New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage

[Mgt280y]

The original Murder One was 'baby's first amp'. I've learned a lot since then and the design has gradually changed over time. This one is a major upgrade, and now it's looking much more like a serious amp. What's changed:

• Input section is different (R6/R11), the original was more like what you'd see in a pedal.
• Preamp stages rebiased with 47k anode resistors (R1 and R2) and the addition of cathode resistors and bypass caps (R9/C19 and R10/C15)
• Grid stoppers added between stages (R12 and R13), R12 is essential, R13 is optional and may be jumpered instead
• New schematic with component values matching the...
• ...new layout
• Tweakable values are asterisked *
• Fatter traces and pads on the layout - for a fatter sound!

The result of these additions is that the anodes are running at much higher voltage, the clean sound is much better than it was - very usable now, and the cranked sound is fatter and has more body.

As this is the Modder's Delight version, any tweaks to suggested values should be considered in conjuction with this article: http://www.diystompboxes.com/pedals/tubedummy.html

I have verified the new layout onto perf, it works really well. If anyone feels like etching me a board or two I'd be proud to accept them!

Good evening all, im in the process of building this verision, done a slightly different layout for pcb

Couple of things is there a verson 7 as the thread references but can find a schematic or layout

I noticed duribng the evolution of the murder 1 the transformer has changed what does this affect and have people used other than 1750a on this verson

Main question is if i wanted to add a headphone out 3.5mm jack how is it added to the schematic and in terms of loading does the 8 ohm speaker always need to be connected/dummy load.

Thinking maybe speaker and head phone sockets on a spdt so i could switch from cab output to headphones

Any help as always much appreciated

[thomasha]

Version 7 of the modder's delight version.
Without the bias switch, but with a preamp out switch.
Look for the vibratone subminiature tube amp thread for more information. I think an 8 ohm load was added in case there was no speaker conected (preamp signal only).

The headphones output requires another Jack, where both speakers are in parallel.
You can't use the same output Jack because amp cables normally are mono, meaning you would ground one side.