Talk to me about DIs

[midwayfair]

Maybe the JLM FET DI kit would suit your needs. The entire kit is $44 AUD, easy to build, he's v helpful also:
https://www.jlmaudio.com/shop/fet-di.html?display_tax_prices=1

This is a good un, I might try it. I built he BAN but left off the DI when I did.

Right now I've got an alice mic circuit I soldered up on perfboard to play around with on the breadboard but haven't really had time to test it to check how it handles the signal levels.

 

[Whoops]

Maybe the JLM FET DI kit would suit your needs. The entire kit is $44 AUD, easy to build, he's v helpful also:
https://www.jlmaudio.com/shop/fet-di.html?display_tax_prices=1

Check the last paragraph in the description:
"The Active DI Kit can be battery or Phantom powered when used externally but needs a output transformer if phantom powered."

So if to run it standalone (without being used as a mic preamp front end) you need an output transformer then the costs can get pretty high.
You have have to add shipping costs from Australia plus import custom fees, here in EU you would pay around 30% of the price of the item+shipping for items that are imported from outside EU

 

[midwayfair]

Check the last paragraph in the description:
"The Active DI Kit can be battery or Phantom powered when used externally but needs a output transformer if phantom powered."

So if to run it standalone (without being used as a mic preamp front end) you need an output transformer then the costs can get pretty high.
You have have to add shipping costs from Australia plus import custom fees, here in EU you would pay around 30% of the price of the item+shipping for items that are imported from outside EU

Or you can just run it off a battery like it says. But a 1:1 transformer is not very expensive and I have plenty lying around unused.

I thought you could get just the PCB for his stuff but apparently this only comes as a kit, which is a bit of a shame.

 

[abbey road d enfer]

keyboard with dual TS outs (this, as you said, should be fine knocking the signal down with a passive, but really I just would want to be able to run a balanced signal 50 feet to the board)
an acoustic with an active pickup -- 1:1, active, or any passive is fine here but would prefer not to knock down the signal

Both have an output buffer with a reasonably low output impedance, that can easily drive almost any step-down xfmr. I never had any serious issue with passive DI's on active* keyboards and guitars.

* Many fender/rhodes are passive!

a guitar, mandolin, and fiddle all with passive pickups (these all need active as I would expect they need ~10M)

There's no debate about the need for an active DI in that case, although advices regarding input impedance may differ

 

[abbey road d enfer]

Roland, unfortunately, doesn't publish the output impedance of my (FP5) or my one of my friend's Rolands. Mine gets noisy if I run a long instrument cable but theirs doesn't. One of my friends plays a Nord .... uhh, one of the Stages (73? 74?), which I'm pretty sure I can run a thousand feet of cable from without it changing the sound.

The diference is almost certainly not due to different output impedance; I'm quite sure it's related to the grounding arrangement. Unfortunately some manufacturers do not take into account interconnection with other brands.

 

[Newmarket]

I think this was called "hybrid" grounding scheme in the classic Ott textbook.

A low impedance at HF capacitor like a ceramic disc, looks like a short at RF frequency but an open circuit at mains frequency to prevent ground loops. A resistor provides a DC path. To support phantom powered microphones this R needs to be low single digit K ohms. For general grounding the R values can be higher.

I guess that is the late Henry Ott ?
It's a pity that his legacy content from his website no longer seems to be available - although I haven't checked "Wayback" etc.
Good stuff on all related matters and esp (for my line of work)) on grounding and pcb planes etc.

I haven't heard the term "hybrid" applied to it before but it sort of fits.
Type of thing I used to do years ago when I first encountered the huge mains hum I heard on plugging the (unbalanced) line out of one amp head into another (both amps mains earthed). And looking for large bodied jack plugs so the components could be wired inside.
ime R value can be really quite low - eg 100R - and be effective.

 

[Newmarket]

Yes, it's a Better to Buy situation.

if you want to spend more cash and waste a lot of your free time go for the DIY route and do the Bo Hansen DI

Thats it, done

Well the OP has previously said that there's an element of "fun" in the idea of DIY.
And imo building a DI is an excellent way to learn more about the basics of level, impedance, grounding etc. without getting tied up in a 'big' project.

 

[Whoops]

Well the OP has previously said that there's an element of "fun" in the idea of DIY.
And imo building a DI is an excellent way to learn more about the basics of level, impedance, grounding etc. without getting tied up in a 'big' project.

The OP asked in the first post the following question
"if this is a better-to-buy situation?"

And my opiniond an answer to his question is
"Yes, it's a better-to-buy situation"

If someone has time in his hands and has fun DIYing stuff, then all good just go for it, it's what we all do around here.
But there's plenty of very good DI boxes for very cheap.


http://orchid-electronics.co.uk/micro.htm
http://orchid-electronics.co.uk/classic_DI.htm

 

[JohnRoberts]

Only here would we argue about personal opinions that clearly vary with circumstance (not only here).

The OP is gathering information, let's try to focus on that.

JR

 

[abbey road d enfer]

"Yes, it's a better-to-buy situation"

I tend to agree, but the question is what to buy?
There are as many available DI boxes than variations we can imagine for DIY.
Some are quite good, but many are mediocre.
IMO a BBS AR116 (not the more recent AR133) is hard to beat. can be found for about 50€, works on P48 AND the earth lift, thanks to the floating DC/DC converter, a real problem solver.
Input Z is only 1Meg, though...

 

[Newmarket]

If someone has time in his hands and has fun DIYing stuff, then all good just go for it, it's what we all do around here.
But there's plenty of very good DI boxes for very cheap.


http://orchid-electronics.co.uk/micro.htm
http://orchid-electronics.co.uk/classic_DI.htm

Don't have an Orchid box myself. But from discussions on other forums (fora ?) there's good reputation for reliability / quality and willingness to modify to suit customer needs.

 

[Newmarket]

IMO a BBS AR116 (not the more recent AR133) is hard to beat. can be found for about 50€, works on P48 AND the earth lift, thanks to the floating DC/DC converter, a real problem solver.

Why the AR116 over AR133.
Had a quick look at the marketing blurb...
"The AR-133 uses an enhanced version of the same audio path as the AR-116, now regarded by many people as a reference standard. The sound quality is legendary, particularly on acoustic and bass guitars."

 

[Whoops]

I tend to agree, but the question is what to buy?

Cheapest DI box in Thomann starts at 11,6€, it’s a “Millenium DI”

Under 50€ you have the Orchid Electronics stuff

Under 100€ you have the Klark Teknik DI boxes and also the Radial SB1, SB2 and SB4

IMO a BBS AR116 (not the more recent AR133) is hard to beat. can be found for about 50€, works on P48 AND the earth lift, thanks to the floating DC/DC converter, a real problem solver.

I serviced two AR116 units last year,
they are not run by phantom power “natively” you need to modify them and install the AR117 circuit for allow the AR116 to be run by phantom power.
The AR117 was an extra and optional circuit that had to be bought separately from the DI





Also I noticed the same problem with the two units I received, they were both suffering from PCB traces oxidation disease, a lot of traces were almost gone. I had to clean very well and Solder Tin all the traces in the PCB to save the devices.
I don’t know if this was a problem of only these two units as I dont know how were they treated in the past or if it’s a common problem with these pcbs after so many years.
But it’s something to consider and be careful about.

 

[abbey road d enfer]

Why the AR116 over AR133.

The AR133 uses a bipolar opamp that is not so good with hi-Z sources. The AR116 uses an outdated LF351, that can be profitably replaced with an OPA134.
Second hand AR133 is about 70€, AR116 about 50.

 

[abbey road d enfer]

Cheapest DI box in Thomann starts at 11,6€, it’s a “Millenium DI”

POS.

Under 50€ you have the Orchid Electronics stuff

I don't know it, so I can't recommend it, but I doubt it has the floating DC/DC converter.

Under 100€ you have the Klark Teknik DI boxes and also the Radial SB1, SB2 and SB4

Not sure about the Radial's but I'm almost certain the KT does not have the floating converter.

I serviced two AR116 units last year,
they are not run by phantom power “natively” you need to modify them and install the AR117 circuit for allow the AR116 to be run by phantom power.

I know, but most of the AR116 's you find second-hand from hire companies are fitted with it.

Also I noticed the same problem with the two units I received, they were both suffering from PCB traces oxidation disease, a lot of traces were almost gone. I had to clean very well and Solder Tin all the traces in the PCB to save the devices.

That is unusual. I see some that are 40+ years old and work like new. Maybe someone let the batteries rot.

But it’s something to consider and be careful about.

Of course.

 

[Newmarket]

The AR133 uses a bipolar opamp that is not so good with hi-Z sources. The AR116 uses an outdated LF351, that can be profitably replaced with an OPA134.
Second hand AR133 is about 70€, AR116 about 50.

Thanks for that detail. Interesting design choice. I guess it depends on what they see as typical usage. But I don't like it when a manufacturer simply days "enhanced" without any further detail.
On the phantom power detail. That's news to me but whenever I've com across one of those it has worked on P48 so never questioned it.

 

[Newmarket]

POS.

I don't know it, so I can't recommend it, but I doubt it has the floating DC/DC converter.

Not sure about the Radial's but I'm almost certain the KT does not have the floating converter.

Wrt Millennium POS - do you know what's in there. Or just aware that it doesn't perform well ?

I think you're likely correct about the isolated DC/DC. It's a bit of unusual solution. But from the product literature I'm guessing the powered Orchid DIs have an impedance in the screen connection that effectively 'lifts ground' whilst enabling P48 operation. Like Bo Hansen DI.

 

[Whoops]

That is unusual. I see some that are 40+ years old and work like new. Maybe someone let the batteries rot.

In this case it was not due to spillage from batteries, as the battery compartment was pretty clean, and the oxidation was generalized in most pcb traces.
Maybe the DI's were kept in a place prone to oxidation, but I don't know.

I remember I was not impressed with the sound, I didn't like it, maybe the visuals of the pcb traces oxidation had some influence on that feeling I can’t be sure since I tried it alone without comparing it to another DI

 

[abbey road d enfer]

In this case it was not due to spillage from batteries, as the battery compartment was pretty clean, and the oxidation was generalized in most pcb traces.
Maybe the DI's were kept in a place prone to oxidation, but I don't know.

Your pic shows there's no resist on the PCB, which leaves the copper exposed to oxidation. I must admit it looks somewhat amateur-ish.

I remember I was not impressed with the sound,

I've never been impressed by the sound of a DI'ed electric guitar, period; for me an electric guitar develops its full potential by making a piece of cardboard move some air. Same for a Fender Rhodes.
OTOH I don't feel the same need for electric bass, Wurly and synths.

 

[L´Andratté]

a guitar, mandolin, and fiddle all with passive pickups (these all need active as I would expect they need ~10M)

If you are talking about piezo pickups, there's a nice situation for DI-DIY (; when deciding to take the "charge amp" route (look at Figure 3).
In my small amateurish experiments it produces a very nice full range sound from the piezo (I just tried with Kalimba...)