Help fine tuning electronics for loading cart

preston1000

preston1000

Active Member
I'm using a Nagaoka MP-50 body with a MP-500 stylus and would be interested in knowing how to figure out where my system needs help for optimal loading of the cart.

1. What audio interface is recommended?

2. Which test record?

3. A software for recording cart output?


Trying to keep it to minimal funds to get through this so I don't have to change a lot of unnecessary items that were not needed.

What I think needs to be done is replace the Sansui AU-717 phono board 47k to something higher, maybe 75k.

Not even sure I'm going about this right.:dunno:
 
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I want it to bring the mids more forward and more detailed highs. The Nagaoka carts are somewhat laid back as is the Sansui AU-717. Don't know how much more to go beyond 47k, that's why I want to test the output of the cart to perhaps get a better understanding what is needed.

Either way, I'm going to replace the tonearm cables with some litz wires, and who knows, maybe that will satisfy my ears.
 
Do you mean replace a resistor on the phono board? Or the whole board? If there’s a 47k resistor you could replace with 75k, you could have the 75k and then adjust down to 47k if desired with plugs in parallel.
 
Bob_in_OKC said:
Do you mean replace a resistor on the phono board? Or the whole board? If there’s a 47k resistor you could replace with 75k, you could have the 75k and then adjust down to 47k if desired with plugs in parallel.
Click to expand...
With op-amp electronics or with valves there's often a resistor near the input of the circuit which defines the input impedance and which could be changed without upsetting anything else. However, discrete transistor circuits are usually not so simple and changing a resistor could change the bias, alter the gain...anything really. I wouldn't recommend changing a resistor without studying a circuit diagram first.
A much simpler option would be to experiment with different amounts of load capacitance at the input. Extra capacitance tends to curtail the extreme high frequencies but puts a peak into the lower HF range that gives the impression of extra brightness. It may or may not work but is less risky than changing resistors.
This page explains it:
http://www.hagtech.com/loading.html
 
The easiest (although not necessarily the cheapest) solution is to purchase an external phono stage with adjustable impedance, capacitance and gain settings. That way, you can accommodate pretty much any cart that you choose to experiment with--all done in one.
 
savatage1973 said:
The easiest (although not necessarily the cheapest) solution is to purchase an external phono stage with adjustable impedance, capacitance and gain settings. That way, you can accommodate pretty much any cart that you choose to experiment with--all done in one.
Click to expand...
One problem with that, though, is finding one that goes above 47k or 50k.
 
Bob_in_OKC said:
@rothwellaudio

How about building a box with resistors in it, to put in series ahead of the phono stage?
Click to expand...
Yes, that's a possibility, but there's also a penalty because you would lose some signal level. For example, a 10k resistor in series with a 47k phonostage would form a potential divider (like a volume control) and you would lose 1.7dB before the signal entered the phonostage. Also, the input capacitance would be in parallel with the 47k resistor but not in parallel with the 10k resistor, so that would skew the frequency response. Finally, the source resistance seen by the phonostage would go up by about a factor of ten, and that would have a negative impact on the noise of the circuit.
All in all, I wouldn't recommend a series resistor unless there was a very good reason for it. Adding one in the hope of making the cartridge sound less "laid back" isn't a great idea in my opinion.
The simple solution would be to buy a cartridge with a less laid back sound.
 
rothwellaudio said:
The simple solution would be to buy a cartridge with a less laid back sound.
Click to expand...

Unfortunately I don't think a new cartridge would be feasible so I will just have to try some options to see what happens. We'll see what happens after the headshell connectors and tonearm wires are replaced, hopefully that will be the end of this rabbit hole.
 
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