justinsweber

OK as promised.

Me like JW... never!

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.

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.

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.

I think you're sporting a similar look...great minds :-)

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 :-).

The pics are of the SS pre I bult... I love it... not sure its something others will get behind.

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 RMS 246mV 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)

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.

I think it has the sound of a $2K amp... the ST35 is very special. If you at Dynakit they now also have a SCA35 which is the integrated version... multiple inputs and Phono pre. They sell the chassis, transformers and etc... youll have to source the PCBs.. but they tell you where to get... If it were my 1st DIY amp... Id go pretty close to stock and follow the wiring diagrams which you can download from multiple sources. Given your goals a SCA35 maybe a better choice... Has power, just more flexible. Re: Sub. Very often the sub amp will take input from the speaker wire... run the speaker wires to it and then from the sub to the speakers... that way the sub does crossover duty and makes life easier for the main speakers... as they will not have to play freq. below the crossover point, ~80hz to -120hz. Most amps, esp tube amps dont advertise freq ext below 20hz. Id call Dynakit parts and takl to kevin... then see the sites he sugests for replacement boards and review the build instructions... the amp is more than 40years old (design) yet is highly sought after... the design was solid and the iron is very good.

Short answer is yes but who cares... tone controls can be helpful for some. I generally perfer Vol and Bal and leave it at that. The problem with removing them is that the circuit requires some tweaking after... more again generally. I think the wiser choice is get a useable unit and refurb... New pots, new switches, Can Cans or PCB and new PCBS... maybe with the NFB mod and call it good. I personally dont make my amps with adjustment as most... myself included are not likely to revisit often enough.