RiStaR Posted July 19, 2013 Report Posted July 19, 2013 Congrats on adding to your collection Wachara!
JoaMat Posted July 19, 2013 Report Posted July 19, 2013 Very nice. Beautiful front and top cover. Like the volume knob.
headinclouds Posted July 19, 2013 Report Posted July 19, 2013 I like that simple case Wachara. Could you say why three sockets and do they have same bias or different?
spritzer Posted July 19, 2013 Report Posted July 19, 2013 Looks good. I was going to finish 3 HV's over the weekend but my laser shop fucked up 2 out of the 3 front panels...
Torpedo Posted July 19, 2013 Report Posted July 19, 2013 Sorry for the fuck up, Birgir. Very nice amp, Wachara
chinsettawong Posted July 19, 2013 Report Posted July 19, 2013 Thanks guys. This amp will take Stax and HE90. I've put an additional 5M resistor for HE90 bias. Should I make another 500V bias voltage for HE90 or will it be OK with 580V? Wachara C.
spritzer Posted July 19, 2013 Report Posted July 19, 2013 They really need to have the correct bias voltage, +500V and 10M. It just so happens you have a nicely regulated +500V in there already. Just take a line from there with a small 10nf bypass cap and a 10M resistor to the Fischer socket. One thing to note, the HE90 should never see more than 1000Vp-p at any time which the HV will easily pass even with a 2V source.
chinsettawong Posted July 20, 2013 Report Posted July 20, 2013 Oh yes! I actually forgot about the +500V that is readily to use. Thanks very much for pointing that out. About the 1000Vp-p, I guess I'll just have to be very careful with that. Wachara C.
PICaudio Posted July 20, 2013 Report Posted July 20, 2013 Congrats for your new amp, looks fantastic. -- o -- Rodrigo
johnwmclean Posted July 20, 2013 Report Posted July 20, 2013 (edited) Very nice chinsettawong. The transformer doesn’t look like a typical Sumr or is it another supplier? Edited July 20, 2013 by johnwmclean
spritzer Posted July 20, 2013 Report Posted July 20, 2013 Interested about the transformer too as I'm looking at other options. The Asia suppliers usually fail to be cheap once I impose strict tolerances and specs such as low max heat rise. They usually underspec the cores and use silly small wires to keep the cost down. I did contact Talema as they are so close to me in Ireland but haven't heard back.
chinsettawong Posted July 20, 2013 Report Posted July 20, 2013 I have my transformers made locally. The maker learned it the hard way when I asked them to make the transformers for my DIY T2. In total, we burnt 5 transformers. So now when I ask them to build me transformers for electrostatic amps, they know that that have to over specs everything. Wachara C.
SoupRKnowva Posted July 22, 2013 Report Posted July 22, 2013 Back when I was first thinking about building a KGSSHV, I remember reading you guys warning about taking the output bias too high, that the transformer/powersupply would run out of steam. Using the stock, non mini power supply, and a 135VA transformer at 500v rails, how high would you guys guess it would be safe to turn up the output stage biasing current without hurting anything? Would something like 15mAs be possible, or would i want to stay below 10mAs? I know that John only took it up a few to 8mAs? Second question, would it be possible to make it so I could socket resistors to test different biases without having to solder all the resistors in each time?
headinclouds Posted July 23, 2013 Report Posted July 23, 2013 on the subject of transformers I and several others have had good service from Toroidy Poland. I contacted him because he was recommended on a diy audio forum.I've used three of his and they all work as intended, although only been in service for a few months so far.They are also quiet in operation.ContactTomasz Lachowski[email protected]Anyone else experience with them?To answer SoupRKnowva's question; I defer to more experienced members, but I'd say the PS is not the problem as far as running out of steam. The max bias current I would use is around 10mA as the transistor is reaching its power limit..........You could find something like an IC socket but I would just solder pins or short length of stiff wire in place and solder the resistors on temporary. Not much less than 100ohm though. There are comments ealier on about calculating the bias. and also the extra drift that comes with the higher bias.
s_r Posted July 24, 2013 Report Posted July 24, 2013 I made a few changes to the inside of my HV recently. Put in the much larger encapsulated trafo and tidied up the wiring a bit. However I haven't figured out what to do with the ground hum at the pot's extreme left. Anything I should try first to see exactly where the issue is? Also SoupRKnowva, I'm not sure about pushing it past 10mAx4 with IXYS parts. It would probably drift a considerable amount.
justin Posted July 24, 2013 Report Posted July 24, 2013 not familiar with the schematic on your board but try a 100 ohm resistor after the pot on each channel
spritzer Posted July 24, 2013 Report Posted July 24, 2013 Is there no direct ground connection from the sockets to the pot? Conduction in those boxes is shit unless you take special measures to get good contacts all over the place. First thing I'd try... I've used one Toroidy transformer and it worked well enough but who in their right mind puts 10cm leads on transformers?
PICaudio Posted July 24, 2013 Report Posted July 24, 2013 Yes, it's a fault on their part, but they have no problem to do transformers with cable length you want if you tell them in the order the long of these leads, I ordered the last transformers with 40 cms long. -- o -- Rodrigo
justin Posted July 24, 2013 Report Posted July 24, 2013 (edited) utsource has had 2SC3675s listed for $1/each for a while now on eBay. as a test, i bought 10 pieces, they were all real, look exactly like my other 2SC3675s so i bought their remaining 910 pieces, which....look different. testing: tested 10 pieces (of the 910pc lot), they all have breakdown voltages around 1025-1050V. higher than the 900v spec but not as high as some other parts ive seen test in the 1150v range HFe is around 50 which is good This is what the 10 pieces look like from my sample purchase: This is what the next 910 pieces look like: Edited July 24, 2013 by justin
headinclouds Posted July 24, 2013 Report Posted July 24, 2013 I've used one Toroidy transformer and it worked well enough but who in their right mind puts 10cm leads on transformers?Yes I didn't give any spec details just a heads up on a supplier who seems OK. I specified 300mm leads.
spritzer Posted July 24, 2013 Report Posted July 24, 2013 Those odd 3675's could be real as I've encountered some odd markings. One didn't look anything like the bulk stuff we bought but tests just the same... Yes I didn't give any spec details just a heads up on a supplier who seems OK. I specified 300mm leads. I didn't order this particular unit but it's something to consider. While we are discussing transformers, I'm talking to SumR now to see if we can get rid of the buzz issues I and some others have had.
s_r Posted July 24, 2013 Report Posted July 24, 2013 not familiar with the schematic on your board but try a 100 ohm resistor after the pot on each channel Putting in 100 ohm resistors did the trick, thanks. It's dead silent from extreme left to extreme right now.
Lil Knight Posted July 25, 2013 Report Posted July 25, 2013 Yes I didn't give any spec details just a heads up on a supplier who seems OK. I specified 300mm leads. How long do they normally take to build a transformer?
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