Hiz preamp for plate reverb pickups.

Studio Mollan

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Oct 26, 2011
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Hi.
I'm looking for schematics, advise on preamps for my DIY plate reverbs. The Bo Hansen di would have worked if it hade a line output. It will be connected to my desks fx return (600ohm).
I'm kind of on a budget so a full microphone preamp with di won't work for me.
Quiet and easy build is preferred.
Anyone with experience on this out there?
/
Emil
 

dmp

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I run the piezo pickups into a active DI followed by a mic preamp.
I have been thinking about this too, however, to simplify and maybe improve things.

What is your budget? You're basically describing a DI mic pre without the input transformer. So it won't be much cheaper.
I've been thinking about using 990 DOAs.
Honestly I'm not sure it will make much difference compared to off the shelf like I'm currently using.
 

Joechris

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Norway
A BB2604 opamp with a fixed gain around 30-35 db should work for a stereo plate pre. A vero board and a few resistors and some caps. Should cost 10-15$ or so...
But you need a power supply that will add to the cost. For a DOA version you need one with FET inputs, unless you have a FET buffer infront.
 

dmp

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Just took a look at the datasheet (OPA2604)
Figure 7 shows a high impedance amplifier with a fixed gain of 40 dB.
Two OpAmps per chip too.
Great suggestion.
 

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Studio Mollan

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Thanks for your great advice guys!
I'm leaning towards the Bo Hansen di project and them running them through my outboard preamps while mixing.

Thanks again!
/
Emil
 

haima

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Melbourne, Australia
dmp said:
Just took a look at the datasheet (OPA2604)
Figure 7 shows a high impedance amplifier with a fixed gain of 40 dB.
Two OpAmps per chip too.
Great suggestion.

That's pretty much what I have made for my EMT140 with the updated piezo pickups...

OPA2604

Very quiet. Sounds good. Cheap. Do it!
 

JW

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Portland USA
Hey guys,

I'm bumping this with a couple questions. I'm planning on building the linked OPA2604 amp for the very same reason: plate reverb piezo pickups.

This is very basic, I'm sure, but what is that tubular thing in the linked schematic? A coupling cap? If so, what value?

Also, it would definitely be cool to use the same power supply supply as my driver amp, which is a John Lindsey Hood 10watt amp like here: http://www.ebay.com/itm/SC-HOOD-JLH-1969-10W-10W-Class-A-amplifier-kit-/160886486402?pt=US_Amplifier_Parts_Components&hash=item257594f582

It needs a 24V DC single ended supply.
Can somebody recommend a cheap +/-24V supply that has ample current in order to tap the positive 24V leg in order to power the driver amp, but not effect the 2604 chip?

 

dmp

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what is that tubular thing in the linked schematic? A coupling cap? If so, what value?

That is just shorthand for a shielded cable. Not a component. Basically you want a single conductor shielded cable going from the piezo pickup to the opamp. Connect the shield to ground.

 
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