Line level analog effects (Noob)

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Jayzon

New member
Joined
Sep 7, 2010
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4
Hi, I have some experience with using guitar pedals for line level purposes (synth/mixer etc), by attenuating and boosting the signal. Since i want to build some dedicated analog effects (flanger, chorus) to use as while mixing, i was wondering  if its possible to upscale/upgrade stombox designs to work at line level and perhaps have provide quality (no need to reamp, less chance of distortion, better s/n etc, better effect?).

I have searched both this site and several stompbox sites (+google), and could not find anything on the subject. Again; im not looking for DI or reamping effects, im interested in the possibility of building effects so that they perform at line level. Of course you could wonder if this is really useful, but i thought it would be a interesting experiment. Why do we have fancy eq's and compressors in the studio and hardly any analog effects?



ps. like the title says, im a noob :D i have some experience building from schematics, but dont understand it enough to design it from scratch.
 
Should be simple enough - just use input- and output stages that interfaces to (sets gain according to) whatever levels that your favotite circuit is happy with. And at the same time possibly make the in/outs balanced.

For a minimum solution, look at e.g. the GSSL input and output circuit.

Jakob E.
 
Yeah, you need some kind of buffer.

I did exactly this.... I threw a bunch of guitar fx in a box and put a buffer at the front and back, as well as using audiox's
balancing card to unbalance/balance the signal.

I did up a home etch file for the "adjusticator" which may be useful to you.  Here's a link:
http://www.groupdiy.com/index.php?topic=35757.0

cheers,
dave
 
Thanks for the quick reply Jakob & Davo.

I understand what you are saying about the input/output stage, but my question is about something slightly different.  

Here is my original line of thought:

- an fx pedal is designed to work at a low level signal, and therefore we change the level of our signal in a extreme way to make the effect suitable for line level purposes (attenuation>effect>amping).
- one way or the other, pedals have other design restrictions / goals than our rackgear (signal levels,   unbalanced, size? power supply? etc). And for line level usage, this is a potential source of quality loss (by design if you will [for this purpose at least])

-the way i see it, studio compressors / eq's are designed for a higher signal level; not just their input/output stage, but also the 'effect' part. And probably use a higher working voltage as well. And mostly use components that are in a different 'range', or quality.

MY IDEA > cant i build better analog effects - for line level purposes - if i make it work AT line level (therefor changing/upscaling the effect part itself), just like the compressors eq's. Instead of working around guitar fx that are designed within a different context.

(I know this is a very crude explanation, but please tell me if any of this is incorrect)
 
There is a modest difference between line level and a hot guitar output voltage (especially with active pickups) but the more significant difference between pedals and rack EFX is the rack gear will typically anticipate a line level balanced input (while you could provide a high impedance guitar input in addition), and there will be an expectation for lower noise floor, higher headroom, with wider frequency response.

IMO this is more than just cobbling balanced I/O to a pedal design, but some pedals way be clean enough. I would expect most pedals to be designed for single supply battery operation. 

JR

 
@JohnRoberts, thank you for your reply.

the more significant difference between pedals and rack EFX is the rack gear will typically anticipate a line level balanced input ... and there will be an expectation for lower noise floor, higher headroom, with wider frequency response.
IMO this is more than just cobbling balanced I/O to a pedal design

You described it a lot better than i did  :D  Its indeed the lower noise floor, higher headroom, wider freq response that im looking for, and i agree that just the I/O wouldn't give this. I am trying to figure out how to do this for a chorus or flanger effect for example. In the meantime someone suggested to me that a possible problem could be that things like the commonly used bucket-delay chips (used for chorus and flange and delay etc) form the bottle neck (freq response, noise etc) and are difficult to 'upgrade'.

 
Back in the '70s I added companding NR around the BBDs to increase dynamic range.. in the early days I used OTA (like CA3080), then later NE570/572 chips.

These days for a studio grade flanger/chorus/delay, I'd be inclined to use digital conversion and reading/writing to memory to create high quality delay. 

This seems like a lot of effort when you can buy EFX pretty inexpensively, and the dominant trend is toward plug ins.

Your effort might be better spent learning to code plug-ins vs. designing efx.

JR

Note: IMO it isn't worth the trouble to use better VCAs to make companding NR since the raw frequency response and dynamic range of BBDs isn't that hot.
 
> the commonly used bucket-delay chips

ONCE commonly used.

Still (again) around for the few players who like that queer sound.

CPUs/DSPs and RAM have got so cheap that most new-model delays, reverbs, flangers, expecially the ones with 99 different effects for $69, do it digitally.

Also: delay (BBD or RAM) cost is proportional to time multiplied by bandwidth. For general use you want well over 10KHz, preferably over 15KHz so your cymbals don't alias/clash. But for guitar you do NOT want much over 5KHz-6KHz; string inharmonicity bites. Guitar speakers all cut drastically above 3KHz-6KHz. So why would a gitar-pedal go much further? Better to use half the RAM and put the pennies into flashier graphics and a bigger retail mark-up.

> in the studio and hardly any analog effects?

Maybe you are too young? I've used all-analog spring reverb and restroom reverb. "Flanging" to me means rolling two tapes and dragging the reel-flange of one of them. I have EQ-ed with a box of capacitors and an old power transformer. "Sampling" means many small scraps of tape, hand-threaded (a one-sound-at-a-time Mellotron). To fade-out when you can't re-copy through a fader, you wave a magnet at the tail of the tape. I had a blast... but at some point the razor-cuts and solder-burns get a little tiresome (I was never rich enough to get it all packaged, nor hire myself to do the fiddly-bits). Working on a DAW is maybe less exciting, but some things are so much cleaner.
 
Jayzon said:
I am trying to figure out how to do this for a chorus or flanger effect for example.

I may be stating the obvious but you could just buy an Eventide and call it a day. You could get a little MIDI controller for real time manipulation.
 
This skill level is well beyond my ability!  But, if you could do the mod you are talking about the new line 6 stuff sounds great.  It could be be a good box to figure out and then you would have a ton of different fx's to choose from that actually sound really good.  M9 and M13 stuff.

Ok, sorry I'll just go back to reading.
 
If you want a full kit, this will do.  http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=96
If I got it rigth you should be able to adjust the gain on the output, for a pro level output.
 
Thanks for all the helpful (and less helpful) comments  :D Perhaps to clear things up (a bit), i know that (and why) effects have gone dsp. I use several digital machines myself. If i could afford an Eventide (like someone suggested) i would absolutely get one, but would probably still be messing around with these electronics. I just like to learn new -to me, i understand that some have been around for a bit longer- things, and be creative. So im aware that perhaps i will not end up with the greatest effects after all. But this is DIY right? :)

With that said, I appreciate all the comments and am researching everything mentioned. I've actually found a really interesting project on this forum and Jürgen Haible's site; the Roland Dimension D (famous chorus) clone. Like the technique JohnRoberts mentioned earlier, it uses some interesting stages to get the best signal into and out of the chips.

http://www.groupdiy.com/index.php?topic=21276.0
http://www.jhaible.de/
 
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