A Muchedumbre XL in the wild

HM in the Netherlands shared a beautiful Muchedumbre XL build with me recently. He adapted his build to use a pair of Telefunken ECC83s (jealous). My notes on tweaks from our emails:

“In the Muchedumbre XL, adapting for different tubes is not so difficult (compared to resistor loads). A tweak to optimize for a 12AX7 in this circuit would be to lower the Rseries value a bit (1k5 in the original schematic). For a 12AX7, a value closer to 1k is optimal but this also depends on the amplifier you’re driving. I would not say this value is too critical unless you have a very low input impedance on your amplifier.
The other value to tweak is the cathode resistor (300 in the schematic for 12AU7). A 12AX7 may be happier with a higher value here. Something around 1k-1k5 gives you more signal swing before grid current which is generally a good thing.”

He also includes a 45 second bypass relay based on the NE555 to save his powered speakers on power on and off.

Beautiful build, HM!

Additional pictures of wiring and testing:

A Muchedumbre in the wild!

As I mentioned in a couple recent posts, my workshop is in boxes while moving. Good news is that those boxes are finally in the new space and just need the shelving built to unload them.

In the meantime, here are some pics of a Muchedumbre build by someone else! As you can see, PB has a very tidy build on a compact footprint. He reported no issues with the simple circuit in our email exchange and says it sounds fantastic! I love the way he’s matched it with the speakers and other DIY components. Very attractive.

I hope to be back posting about my own adventures again soon. First step is to measure the new space and start laying out the shelving and workbenches for the shop…