Rackmount DI

Hey Guys,

I have been lurking around for a while, picking up as much knowledge as I can. I don't know much when it comes to electronics, so I am asking for your help.

I am in need of a DI / REAMP device. and am wanting it rackmounted. I would like something similar to an off-the-shelf product, but really don't want to spend $800 for it.

I have put together a schematic of the DI portion, and would like assistance / opinions / in determining what is right, what is wrong and how to correct it.

Any help would be appreciated.

https://skydrive.live.com/embed?cid=7D1AC6A046B1BCD3&resid=7D1AC6A046B1BCD3%21196&authkey=AK2UOZVj6U_zhfY

The first thing I noticed is the 10K pot. Most instruments (e.g.guitars) like to look into a very high impedance - around 500K or so but in the schematic you posted to instrument looks into the 10K pot which is far too low.

Cheers

Ian

Thanks for the info. I didn't think about that.

I am wanting that portion of the circuit to act like a sort of boost / overdrive pedal to overdrive the front end of guitar amps the higher the pot is turned. If it is left low, then it doesn't add much.

I am hoping this part of the circuit is full, flat frequency response and clean gain.

I have updated the drawing to a 500K pot. Thanks

https://skydrive.live.com/embed?cid=7D1AC6A046B1BCD3&resid=7D1AC6A046B1BCD3%21197&authkey=AFJwtJbFH6yUkic

OK, but you have left the 47K and 330pF across the pot. What are they for?

Cheers

Ian

Are you planning to use the "boost out" only when fed from a line level?
It will only attenuate and LPF the input signal but no boost will happen.

Letting the input unconnected when muted will create excessive noise.
I would use a dual throw switch that grounds the input when muted.

Not sure about ground lift switches 2 and 4.
Those outputs are unbalanced so they need ground connection in order to work.

I don't really know the jlm baby animal neutral but it looks like a mic preamp.
Are you sure this product is right for your purpose?
What's the input impedance? Most mic pre's have a impedance around 1,5Kohm which is way too low for high impedance instruments.
Do you want a line-level output or do you want to be able to use it in live situations and send it to the pa system.
Putting out +26dBu will overdrive FOH desks and splitters.

DI's and preamps are very different devices, each with a specific purpose. Unless you want a DI/preamp combo for studio use, I wouldn't use the JLM.
If you want the 60ish dB gain most preamps offer to go straight to "tape", you will still need a high impedance buffer.

This will not be used in live situations. only recording.

Like I said previously, I dont know much about this stuff. I am looking for guidance on this and appreciate everyones comments.

I pieced this together from a couple of schematics I found floating on the web.

What would you recommend in place of the JLM? I would like to see about +26 - +30dBu

So in fact you want a preamp with a DI input.
The JLM will do fine as they seem to offer an optional Fet/opamp DI input module.

26dBu would be more then sufficient but you can go higher by increasing voltage rails as long as the opamps can stand it.
I see no point though.

If I'm correct, you want to use the boost output as a clean boost pedal for overdriving your amps only.
I would suggest you connect the pot meter somewhere on the output of the jlm, before the transformer.
Otherwise you won't get any boost. The level will depend on the preamp gain setting though.

the balanced out of the JLM would be for DI signal recorded to DAW. I'll have to give using the JLM here some more thought.

The "Boost" part of the circuit would be used as you said for overdriving the front end of the guitar amp.

Any easy way of adding an Input Z pot at the beginning of the circuit, say between 10K and 10M?

Doesnt jensen have a reamp circuit design that you could integrate?

Yes they do. That is what I plan on doing.

I'm just trying to get this side worked out first