DIY DI box for recording guitar Amp

[eraz]

Hello there, I am looking to build my own DI box for capturing the direct signal of my amps. A dummy load is not needed, as my plan would be to leave the cab connected using a through output, so the power amp sees the correct impedance load of the cab. Are there any projects out there, or is someone interested in helping me?

I have some basic understanding and experience in building/soldering DiY kits, but when it comes to designing something from the ground up, I am a complete noob!

Cheers!

 

[Matador]

Do you mean recording the signal being sent to the speakers?

 

[eraz]

Exactly. A box I can put in between the guitar amp and the cabinet to capture the signal which comes directly from the power amp!
There are boxes out there which do that, like a Suhr RL or a Captor X, but they all also have a reactive/resistive load in it, which I don't need/want.

 

[dmp]

You could make an attenuator to plug in with the speaker with a high value potentiometer and a cap, then connect that output to any DI, passive or active. You need to reduce the level a lot for it to work with a DI and line level interface. I did this years ago and it worked fine.

 

[Matador]

This is common on a lot of guitar amps. Just pad down one of the speaker taps to reduce the amplitude down to line(ish) levels.

See: https://diagramas.diagramasde.com/audio/sovtek_mig100h.pdf

5K into 200ohms, or about a 30dB reduction.

 

[eraz]

This is common on a lot of guitar amps. Just pad down one of the speaker taps to reduce the amplitude down to line(ish) levels.

See: https://diagramas.diagramasde.com/audio/sovtek_mig100h.pdf

5K into 200ohms, or about a 30dB reduction.

Thanks for the schematic.
So this would work for a 30dB reduction as you say?
But according to the schematic only for a 8ohm output on the power amp, or doesn't it really matter, if I then would choose to use the 16ohm output?

 

[JohnRoberts]

I recall vaguely from decades ago that Peavey sold an accessory box for that (ID-1 something?). It involved a step down pad, and IIRC some EQ sound shaping to mimic guitar speaker response.

JR

 

[Matador]

or doesn't it really matter, if I then would choose to use the 16ohm output?

The voltage on the 16ohm tap will be higher, so you need more padding to bring it back down (maybe 100 ohm instead of 200 ohm) to the same level as the 8 ohm tap.

 

[eraz]

The voltage on the 16ohm tap will be higher, so you need more padding to bring it back down (maybe 100 ohm instead of 200 ohm) to the same level as the 8 ohm tap.

Thanks for the information!
So what I have drawn should work in theory?
I suppose the volume going to the speaker directly won't be affected noticeably and the load presented to the amp, won't really change as well?

 

[dmp]

16 ohm tap will only be 3 dB higher than 8 ohm
5k in parallel with 16 ohm lowers the load to 15.95 ohm. I don't think it would be noticeable.

 

[GratefulEight]

Thanks for the information!
So what I have drawn should work in theory?
I suppose the volume going to the speaker directly won't be affected noticeably and the load presented to the amp, won't really change as well?

DIYRE has a kit for what you’re looking for, which might be easier or at least provide some useful information. FE2 Direct Input Box Kit

 

[eraz]

DIYRE has a kit for what you’re looking for, which might be easier or at least provide some useful information. FE2 Direct Input Box Kit

That one uses a transformer. I'd like to keep the signal path as clean as possible, do I need one for what I want to achieve?

 

[eraz]

... (maybe 100 ohm instead of 200 ohm) ...

The resistors in there the 5k and the 200 ohm, do they need to be 100W resistors or something similar, or can there be used lower wattage resistors just fine?

 

[Matador]

can there be used lower wattage resistors just fine?

Ohms Law tells you the answer. If the secondary is swinging 28V to put about 100W into 8 ohms, then that same 28V will only put less than 0.25W into 5.2K. So 1/4W resistors will work just fine.

 

[Whoops]

Exactly. A box I can put in between the guitar amp and the cabinet to capture the signal which comes directly from the power amp!
There are boxes out there which do that, like a Suhr RL or a Captor X, but they all also have a reactive/resistive load in it, which I don't need/want.

There are many DI boxes that can accept Speaker level and that don't have a dummy load inside.
You can get them for cheap nowadays, cheaper than building one.

I highly recommend the the Hughes & Kettner Red Box, it has a speaker simulated output in case you need it:

https://reverb.com/item/63041794-hughes-kettner-red-box-cabinetulator-d-i-mkiii



You also have the Peavey EDI, EMO DI BOX and the Palmer The Junction DI Box.
All of them accept Speaker Level and you can get these units for cheap in the used market being it Reverb or Ebay.

 

[eraz]

There are many DI boxes that can accept Speaker level and that don't have a dummy load inside.
You can get them for cheap nowadays, cheaper than building one.

I highly recommend the the Hughes & Kettner Red Box, it has a speaker simulated output in case you need it:

https://reverb.com/item/63041794-hughes-kettner-red-box-cabinetulator-d-i-mkiii
View attachment 105134


You also have the Peavey EDI, EMO DI BOX and the Palmer The Junction DI Box.
All of them accept Speaker Level and you can get these units for cheap in the used market being it Reverb or Ebay.

View attachment 105136

View attachment 105137

View attachment 105138

View attachment 105139

Thanks for the info, but these all have a baked in IR response right? I'd need the direct raw sound of the amp!

 

[Whoops]

Thanks for the info, but these all have a baked in IR response right? I'd need the direct raw sound of the amp!

I'm not sure if I understand what is a "baked IR". If you talking about a filter to mimic Speaker response, then it's switchable on/off in the RED Box and the Palmer Junctions so you have the choice for Raw or Equed output, as for the EMO DI it doesn't have any EQ, so it's always Raw.

As for the Peavey I don't remember if you can turn the EQ off or not. (maybe you can with the "Timber adjust" )

 

[amplexus]

That one uses a transformer. I'd like to keep the signal path as clean as possible, do I need one for what I want to achieve?

Fairly certain all of the commercial boxes will have a transformer if they're presenting a balanced output. If you don't care or want a balanced output then you'll likely need to roll your own.

 

[CJ]

You don't want the direct sound of the whole amp. It might be ok for live but it is noisy for recording unless the amp is super quiet. Ampeg has had a preamp out on their amps since the 60's. Most new amps have a di jack. A simple resistor divider will probably need a cap or two to get the freq right.

Also, a di jack leaves out the sound of the speaker and cab which can be 90 percent of the grit which is exactly why people mic tube amps. Try a pair of 57's, one directly at the cone and one angled at 45 degrees. Move them around until you get the magic 3d sound.



Maybe dial up a new fender schemo for ideas.

 

[Whoops]

You don't want the direct sound of the whole amp. It might be ok for live but it is noisy for recording unless the amp is super quiet.

I have used this method many times in the studio, not for guitars as I only like guitar sound through an amp and speaker to I mic the cabinet, but I used it regularly for recording Bass.
Just straight out of the amps speaker output into a Red Box or Emo DI, and then used the amp cab for monitoring or if removing the cabinet I connect there a resistive dummy load.
I used this with many different bass amps, no noise problems and the sound is pretty good, choose the bass amp head to taste.