You're getting ahead of yourself heheh. It's great to watch, in the end what matters is how good it sounds and I'm afraid I can't be there to judge it for you. My advice for the hairdryer is serious, heat up gently and off it should go - just make sure you're on the lowest setting. IPA (Isopropyl Alcohol for noobs) should clean off any residue.
That looks awesome with little bumps, I would squeeze a beefier condenser in there somewhere, just because I'm difficult...
If I was to redesign the thing I'd put Audyn/Nichicon caps in it.Originally Posted by Manu
I tried my hand at writing a user manual for the xover:
Link to Dropbox
I think it turned out ok, the illustrations are sort of messy though.
It's missing THD specs too.
Did some THD measurements, first of all I created a 1kHz sine wave at 0,8 amplitude in Audacity.
Then I played it through my smartphone into the unit (a mixer in this case) and via an USB soundcard back into Audacity.
The resulting is a spectrum analysis of the recorded soundwave showing the system under test.
I also recorded the same sine wave without the unit being measured in the signal chain with volume compensation (the resistance of the unit was 206ohms so I just lowered the volume)
After that I took the square root of the upper harmonics and divided that by the fundamental frequency from both of the signals and subtracted the "clean" signal from the one with the mixer in it.
Like (√1dB..+ndB)÷100 (I worked on a scale from -100dB to 0dB, the recorded sine waves were normalized to 0dB).
I ended up with a THD figure of <5,16%, is this normal for a passive mixer? I saw power amplifiers doing <0,1% THD.
Asking for future in mind in case I measure the xover THD and revise the manual.
Due to rather problematic supply of preamplifier kits I decided it's for the best if I designed my own.
After 4 days of breadboarding and countless tests I came up with a simple yet effective design.
Here's the schematic, If I understood correctly it's a fixed-base biased, common emitter amplifier circuit :
With a 9V supply it's LOUD, a bit distorted but ok for a first try I guess.
Here's the THD at 1kHz :
By using the formulae above I got a THD of 2,25%.
Any thoughts?
Here's the design on a stripboard :
It was my first time doing a circuit from breadboard to stripboard so it isn't exactly like in a textbook.
Not bad for a first try, though 2.25 THD is a bit much, would that be because of using cheap components?
I used a 0.11€ transistor (BC547B general purpose amplifier)
Also bought some NE5534 opamps for testing.
EDIT : the circuit above is already in a DIY DJ mixer as a headphone amplifier.
Last edited by efinque; 04-09-2024 at 10:42 AM.
Yeah I guess buying more expensive components will help towards the performance - back when I was experimenting with filters and whatnot, it took me many months of going back and forth with various components to finally get it right.
I instantly swapped the transistor amp to the NE5534 one when I heard it.
The only downside was the headphone volume stopped working, I fixed this by wiring the pot after the preamp and now it works.
Those NE5534 cost 1,50€/pc, not too bad. I could cut the costs by fabricating my own PCBs but the stripboards were perfect dimension-wise.
With the same pinout I could test different opamps, like the Burr-Brown or TL071.
EDIT : after this preamp venture of mine I'm looking to rebuild the xover with my own designs for reference, I'll keep you informed!
Last edited by efinque; 04-14-2024 at 11:12 PM.
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