beta22 phase1 - Page 4

been working late it my weekends and massive overtime so i havent been able to think about my project much.

i decided that i am gonna do it right. 2 box it is and im going to attempt a similar layout, umbilical as my RSA apache. f--- the budget; i am working enough overtime these days anyway



um i guess i am officially deeply biased into class A. at .0752V on the mosfets i cannot hold my finger on the heatsinks for more than 3 seconds. i thought i had a pretty good tolerance for pain. i might go back down to like 135ma quiescent current to spare my single O22 the abuse.

all boards zeroed out to no DC offset.

the advice i can offer to anyone building these things is do not screw up on the Q1 to Q4 because you WILL be sorry. i think 1% match on the QUAD is necessary to be safe. q1=q2 and q3=q4 is gambling. toss the outliers and buy more to find a better match seriously.

i think matching the mosfet quad is important too if you want to biase a more aggressively. i can tell that the outliers run at much different temps than the ones that were well matched.

I've been working a lot so this project has taken the backseat lately. I got my enclosure finally and it's great. All i need is to get this thing drilled and ill be golden.

yeah i am running the single sigma22 since im going to use this with headphones only for now. if i feel the need to add another later i bought a box that has extra room for the addition. The unshielded toroidal trafo is outside, i kind of made a cheap big plastic wallwart for it far away from interfering with the b22 itself. or i could tap and step down from the 36v lines going into my sigma..ugh too much stuff

i bought the JTA from TPA. i really dont mind the extra complexity and space sacrificed for extra steps, the biggest complication is powering it. it adds an extra trafo and big headache in terms of my umbilical solution

i used a 8 lead speakon in order to carry the AC secondary lines. i hope that is okay. the speakons say not to use them for AC mains, but i guess secondaries isnt as bad?

i thought long and hard about the enclosure and i even came Way under my expected budget to get more than what i expected. I shopped around context engineering front panel express par metal. They are so damn expensive....okay context wasnt that expensive but they took a month to give me a quote and wouldnt answer my questions.

This is from modushop. hifi2000. The 10mm thick front panel by itself would cost a fortune if i bought it from the USA (FPE wanted like $40 for 4mm thick and that was only raw material price). I spent way less shipped from italy and converted to euros than i would if i bought it here plus this thing looks awesome. i am very impressed and i would definitely buy again from this place when i do my next build (which might be in the near future)

modushop.biz

i bought the inner-bottom and top grill options.
i am not going to do anything fancy with this. just simple in out and volume control. i like that clean look.

The JTA was in stock when i bought it. They make new batches so you have to wait (maybe longer since they are focusing on the buffalo2 production right now). Buy it when you see it because even i was thinking about buying a lot of them for future builds.

any suggestions on wire routing? i am keeping the b22 boards up front like that, power leads flowing underneath the galvanized steel floor board. Signal wires are on top of the boards probably going right down the middle of the enclosure (also to save money because SCSCAg is expensive hookup wire). The sigmas are in back in order to keep the unregulated leads from an umbilical inlet(s) (probaby put them in the rear bottom corners) as short and far away as possible from the b22 boards. I chose to do the external toroid in a small plastic box (like a wallwart) for cost/effectiveness reasons. All the audio inputs will be located around the center of the rear panel which is far away as possible from the unregulated stuff in the corners.

I have my dead ultrasone headphones i ripped out their MuMetal shields maybe i can use them to shield the area where the umbilical enters? anyone have any dead ultrasones they want to donate? hehe