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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: nOrD on February 28, 2010, 08:31:37 AM
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Hi all,
I would like to extend my gear with a good quality preamp but do not have enough money to buy a Sound Device, for instance. I have some knowledge in electronics, mainly analogue audio and has built some amps, circuits before.
What I would like to realize is a quiet linear portable amp with two balanced I/O, switchable phantom power. Rather minimal design but quality parts. I have a little stock of caps, resistors, wires, etc at home.
Does somebody could help me with circuit and PCB design to think of? Cheap kits are also very welcomed :)
Thank you,
nOrD
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Fixed or variable gain? Battery power? Size requirement?
Fixed gain (I think about 30-40dB), battery power by RB-270 (9VDC/5400 mAh), size depends on the covering box required, but something about 200x100x50 (in mm) would be perfect, I guess.
I forget to mention that I have a lot of tubes, from tiny nixies to larger types though DC/AC power conversion throw me away to think about anyway loved tubes for this project.
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The preamps in the R-44 are very good; why do you want to replace them?
I mean, I use an outboard Grace V3 for channels 1 and 2 most of the time, but that's because I find the metering on the V3 much clearer and I can select the low-cut frequency. It's not because the R-44 has bad mike preamps by any means. I've used them and gotten very good results.
I'm just asking. You might really have a reason.
--best regards
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The preamps in the R-44 are very good; why do you want to replace them?
I mean, I use an outboard Grace V3 for channels 1 and 2 most of the time, but that's because I find the metering on the V3 much clearer and I can select the low-cut frequency. It's not because the R-44 has bad mike preamps by any means. I've used them and gotten very good results.
I'm just asking. You might really have a reason.
--best regards
Hi DSatz,
Sure, I do agree with that R-44 has great preamps. The main reason behind my wish to add a preamp is that when I use my shootgun mic (AT815b) I need some more gain. I know that this is because of the relative low sensivity of this type of mic (actually -39dB with PP) and I would like to regain that "loss" by using a good preamp.....
or a stepped attenuator with transformer or with a series of resistors:
http://www.iagaudio.com/steppedattenuator.htm
http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_ATTENUATORS_13.html
http://www.sacthailand.com/Transformer_Attenuator.html
I used similar transformer attenuator between my CDP, turntable and power amp, and can tell you, it has make rounds of many expensive high-end preamps. Only impedance matching would be considered with such an attenuator, and voila: we get a unit that needs NO battery, can fit in your pocket, has NO electronics - just to mention first coming arguments.
I wonder if somebody runs their recorder with attenuator as preamp? I am very interested.
Greets,
nOrD
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An AT815b has ~12 mV/Pa sensitivity, which is certainly not low; Schoeps "Colette" series mikes have very similar sensitivity, and my R-44's mike preamps have well more than enough gain for them. So I just don't see your problem.
--best regards