Build Your Own Passive DI Box (easier than you think)

Many of our commercial customers have shared their praise of the Hammond 1140-DB-A, so we designed this Passive DI Box around it (passive, meaning it doesn't require power). Being passive, there are some limitations to its use. It would be ideal for use with guitars that have medium/high output passive pickups and active pickups. But , being a higher grade transformer with low noise, it could arguably be used with quieter sources as well (within reason).
Get more detailed instructions on our site:
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[@Hammondmfg]

Nice job gentlemen!

[@TehSyneS]

so much more detail with the di box.

[@stillhereandstill6401]

Great video!

[@scottg7628]

If I wanted to make a stereo DI version of this, would I just replicate this same thing twice in one enclosure? Would I need two Hammond Transformers? Thanks!

[@NextGenGuitars]

Yes to all questions. 👍

[@dongwarrenmusic]

please do some diy transformer winding on that, then we can call it a full DIY.

[@rudygomez6996]

active di box adds power where? Primary side or secondary side of transformer, and why does that raise impedance?

[@NextGenGuitars]

Unfortunately, those are questions you'd need to ask your local tech. Wish I could help!

[@nathanaelbingier4598]

could this design be used to take a di between an amp head/cab? if not, what changes would need to be made to the design to accomplish this?

[@NextGenGuitars]

That would be a totally different product/design. You'd need something like a Radial JDX.

[@ChanhoChung-fw3hv]

Thanks for good video. Are there any budget replacement for transformer?

[@NextGenGuitars]

There are many other options out there in other price ranges. We don't stock any, so I can't point you to any in particular, but they are out there.

[@trnmkhngthnh]

I plan on putting a passive DI circuit like this inside my bass Can i just skip the input jack in the circuit in wire the electronics in my bass directly to the output jack of this DI circuit?

[@NextGenGuitars]

Yes, but then you wouldn't have a standard 1/4" out. I would still connect at least 1x 1/4" jack, so you have the option for both DI or standard 1/4" out.

[@trnmkhngthnh]

@@NextGenGuitars yes i would love to have both the 1/4” and the XLR. I plan on basically jam a passive DI box inside the cavity on my bass but i still dont know how to wire it since im still new to electronics and stuffs. A wiring diagram would help, if possible. Many thanks mate

[@NextGenGuitars]

@@trnmkhngthnh You can use the schematic/diagram from the blog link. Just treat the two 1/4" jacks as if they were one, and remove the ground lift switch.

[@onzkicg]

Where to buy that kind of transformer? also- what’s best wattage of soldering for this kind of job?

[@NextGenGuitars]

We sell them. :) But they are kind of pricey. There are also numerous other options on the market, as have been mentioned in other comments on this video. Soldering iron temperature depends on what type of solder you use, and if your iron is digitally controlled. Mine is set to 675F. 600F-700F is common. Some go as high as 800F. Again, depends on what you're soldering and what type of solder you use. Rock on!

[@mohitrahaman]

Can you do a circuit for cabsim toggle with this?

[@NextGenGuitars]

Not for this type of passive (doesn't require power) design. An analog cab-sim is essentially an EQ circuit, which requires a boost, which requires power.

[@thetubelaboratory]

Any feedback on the quality of this DI Transformer?

[@petercornell2002]

Hammond make excellent transformers. I ave used them many times for various projects.

[@Wizardofgosz]

Hammond makes great traffos. Also look for Lundahl, Sowter, Cinemag, Ed Anderson, Carnhill. I've made active DI boxes with all of those and they're excellent. I also have a passive box with a Lundahl (more similar to this build) and it's nice, also.

[@Wizardofgosz]

I mean, just as a general rule of thumb, good transformers cost good money. You get what you pay for. This retails for around $70. That price range tells me it's quality. There is one transformer that breaks that rule, and it's a company called Oxford Electrical Products. Their traffos are really inexpensive and really good quality and sound terrific.

[@regortex3364]

Richard Wielgosz - yeah $70.00 or less, unless you live in the country they’re made in, $95.00 in Canada. Hoser tax.

[@NextGenGuitars]

These retail for at least $90+ CAD worldwide. More than double that in some places. No applicable hoser tax. 👍

[@BrazenNL]

Any tips on something simple like this to remove phantom power, so XLR in/out?

[@NextGenGuitars]

This will do the trick: cdn.instructables.com/F26/3UK3/J3AFDUIK/F263UK3J3AFDUIK.LARGE.jpg

[@Wizardofgosz]

I don't even understand the question. If you don't want phantom power on, turn it off. Also, the transformer in the passive box BLOCKS phantom power.

[@BrazenNL]

@@Wizardofgosz Thanks. Some cheaper boards only have an on/off switch for all strips.

[@NextGenGuitars]

@@Wizardofgosz Many boards only have a master phantom power button that applies it to all channels. If you're using several mics at once (like when micing a drum kit), some of the mics may require phantom power, requiring you to turn it on. However, some of the other mics you're using (ribbon mics for instance) could get damaged by the phantom power being applied. Thus, you'll need something to "block" the phantom power to protect those mics on those channels.

[@Wizardofgosz]

@@NextGenGuitars My guess is if they're using a Mackie 1202 they don't own any vintage ribbon mics. Modern ribbons have protection against being damaged by phantom. I'm wondering what they're actually doing.

[@ivanl7700]

what is the awg size of the cable used inside?

[@NextGenGuitars]

We just used the leads coming from the transformer. In this case, it doesn't matter much. I wouldn't go smaller than 24AWG, simply for my comfort working with it.

[@onzkicg]

Any buffer pedal in between?

[@NextGenGuitars]

Nope. DI straight into the computer.

[@AkiraNatchi]

I just imagine that with cheap transformers like $10-35 ones, it's Ok for guitar players but For nice audio use, needs $50-100 transformers ;( Any good plan to find nice tranfo ?

[@NextGenGuitars]

The one used in this video is an expensive pro-grade audio transformer. I'm sure there are cheaper ones out there, but I don't know of any off hand to point you to.

[@Mr.Alvin_Rocks]

Carn you make a diy for an "Active DI Box" , guitarist need that because of the passive pickups

[@Mr.Alvin_Rocks]

Can*

[@NextGenGuitars]

Would be cool, but we don't really do videos (or much social media of any kind) any more.

[@michaelrock]

Is the same way to make a reamp box?

[@positivecritic5077]

Procedures and components are a little different but similar

[@michaelrock]

@@positivecritic5077 thanks

[@wahyudjogja4753]

How much price db a 1140??

[@NextGenGuitars]

Around $75 USD, but it depends where you buy it.

[@wahyudjogja4753]

other than db a 1140, is there any other alternative to make a passive direct box?

[@NextGenGuitars]

@@wahyudjogja4753 There are many other transformers that can be used, but none that we sell. You'd have to search.

[@wahyudjogja4753]

in Indonesia there are those who sell isolated 600 ohm: 600 ohm transformers, can they be used too?

[@NextGenGuitars]

@@wahyudjogja4753 Those would not accomplish the same thing and would be used for other purposes. You want something with at least a 10:1 turn ratio.

[@chrish7336]

I know this is an old post but I have to ask, within the first minute seeing your schematic how are you creating the Balanced output. Yes I know this technically works but it is not truly a balanced output. You are basically making an isolated Pos to ground signal. Are you supposed to have a ground/neutral center tap on the secondary of the transformer to create the Proper positive and Negative signal for XLR pins 2 and 3? At the same time, I can see how if Phantom power is applied it would protect the keyboard/guitar, but this really isn't a Balanced output, it is still technically unbalanced.

[@NextGenGuitars]

If you follow the layout and schematic, you'll see that the 1/4" input goes to the primary (20K; unbalanced), and the XLR output comes from the secondary (1.5K; ~12:1 turns ratio; balanced). The transformer is converting the signal from HiZ to LowZ AND from unbalanced to balanced. www.hammfg.com/files/parts/pdf/1140-DB-A.pdf

[@chrish7336]

@@NextGenGuitars I do see that in the write up and in the diagram. I would have to see it actually function with test equipment. Though the way it shows, it cannot produce a negative signal to match the positive signal without a zero reference in the middle of the secondary. While the inversion at the mixer/amp will strip interference from the xlr input, this is not technically a balanced signal. Even if it is being called one. Again, I do see what the diagram is showing and it is the same for Jensen, and Radio Shack. It works, but electronically it is not accurate. If you happen to have a O-scope you can use, possibly even with a multimeter, with a tone in, read pins 2 and 3 of the output to ground. They should be opposites but you will find it is not. If it is opposite then everything I have ever learned in Electronics is wrong.

[@NextGenGuitars]

@@chrish7336 They call it a balanced signal coming out of the secondary, so we're calling it a balanced signal. In fact, nearly every company making passive DI Boxes use this type of transformer (different brands, but similar designs). Maybe there's more going on inside the transformer than we can see in the specs. I wish I could help, but these would be questions for the DI transformer manufacturers, not for us. Interesting question nonetheless.

[@chrish7336]

@@NextGenGuitars True, As I mentioned, they are all pretty much the same, and I understand the concept, I just don't agree with the terminology and didn't know if you had any additional information. It works and that is truly all that matters.

[@NextGenGuitars]

@@chrish7336 It's an interesting question. I wonder what the engineers would say.

[@regortex3364]

made in Canada, $95.00 in Canada. Seriously??? No wonder Canadians don’t buy Canadian. There’s a reason we’re called hosers, we get hosed. I was going to buy two of these until I saw the price. Sowter, Cinemag or Lundahl is what I’m buying.

[@NextGenGuitars]

Hammond's Pro Audio series transformers are targeted at the high end performance market. Very linear, very low noise, very low distortion, etc. Not really after the DIY market. As with the few brands you've mentioned, there will always be other more budget friendly options on the market. All depends on your needs for your project. Rock on! Best of luck with your project!

[@regortex3364]

Next Gen Guitars - you say they’re not really after the diy market?????? Since there isn’t a single brand of Di that uses this model of Hammond transformer, what market are they after? The brands I mentioned are the elite cream of the crop, the most highly rated, proven and expensive you can buy. Hammond is completely unknown for their Di, and audio transformers in general. They enter the game by being the most expensive you can buy, out of the gate, with zero track record. I’ve seen prices around $68.00 US, and here in Canada where they’re made $94.99-102.99, this is the problem I have with Canadian companies and why buying Canadian will never be a thing for “hosers”. My rant has zero to do with you or your company, you made a cool video and I applaud that. Cheers 🍻

[@NextGenGuitars]

@@regortex3364 Out of the gate with a high-spec transformer, beating most of the competition in terms of frequency response, low-noise, and low-distortion. However, all at a very high cost. Maybe not the best business move, but it's the route they decided to go. Cheers! 🍻

[@regortex3364]

Next Gen Guitars -yeah everything about it looks good except the price, disappointing. I can afford it, I won’t go near it out of principle. Back in the day when Radial was starting out, I wanted one of their Di’s, I called them and asked if I could pick one up (I live in the same city), they told me I had to order it through a US distributor as their was no local distributor at the time, I live 10 minutes away from them. If I was someone famous I would have gotten the factory tour and handed one for free. They can piss off, no loyalty from me or money. I know I sound like a bitter prick, don’t care, but when I hear “buy Canadian” I just laugh. Like I said, none of this has anything to do with your company, just venting haha. Cheers to you 🍻

[@endridchill5697]

Pretty sad eh? Makes me want to wind my own. Globalism makes it so they cannot produce solar panels where they are needed.

[@jkls36912]

Good video. Just a head of warning you shouldn't use your hands when using a unibit you should clamp the box down or use vise grips. Take it from a guy who is use unibits for 20 years. Tearing your hand up it's not fun. Lots of blood.. Haha

[@NextGenGuitars]

Definitely! It was stupid to do it that way! No doubt!! 👍

[@gillihansmobilewelding]

Real pros don't make videos, they make comments on videos.