GeorgeP Posted March 5, 2016 Report Share Posted March 5, 2016 That's good news. And yes, current limiting is happening. It is the 30ohm on the -500 that does it - drop it to 25 or thereabouts. On Paul's T2 traffos, someone else from that same buy is getting a lot of hum as well. My set is quiet though, so go figure. Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 5, 2016 Report Share Posted March 5, 2016 Well the hum thing is pretty disappointing. Every transformer that Paul has wound for me is as silent as the grave - including the T2 ones. When he was head designer for Avel Lindberg in the 1980's through to mid 1990s he designed transformers for Krell and umpteen other high end and pro audio companies. If you are getting hum, seriously please take it up with Paul - he will be more than keen to sort it out. I'll mail him and let him know that there is a problem in advance. Quote Link to comment Share on other sites More sharing options...
nopants Posted March 5, 2016 Report Share Posted March 5, 2016 Thanks Craig, Paul is going through some health problems last I wrote so I was hesitant to email him again. I'll drop him a line soon though. I guess I should try to order a transformer or two for the carbon while I'm at it, given the circumstances. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted March 6, 2016 Report Share Posted March 6, 2016 Regarding transformers and humming. Is it the transformer itself that hums? Or is it something else that hums due to the magnetics caused by the transformer? Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 6, 2016 Report Share Posted March 6, 2016 A DC offset on the mains can cause hum. Usually caused by a local industry pulling power out on half cycles, so either the top or the bottom of the mains waveform is flattened (but not both, or not equally). What happens is that the effective DC offset biasses the core of the transformer, and you hear harmonic distortion through magnetostriction in the core. There is a good article, and method to remove it here http://sound.westhost.com/articles/xfmr-dc.htm Basically two big electrolytics in opposed series, or back to back parallel, with diode clamps across them. In series with the live power. Worth a bash since some have silent transformers and others don't, which could well come down to local variation of mains quality. 1 Quote Link to comment Share on other sites More sharing options...
MLA Posted March 6, 2016 Report Share Posted March 6, 2016 There's a board for everything (almost)... http://sjostromaudio.com/pages/index.php/hifi-projects/109-dct02-the-dc-trap-high-end-style?showall=1&limitstart= http://sjostromaudio.net/shop/mains-circuits/11-dct02-dc-filter-for-toroidal-transformers.html Quote Link to comment Share on other sites More sharing options...
JoaMat Posted March 6, 2016 Report Share Posted March 6, 2016 Thanks! Great have you guys around. Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 6, 2016 Report Share Posted March 6, 2016 1 hour ago, MLA said: There's a board for everything (almost)... http://sjostromaudio.com/pages/index.php/hifi-projects/109-dct02-the-dc-trap-high-end-style?showall=1&limitstart= http://sjostromaudio.net/shop/mains-circuits/11-dct02-dc-filter-for-toroidal-transformers.html I'd forgotten that there was a kit. I've bought things from these guys before - and they are very cheap and exceptionally high quality. Multilayer 4 oz copper is kind of standard. And they do the lowest noise variant of the Jung super-regulators. Quote Link to comment Share on other sites More sharing options...
nopants Posted March 6, 2016 Report Share Posted March 6, 2016 (edited) George's suggestion to up the current limit worked like a charm, everything's up and operational. Sounds good, a bit of popping/clicking but nothing too noticeable. How should I go about tracking that down? For my personal use I don't know if I care enough yet, but I might try to fix it when I redo the internal wiring/etc. Knob courtesy of insanity, I probably should have measured it before sticking it on Edited March 6, 2016 by nopants 1 Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted March 6, 2016 Report Share Posted March 6, 2016 Try the 6dj8 first regarding the clicks and the pops - that's where I would look. Quote Link to comment Share on other sites More sharing options...
nopants Posted March 7, 2016 Report Share Posted March 7, 2016 I do have a spare quad somewhere, I'll dig those up. I've been searching for some info on making the lsk389 adapters as 6dj8 subs as well, does anyone have any links? I have a bunch I bought from pete millett for no good reason. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted March 7, 2016 Report Share Posted March 7, 2016 Made those a couple of years ago. All information you need can be found here. 3 Quote Link to comment Share on other sites More sharing options...
mwl168 Posted March 7, 2016 Report Share Posted March 7, 2016 7 minutes ago, JoaMat said: Made those a couple of years ago. All information you need can be found here. I have a dumb question. How do you supply the power needed? Quote Link to comment Share on other sites More sharing options...
JoaMat Posted March 7, 2016 Report Share Posted March 7, 2016 (edited) Only change to PSU was reducing +250V to +150V. For amplifier I changed batteries from 740V to 640V. Also the 68V grid voltage was reduced to 33V, but that is taken care by the resistor on the small board with two 2sc3840. Maybe one should build a modified T2 with lsk389 for input and EML 20B-V4 for output.... Edited March 7, 2016 by JoaMat 2 Quote Link to comment Share on other sites More sharing options...
s_r Posted March 8, 2016 Report Share Posted March 8, 2016 So after not doing anything with my T2 for a while, I'm considering buying a scope to try to track down the problem. Would this scope & HV probes be enough to find whatever is causing the noise? Quote Link to comment Share on other sites More sharing options...
nopants Posted March 8, 2016 Report Share Posted March 8, 2016 I was about to say there's a cheaper one out there then I realized what the CAD - USD rate has become...my condolences Quote Link to comment Share on other sites More sharing options...
JoaMat Posted March 8, 2016 Report Share Posted March 8, 2016 This is what it looked like with adapter boards replacing the small tubes - ECC88/6922/6DJ8. 2 Quote Link to comment Share on other sites More sharing options...
G600 Posted March 8, 2016 Report Share Posted March 8, 2016 Anybody tried PCC88 / 7DJ8 tubes with the beast ? Any reason not to ? Quote Link to comment Share on other sites More sharing options...
GeorgeP Posted March 10, 2016 Report Share Posted March 10, 2016 aren't the voltages different from the 6dj8? Not something I would recommend or experiment with on a T2. Quote Link to comment Share on other sites More sharing options...
spritzer Posted March 10, 2016 Author Report Share Posted March 10, 2016 Only the heaters are different so once that has been accounted for there is no difference. Quote Link to comment Share on other sites More sharing options...
G600 Posted March 21, 2016 Report Share Posted March 21, 2016 I have installed a quad of Philips Herleen ECC88. Definitely sweet with xf2 EL34. 2 Quote Link to comment Share on other sites More sharing options...
peranders Posted March 23, 2016 Report Share Posted March 23, 2016 On 6 mars 2016 at 8:00 PM, Craig Sawyers said: I'd forgotten that there was a kit. I've bought things from these guys before - and they are very cheap and exceptionally high quality. Multilayer 4 oz copper is kind of standard. And they do the lowest noise variant of the Jung super-regulators. ... not quite. The DCT02 has two layers and 105 um (3 oz.) copper. The small super regulator boards has 4 layers with 70+35+35+70 um. All high current tracks are doubled = 140 um if you add both of the sides. At the moment two designs have 4 layer boards. Quote Link to comment Share on other sites More sharing options...
Craig Sawyers Posted March 23, 2016 Report Share Posted March 23, 2016 Nice to see you on head-case Per Anders - you are doing a fine thing for affordable DIY audio modules. Quote Link to comment Share on other sites More sharing options...
JoaMat Posted April 2, 2016 Report Share Posted April 2, 2016 T2 with Emission Lab’s EML 20B-V4. Transformer to left is for filament 4 x 5.0V. Adapters are made by some help of a 3D printer, Teflon tube sockets, slauthered Neutrik XLR connectors, two pole male connectors. All held together with really good Loctite super glue. 4 Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted April 3, 2016 Report Share Posted April 3, 2016 great way to do this, however some heatshrink over the green things to avoid touching the terminals which are at -500v Quote Link to comment Share on other sites More sharing options...
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