Aion Fx L5 pre w/ XLR out?

[Diynot]

So I got caught up in the Aoin fx sale frenzy and ordered the L5 pre Board. I had been looking at it for a while, but never pulled the trigger because of the lack of a balanced out. Well that and the $16 converter, but why let a little thing like money get in the way…. I know I had asked before ab making my own direct box and was pointed in the direction of one of the THAT chips, but then I got to thinking, the MBP Sludgehammer has balanced out w/o the use of the fancy chip so my ask is, can this block:

Starting with R33 (or should it be everything after C26) just be tacked on to this:
If it’s that simple, would it go after R81? Thoughts, pshhaws, or you’re just fucking nuts to be had here?

 

[darwin999]

For XLR, you need a balanced bipolar output. I might suggest looking at either (1) some TI DRV134 or THAT 1604/1646 balanced line driver chips, and you might benefit from a bipolar supply (for more headroom); or (2) an audio transformer with a center tap on the output side. The other thing you need to address is the signal amplitude, since XLR is a line level output. The requisite gain will depend on where you pull the signal on the L5 - that would have to be measured (or calculated). For (1) you could just use a decent opamp (TL072, etc.) in front of the balanced line driver chip to provide the necessary gain (you could/should include a pot for amplitide adjustment), and for (2) you can again use an opamp and/or get the right turns ratio for your transformer.

You might also read the write-up by Elliot Sound Products from down under:
https://sound-au.com/project51.htm

Whatever you try, breadboard it first! Hope this helps. Good luck!

 

[darwin999]

Here are the datasheets for those 2 line driver chips, plus another doc of potential use.
TH Custom also sells a balanced line driver PCB that you might look at (build doc attached as well).

 

[Diynot]

@darwin999 thanks for all the info. I think when I was looking at doing just a standalone di box I ended up ordering a that1646, but got lost in the weeds and ended up buying a quilter amp that had an xlr out. I’m thinking it out a little more, I would still need some sort of cab sim after the L5 so the xlr out would need to go after that. The ask then is can I incorporate the xlr block to the unicab? since you seem to be well more circuit versed than I, I have to ask, how is the sludgehammer able to be equipped with an xlr using only a TL072 for L/R channels as per the above schem? There is a unicab build report around here that used an even simpler XLR circuit than even the sludgehammer, what am I missing? I will def check out the TH customs board.

 

[darwin999]

@Diynot,

how is the sludgehammer able to be equipped with an xlr using only a TL072 for L/R channels as per the above schem?

Very good question! I was too glib and frankly incorrect in that part of my earlier comment (so I just edited them so I don't mislead others). You're right, you don't need to have a bipolar supply, you just need to have the ac components on the two XLR signal wires 180° out of phase from each other. That 180° phase alignment gives you the signal-to-noise benefit of XLR cabling. That can be achieved with a single-sided supply by adding enough DC voltage to both signal wires so that both signals lie within the supply voltage range - e.g., between 0V and 9Vdc. A bipolar supply would allow one to remove any DC voltage from those signal wires (+ more headroom), centering them around 0Vdc. My original comment was coming from looking at example balanced circuits that did use bipolar supplies, and (incorrectly) assuming XLR doesn't like *any* DC voltage. But that probably isn't true, any instrument w/ an XLR input is likely capacitively coupled to remove any (modest) DC voltage. Good job for being alert!

With regards to your other question regarding your signal chain, can you first say a bit more about your amp and intended setup? You say you have a Quilter amp - e.g., is that the Phantom Block, the SuperBlock, or one of their amp heads? Where are you feeding the final signal at the end of the chain (e.g., speakers, recording gear, PA system, etc)? Understanding your setup better would help me (and others) better answer your question correctly.

 

[Diynot]

@Diynot,

Very good question! I was too glib and frankly incorrect in that part of my earlier comment (so I just edited them so I don't mislead others). You're right, you don't need to have a bipolar supply, you just need to have the ac components on the two XLR signal wires 180° out of phase from each other. That 180° phase alignment gives you the signal-to-noise benefit of XLR cabling. That can be achieved with a single-sided supply by adding enough DC voltage to both signal wires so that both signals lie within the supply voltage range - e.g., between 0V and 9Vdc. A bipolar supply would allow one to remove any DC voltage from those signal wires (+ more headroom), centering them around 0Vdc. My original comment was coming from looking at example balanced circuits that did use bipolar supplies, and (incorrectly) assuming XLR doesn't like *any* DC voltage. But that probably isn't true, any instrument w/ an XLR input is likely capacitively coupled to remove any (modest) DC voltage. Good job for being alert!

With regards to your other question regarding your signal chain, can you first say a bit more about your amp and intended setup? You say you have a Quilter amp - e.g., is that the Phantom Block, the SuperBlock, or one of their amp heads? Where are you feeding the final signal at the end of the chain (e.g., speakers, recording gear, PA system, etc)? Understanding your setup better would help me (and others) better answer your question correctly.

I ended up buying a Superblock UK and am running it straight to FOH via the XLR. It works really well and I am pretty happy with it, but what kind of guitar player would I be if I was actually 100% content. I’ve built several different pre pedals and would just like to have the option to put them in rotation while maintaining the ease of an xlr connection to FOH. I’m just not ready to go digital. I found a Craig Anderton project that uses an ne5532 or TL072 with 2 9v batteries for the bipolar supply https://craiganderton.org/build-a-guitar-to-xlr-preamp-for-guitar/. Interesting project, but ultimately not feasible for my intended application

 

[darwin999]

Looks like your SuperBlock has an effects loop, is there an issue for you w/ placing pedals there?
That looks to be stompbox friendly, standard 1/4" phone plug, presumably closer to instrument-level signal amplitude.

 

[jwin615]

TLDR
XLR isn't just line level.
It's also MIC level
That's where DIs live.
If you want to build a DI, you need mic level out. If you build a DI with line level out, most sound guys/gals will make you plug into
.
.
.
.
...
Another DI.

 

[Diynot]

Looks like your SuperBlock has an effects loop, is there an issue for you w/ placing pedals there?
That looks to be stompbox friendly, standard 1/4" phone plug, presumably closer to instrument-level signal amplitude.

Good call on the effects loop. I’m not sure how hot the signal out of that XLR is. At this point, I have put so much thought into the idea of adding an XLR to the Unicab it’s going to happen just to say I can.

 

[jwin615]

Good call on the effects loop. I’m not sure how hot the signal out of that XLR is. At this point, I have put so much thought into the idea of adding an XLR to the Unicab it’s going to happen just to say I can.

If you're coming out of a DI transformer, it's gonna be mic level out.

 

[Diynot]

If you're coming out of a DI transformer, it's gonna be mic level out.

It has been a little hard finding info on the exact nature of the line out on this thing online. I may consult the man himself. All I know is it sounds good and gives me the connection I need. To be honest, I am new to this whole ampless setup and the sound folks are all volunteers and know only slightly more than I do. That said, the mix is shite no matter what. I just want to show up with light gear, plug in, and play. So tell me this, is the sludgehammer putting out instrument level from it’s TRS/xlr?

 

[DailyDovetails]

For my amp less setup I go into a mixer and then XLR out. I have a mix of line and instrument level connections in it and just adjust the range so they match at the mixer. I wonder if anyone makes a small pedalboard friendly mixer with XLR outs.

 

[darwin999]

What's not clear (to me) is where that effects loop sits (before vs after) with regard to the amp emulation. (You could probably answer that by comparing the output at the effects loop vs at the XLR using an audio probe or oscilloscope, with the amp gain set high.) If the loop comes after, then all effect boxes could go there in an appropriate order, including delay/reverb & speaker emulation. If that effects loop is before the amp emulation, then (a) if you keep those amp models acting lightly, then again you can use the effects loop for almost anything; or (b) if you're cranking those amp models significantly, then use the effects loop for distortion boxes and you probably should put time-based effects (delay/reverb/chorus) & speaker emulation on the XLR output (and then output level questions need to be explored). If the XLR signal level is not set too high (looks like the master adjusts the XLR output), such pedals probably can handle it. In every rig there always end up being questions to explore, lol...

 

[Diynot]

What's not clear (to me) is where that effects loop sits (before vs after) with regard to the amp emulation. (You could probably answer that by comparing the output at the effects loop vs at the XLR using an audio probe or oscilloscope, with the amp gain set high.) If the loop comes after, then all effect boxes could go there in an appropriate order, including delay/reverb & speaker emulation. If that effects loop is before the amp emulation, then (a) if you keep those amp models acting lightly, then again you can use the effects loop for almost anything; or (b) if you're cranking those amp models significantly, then use the effects loop for distortion boxes and you probably should put time-based effects (delay/reverb/chorus) & speaker emulation on the XLR output (and then output level questions need to be explored). If the XLR signal level is not set too high (looks like the master adjusts the XLR output), such pedals probably can handle it. In every rig there always end up being questions to explore, lol...

The loop is after the pre, before the reverb and master. I run my nova delay and arachnid in the loop and my VB2, boost, BD2, and cosmopolitan before the pre. I run the gain around 11 and master at 12, compression between 9-11 depending on guitar. If I were to insert the L5 into the effects loop return, I would of course lose the effects loop altogether.

For my amp less setup I go into a mixer and then XLR out. I have a mix of line and instrument level connections in it and just adjust the range so they match at the mixer. I wonder if anyone makes a small pedalboard friendly mixer with XLR outs.

Does the mixer itself boost/cut to line/instrument level?

 

[DailyDovetails]

The loop is after the pre, before the reverb and master. I run my nova delay and arachnid in the loop and my VB2, boost, BD2, and cosmopolitan before the pre. I run the gain around 11 and master at 12, compression between 9-11 depending on guitar. If I were to insert the L5 into the effects loop return, I would of course lose the effects loop altogether.

Does the mixer itself boost/cut to line/instrument level?

The one I have is an older one but you can set it to different gain ranges. Not sure if it’s mic or instrument, it goes direct to monitors. I had an interface in the past that would do instrument level for 1/4 connections and line level for XLR. I’m thinking there are probably newer mixers that do that.


Looking at the setup you have I would probably set the cab sim to FRFR. Then I would in the loop start with anything you want to see a boosted signal like analog delay or chorus ect, then UniCab then any digital modulation or delay you have. Set the UniCab level low to where it doesn’t clip the digital delays and boost it at the very end of the chain if it needs it to sound clear. The UniCab will only cut so far tho. I have considered putting a pot near the end of it as a master volume.

From there if you want to run other preamps you could make a Y switch that bypasses the input of the super block and dumps directly into the effects loop. Just set the 2 for unity.

If you wanted to add a mixer from there you can start doing things like split your signal and run 2 different preamps on separate channels. Run your modulation and delays wet dry ect. When I run into the mixer I usually set my clean channel so that it just barely sets off the clipping indicator and adjust the rest to by ear to it.

Note I haven’t used your setup so take that with a grain of salt but mine is similar and that’s what I do.

 

[darwin999]

Does the mixer itself boost/cut to line/instrument level?

I was referring to this line in the manual (attached): "MASTER: Controls the power amplifier volume as well as the LINE OUT volume."

 

[Diynot]

I was referring to this line in the manual (attached): "MASTER: Controls the power amplifier volume as well as the LINE OUT volume."

That was in response to DailyDovetails mention of using a mixer with line/instrument level

 

[LukeFRC]

This might be a stupid idea and not really the spirit of what you want to do…

But I would buy/make a DI box - and stick it on the bottom of my board - and then run whatever I wanted into it.

 

[Diynot]

This might be a stupid idea and not really the spirit of what you want to do…

But I would buy/make a DI box - and stick it on the bottom of my board - and then run whatever I wanted into it.

Sort of what I would be doing at this point since putting a DI/XLR directly in the L5 (or any pre/dirt/whatever) and direct to FOH, would not sound great w/o a cab sim. So now it’s become, how do I add an XLR to the Unicab.

 

[DailyDovetails]

Sort of what I would be doing at this point since putting a DI/XLR directly in the L5 (or any pre/dirt/whatever) and direct to FOH, would not sound great w/o a cab sim. So now it’s become, how do I add an XLR to the Unicab.

Not sure if you saw this but I just happened to come across it and thought it might be of interest to you.

Unicab with input switch, thru and balanced XLR out

After some helpful posts in this thread and a lot of thorough recording tests (vs going direct or my homemade ISO cab) I finally boxed up my Unicab. As usual, my splatter/spray nonsense resulted in some weird texture effects. I stole a few additions from elsewhere, like the following...

forum.pedalpcb.com

Simple DI box - Tataylino.com

Last time I have featured an active Di box circuit. Here is a more simple circuit that only uses 1 JFET instead of an OPAMP.

tataylino.com

Looks like it would be easy to try.