Transparent/Hifi sounding active DI box?

Hallo, this is my first post, I am a bass player from Croatia and I wanna build new DI box ;D

So here's the story: I have built a passive DI box with Cinemag CM-dbx transformer, it is a great unit, but I find it too much smooth and  vintage sounding for my application - modern pop live band.

Recently I tried Radial J48 and Avalon U5, and both sound just perfect, full and in your face modern bass sound.

Are there any High quality or high end active DI box projects, preferably transformerless, that would be comparable to Avalon and Radial? 

ps, I took a look at Bo Hansen's DI. how does it it work, regarding it is still a transformer DI?

thanks!

Most DI boxes use a transformer for ground isolation and balancing the output line. If you just want a transformerless DI, use a JFET transistor input stage, followed by an electronically balanced line drive stage.

Hi Seriola

What about the Red Di project on the pages?

The Hansén di-box is VERY transparent and good sounding. Outperformed our studio's BSS and Jdac(sp?) boxes.

Jakob E.

the radial j48 have a low input impedance in my opinion for string instruments without active circuit.
bo hansen di box is a winner.

You can make a clean high impedance DI from any number of off the shelf FET input op amps.

You can even power it from 48V phantom if the current draw is not excessive.

You need to pad down the output to not overload the mic preamp inputs. This can be accomplished without transformers.

You do not have the ground isolation like a transformer DI but it's hard to lift the ground while using phantom power.

This can be pretty inexpensive and deliver far flatter performance than even expensive transformers.

Good for studio use, may not always work in live situations with dodgy stage power vs. FOH.

JR

thanks for all answers

BYacey: I would like to build a high end DI box like Radial J48, If possible. I've already owned cheap and mid priced DI's, wasn't happy with them . Some had hum/ground issues, some didn't transfer sound as well as they should.

peterc: so far, I would like to avoid tube stuff. don't have any experience with Reddi, but I don't like sound of tube amps at all.

I think I'm gonna try with Bo Hansen DI in the end, as it is the best documented project of this kind.

You could use the Bo Hansen circuit, remove the transformer and built an electronic balanced line driver stage, and attenuate the gain by about 20db or so.

You could also do something similar with the Countryman circuit which has a 10meg ohm input impedance.

for years I was intrigued by the J48 design I wanted to see a schematic of it. I was intrigued by the small transformer in it. some months ago I borrowed one from a friend and I did a reverse engineering of it and I was very disapointed.
first it have a 220k input impedance. For guitars or bass you want at least 1M, most serious DI boxes(bo hansen, countryman) have a 10M input impedance.

after drawing the different parts of the circuit and really understand how it works, I had no desire to compile all the drawings into one.

the audio topology is very close to this one http://sound.westhost.com/p35-f3.gif

to be fair I think it is a good di box for keyboards or other low impedance sources,  I was disapointed because I was expecting something new or unusual.

That schematic from Rod Elliot's site has less than 23k ohm input impedance.

yep very low, provably good for line or synths.

With the TL072 you can simply increase the value of R1 and R2 (to 2.2 M.ohm or so), to get a higher input impedance.
(Of course you have to remove/switch off the 22K + 1K pot if you are using the 'Line' input)

12afael said:

For guitars or bass you want at least 1M, most serious DI boxes(bo hansen, countryman) have a 10M input impedance.

Click to expand...

Old thread, but I'm on the DI boxes impedance subject at the moment.

As far as I can see the Bo Hansen DI has 1 Mega imput impedance and not 10 Megas

While this is not a DIY recipe, the cleanest, most neutral DI rig I've used for guitar or bass re-amping is a Radial JDI (the Jensen DI transformer in a box) into a Millenia HV3 mike amp. The basic point I'm making is that with any sort of electric guitar type source, a great DI transformer into a super clean, transfomerless mike amp will work really well. For really tweaky sources, then a JFET active DI can probably be better, since it can be a really light load, but still, the high impedance of an HV3, reflected through a Jensen DI transformer actually works amazingly well with zero grounding headaches. Worth trying...

+1 for the Jensen DI transformer in a solid, steel box  ..  with a pad and ground lift

Sheer heaven for clean egtrs, basses, piezo acoustics etc.

Balanced connect into a 'chineve 1081'  mic input (which has a mic transformer) ... and onto the main mix.

I put the 'thru' on the di box to my pedal chain and back to the main mix.

...

I have a lot of options for HiZ inputs  - but the jensen for di has to be best for fidelity,  and 'unhyped' sourcing into the audio chain.

My cheap 'tnc 1081' chineve saga DIYs are still going great ... nearly 10 years, I believe, since I modded them up good.

Nowadays, with a bit more investment, the WA and Heritage pre+eq offerings would have to be pretty good - but at 3x the price

Monte McGuire said:

While this is not a DIY recipe, the cleanest, most neutral DI rig I've used for guitar or bass re-amping is a Radial JDI (the Jensen DI transformer in a box) into a Millenia HV3 mike amp. The basic point I'm making is that with any sort of electric guitar type source, a great DI transformer into a super clean, transfomerless mike amp will work really well. For really tweaky sources, then a JFET active DI can probably be better, since it can be a really light load, but still, the high impedance of an HV3, reflected through a Jensen DI transformer actually works amazingly well with zero grounding headaches. Worth trying...

Click to expand...

I'm sure you know, reamping is a very different matter, since the xfmr is driven by a low-Z source. No doubt a good xfmr such as the aforesaid Jensen excels in stepping down line level to mic level.
The issue of passive DI is that they are correct for amplified keyboards and active bass. With passive bass, results can be mitigated, depends on what you expect in terms of sound. If the bass is acting in its typical support role, where treble/hi mids are rolled-off, it works fine, but for anything else it justs doesn't work correctly, and there's always the issue that the potentiometer taper is altered, which may or may not be a problem for the player.
And for guitar, I've never found any case where the result was close enough to a miked amp, unless using a ton of plug-ins.
Clean electric guitar strumming is just plain boring anyway, DI'ed electroacoustic is just pretence compared to a mic'd acoustic.
After many years trying (BTW I made a large part of my living manufacturing DI's) I don't even give a thought about DI'ing guitar, except for laying basic tracks that will never make it to the mix.

I guess I wasn't clear - the point was to capture a true DI signal to be re-amped later. So, it was an instrument (electric guitar) into the Jensen DI transformer into the Millenia HV3 into the workstation.

The 'end of the day' tone was very satisfying, when the signal finally came back from the workstation and DAC to a passive pad and a 1:1 iso transformer to the new amp.

So even though the original DI loading might not have been the canonic 1MΩ load, it really seemed to make no difference at all once the DI signal finally went to an amp. My point is that an obsession with this arbitrary high Z load might not be productive, especially since a few easily available building blocks are probably already in the studio.

Edit: the whole point of re-amping the guitar was that the artist insisted on tracking through this miserable Johnson J-Station (another version of a Line 6 Pod) and I was pretty sure that when it was time to mix, the J-Station would be very annoying, and having a DI to use with a real amp would help save the mix. That was a correct decision, and preparing for an inevitable re-amp allowed some measure of 'client comfort' to postpone the decision he'd eventually have to accept. The hassle then became the need to keep 3 tracks for each guitar performance: 2 from the J Station and one from the DI, and to mess with the time alignment to allow ridiculous micro-editing that was also needed. Quite the Frankenstein approach, and not the way it should have went, but hey, it worked.

What model is the Jensen transformer people are using?

Mostly I just need a suitable transformer to isolate multiple guitar amps / pedals.

Monte McGuire said:

I guess I wasn't clear - the point was to capture a true DI signal to be re-amped later. So, it was an instrument (electric guitar) into the Jensen DI transformer into the Millenia HV3 into the workstation.

Click to expand...

Understood. Indeed a high quality passive DI is adequate in that case (as long as the volume pot is left alone, I would think), and an amp is going to shape the sound. I believe your example illustrates quite well my caveat regarding DI'ing guitar: "just don't expect it to sound good as it is".

http://www.jensen-transformers.com/transformers/direct-box/

I think the Radial DI which uses the jensen is quite good! - I did mine from a cheap but very solid steel donor DI box chassis and replaced the crapola traffo with the jensen.

It gets most use with a strat with stacked noiseless pups  - the detail that comes across is superb. A little EQ and thickening from the chineve 'peoples 1081' makes it about as good as it gets for clean.  And *totally* silent too!

Seems to maintain the myriad delicate harmonics that great guitars  make ....  better than my active ss di units.

I usually play with the guitar volume pots slightly backed off ...  the treble dips a little bit, but that usually is what I eq into.