justinsweber Posted April 15, 2014 Share Posted April 15, 2014 (edited) Hey Everone, As usual Im completly sleep deprived as is Ryan my biz partner... but we got a few new ideas worked out... The day to day building is easy to schedule, but working out new ideas take some seriosu time. We completed the Stereo 15 with 100% custom iron provided to be the easy success. Ryan spent a ton of time prototype 2 enclosures for preamps we built... We had hoped to use them at shows this summer but that seems less likely. Ive had this idea for a long time... happy to see it on my bench now. Edited April 15, 2014 by justinsweber Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 15, 2014 Author Share Posted April 15, 2014 we are getting 5mV P-P of noise at idle with inputs shorted which makes it the quitest thus far.. I think its largely due to the shield the power transformer uses. Maximum Power @ 1kHz = 15 Watts RMS246mV P-P = 1 W RMS 10 Hz (-0db) - 27.4 kHz (-1db)550mV P-P = 5 W RMS 18 Hz (-1db) - 22 kHz (-1db)796mV P-P = 10 W RMS 26 Hz (-0db) - 15.5 kHz (-1db) (Before Distortion) Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted April 15, 2014 Share Posted April 15, 2014 (edited) I thought you were doing a SS pre or are the pics of 2 different things? Edited April 15, 2014 by CECAA850 Quote Link to comment Share on other sites More sharing options...
joessportster Posted April 15, 2014 Share Posted April 15, 2014 Beauty, as usual Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 15, 2014 Author Share Posted April 15, 2014 The pics are of the SS pre I bult... I love it... not sure its something others will get behind. Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 15, 2014 Share Posted April 15, 2014 I may need to road test that preamps for 3-6 months, or until you build a better one. Really beautiful piece. Dave Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 15, 2014 Author Share Posted April 15, 2014 Its all Ryans wood work! The Wiring on point but the wood is what catches the eyes... using a CNC mill would make life a ton easier :-). Quote Link to comment Share on other sites More sharing options...
Schu Posted April 15, 2014 Share Posted April 15, 2014 Does your partner dove tail or mortis and tenon? Your guys stuff always looks so nice. Quote Link to comment Share on other sites More sharing options...
toolz Posted April 15, 2014 Share Posted April 15, 2014 Sweet. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted April 16, 2014 Share Posted April 16, 2014 The front knob layout looks familiar Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 16, 2014 Author Share Posted April 16, 2014 I think you're sporting a similar look...great minds :-) Quote Link to comment Share on other sites More sharing options...
erik2A3 Posted April 16, 2014 Share Posted April 16, 2014 Can you explain circuit topology of the input/driver and output stages? Exteriors of amps are always nice, and the top chassis plate always works well for mounting hardware. Makes it easy to work on as well. Do you have any 'under the hood images' Justin? Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 16, 2014 Author Share Posted April 16, 2014 This amp is the same as my Stereo 15… making use a 12AX7/12BH7 combo with pairs of P-P EL84, no ICs for regulation. The major upgrades are the new iron and bypassing the diodes. My web designer is coming tonight and will take some pics… hopefully I’ll have them back by Monday. The circuit is a reworking of Halfers/dynaco’s original… few new ideas. What became evident in bench testing is that the iron beats the circuit. The iron was able to go lower and higher than the 10hz-20hz we measured, but was more limited by the feedback network. My Tech has access to Decca cap boxes and resistor networks and we tried a few more options… really couldn’t get more out of it… Its very very flat response and significantly improved LF control. The tube rectifier question was to get out of using snubbing caps to mange HF noise. I generally am not one for Tube rectifiers, but this setup has me very happy. The amp will be on its way to its new home soon. I’ll be doing 10 hours of listening before she leaves. I even secured a Japanese Mullard 5AR4 to sweeten the sound for the user. I think tubes that it will be shipped with, will include Solvtek 12AX7/ RCA12BH7 Solvtek EL84Ms and the Japanese Mullard 5AR4. The new power transformer made much of this possible… I tried 3 different transformers from 2 different companies all with terrible results. The new transformer has no mechanical hum, has an internal shield J, increased filament current reserves and a separate 5v 4 amp winding. In time I will transition all the amps to this unit… added $60 more in cost but I think its worth it. The amp is weighing in at 30lbs now, which has a lot to do with the new power transformer. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted April 16, 2014 Share Posted April 16, 2014 I tried 3 different transformers from 2 different companies all with terrible results. The new transformer has no mechanical hum, has an internal shield J, increased filament current reserves and a separate 5v 4 amp winding. In time I will transition all the amps to this unit… added $60 more in cost but I think its worth it. The amp is weighing in at 30lbs now, which has a lot to do with the new power transformer. Would Big Ben benefit from this? Quote Link to comment Share on other sites More sharing options...
Guest David H Posted April 16, 2014 Share Posted April 16, 2014 I tried 3 different transformers from 2 different companies all with terrible results. The new transformer has no mechanical hum, has an internal shield J, increased filament current reserves and a separate 5v 4 amp winding. In time I will transition all the amps to this unit… added $60 more in cost but I think its worth it. The amp is weighing in at 30lbs now, which has a lot to do with the new power transformer. Would Big Ben benefit from this? Big Ben was incredibly quiet in my system. Dave Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 16, 2014 Author Share Posted April 16, 2014 Bigben is about 8mv-10mv at idle which is higher. that said, has never been audable with an ear inside a large horn... Just the benifit of Oscope and measurement. I dont currently have a plan to update big ben anytime soon, its outputs are already significantly over specd. I really like the compromises made for big ben currently... I doesnt need snubbers yet I cant hear or measure any switching noise. The Stereo 15 is an incredibly solid performer, but I had worked for the last 8mo to get new iron made... it didnt make sense to just do an upgrade of outputs when the baseline was so good already, so I went a bit nuts on the one in the pics... new Iron all the way around. Quote Link to comment Share on other sites More sharing options...
justinsweber Posted April 16, 2014 Author Share Posted April 16, 2014 Heaven and earth bend for a good rib eye. Rib eye from the BBQ, some Johnny Walker Gold-n-Coke (No judging !) and mashed potatoes. Or full rack of beef ribs and mac-n-cheese, peach cobbler and ice cream. Quote Link to comment Share on other sites More sharing options...
mungkiman Posted April 16, 2014 Share Posted April 16, 2014 Can't judge until I know what Gold-n-Coke is. Goldschlager??? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted April 16, 2014 Share Posted April 16, 2014 Can't judge until I know what Gold-n-Coke is. Goldschlager??? Johnny Walker Gold and Coca Cola. Quote Link to comment Share on other sites More sharing options...
mungkiman Posted April 16, 2014 Share Posted April 16, 2014 Good to know. I "grew up" on Bourbon and OJ. Quote Link to comment Share on other sites More sharing options...
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