Trans-fi Terminator T3PRO opinions please...

Spirit, with respect, that sounds a lot like an ad hominum sneer. We are all, I would have hoped, governed by what is observable. That is science. That is my way. The other way is superstition.

I stand by what I wrote.

I’m confused by some of the above comments about measured pressure.

Rated pressure for these pumps is inverse to air flow. Max flow occurs at min pressure(ie. with free-flowing air unburdened by tubes, tanks, or air manifold). For example, the paralleled dual outlets of Rena 400 are claimed by the manufacturer to produce 4 psi max. Under full load-- with a pressure gauge placed at the end of my 20' silicone hose whose output is stopped up at the outlet to block air flow to zero-- my Rena 400 produces 3 psi max. After connecting the hose to the Terminator air manifold, max measured pressure drops to around .3 psi. Then with the Rena’s output adjusted downward to the point of obtaining the minimum pressure required to prevent skipping(which is Vic’s recommended set-up to minimize turbulence) measured pressure falls to around .1 psi.

However this is not the way that I measure or regulate pressure. I position a high-quality brass needle valve close to the Terminator air manifold, downstream of a co-located 5 psi Wima dial gauge. This way the dial reads the back-pressure behind the needle valve instead of pressure between the needle valve and the air manifold. With the Rena’s outputs turned wide open, the dial now reads across the full sweep of 0-3 psi. As the needle valve is opened up to introduce flow to the tonearm, the pressure drop below the base line of 3 psi measures the pressure lost through the manifold to float the tonearm slider. The minimum pressure drop required to prevent skipping is 1 psi. This is indicated on the dial as a drop from 3 psi to 2 psi. Simply put, it takes 1 psi of pump pressure to operate the tonearm.

Why is this significant? First, it demonstrates that a pump with a 1 psi output is necessary and sufficient for Terminator. Second, it demonstrates that the Rena loafs at one-third of its capacity in this application. A higher pressure or higher flow pump need not apply. The only remaining meaningful variable is the smoothness of the air flow.

It’s conceivable that the Hi-Flow pump pulses less or that a leaky flow tank with cotton balls inside further smooths pulsing. Other differences may include the quality and positioning of the pressure regulator. I can hear the difference in turbulence between a smooth brass needle valve and a cheap plastic aquarium valve. I like positioning the brass needle valve as the most downstream link in the chain. This might help filter pulsing of the spring mechanism of the upstream dial gauge.

I may try the Hi-Flow pump, but am first inclined to add more and larger smoothing tanks-- only a gallon plastic can so far. There seems to be a wide range of opinion in the fish community about whether the Rena is loud or quiet. YMMV. There is a youtube video of a guy quieting pump vibration down considerably by hot-gluing the pump motors to their chassis mounting points. I may try this.

Terry, no sneer intended. It's just that I relayed users' ideas on more powerful pumps, and he's perplexed because it's a deliberate low-pressure design.
Can you describe in a great deal more detail what the schematic on such an arrangement is? I would be curious to investigate.

A thoughtful post, Dgarretson.

Even so, I do not agree that you have demonstrated that a pump with a 1 psi output is necessary and sufficient for Terminator. First a technical quibble: as you note, P and V are inversely related, so that it makes good sense to speak of pressure at a specific load, to wit, the pressure at the volumetric load of the Terminator. I am not sure that your measurement technique accomplishes this, but have not thought about it much - is this a standard engineering technique?

Second, it seems to me that you have demonstrated that Terminator works at 1 psi (your technique), but not that 1 psi is optimal. I have measured the pressure in the line, after regulation, and this is clearly different - the saddle floats at a much lower pressure, and so my measurements are approximately 10% of yours.

My conclusions are the same as yours: just as pure DC improves amplification, pure air (pressure) improves flotation. The question arising is, what is the cost/benefit curve? Or, how heroical should we get? Since I didn't know the answer, I bought a more powerful pump so that I could waste energy in smoothing, and the results are, to me, well worth it.

Terry9 wrote "I have measured the pressure in the line, after regulation, and this is clearly different - the saddle floats at a much lower pressure, and so my measurements are approximately 10% of yours."

As I noted in my post, I too measured around .1 psi after regulation-- so on this point we agree. The 1 psi drop upstream of the regulator merely indicates how much pressure is needed from the pump to produce .1 psi at the arm. At 3 psi max capacity the Rena can make .3 psi at the tonearm. So unless you want more than .3 psi at the tonearm you don't need a stronger pump.

I believe the basic math is that at margin of air pressure necessary to float the slider, the volume of air flowing through the manifold is identical with either pump. The pressure/flow relationship is a function of the pressure drop through the system-- not of pump output. The slider doesn't care about the air flow-- only that sufficient vertical force/pressure is applied to conquer gravity. However, the pressure/volume relationship changes when you introduce a leaky tank or air line. A larger pump may be needed to make up for that loss.

I can't conceive how a leaky tank could help, unless this somehow smooths pulsing.