RGR Model Four pre-amp and capacitance

[wizargoz]

Just got a great looking preamp- RGR (Robert Grodinksy Research) Model Four- but haven't hooked it up yet. (1st 2 Pics below are from AK member House de Kris's gallery). 3rd pic shows the capacitance loads for different cartridges on the preamp back..

My question is: If my Audio-Technica cartridge stipulates 100-200 pF, then I would probably choose the "130pf" inputs on the back, correct?

[House de Kris]

Method for determining switch position is relatively easy. Here's the equation:

preamp load = cart spec - cabling capacitance

So, for example, if your cables contribute 150pf of capacitance, I'd recommend the 30pf load.

[markn2wae]

The 130 PF input selection seems right to me, there may be special "mods" you could do to get it "right on", but I leave that to the "specialists" who know this gear best.:thmbsp:

No damage will be done if you "experiment" with the setting, just turn down the volume all the way when you switch settings.

The worst you can do is to have poor sound quality from the phono section at the wrong settings, although if your TT has very high capacitance in its wiring, you may have to use the lower setting, but not likely.

Mark T.:music:

[wizargoz]

Hey, House de Kris, do you still have your RGR Model Four?

So, I would also factor (as a negative) cable capacitance into the EQ? That may be a bit hard as I am using all old TT's like Pioneer and Technics, and do not have original manuals, so I'm not sure if I can get that information ...:scratch2:

[House de Kris]

Yes, I still have my RGR Model Four. Yes, subtract the cable capacitance from the desired total load to determine the switch setting. 100-200pf is a pretty light load for a cartridge to ask for, so most likely the correct position will be 30pf on the preamp. But, as always, and as Mark suggests, experiment!

[wizargoz]

Here she is out of the box, and another pic with my B&K Sonata PRO-10MC.
Loved the B&K but missed the tone controls!

[sheltie dave]

Robert is still alive and kicking up in Skokie, Illinois. This line of preamps is one of the all time audio sleepers, with a great phono section that has more than a few audio friends in town scratching their heads. It doesn't look like a world beater, doesn't cost much, and doesn't have the name, but it delivers when recapped. :tresbon:

[wizargoz]

Well, hooked up to my tube amp now, it sure sounds sweet!