guitar reamping box

[TimWaldvogel]

i have been through pages and pages and pages of transformers and inductors. and all these diy forums of people saying they made their own passive reamping box\interface.
this is all i really need to do...
i need to plug an xlr output from my interface and send a signal to my guitar amp. the impediance on the female mic input idk about. i know the boxes were using 600:600 ohm transformers...
i just need my amps to think they are seeing a guitar. and my interface to be getting the right impedance

can you help me please?

can i just use op amps to do this. and make it run off 9-18v?

this is where i got the idea

http://www.recordingmag.com/resources/resourceDetail/314.html

[TimWaldvogel]

How do you set the input and output impedances of a op amp gain stage

[ashcat_lt]

IMNSHO a reamp box is almost always unnecessary.

Your amp doesn't care what's plugged into it.  The important part of the guitar>amp interface is that the guitar's pickups see an appropriately Hi-Z load.  Presumably, you've already taken care of this.  This output of your interface is such Lo-Z that it can very easily drive any guitar amp. 

The output might be a little louder than what you'd get out of a passive guitar, but there are volume controls (either analog or digital) to compensate for this.

There might be an issue of a ground loop between the interface and the amp.  The first thing I'd try to remedy this would be to plug both objects into the same power strip.  If that doesn't work, you might try lifting the shield of the cable connecting the two devices.

A "proper" reamp box does usually include a transformer, but I've never heard of using a 600:600.  The transformer should step up the impedance, like a passive DI in reverse. Like I said above, it's not necessary.

This will actually step up the voltage, so these things usually include a passive attenuator, but we've already got a volume control.

The transformer is also used to unbalance the connection.  With most modern gear, you can accomplish this (and buy a little attenuation in the process) by simply lifting the - connection.

It also isolates the chassis grounds between the two devices to alleviate ground loops.  Better ways to deal with that, remember?

I say get yourself a mic cable and a 1/4" TS plug.  Cut off the end of the mic cable which doesn't fit into your interface output and wire the + to the tip of the TS, shield ground to the sleeve.  Leave the other wire disconnected.  Maybe tape it off so it doesn't make any accidental contacts.  Plug it in.  Should work fine.

[TimWaldvogel]

Hmmm I guess I could do that. Some guys argue most of all that the time the impedance going to the amp needs to be correct. Is there a transfoer radioshack sells that I could make one with? Also does it matter that I will be using my pedalboard? I also already have a mic cable that goes from xlr female to ts.

I just think the closer I emulate the impedance of a hot electric guitar pickup the better   

[PRR]

> output from my interface

WHAT "interface"?

> emulate the impedance of a hot electric guitar pickup the better

Unlikely.

If this "interface" clearly says MIKE output, buy a XLR-1/4" cord (Banjo Center has 'em) and plug-up.

If it is LINE output, this will probably overload or need drastic turn-down in the interface. You have to buy two resistors.

In very tough cases you will also have to break ground. Here's where the transformers come in. You could use R.G.'s active splitter (note that it does nothing special to "emulate the pickup").

[TimWaldvogel]

Turns out after some research. The standard xlr to ts connecors have transformers in them to match the impedance and they are like 15-20 bucks. That's the plan I guess. And it should handle fine going into my boss tuner and the rest of my pedalboard. I have lots of buffered pedals :-/ lol

[ashcat_lt]

Did you ever worry about "impedance mismatch" when plugging from a pedal to your amp?  How 'bout from one pedal to another?

The out-Z of most pedals is very low, possibly even lower than that of your interface. 

The concerns you hear come from folks who don't understand the issue and believe the hype.

If you're looking for the filtering and saturation from a cheap transformer those "Line Matching Transformers" from RadioShaft will deliver, but if youi want a good clean transfer from your interface to a pedal or amp, just plug the thing in.

[TimWaldvogel]

Ok works for me. 
our studio is one step closer to our Full setup now lol.

[Joe Kramer]

This may be what you're looking for:

http://www.jensen-transformers.com/as/as092.pdf

I made one using this 10K:10K transformer from Edcor:

http://www.edcorusa.com/Products/ShowProduct.aspx?ID=306

Built it just as it is in the schemo, works like a charm.  Can convert balanced or unbalanced line level into guitar amp or guitar pedal levels.

[ashcat_lt]

Can somebody please explain to me how a 1:1 transformer (600:600, 1K:1K, it all reduces the same) converts anydamnthing?  Won't the primary reflect the same impedance that sits on the secondary side?  And won't the secondary have the same voltage as the primary?  Am I missing something?

[TimWaldvogel]

Well the Example i saw used a 680 ohm resistor in series with one side of the transformer and a 1 Meg on the oter aide... Idk exactly... But it was using the transforme to convert the signal and to amplify it passively... However a transformer works idk... And it saw the impedance of 680 ohms on the mic side and 1 Meg on the guitar side with a variable impedance ( a audio taper  pot) to change the simualtion of the guitars output impedance   

[TimWaldvogel]

Does edcor have a way to order online? Cause I can't figure out how lol

[ddr]

Here is the direct sales page:

http://www.edcorusa.com/Articles/ShowArticle.aspx?ID=23

[Paul Marossy]

Forgive my dumb question, but what it the point of "re-amping" anyway? I just read a little blurb about it in the latest issue of Guitar Player magazine, but the concept still doesn't make any sense to me. 

[TimWaldvogel]

 point is that there is alot of time and effort tht goes into recording electic guitar. But with reamping you have endless options. If you record a guiar track and you hate the tone later. Yougotta bring the musician back in to retrack it. With reamping you record the dry signal going into the computer. So pretty much what you pickups sound like before an amp. And you can go back an experiment with mics, room mics, multiple mics, Mic positions, speakers, amps, pedals, effects. Everything. And rerecord it with the tone that best serves the song/music groups style... Anoter thing is, nobody but the producer will ever know how that tone was accomplished. It's cuts ou the need for the musician to always be there and cuts out the need for an engineer for guitar tracking.

[Paul Marossy]

Oh, so it has to do with a pre-recorded guitar track. OK, I get it. I was thinking it was something different. *slaps forehead*

[TimWaldvogel]

yea its pretty awesome. like you can get a vibe from what the band wants  by what kind of ton they like on a cheap virtual amp software. and make it sound better through some nice mics and amps. i have hated my tracked guitar tone a million times.  and with reamping i actually have the chance to go back and rerecord it easy :-)

[Paul Marossy]

I could see the benefits of having such a device at your disposal. I usually record direct from my multi-FX unit with my own made from scratch presets that I have taken a longgggg time to perfect (as in years of tweaking). That way, I totally bypass guitar speakers with all of their quirks that really bother me. All of my MySpace tunes were recorded like that. Unfortunately, I can't recreate that sound in a live setting. 

[TimWaldvogel]

just ordered a 10k:10k transformer from edcor like he just said he purchased above... and you said i can wire it exactly the same as the jensen transformer schematic?

[TimWaldvogel]

i understand that guitar speakers can be difficult. but its practice and effort at working with the diff. SPLs and FREQ. responses in the different positions that makes somebody a good studio musician\producer. we have a little studio we work in and bring people into. thats how i plan to  market myself around here with any builds i do. i can just le them try out my pedals and compare it to the stock version circuits that modify and upgrade the parts for. i dont really sell them. but that how i can sell my business and my repairs ll