I know the stock loading for MM in these units is 100pF, but I’m wondering if the input caps could be changed to something lower, like 47 or 50pF, or possibly even by-passed to -0-. I have some AT carts, and vintage Technics carts, that prefer total capacitance of 200pF or less. With standard phono cables having 150pF, keeping the phonostage as low as possible is desirable.
I know some folks may say a difference of 50 or 100pF will not make an audible difference, but with these particular cartridges, I’ve experimented (with other phonostages), and can tell a difference. Other cartridges are immune, but with these AT and old Technics MM carts, it really does makes a difference.
Thanks for any input!
Thanks for the welcome. Anyone have input on changing the MM capacitance load?
That’s something you need to contact Darren about directly as I hope no one here is going to encourage you to crack open the unit and do surgery. In addition to voiding the warranty you don’t know what other unintended consequences it could have. If you haven’t bought one yet then you will still need to contact Darren to see if the factory will make the changes for you.
For impedance, you’re exactly right that 47k is the norm for MM. However, capacitance is a different story, and can make a difference with some MM carts.
I probably should contact Darren. I thought he might check-in here periodically. Hmmm…hope I can find his direct email.
EDIT: I’ve had my Stellar Phono Pre awhile now, but feel it is not measuring up with MM carts to my other phonostages, so am hoping to rectify this capacitance issue.
Check the M1200 thread as he was on it last week.
I always thought capacitor settings had no effect on MM carts, so also interested in how this works. Why only some MMs? Are there different ways to wire a cart?
edit: OK, I think I see why from this webpage: Hagerman Technology LLC: Cartridge Loading. Do these vintage moving magnet cartridges have low inductances?
What I would do first is move to some ultra low capacitance cable such as: Stereo Cables at Blue Jeans Cable.
These blue jeans are spec’d at 12.2 pf/foot. That is pretty low!
It’s a better option than voiding your warranty or causing a potential problem in the unit. The capacitance is there not only to control the Q of the HF response but to form a low pass filter so that the input stage doesn’t pick up RF.
There are a lot of options out there for cables that will minimize the capacitance that you add on top of the 100pF. Remember, the length of the cable directly correlates with the amount of capacitance it has. To calculate the final capacitance of a cable, find the pF/foot spec and multiple that by the cable length in feet. Obviously, you can minimize capacitance by going with an ultra-low spec’d cable and minimizing the length of that run.
Hi Darren, and thanks for your reply. Unfortunately, the phono cables on all but one of my turntables are either hard-wired into the chassis, or have a 5-pin plug connection into the base of the tonearm, so I would need to re-work the terminations. Ugh.