Finally finished one channel and did some testing.... THE MOMENT OF TRUTH is coming! Will it work or not???
Woohoooo!!!!! YES!
At first I wasn't getting any signal and was in a bit of panic... I'm thinking "oh no... what did I do wrong?"
Told
myself I need to calm down and re-check everything step by step. Found
out I have a loose connection since everything is just temporarily
affixed with tape and alligator clips. Secured that connection and now
we have continuity.
Device Under Test
Then
I heard music... coming from my signal source... YES! It works and
passes signal. Sounds good too! Pretty stoked about it. Check the
gain settings, it works... check the trim, it works. I tested it
with a line level input and an SM57 dynamic mic, and yes, sounds
great. I haven't tested it yet with condenser mics since I don't
have the switchboard hooked up yet... (the switchboard has the 48V
phantom power converter).
After an hour of music listening, hooked it up to my signal gen and oscilloscope to see out how things are.
Check
it out... here's the square wave response at 1Khz. Notice how
clean and sharp the square wave response is... no ringing, oscillations
or instability at either the rising and falling edges!
Square Wave Response 1Khz
Did
some output measurements while we're at it... how high an output can we
go before clipping or instability. I'm not expecting it to be high
(like +27/28dBu) since we're not using high supply voltages here, just
a DC-DC converter PSU... but let's see what can we get...
Not bad.... not bad at all. Some readings....
15Hz @ 32Vpp = +23 dBu
20Hz @ 35.6Vpp = +24dBu
1Khz @ 37.7Vpp = +24.7 dBu
22Khz @ 31.1Vpp = +23dBu
100Khz @ 24.4Vpp = +20dBu
200Khz @ 14.65Vpp = +16.5dBu
Output waveform at 100Khz.
What's the Next Step?Build the 2nd channel on the TS-2 preamp board, then test together the Motherboard and Switchboard...
Metalwork/CNC for the case, verify measurements and hole locations
So
far, I'm pretty pleased with how everything is working out, from
concept and design on paper, to CAD, to a working prototype.