The ultimate DI for guitar and bass.

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Tomsk
Posts: 3
Joined: Thu Nov 08, 2012 12:50 pm

The ultimate DI for guitar and bass.

Post by Tomsk »

As a producer and guitar player, I have always been quite fastidious about guitar tone. I have a broad selection of mics and speakers, and final versions of my songs have always involved organic amps and lots of mics.
Well, hell has finally frozen over and I have purchased Guitar Rig5.

One thing that became obvious was that I needed a new DI, one that was low noise, had some options available for different tones, and was capable of +20dBu output with a minimum of components. Enter the'Ultimate DI'.

Well that statement of course is tongue in cheek, as anyone who has earned their stripes in audio would know. But I am glad to say that after construction, the result exceeds expectations. The result is a super low noise unit with +20 output and great tone, better than anything else I have used.

Using a virtual amp package is the first time most folks find out how quiet their recording setup really is. We have all heard the dreaded 'waterfall' between chord or notes and wondered whether we could get a quieter input. Well this might be the answer for you.

This DI is based on the (JLM)25HVFET and the JLM111DC output transformer. And that's it. The audio passes through a further two capacitors and one resistor (which is optional) and then the transformer (optional, only if you really like the balanced output and the 'feel' of a transformer under the fingers). I have included a picture of the final assembly and the final circuit. I am happy to post the veroboard plan if anyone wants to see it.

Now here's the drum. You can use the 25HVFET or the JLM 'Hybrid' opamp based module without changing anything in the circuit. This means you have several options for sound and budget. You can use a variety of op amps
in the 'Hybrid' module. I like the 'TL072', so I made the power supply 32 volts to be able to include standard Op-Amps. Feel free to go to town with the power supply voltage if you want.

I have lots of skill using 'Veroboard', but if you are not an aficianado of the aforementioned, you could possibly use the 'Dingo' or 'Baby Animal' boards. You will need to adjust the layout yourself.

You can see from the photos that I have included 3 switches. One is earth lift, one is power, and the third switches the transformer from 1:1 to 1:2 mode. This gives the option of 6dB gain without noise, and you have to love that. For most of my 'hot' guitars, I have to use the unit with the gain set to minimum, and the transformer set to 1:1. The rear humbucker on some guitars can have a huge output if the destination impedance is high.

Yet to be installed is perhaps a switch and another cap in the non inverting to ground connection in order to provide a bass rolloff when required. So far for me it is not a priority.
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Tomsk
Posts: 3
Joined: Thu Nov 08, 2012 12:50 pm

Re: The ultimate DI for guitar and bass.

Post by Tomsk »

As an extra function of this unit, also works really well as a level booster for overdriving a valve amp. It may well be the quietest clean boost you can get.
Can use with the transformer, or just straight out after the op amp.

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Joe Malone
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Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
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Re: The ultimate DI for guitar and bass.

Post by Joe Malone »

Super cool 8) :D
Joe :-)
JLM Audio
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