Hello!
I'm looking to build a 4xKT88 guitar/bass/organ amplifier that is based on a Marshall 2203 that will hopefully put out around 150w at a B+ of 550ish volts using the Hammond 278cx power transformer and the 1650t output transformer. The preamp will be stock 2203 with the exception of a couple of possible tonestack mods to make it more bass friendly.
With all of that in mind, will the rectifier and filtering of a stock 2203 be sufficient for such a build?
Thanks in advance!
I'm looking to build a 4xKT88 guitar/bass/organ amplifier that is based on a Marshall 2203 that will hopefully put out around 150w at a B+ of 550ish volts using the Hammond 278cx power transformer and the 1650t output transformer. The preamp will be stock 2203 with the exception of a couple of possible tonestack mods to make it more bass friendly.
With all of that in mind, will the rectifier and filtering of a stock 2203 be sufficient for such a build?
Thanks in advance!
You are going to need more filament current .
KT88 =1.6 amps X 4 = 6.4 amps plus .3 X 4(conservative guess for preamp tubes) 1.2 amps.
7.6 amps on a 6 amp filament winding.
KT88 =1.6 amps X 4 = 6.4 amps plus .3 X 4(conservative guess for preamp tubes) 1.2 amps.
7.6 amps on a 6 amp filament winding.
Good catch! I'll add a filament transformer to this build. Does everything else seem sound?
550 B+ is a lot for CP KT88 or 6550 screens. Another way to do it is to get a 220 volt secondary transformer @ 800ma- 1amp output and configure it as a voltage doubler so you get 300volts and 600 volts B+. Use the 300v for the screens and 600 volts for the plates. Ideal OT primary impedance would be a little higher; like 2500 ohms for 4 KT88s but your 1900 ohm Hammond will work good too. This will make a killer bass amp.
Use 1N5408 or UF5408(?) 3 amp 1000 volt diodes in the power supply.
Use 1N5408 or UF5408(?) 3 amp 1000 volt diodes in the power supply.
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