Thanks Merle.

Are you happy with the GS3 with modified MP? Or is it hard to reproduce a shot since you can not store a profile like on the Strada EP?

Niels,

Yep, still happy with it. If I were in the purchasing phase again I'd buy the same machine for the same reason I did then - great look and size, 110V power, no outboarding of a pump, runs off a reservoir, great performance, and world class support. But that's me.

Everyone has different needs and desires, so choose the machine that hits all or most of your checkboxes.

Anyone heard of any updates for retrofitting the new conical valve and steam wand?

I haven't seen anything official, but I noticed the parts manual for the linea PB (pdf not webstore) has been updated with the conical valve group parts which should let you come up with a parts list and build your own "kit" (as was done with the Strada MP parts manual to make the kit for GS3 MP previously)

Page 34,35:
http://www.lamarzoccousa.com/wp-content ... V2.3BW.pdf

Its on my todo list.

After reading all 9 pages looks like the overall comments are split but my opinion and cash will be to get a Slayer as it's repeatable or I believe more repeatable that the new LM
I thank you for all the info
Bill

Just trying to understand here, as I'm a new owner of a GS3.

The current model I just received last December, doesn't have the new conical valve upgrade. However, I'm still able to control the water flow rate after i've activated the pump and the pressure stays at 9 bar.

On the slayer, as explained by others, doing similar thing but instead it has a needle to control the flow rate.

In both of these machines, there's no pressure profiling but instead it's flow rate profiling. Am i correct?

There is no difference between pressure and flow rate other than how you view what's going on.

Ira

So then, the new upgraded GS3 MP is the added "pressure profiling" feature which allows us to control the group head pressure. But in Slayer, there's no such feature?

I've also been told that the separate mod kit you buy before they launch the upgraded MP version with the new conical valve has difference between them.

Is there anyone from La Marzocco can verify this?

ira wrote:There is no difference between pressure and flow rate other than how you view what's going on.

It's true that flow and pressure are linked, but the terms 'flow profiling' and 'pressure profiling' have specific meanings for pulling espresso shots.

The flow profiling provided by the Slayer needle valve is intended to control the flow rate of water into the puck during pre-infusion (which they call pre-brew). This is the period when the basket is filling with water. There's no pressure at the puck until the basket is full, so it's all about the flow rate.

Once the basket is full, pressure begins to rise. The rate of the rise to maximum pressure is also a function of the needle valve setting (along with the fixed 0.7mm flow restrictor that's always in the water path.) With a smaller opening at the needle valve you get slower pre-infusion and a slower ramp to max pressure. With a larger opening at the needle valve, you get faster pre-infusion and a faster rise to max pressure. Essentially, the ramp from basket-full to max pressure is a pressure profile.

So the needle valve does both flow profiling and pressure profiling. But there's only one setting for each shot that defines pre-infusion time and ramp speed. After max pressure is reached, the needle valve is bypassed and the pressure will gradually decline as the puck resistance decreases due to water passing through it. That's a pressure profile as well, similar to what a lever machine does. It's a function of the preset pump speed and the puck density, so you really can't control it much. In contrast, rotary pumps with bypass valves maintain constant pressure at the puck.

I've heard it's possible to adjust the speed of the Slayer gear pump while pulling a shot, which means it can do manually controlled pressure profiling at any time during the shot. My sense is that the machine wasn't really designed for this because it's done through the front-panel interface and might not be as easy as using a lever or a paddle or a potentiometer.

The new GS/3 MP can also do flow profiling and pressure profiling, but it's manually controlled during the shot rather than being preset like the Slayer. For slow pre-infusion, you move the paddle to the right just enough to open the valve. My understanding is that the new conical valve gives you a lot more control over the pre-infusion time. Once pressure begins to rise, you can move the paddle further to the right until you reach maximum pressure. The rate at which you move the paddle controls the ramp speed. As far as I know, you can move the paddle to any position that keeps the pump running to further profile during the shot. So, the new GS/3 MP offers dynamic and easier control over flow and pressure profiling, but the profiles may not be as easy to repeat as they are on the Slayer. Based on my experience with a pot-controlled variable-speed gear pump, I believe it isn't all that hard to repeat shot profiles once you've practiced it for a while.

Incidentally, the purpose of slowing the pre-infusion is to make it possible to grind much, much finer. This is helpful when pulling very light roasted coffees that are difficult to extract or even coffees roasted for brew. Of all the profiling options, I've found that this has the most impact on taste. A slow ramp down can take the edge off a light roast, but the effect is more subtle.