Topic: Pre-amp for Nak CM300s?

[dgale]

FWIW, in my early DAT days (and pre-Neumann days), I used to run my cm300s into my old Sony D5 for it's pre and send the analog line out to my Sony D7...I just liked the sound of the D5 better than straight to the D7, as well as giving me L/R level control I didn't have with the D7...and of course since I wasn't actually running the cassette deck, anlaog generations were a non-issue.  I realize it's not very germane here but this discussion made me think of that - I always liked the sound of the 300s and the D5.  Matter of fact I'd consider dusting off the D5 to do this again if/when I dusted off the 300s...too much gear collecting dust I guess.

[dgale]

The last time I remember running my nak300s was at a LL show in Bend OR in July 2000...makes me realize I better go check that the batteries weren't left in the mics...yikes!  Time flies.  At a minimum I'm sure the batteries are dead and I recall they were a pain to replace, although maybe less so these days with the internet being what it is.

[acidjack]

I used to run mine into the Zefiro InBox aka the Denecke AD20.  Not the cheapest option, but it's small, has dual volume control... I guess the only problem is that it can't output digitally to the R-09HR...

[dgale]

I used to run mine into the Zefiro InBox aka the Denecke AD20.  Not the cheapest option, but it's small, has dual volume control... I guess the only problem is that it can't output digitally to the R-09HR...

The R-09 doesn't have a digital input, so this is a non-issue. 

[fmaderjr]

The R-09 doesn't have a digital input, so this is a non-issue.

That's why acidjack said the only problem was that it couldn't output digitally to the R-09HR.

[JEMS]

I have been using a Naiant battery box to power my Busman modded Nak 300 capsules and it is working brilliantly. The modded caps have mini XLR and the Naiant box has two mini jacks in so the cable is mini-XLR female to mono 1/8 inch. The Edirol appears to love the feed coming into it from that. Very workable for stealth.

[Roger Gustavsson]

What about this solution for the Nakamichi CM-100/CM-300? Are there any faults in my schematic? The output is impedance balanced. There are AC-coupling capacitors at the input of my soundcard.

http://www.twin-x.com/groupdiy/albums/userpics/Nakamichi_and_SSM2019%7E0.GIF

I can be put in a small enclosure, like Hammond 1455C1201.


Roger

[Roger Gustavsson]

Thank you for your advices!

Here is a revised schematic.

http://twin-x.com/groupdiy/albums/userpics/Nakamichi_and_SSM2019%7E1.GIF

The data sheet of the SSM2019 have a simpler RF filter, just a capacitor across the input terminals of the IC. So my 15R series resistors and the parallel 220pF capacitors interfere with the shunting capacitor?

Will there be any risk of having interference on the supply to the JFET? (That was why I through in a capacitor in my original schematic)

How much do I have to worry about the DC offset? Will it not be taken care of at the input of the soundcard (DC-blocking capacitors there)?



Roger

[Roger Gustavsson]

I would probably build the amp without and measure high-gain performance through a full battery cycle, and add a compensating load if necessary.

Could that compensating load be feeding a LED from the negative supply, a power indicator? The Idss of the JFET is about 1mA.

[Roger Gustavsson]

mshilarious,

Will this solve the problem with the input offset?

http://www.twin-x.com/groupdiy/albums/userpics/CM-300_with_preamp.GIF


 
Roger

[dave570]

OK, so I have the MX-100 now and a battery box to power it for 4-5 hours of recording. I know the MX-100 has L, R and Blend for the 3rd mic. Although I do have 3 Nak 300s, my t-bar holds only 2 mics and so I can't really put the 3rd mic up. Are 3 mics required or can I get away with just 2 mics into the MX-100?

[gdplusmore]

yes...just turn the middle blend nob down all the way...