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Can I use a passive DI in reverse in replace of an (expensive) re-amp box? Effects Pedals, Units & Accessories
Old 23rd August 2015
  #1
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Can I use a passive DI in reverse in replace of an (expensive) re-amp box?

Im a cheapskate - would the level mismatch cause me problems?
Old 23rd August 2015
  #2
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Quote:
Originally Posted by NovaClyde View Post
Im a cheapskate - would the level mismatch cause me problems?
Yes, the transformer will raise the voltage even higher. If you really need a galvanic isolation, you could try using it in a normal direction. Otherwise you could simply use a line output.
Old 23rd August 2015
  #3
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Pollo's Avatar
 

I have a Radial JDI, passive DI box. According to the manual you can use it for what you are asking.

I tried it once but it didn't work so well. The level was way to loud. You can turn down the output of your soundcard really low but that lowers the bit depth and deteriorates the signal.

But with some passive attenuation in between it might work...
Old 23rd August 2015
  #4
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Quote:
Originally Posted by Pollo View Post
You can turn down the output of your soundcard really low but that lowers the bit depth and deteriorates the signal.
wait..what?
Old 23rd August 2015
  #5
Gear Maniac
 

If you own a soldering iron you can get a proper reamp box for cheap from DIYRe. It took me about an hour to put mine together while eating dinner and works great.
Old 23rd August 2015
  #6
Gear Guru
Reamp boxes were designed for a reason. In the scheme of things, they aren't that expensive compared to good pedals and amps and mics etc. If you are even contemplating reamping, don't cheap out. Otherwise you may as well use freeware amp sim plugins.
Old 23rd August 2015
  #7
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nosebleedaudio's Avatar
 

if you use a passive DI box, use it in the normal In out, its a step down with a 20dB loss, what you need...Less level...
DO Not use it reverse, that would be a step up...bad idea...
But, it will not even be close to a Properly Designed ReAmp box, several things are different...

Last edited by nosebleedaudio; 23rd August 2015 at 10:47 PM..
Old 24th August 2015
  #8
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this one's not expensive: Radial ProRMP | Sweetwater.com
Old 24th August 2015
  #9
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Quote:
Originally Posted by hopeless_opus View Post
this one's not expensive: Radial ProRMP | Sweetwater.com
Palmer Daccapo is even cheaper, but if the distance between the mixer or interface and the amp isn't too large and they are connected to the same ground (no need for galvanic isolation), I don't see a reason why a simple attenuator (or using the aux master or whatever to reduce the level) wouldn't work. If you need galvanic isolation, you could use almost any gear with a transformer balanced output (and an attenuator).
Old 24th August 2015
  #10
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BillSimpkins's Avatar
I've re-amped in so many wrong ways I lost count ..... converters plugged straight into amp, converters to wah pedal to amp, converters to console to amp, HEADPHONE OUT OF A DAT MACHINE TO AMP, converters backwards through DI to amp, converters to preamp to compressor to amp, etc.... and SUPRISE ... the records sounded just FINE. I've gotten great results from driving preamps and outboard gear and straight into the amp. THE HORROR!*


* Not dissing proper reamping.
Old 24th August 2015
  #11
Gear Guru
The Ebtech Line Level Shifter is a cool box that I would recommend having for all sorts of uses. That steps up or down, depending on what way you connect it. It gives passive transformer isolation to prevent ground loop hum - and provides balancing/unbalancing ... a useful box. I haven't tried it for reamping, since I own 4 JCR boxes, but I have no doubt it would do the job ... it would give you a pair, and part of the fun of reamping is driving multiple amps ...
Old 24th August 2015
  #12
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Quote:
Originally Posted by jetam View Post
Palmer Daccapo is even cheaper, but if the distance between the mixer or interface and the amp isn't too large and they are connected to the same ground (no need for galvanic isolation), I don't see a reason why a simple attenuator (or using the aux master or whatever to reduce the level) wouldn't work. If you need galvanic isolation, you could use almost any gear with a transformer balanced output (and an attenuator).

theres quite a few mixed messages in this thread now - some people saying its a must to use a dedicated re-amp box, some saying a passive DI set correctly with an attenuator to manage gain (at what stage in the signal chain would I need this attenuator?) Some saying other products that are neither dedicated Re-amp boxes nor passive DI's exactly..

Im using a UFX1204 hybrid desk (it is both my analogue desk and interface) so I can have the amp very close if needed.
If I use an FX send on the desk to send the signal I can have some control over the level sent.
Do I need the DI after the desk FX send before the amp?
Old 24th August 2015
  #13
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JulianFernandez's Avatar
 

Quote:
Originally Posted by Pollo View Post
I have a Radial JDI, passive DI box. According to the manual you can use it for what you are asking.
Quote:
Originally Posted by nosebleedaudio View Post
if you use a passive DI box, use it in the normal In out, its a step down with a 20dB loss, what you need...Less level...
DO Not use it reverse, that would be a step up...bad idea...
But, it will not even be close to a Properly Designed ReAmp box, several things are different...
Guys @Radial (who actually sells reamp boxes) says you can use their DI box in reverse as an reamp box... What the **** they know, right?

Last edited by JulianFernandez; 24th August 2015 at 09:33 AM..
Old 24th August 2015
  #14
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Still no clear answers here - can someone lay this to rest?
Old 24th August 2015
  #15
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JulianFernandez's Avatar
 

Source: http://www.radialeng.com/pdfs/manual-prodi-prod2.pdf

RE-AMPING WITH YOU RADIAL PRO DI
The term re-amping comes from taking a pre-recorded guitar track and sending it back through a guitar amplifier to reamplify
it, and then re-record it again. This trick has been used since the 1950s with artists as diverse as Les Paul, the
Beatles and Steely Dan.
It’s simple to do: plug your electric guitar into the PRO DI and send the thru-put to your guitar amplifier. Connect the balanced
output on the PRO DI directly to your recording system and record a clean guitar track this way. Put a mic in front of
your guitar amp as usual and record it to another track at the same time. You will now have both the amplified sound and
the direct clean sound recorded on separate tracks. Now take the clean recorded track and send it back through the PRO
DI in reverse. To do this, you will have to get a female to female XLR turn-around adaptor, as you will be connecting the
output of your mixer to the XLR OUTPUT of the PRO DI. Keep the mixers output level low to avoid saturating the PRO DI's
transformer which would cause distortion. Now, simply connect the INPUT (remember, we’re connecting this in reverse)
on your PRO DI to your guitar amplifier and/or effect pedals inputs. Using your PRO DI in reverse to re-amplify your sound
can be great fun and adds tons of creative options to a recording. This now lets you listen to various distorted sounds and
create new tones while you are sitting in front of your studio monitors.
Old 24th August 2015
  #16
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Quote:
Originally Posted by NovaClyde View Post
theres quite a few mixed messages in this thread now - some people saying its a must to use a dedicated re-amp box, some saying a passive DI set correctly with an attenuator to manage gain (at what stage in the signal chain would I need this attenuator?) Some saying other products that are neither dedicated Re-amp boxes nor passive DI's exactly..

Im using a UFX1204 hybrid desk (it is both my analogue desk and interface) so I can have the amp very close if needed.
If I use an FX send on the desk to send the signal I can have some control over the level sent.
Do I need the DI after the desk FX send before the amp?
Nobody can tell if you need the DI.
If you have grounding problems, you need an isolation transformer (DI/passive reamping box) or an active reamping box with floating inputs. If you don't have a problem with the ground/different potentials, you can use the aux send directly if your mixer isn't too noisy.
Why don't you simply try it?
Connect the aux to the amp, start with low level and if it works, it works. If it hums, you need to galvanically isolate the amp from the mixer, although you might also manage to solve the problem by additional grounding.
Old 24th August 2015
  #17
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by JulianFernandez View Post
Guys @Radial (who actually sells reamp boxes) says you can use their DI box in reverse as an reamp box... What the **** they know, right?
NOT MUCH...
Just like I said, its a STEP UP transformer in reverse...
Ask a REAL tech at Jensen....

I have been using/Building DI boxes far longer than Radial has been in business...
Old 24th August 2015
  #18
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JulianFernandez's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
NOT MUCH...
Just like I said, its a STEP UP transformer in reverse...
Ask a REAL tech at Jensen....

I have been using/Building DI boxes far longer than Radial has been in business...
Radial´s PRO DI doesn´t use Jensen transformers...
Old 24th August 2015
  #19
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by JulianFernandez View Post
Radial´s PRO DI doesn´t use Jensen transformers...
It's STILL a step down transformer used Normally...
In Reverse it's a step UP Transformer...Plus The Output USED as a Input CAN NOT handle the +20dB levels that CAN be present...

Anyone who makes a DI Passive Transformer will be the same, basically...Except for distortion, input level capability, CMRR.. ect...

IM telling you the facts, you can use yours how ever you choose...
Old 24th August 2015
  #20
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JulianFernandez's Avatar
 

You know a lot more than me about this, man... I shut up and listen; seems like the guys at Radial should do their homework...
Old 24th August 2015
  #21
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foldback's Avatar
Radial BOUGHT JENSEN TRANSFORMERS, this is not new news.

Nosebleed is right and explained it all in his first post. A REAMP box is a transformer, much like a D.I. transformer but with different values. Why? Because transformer design is based on math.

You can use a D.I. to achieve what a proper Reamp transformer does but you don't use it backwards, you use it in the normal direction so it steps down the voltage from your converter output to a proper level, similar to what might come out of a humbucking or single coil electric guitar pickup.

Converters have low impedance balanced output and put out BIG LINE LEVEL SIGNALS.

Passive guitars put out small, high impedance unbalanced musical instrument-level signals (much much smaller than line level).

WHAT DOES A REAMP BOX DO?
A REAMP transformer steps the voltage from a converter or other line-level source output down to a small, unbalanced guitar output level, this is a signal level size that the guitar amplifier input is expecting to receive from a passive electric guitar.

The final important feature from the REAMP box is ground isolation, this is where transformers are unmatched for galvanic isolation, the input is not connected to the output via hardwire so there is NO ground-loop (provided the ground loop switch is invoked).

The Radial REAMP box mentioned earlier for $99 is a real deal, Radial bought the rights to the REAMP name and they bought Jensen Transformers so they have the engineering talent and production capability to build a proper product for a good price. In this case they use mass production to lower the price for a commercial product to an all new level of affordability.

I've wound hundreds of custom transformers over the years but in this case I would just buy the Radial and get on with making music. If you can't afford the Radial box then the chances are you can't afford a good transformer either, last time I ordered Jensen D.I. transformers (my personal favorite) they were almost $80 each delivered. The other components required, enclosure, jacks, pot, labor fabricating, etc, would all raise the price higher than what Sweetwater is already selling the finished Radial REAMP box for.

Good luck and good music to all!
Old 24th August 2015
  #22
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by JulianFernandez View Post
You know a lot more than me about this, man... I shut up and listen; seems like the guys at Radial should do their homework...
If I was going to use a Passive DI for reamping I would;
Connect the Output of my console ect to the 1/4" Input of the DI, wire a XLRF to a 1/4" connector (Pin 2 to tip, Pin 3 sleeve, plus add a 1K Resistor across Pin 2 & Pin 3), this should work fine...And Ground the amp normally, lift the ground on the DI box...Since there is NO connection to Pin 1 on the XLR Output the ground lift does nothing...
Old 24th August 2015
  #23
Gear Guru
It's a bit like asking if you can play death metal with a banjo. The short answer is yes - yes you *can*. The question is whether you would want to for any period of time.
Old 24th August 2015
  #24
Gear Addict
 

What is the problem? Buy a reamp box. If you think it's too expensive, you have probably chosen the wrong industry.
Old 24th August 2015
  #25
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Pollo's Avatar
 

Some interesting things beign put forward here.

Apparently Radial are talking BS in their manual for the JDI. Myself i'm using the X-Amp for reamping. It's not passive.

The Pro RMP looks interesting. It' a lot cheaper than the X-Amp.

This transformer stuff I don't fully understand. From what I had pieced together the transformer in the JDI was used for (1) electric isolatation and (2) impedance matching. Since the level of an electric guitar is lower than line level, I would think that the transformer would step up the signal, used in the normal direction. Wouldn't that step down the signal if used in reverse?
Or is it that the impedance matching (from high to low) can only be achieved by a step down transformer?
Old 25th August 2015
  #26
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Quote:
Originally Posted by Pollo View Post
Or is it that the impedance matching (from high to low) can only be achieved by a step down transformer?
Yes, the transformer ratio reflects the impedance and the voltage ratio.
If you have a 2:1 transformer that's connected to a 600 Ohm load the source will see a 2400 Ohm load. The voltage on secondary will be a half of the voltage on the primary, but the current (through secondary) will be double.

Last edited by jetam; 27th August 2015 at 02:21 AM..
Old 25th August 2015
  #27
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by Pollo View Post
Some interesting things beign put forward here.

Apparently Radial are talking BS in their manual for the JDI. Myself i'm using the X-Amp for reamping. It's not passive.

The Pro RMP looks interesting. It' a lot cheaper than the X-Amp.

This transformer stuff I don't fully understand. From what I had pieced together the transformer in the JDI was used for (1) electric isolatation and (2) impedance matching. Since the level of an electric guitar is lower than line level, I would think that the transformer would step up the signal, used in the normal direction. Wouldn't that step down the signal if used in reverse?
Or is it that the impedance matching (from high to low) can only be achieved by a step down transformer?
used normal its a step down, 20dB loss..
Old 26th August 2015
  #28
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Pollo's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
used normal its a step down, 20dB loss..
Yes, of course. I understand now. It is supposed to bring the signal down to microphone level, not up to line level. That was my mistake.
Old 26th August 2015
  #29
OP,
Did you try it?
Did it sound good?
Sometimes the best lessons are the ones you learn yourself.
Years ago I tried reamping several different ways and it never sounded good.
Then I bought a reamp box and it sounded great.
I wish I had bought a reamp box initially. Would have saved me those hours of fooling around. But then again, I wouldn't be able to tell you this story.
Old 26th August 2015
  #30
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bogosort's Avatar
Quote:
Originally Posted by jetam View Post
Yes, the transformer ratio reflects the impedance and the voltage ratio.
If you have a 2:1 transformer that's connected to a 600 Ohm load the source will see a 1200 Ohm load. The voltage on secondary will be a half of the voltage on the primary, but the current will be double.
A nitpick, but the impedance reflected to the source goes as the square of the ratio: a 600R load looks like a 2.4k load at the primary of a 2:1 transformer. For example, 10V at the primary puts 5V across the load, making the current through the secondary 5/600 = 8.33 mA. Because power is conserved the current through the primary must therefore be half (not double) the current through secondary: 10V and 4.16 mA produces the same power as 5V and 8.33 mA.

So from the perspective of the source, 10V is producing 4.16 mA, which makes the load 2.4k (four times 600R).
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