The Amp Garage

pdf, I see on the 5F6A schematic when the non-use channel's volume is full down the 270k mixing resistors actually form a voltage divider to cut the active channel's input signal in half but I don't see the mixing resistors in parallel.

pdf, I don't see how the bright and normal channels are parallel electrically. They appear to be separate until they hit the 270k mixing resistors, the controls are only connected through ground. Regarding the power tube shared cathode resistor, during my research I never found a 12AU7 or 12BH7 powe...

I'm going to evaluate the feedback loop closely since like you say it may not be necessary at all with non-bypassed triode power tubes.

I've always heard the almost 3x increase in feedback on the Marshall JTM45 over the 5F6A was an accident.

You're really killin' it with these! Thanks again for sharing your work. Do you have a preference between this and the 5e3 micro? Or is it just like asking if someone prefers a bassman to a tweed deluxe? I haven't built the Bassman yet but the Deluxe Micro exceeded my expectations--it's a very cool...

This is my latest micro amp project, the Bassman Micro tube guitar amplifier. It's a compact, moderately easy to build, three tube, 3 to 5 watt output practice amp (around 3 watts with a 12AU7 power tube and around 5 watts with a 12BH7). The Bassman Micro's single channel preamp circuit was inspired...

martin manning wrote:I figure that 1.2A at 6.3V on the secondary is 6.3/120*1.2 = 63mA on the primary ;^)

Cool, you learn something every day.

eniam rognab wrote:just curious, why are you spec'ing a two amp fuse? i would think the lower you can get away with the better

I have 1.2 amps of just tube heat so I figured I'd need a 2 amp fuse.

I'm beginning the design stage of my next project amp, the 5F6A-M Bassman Micro. It uses three 12A*7 tubes and features a cathodyne phase inverter and true push-pull 12AU7 or 12BH7 power tube.

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Did some more comparison playing today. I ran my H&K Tubemeister 5 (single 12BH7 power tube) through my Weber 12A125A alnico 12" and JBL E130 hemp cone 15" speakers along with the Deluxe Micro. The biggest difference in tone is the Deluxe Micro's low end. It's always there no matter how hard you shr...

For comparison I measured the output of my my Firefly (2 x 12AX7 preamp and 12AU7 self-split push-pull power tube) puts out 154 milliwatts of clean power and 1.12 watts max with distortion.

Tonight I put the Deluxe Micro through its paces with pedals and fx. Hooked up a POD 400HD and tried everything. I also tried a Seymour Duncan tube overdrive, Boss PS-6 Harmonist and boosted EQ. The amp's two volume controls allow you to use pretty much anything with good effect. The main volume con...

I did some more tweaking to the amp design and the little Deluxe Micro sounds fantastic. It's absolutely killer tweed with a 12AY7 in V1 and it gets snarly mean with a 12AX7. I made four design changes during the test and tweak phase. The first was to drop the Master Volume pot from 1M to 500K to at...

The guy that did the second build has promised to record some clips when he gets the amp back together. It's apart for chassis paint and finish.

Synchu wrote: I have a 14K:8 reverb transformer around and may go crazy with couple of AT7s or AV7s as output - Twin 5e3 Micro

The tweed Harvard/Princeton vol/tone circuit may work better but the amp is a "Deluxe Micro" so I'll stick with the Deluxe configuration.