The speaker is an 8" Visaton W200S woofer in tiny cabinet, around 5-6l only. It is a HiFi speaker, so it's efficiency is only 88dB but it has a low fs of only 30Hz which helps in this small box. I did some simulations with Visaton's Boxsim SW for a vented design but that would have produced a too large maximum cone excursion. I had the speaker already, so it beat the alternatives by being free, if I had to buy one I probably would have picked the Visaton BG-20 instead.
The cab is made from thin 9mm plywood and cross braced internally to add some stiffness. the W200S has a large flange on the outside so I had to 3D print little spacers for the speaker grille clamps. The top of the cabinet has room for a half width 19" enclosure that just slides inside.
The amp is a mashup from three major parts:
The preamp is a Behringer Bass Driver DI BDI21 PCB with some tweaks ~$25
The power amp is a TPA3116 2x50W Class D amplifier PCB from China ~$15 (eBay or Aliexpress)
a 24V, 5A, 120W switching power supply, removed from it's casing ~$15 (eBay or Aliexpress)
the half width 19" case I got from eBay, it was for a wireless mic receiver initially, so I added new front and back bezels to cover the existing holes.
The back has a 2nd input and the XLR DI output of the BDI21 preamp. The green jack is a direct input to the power amp so that other preamps can be used.
All the front controls are the original BDI21 ones, the two slide switches are well known BDI21 tweaks that remove the midrange scoop and the speaker simulation filter from the signal chain. the BDI is powered from a 9V linear regulator and has the footswitch permanently engaged.
I have neither golden ears nor an acoustic measurement setup, so I can only say it sounds good enough to me to play and practice at modest volumes. With 2x50W and more efficient speakers, the amp can get quite loud but I have not tested that much yet.
1 comment:
I don't know if it's officially a "practice amp" but I'm gonna keep praising the Fender Mustang I until someone makes me stop. view
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