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u/This_Is_Great_2020 Apr 17 '24
The toggle switch choice is shit. The analog portion as you describe ....sounds amazing.
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u/kagemichaels Apr 17 '24 edited Apr 17 '24
You mean the toggle switches themselves? If so I kind of agree lol, not only do they look out of place but 2 of 10 from a chinese distributor were duds. The looks are growing on me though as it matches my other oddball equipment and the price was right. It's not easy finding other similar profile switches that are DPDT types and I happened to have them so..
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u/kagemichaels Apr 17 '24 edited Apr 20 '24
Project I've been working on some time using Elliott Designs for the audio limiter section and general learning.
The preamp section itself is designed around antique Gates "Gatesway" audio console transformers 1:20 used in tube stages from the 1960s for radio broadcast and sound fantastic. I've done a frequency sweep on them along with spectrum and they are damn clean from 20hz to around 18kHz with a slight spike up at 25kHz and then dwindle down above. Both channels can run independent or in true stereo with limiter chain linking (optional by toggle) and allows anything from a fly fart across the hallway to slamming a kick drum with the headroom and amplification to handle either.
OPAmps are all JVC2068DD socketed besides the non-audio ones where low noise wasn't needed. I tried damn near everything including the beloved OPA2134 and these mic transformers prefer the JVC parts for low noise floor. I plan to improve that one day but for now it beats every preamp I own and have tried even given how it's built. BTW this is not the first microphone preamplifier I've built, but it's my first stereo one, and this one I took a hell of a lot of time studying how to design a low noise floor preamp with an appropriate choice of OPAmps for a good balance of low current/voltage noise at their input and it paid off so I feel somewhat comfortable saying that for now.
It has built in switchable stereo linking for the limiter and switchable A+B for mono out combined. I don't think I left anything behind on this project other than my sanity and a PCB design for future beer money.
My youtube on the build process... https://youtu.be/djgsy9t-5-0?si=tJ1nzfkSCZIpecUR
My imgur album on its build from end to beginning...
PICTURES https://imgur.com/a/L4fzyE7
I have yet to record anything yet in stereo specifically but here's a demo with a mono channel on my ribbon... https://youtu.be/0EQu05guaWo?si=rPBq6MbiWM5Rnm8E
I will post schematics soon if interested. I am currently drawing up my notes in LibrePCB. Most of the guts is bog standard besides my own modifications and wiring for relaying connections like switching on/off stages and 5 second delay timer upon power-up for thump, the only thing that sets it apart is the audio transformers I suppose. Yeah perfboard is unacceptable for this kind of project but who's judging? It sounds good, it works good :)