2. analog
  3. 1139973790

MacCormack Upgrades from SMc Audio?

Hi all, My Phono Pre-Amp is a MacCormack Micro Phono Drive bought back around '96.

Just doing some surfing today, I stumbled upon Steve MacCormack's site, and see that he lists two upgrade revisions for the Micro Phono Drive, and also produces a better outboard Power Supply versus the original Wall Wart that came with the unit.

From the sound of his description, his better revision B upgrade essentially replaces just about every component in the unit, going to better Burr-Brown Op Amps, trimmed RIAA Stage, Vishay components, etc, etc. The cost of this upgrade is said to be $500, and this was actually what I paid for this unit new when I bought it.

Also, the Outboard power Supply costs $275, WBT RCA's another $60 Whattya think?
markd51
markd51 OP
763 posts
 
I'll have to give this a try. I know I have the 3 sets of resistors still that was originally supplied with the Unit. Just hope that the paperwork is with it, so I can identify which was which.

Guess the most important thing is to make sure I match the pairs that I throw in, as it takes two of the same value to be installed.

From what I remember from the instructions, two would be inserted into thier respective "ports" I'll call them, by bending the wire ends, making the resistors's wires look like little a little "U" and inserting them.

What should I expect with the values that Steve has mentioned eralier?
Better restraint?, smoother sound? Or?

I'll report back when I have more. Thanks, Mark
markd51 OP
763 posts
 
Hi Again, So what would you folks feel would be the best loading for my original Hi-Output Glider with AQ PT-6 Arm?

I read mention of a general practice of loading to 25 times that of the Internal resistance? Does this mean the Cartridge's Internal Impedance? If so, My Glider is listed at 85 Ohms Internal Impedance, in which number I come up with is 2125?.

Thier recommended loading is very vague, from 1000-47,000 Ohms. What would be the best place to start with this MC? Mark
markd51 OP
763 posts
 
I'm thinking my suspicions, and computations are correct, and that approximately 22K would be a good place to start with the Glider?
I may not have the correct resistors then in this case, and might need to buy them? Where can I buy these Caddock resistors from? What do I ask for? Sorry for the dumb questions! lol Mark
markd51 OP
763 posts
 
I have just found my little bag of 3 pairs of resistors that were included with my McCormack Micro Phono Drive. Thier values are 1K ohm, 200 Ohm, and 100 Ohm.

It states in the manual, that these resistors are to be used in parallel with the 47k ohm resistor already installed from the factory, and to insert 1 for each channel in the sockets marked R/C1 and R/C2.

It says NOTE, if you wish to calculate the total load resistance with these resistors installed, use this formula:

R(total)= 47,000 x R(user) / 47,000 + R(user)

What should I use? If I don't appear to have what I need, what resistors will I need?

Sorry for being dumb about this, math was never my forte, and thank you all in advance. Mark
swampwalker's avatar
swampwalker
5,138 posts
 
I had a Glider Lo output and found it sounded best loaded at 100 ohms. If you do a search, you will find a formula in a recent thread for calculating total resistance of 2 or more resistors in parallel. That is probably what you would end up with if you are inserting additional resistors, but leaving the 47k load in place. And your description of how to insert them sounds correct. I found it to sound more alive. Not brighter but less flat.
More to discover