Question about optimizing the Eros 2 for specific cartridge

[brianbuntz]

Hi all,

I'm about to build my second Eros 2 and wanted to optimize it (if need be) for a specific cartridge -- either the Nagaoka MP-300 or Nagaoka MP-500, which have essentially identical specs (but a different shaped stylus).

Here are the relevant details from the MP-500 (which match those of the MP-300):

•Output voltage: 3 mV (5 cm/sec)
•Impedance: 47 000 ohms
•Dynamic compliance: 8.5 x10-6/dyne

Would the amp benefit from more capacitance? Some experimentation may be in order, but would appreciate any recommendations.

[Paul Birkeland]

This article would appear to suggest no more than 150pF:
http://www.nagaoka-deutschland.de/pdf/TESTBERICHT%20AUDIO.pdf

Luckily with the Eros the input capacitance of the EF86 gain stage is really low, so it's mostly down to the capacitance of your cabling.  You could certainly try swapping out the 47K resistors at the input with 100K, but I think you'd want a test record and a scope or FFT to get a good picture of what's going on.  You could also try adding capacitance maybe 47pF at a time, up to maybe no more than 200pF.

[brianbuntz]

Thanks, Paul.

I just obtained a test record, but don't have a scope, so perhaps I'll get one. Otherwise, I'll try experimenting with capacitance at 47pF, as you suggest. I should get the kit today, so will report back after I make progress with assembly.