JRDG Company Special – Concentra MM/MC Phono Modules
Available around 1998
Retail price in 1998 in the Netherlands 884 euro
Likely also compatible with the Concerto pre/integrated amp.
With thanks to Joachim for the detailed pictures!
If you have more information like price or introduction date, do please let me know.
More Jeff Rowland
Jeff Rowland Company Special Main Page
Jeff Rowland Company Special Phono Stages
Dear Sir,
I bought few years ago a Phono card for my Concentra from Jeff Rowland. I lately change my cartridge, switch from Mm to Mc. And I would like to know the right position of the switch on the phono card. A big thank you to you if you can help.
Regards
Hi Asti Marco, I do not have any documentation detailing this but from looking at the pictures this should be straightforward. The practical difference between MM and MC is merely the amount of gain, which you can set according to your need with the “gain” dip switches and use whichever sounds best. Basically, and usually, MC’s have lower output and need more gain. Don’t worry, as long as the amplifier’s volume control is not turned up very loudly, you cannot cause any damage. The load can then be used as per taste. In general, higher Ohmic values yield the most dynamic and lively sound while lower values dampen the sound to restrict overly bright cartridges or simply to achieve the best sound according to taste.
Thank you. Very helpful.
I saw the pictures (Figure 10: detail of phono card PCB) I notice there are only two positions of the switch: down is off , in the meedle on. That’s right?
Thank you again for your time and help.
Marco
DIP switches usually only have two positions and these seem to be the same. When referring to resistors being switched in the circuit, On = same as Close (as in closed circuit, meaning that the resistor is connected) and Off = same as Open (resistor not connected). When there are two DIPs side by side, potentially there is the option to combine two resistors to achieve a third value. Do note that while I think that everything I shared so far is correct, it is conjecture as I have never used a JRDG phono module. I have just emailed Jeff Rowland. If I receive more information on the subject then I will let you know.
Hello Christian,
you are a great Man.
Best week end to you.