kevin gilmore Posted November 29, 2016 Author Report Share Posted November 29, 2016 that might be a bit low, certainly the 1uf caps are too big for the current board size Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted November 29, 2016 Author Report Share Posted November 29, 2016 i was going to use the .47uf 600v caps, those are definitely too big Quote Link to comment Share on other sites More sharing options...
spritzer Posted November 29, 2016 Report Share Posted November 29, 2016 The 1uf/450V caps I use are pretty small. We might cram on some small film caps too if the board will allow. Quote Link to comment Share on other sites More sharing options...
spritzer Posted November 29, 2016 Report Share Posted November 29, 2016 I just finshed the board and we might be able to fit some SMD caps but through hole are out of the question. Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 12, 2016 Report Share Posted December 12, 2016 Working +-399vdc 18.5ma bias lots of gain, power, noise free, good bass. aluminum plate 57C in center after 30min 8 Quote Link to comment Share on other sites More sharing options...
spritzer Posted December 12, 2016 Report Share Posted December 12, 2016 Looks good. The new layout is pretty much ready but might be a while until we release it. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted December 12, 2016 Report Share Posted December 12, 2016 Nice! 18.5 mA through output transistors? Nearly 2.5 W each. Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 12, 2016 Report Share Posted December 12, 2016 23 minutes ago, spritzer said: Looks good. The new layout is pretty much ready but might be a while until we release it. if you want someone to test the new layout.......... Quote Link to comment Share on other sites More sharing options...
joehpj Posted December 12, 2016 Report Share Posted December 12, 2016 Is there any problem to set the mid point? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted December 12, 2016 Author Report Share Posted December 12, 2016 no way to set the midpoint, on congo5's unit, it is about 5v (well there is, but its a pain, have to trim resistors) Quote Link to comment Share on other sites More sharing options...
joehpj Posted December 12, 2016 Report Share Posted December 12, 2016 5V seems acceptable. I was thinking if someone was bad luck enough to have a bunch of sands far away from average hfe will be a pain to set the mid point. Is it possible to put a svr somewhere to do the trimming job? Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted December 12, 2016 Author Report Share Posted December 12, 2016 its a cfa and the gain is high enough that trimming is probably not necessary. But i will look into it Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 13, 2016 Report Share Posted December 13, 2016 listening / measuring again. on startup the outputs are positive, which is safe, good. I added a fan to my heatsink plate, lowered temp = lower bias. on start bias is ~13ma and climbs as it warms up. if my fan lets it. which may be why offset is different today. and also running on mains instead of variac. rails at +-394v, outputs to ground are all positive, 10v and under. no adjustment needed here. I call this a Big Win Its to cold to feed ducks, glad I made this. Thanks 2 Quote Link to comment Share on other sites More sharing options...
joehpj Posted December 13, 2016 Report Share Posted December 13, 2016 Bias current seems to have positive correlation with temperature. That means this amp may blow itself without adequate heat sink? Also, the performance will be different in winter or summer. Please describe the sound. Anyway, nice job. It's time for some fancy casework. Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 13, 2016 Report Share Posted December 13, 2016 these are positive tempco devices, as are most things. it does seem more sensitive to rail voltages. Could that be a way to autobias the thing? Do think it sounds better warm I am in awe of the simplicity of the circuit vrs SQ Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 15, 2016 Report Share Posted December 15, 2016 if you don't mind a warm case, this seems to be enough heat sink 3.5" x 9" + case bottom after one hour its 40 degrees rise from ambient 70/110 9 Quote Link to comment Share on other sites More sharing options...
spritzer Posted December 16, 2016 Report Share Posted December 16, 2016 The great thing about this amp is its simplicity and that it can be used with the affordable off the shelf Antek transformers. Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 16, 2016 Report Share Posted December 16, 2016 Finally... simple enough I can understand some of it. Best $50 I have spent in a long long time (had a few parts already). Having listened for a few hours now, Will describe the sound. Fuck me. Quote Link to comment Share on other sites More sharing options...
spritzer Posted December 16, 2016 Report Share Posted December 16, 2016 I need to prototype this one soon. Just what I needed...more stuff to prototype... 1 Quote Link to comment Share on other sites More sharing options...
nopants Posted December 16, 2016 Report Share Posted December 16, 2016 i have a 330v edcor left over which would be perfect for this project. which psu version is that? i don't remember the lv electrolytic being situated like that Quote Link to comment Share on other sites More sharing options...
congo5 Posted December 16, 2016 Report Share Posted December 16, 2016 its from the KGST GB, bhultraminipsv4 I think 1 Quote Link to comment Share on other sites More sharing options...
sbelyo Posted December 16, 2016 Report Share Posted December 16, 2016 I think I want to dip into the electrostatic pool. Is this a good place for me to start? Quote Link to comment Share on other sites More sharing options...
sbelyo Posted December 16, 2016 Report Share Posted December 16, 2016 I'm hoping this stays somewhat simple. I'd like to build one as my first. Quote Link to comment Share on other sites More sharing options...
nopants Posted December 16, 2016 Report Share Posted December 16, 2016 only one HV power supply necessary, and 4 copies of a small board. Seems like it's either this or the SRX+ Quote Link to comment Share on other sites More sharing options...
gepardcv Posted December 17, 2016 Report Share Posted December 17, 2016 (edited) I'm intrigued by this design. Have to think about how to absolutely minimize chassis size with some small external heatsinks, and maybe use split GRHV PSU boards (not that there's anything wrong with the mini-BH, and it might win out for me in the end). (Not that I need to make yet another electrostatic amplifier...) Edited December 17, 2016 by gepardcv Quote Link to comment Share on other sites More sharing options...
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