2014 As far as I have seen, it looks like custom is the way to go for 280v.
spritzer Posted July 20, 2014 Report Posted July 20, 2014 Antek has a very nice transformer at 275V (i.e. close enough) and then you just need a 30VCT transformer for the +/-15V supply
insanity Posted July 20, 2014 Report Posted July 20, 2014 I saw that one, but it's not in stock at the moment. Antek has a very nice transformer at 275V (i.e. close enough) and then you just need a 30VCT transformer for the +/-15V supply
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