USB Audio Interface -> 1M Ohm Impedance -vs- 470kOhm Impedance .... Differences ?

[Sedaxel]

To sum up, I guess the Hi-Z inputs in interfaces or consoles are there just to provide a built-in Di box. If you already use a DI box, or a buffer, you´ll not need the Hi-Z input.

Then, there are several HI-Z inputs in interfaces that are marketed as cool ones... like the Jfets of the Audient ones, and those kind of things. It would be similar to sell you that a Radial DI box has a cool sounding transformer, etc.

 

[Gary_W]

But if you’re using Kemper, Helix, any other outboard gear that’s already doing it so no need for a buffer pedal.

If you’re going straight in and using computer plugins for Amps then yes. But even then I’m not convinced you’ll notice 470k vs 1 meg

 

[Sascha Franck]

That´s because passive DIs, based on transformers, don´t have a "fixed" impedance. They have a ratio instead.

That doesn't seem to be true. The Palmer DIs all have fixed input impedances. At least that's what Palmer is saying.

 

[Sedaxel]

That doesn't seem to be true. The Palmer DIs all have fixed input impedances. At least that's what Palmer is saying.

A transformer based passive DI box has an impedace ratio. I´m pretty sure of this, I studied it several years ago because I made my own Di boxes. I had some audio transformers theory and the way to calculate circuits input impedance (which, of course, I have forgotten almost completely).

I studied also several DI boxes circuits and schematics (I was so brave becasue... they´re simple as hell). The input impedance of one of these boxes depends on the input impedance which goes after the box.

Active Di boxes are different, though. They have fixed input impedance, because even the ones that have a transformer, are using it just to balance the signal.

 

[Jarick]

Are you finding issues while using the device? If not I wouldn't worry about the input impedance. It's honestly not that big of a difference.

 

[Sascha Franck]

A transformer based passive DI box has an impedace ratio.

So why does Palmer say different? Even Radial offers exact values for their Pro DIs input impedance.

 

[Boudoir Guitar]

I noticed a difference with various things that were 500k. Super minor, and very easy to completely negate with a little EQ.

Every buffer I’ve ever used sounded too bright compared to directly into amp or 1M audio interface input. Harder to EQ out, but pretty easy to EQ out.

If you already have an audio interface you are happy with, I don’t see why you’d want to buy this thing if the purpose is to run guitar direct.

 

[Sedaxel]

So why does Palmer say different? Even Radial offers exact values for their Pro DIs input impedance.

Well it´s physics. A transformer just couples primary and secondary by an electromagnetic field. The number of turns in the primary and in te secondary have a relation, so is the voltage, and that translates in a impedance relation (the turns squared). They always have that relation. If you fix one connecting a preamp, the other end of the transformer sees that impedance stepped accordingly to its impedance ratio (turns ratio squared). This is so, period.

Why Palmer or Radial states a fixed impedance, I guess it´s for simplicity. Theses boxes will be used for the same things most of the time.

Actually, this is the JDI specs, and you can see the "typical" indication in the impedance data:

 

[Sascha Franck]

I don’t see why you’d want to buy this thing if the purpose is to run guitar direct.

Super low latencies, best driver support ever.

 

[Boudoir Guitar]

Super low latencies, best driver support ever.

But if he already has an interface he is happy with, who cares? Maybe it has better null testing…

 

[JiveTurkey]

But if he already has an interface he is happy with, who cares?

 

[TheTrueZoltan!]

You could also just do the right thing, put active EMGs in your guitar and then not give a shit about input impedance anymore.

 

[DieSchmalle]

That doesn't seem to be true. The Palmer DIs all have fixed input impedances. At least that's what Palmer is saying.

Can you provide a quote from Palmer that includes their passive DI boxes?

 

[BenIfin]

But if he already has an interface he is happy with, who cares? Maybe it has better null testing…

No - as per my OP - been offered an OG "Blue RME Babyface" which has an Instrument Input Impedance of 470k ..... In my hardware modelers Ive tended to stick to 1M Ohm so was wondering what the differences may be ... and now with the mention of buffers, it seems like a very easy "fix" to add a simple buffer before I go to the RME Line Input - assuming I grab it for a laptop rig.

Thats all. Just asking questions that I have no idea what the answer too is.

 

[ian_dissonance]

You could also just do the right thing, put active EMGs in your guitar and then not give a shit about input impedance anymore.

This is the way.

 

[Boudoir Guitar]

No - as per my OP - been offered an OG "Blue RME Babyface" which has an Instrument Input Impedance of 470k ..... In my hardware modelers Ive tended to stick to 1M Ohm so was wondering what the differences may be ... and now with the mention of buffers, it seems like a very easy "fix" to add a simple buffer before I go to the RME Line Input - assuming I grab it for a laptop rig.

Thats all. Just asking questions that I have no idea what the answer too is.

A laptop rig that requires a pedal in front... woof.

 

[Sascha Franck]

Can you provide a quote from Palmer that includes their passive DI boxes?

ProDI Specifications - Radial Engineering

www.radialeng.com

 

[BenIfin]

A laptop rig that requires a pedal in front... woof.

What can I say ...... I'm bored :)

 

[Sedaxel]

ProDI Specifications - Radial Engineering

www.radialeng.com

View attachment 53547

I´ve reviewed my notes and technical docs about this. Didn´t remember exactly how was it meant to be.

The input impedance is not an absolut impedance (just as I explained in this thread). That value (140kOhm) is a value measured in a test circuit which has a secondary impedance of 1kOhm. This is, a step-up of 140:1, aprox. That´s a measured impedance in that circuit, applying a 1kHz signal at 0 dBu. The theoretical value of "squared turns" is an aproximation, given the impedance varies a little depending of frequency and amplitude.

That´s why Radial (or Palmer or Whoever) states that impedance. It´s just an inaccurate way of giving the info, which nobody will care, by the way.

At the same time, the stated output impèance of 150Ohm is measured in a test circuit that "aprox simulates" a guitar pickup. They remove the 1kOhm impedance of the previous test, and just measure the resulting impedance.

You can see that in this pic, from the Jensen official specs. The circuit 1 is the one used to measure those impedance values:

So, yeah... Manufacturers just give a value that can be misleading because they don´t tell the full story.

Everything is as I explained before. With a passive, transformer based, DI box, if you´re connecting the output to a preamp in the 2kOhm ballpark, you´d maybe notice the lack of higher impedance (you´ll be around 250-300kOhm). If your preamps are a bit higher impedance, you´ll have great respose. My DI boxes behave excelently in that regard when connected to a mic preamp in Behringturd X32 mixers (as an example), because they´ve got higher impedance than other preamps. Connecting a strat and comparing it to other boxes, playing clean you notice all the bright frequencies of the pickup. I didn´t compare it to a Radial (We had none). But compared it to a Palmer, a Behringturd and a couple Milleniums... mine kept more frequency content, while being the least noisy (maybe tied to the Palmer). The transformer is everything in these boxes. My buddy calls it "the Radial" when he talks to other guitarists about the box... even though I told him 10 times it has a cheaper transformer (well, it´s a 50€ made-in-the-UK one, not a chinese cheapo). He just feels it great and don´t care for technical details.