After a year of playing with a Baratza Vario and Pavoni, and recently getting a La Spaziale Mini II, I still have yet to make a shot that is as good as some of the best shots I've ever had. I've heard tons about how a Pavoni at its best is pure heaven, and how a La Spaziale is as good as machines twice the price, but I still cannot get to the result I want: A slow, thick, drippy shot that takes 30 seconds to pour and is a deep reddish brown. It doesn't seem to matter how fresh my beans are, where I got them from (Counter Culture, Intelligentsia, local roasters, etc...), how hard I tamp, how much I grind, etc...

With the La Pavoni, the best I could do was choke the machine, then back off a bit and get a thin steady stream that seemed to blond too early and didn't produce heaps of crema. I found that a relatively light tamp and fine grind worked best, but that said, the shots were always thin and lacked body. I was grinding about 12g of beans into the Pavoni basket. Overdosing choked the machine, underdosed shots were undrinkable.

With the La Spaziale, I am very happy with the taste and the initial crema (if I sip slowly and just get the top layer on my tongue) but there is something wrong with a shot that takes only 15 seconds to produce and easily gets to nearly 2oz in the cup. The crema has some decent mottling but is overall light and once it settles, is a layer that I find to be pretty thin (I've seen shots that even after settling were half crema). I went through an entire 12oz of beans tonight experimenting -- dosing up to 15.5g in the double basket, griding finer, tamping harder...but the same result: If I went too fine and choked the machine, backing off a bit only resulted in a slow-pouring thin shot with even less crema than coarser grinds and faster shots were producing. It still seemed to blond too early (at the 15s mark), though. Overall, I seem to have had the most success with a slightly coarser grind than the La Pav and a much harder tamp, though I haven't really fully explored grinding much finer and tamping much lighter -- filling the double basket with a very fine grind seems like way too much coffee.

I understand I'm not a master barista by any stretch but I do have a good idea of the result I want and can't seem to achieve it. I've used a naked portafilter to try and diagnose, and while there's definitely a bit of channeling, I've certainly seen nice shots poured that didn't look technically much better than mine. I would've thought that with my equipment (particularly the addition of the Mini II), I'd be close to what I wanted but I'm not happy with peak flavor coming in a virtually-gushing 15s shot -- I have to be able to do better than that. Any ideas?

Although Lever and pump machines would possibky require different grinder setting i would say grind finer and/or tamp firmer. I cant tell from your post if you have played with those variables but grinding finer will definetely help. Also perhaps you can adjust water/pump pressure?From experience, i wouldn't play with more than one variable at a time. i would start with adjusting grind

Updose! Go as high as you can, and adjust grind to produce your 30 second shot. You'll have a darker shot.

I think that your going to want to grind finder to get the slow, drippy shots and adjust the other variables (dose weight, tamp, distribution) to prevent choking the machine.

With my Gaggia Factory (~=La Pavoni Pro) I have to grind fairly fine, finer then I was used to with my La Peppina and I dose at 14 g. The 15.5 g in La Spaziale also seems on the low side and I think you have room to increase the dose.

I would try 14 grams in the La Pavoni (if your still pulling shots on her) and probably 16 - 18 grams on the La Spaziale (no real experience on this one) and adjust the grind again to back it off just from choking. Maybe back off on the tamping and just make sure you've got a good leveling tamp and let the dose and grind do the work.

As for color, I think a lot of that will come from the type of the bean, though the darkness of the crema will depend on the dose and grind.

Check that you're not applying downward pressure on the tamper when you polish the top of the puck. It's really easy to break the seal between the puck and the basket and cause a lot of the issues you're finding with your shots.

There is no way for any of us to know.
The correct advice is already above. Find someone who is a good barista, get them to help.

Perhaps it's a problem with the Vario. Maybe you should do that allen key thing that I've seen people talk about doing to it.
And if tamping is that important to you get a bathroom scale and tamp the same every time...

You are working with a set of mental constraints (low dose, slow, drippy, 30 second shots, with lots of crema) that will have making bad shots forever. You are trying to make a low dose ristretto that flows and tastes like a very high dose ristretto/normale, pulled on an LM, Seattle style: this is a truly bad idea on a La Pavoni, and if you actually want crema and body, it's a lousy idea on the Spaz as well (unless you can use a triple basket with about 21 grams).

Weigh and time your shots. They should run around 25 seconds and weigh about 1.5 times as much as the coffee dose (67% brew ratio). This is the sweet spot that works for lots of machines. With fresh coffee, a shot in this range will have both crema and body.

Now stop changing your tamp -- it's not a variable. Use the same distribution and tamp routine every time. Do as little as possible and as light as possible consistent with not getting channeling.

If you stay in the 25 second/67% brew ratio ballpark, grinding coarser and dosing higher will get you stronger tasting shots, grinding finer and dosing lower will get you sweeter tasting shots.

That's all.