I borrowed a friend's Lelit Elizabeth.
My results with the La Cabra were similar - muddy flavors, no brightness.
Then I switched to a light roast single origin from Soul Work. On the Pro 300, this coffee was similarly muddy flavors, sour. But, on the Elizabeth the shots were bright, sweet, and fantastic.
The Elizabeth was set at 203F. I noticed the water from the Elizabeth was warmer than the Pro300 also set at 203F.
As an experiment, I measured water from both machines in a room temp glass. Not a perfect experiment, but the Elizabeth water was ~150F and the Pro300 was ~140F. Setting the Pro300 to a temp of 207 on the PID resulted in water closer to 150F.
I was only able to borrow the Elizabeth for a day. I don't have a scace. I realize these aren't perfect experiments.
Over the weekend, I bought a medium roast espresso blend from Olympia Coffee that had been rested for 12 days. The recipe in the shop was 18g -> 38g yield -> 27s on a Arduino Mythos.
Using my Pro300 set at 207F, my results were again mediocre: sour, muddy flavors.
18g dose -> 40g yield -> 27s -> 7.1 TDS
18g dose -> 38g yield -> 30s -> 7.6 TDS
18g dose -> 45g yield -> 30s -> 8.2 TDS
I'm in a position where I'm confused. I feel like my technique should be yielding better results. I've had the Pro300 for 4 years and have had more failures than success. The possibility of a temp problem may be a factor - up until last week, I've been pulling shots at what I thought was 203F. I originally paired the Pro300 with the Profitec T64 grinder. I assumed the bad results were from that grinder. But, now with the Option-O P64 I continue to see bad results.
I'm still willing to consider I'm at fault
Any thoughts on what to do next?