New to 51x - Help needed to develop project board please

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irfrench

Well-known member
Joined
May 21, 2012
Messages
202
Location
UK
Hi,

I'm new here, and to DIY in general - however recently I took the plunge on a 51x setup.  As it's Christmas(ish) I've got a bit of spare time so thought I'd cut my teeth at developing a self-etch project for the 500/51x format.

I'm from a guitar background and have used a DIY version of the Monic Saximiser (not sure if I can reference TMs here?) which instead of the NJM2150AD uses common components, so I thought this would be a nice simple project to kick off with.

In doing so I have needed to add a few things, it'll be easier to list them:

- Balanced Line Receiver (sound.westhost.com)
- Millennium Bypass Circuit (geofex.com) [Can only find DPDT pushbutton in eagle lbr]
- Filter/EQ circuit (freestompboxes.org/madbeanpedals.com)
- Balanced Line Transmitter (sound.westhost.com)
- Clipping LED indicator (sound.westhost.com)

I have attached the schematic I've drawn up, I have also done a board layout (primarily because I was not sure if I could squeeze all that onto a single-sided 500 size board!).

As I say, I am very new to this, still, so in all honesty don't know how to stitch circuit elements together. If anyone can offer any advice it would be gratefully received.

I'll post the board layout in a sec.

Many thanks,
Ian
 

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Between pins for +16 and -16 you have another ground reference, 0V, you should use this as dirty ground, putting some caps from supply rails near of each IC, this will improve stability, 100n from each rail to ground at each IC as near as you can from that IC, some electrolytic caps too, 22µ or 47µ in parallel with 100n ones. You should do this from +16 to ground near led too.
Also use this ground for the peak indicator ground, so switching clicks don't make noise in the audio...

In the scheme you are missing PS voltage to turn on the led... here again add caps and use dirty ground.

If you use relay bypass you could avoid milenium for the led and the long signal traces from the back of the PCB to the frond, using 2 DPDT relays you could use balanced true bypass.

JS
 
JS,

Thanks for that, I hadn't noticed the extra GND between 16v supplies.  I take it the good practice guide is to have audio GND on one pin and power on the other?  I'll give it a tweak.

- "In the scheme you are missing PS voltage to turn on the led... here again add caps and use dirty ground."

Thanks - I can't believe I missed that!

I'll revise the schematic to add as much of the power filtering as I can (Cemal - who is supplying the 51x kits also suggested this)

I'll have a look around for the relay switching, true-bypass would be the ideal as it'll avoid the unbalance/balancing circuits I guess.

Are there any comments on the circuits, and/or how they've been barbarically thrown together?  ;D


Thanks for your help.
Ian

 
About the circuit nothing to say, maybe the way it's drawed, maybe in a couple of days with some more time I'll look it closer, a lot of jobs this weekend... a couple of bands to make sound live (and alive, if I can)

JS

EDIT: the only thing I can say quickly is that most of the nice sound of this kind of exciters/enhancers cames from the dynamic processing, you could build one with something much easyer to find like LM3080 or LM13700, or some clipping for getting harmonics from hi frec... I have a guitar enhancer from boss, a great but discontinued pedal, I've seen it once used at a shop, I listen to it and bought it right there, never seen again any other of this... It has a tuneable HPF to a VCA and a summing amp, input signal +processed or -processed, controls are sens, freq and mix with an inverting option in that pot, a great animal, I love it, if you have a cheap guitar and a cheap amp it gets all the harmonics up to a much better sounding, using it with some duncan mics and a nice tube amp make it sound much reacher too, something like an acoustic, but not so harsh as an acoustic simulator.

Anyway your design will do something, but more like an strange eq than anything else I guess, guive it a shot, maybe in a proto board and listen there how it sounds... A TL074, 2 pots and some resistors and caps, not so hard for a proto.
 
Righty tighty.

JS - Thanks for the advice.  The circuit is based on a stompbox/rack unit by a well known company (am I allowed to say who and what?) so I have used it a number of times and like it's function/sound.



So I have added:

- True bypass relay switching.  My 'understanding' is based on Igors switching schematic.  My main assumption being that as it will be supplied off the regulated +16v supply and I've considered 12v relays I don't need(?) to add a resistor in series to drop the +16v (datasheet says operating voltage 9v->18v).  I've also assumed a latching switch is required.

- Second ground run (0V), unhelpfully I've referred to it as GND2 in the schematic.  All IC, relay and LED power uses this reference.

- Power filtering as close as possible to each opamp, and the Status LED.

Hopefully this is getting nearer the mark!  I'm a little gutted that there are a good number of jumpers on the board, but this is meant to eventually be available as a home-etch project so I'm trying to keep it single sided.

Thanks for having a look over it, and if anyone else has any suggestions I'd love to hear them.

Ian
 

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New board

EDIT: I'll tidy up the board once I know it's looking useful!
 

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Darn it.

I just realised that the relay switching is wired wrong... I'll update that.  Other comments still welcome though!  :D

Thanks,
Ian
 
A simple mod to add "harmonic enhancer" (or exciter or whaterver) would be to split the 10K resistor into 2 resistors... 2x 4K7maybe for R16 and add a switch with a couple of clipping diodes to ground... so there you will be adding distortion only to highs and creating new harmonics up there... if you are a guitar guru will be easy to you find the diodes that sounds better for you, I used to have a rotary switch with a lot of diodes to select in a testing rig wich diode combination (symetric or not, Si, Ge, Led, etc) sounds better for each pedal... Remember the level in there is line and probably you will need series of diodes to not clip it so low, also you could add a pot in series with diodes to soft the clipping and combine series of different diodes... there is a schem arround that use a pair of Si diodes and 4 pairs of Ge diodes with a Hi shelving boosting that says to emulate tape distortion, I'm not saying you to do this, but may be a nice combination of diodes to try.

Schem attached, I've seen it in a lot of places, I don't remember from where I have this gif, excuse and tell me if I bother someone.

JS
 

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Hi,

Thanks for the suggestion.  In a weird coincidence I recently added something very similar to the Poormans Pultec I am building.  As I was just using a simple IC based balancing circuit (Ruffrecords helped with that) and not tubes I wanted the option to add a bit (OK, actually a LOT) of grit - see attached schematic.  In hindsight the 20k trimmer was total over kill, I'm guessing a 1k would be a bit nearer the mark.

http://irfrench.tumblr.com/post/38320922790/a-diary-of-always

The effects of which can be heard here: https://soundcloud.com/minoian/distdrumsbat41-h

Obvs that was done with a much less subtle end goal in mind, but I had not thought to just excite the top end.  If it were to be added (and given the amount of space free on the board that may well be done - just because!) I guess the pot to ground could be added to the front panel to vary the amount of 'excitement'.

Thanks for the .gif - I seem to remember that too - gimme a sec... it was from here http://www.261.gr/limiters.html, I guess the advantage of that is that the switch would be a simple yes/no rather than a tweakable pot - if thats a good thing.

The only other mod I've considered which would move it away from the standard SonicStomp/Maximiser would be adding a MID control (change 39k resistor for 15k and add another 50kB pot in series).  The circuit seems to generally be liked for it's simplicity and the "punch" and "clarity" it adds.  So i may just leave it as is.  Is that too sensible/boring and a missed opportunity?

For reference this circuit is based my experiences using this project:
http://www.madbeanpedals.com/projects/Bloviator/docs/Bloviator.pdf

Thanks again,
Ian




 

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Right,

So a bit of thinking and it makes sense to make this a not-off-the-shelf-but-can-be-if-you-want-it  project.  As such I have included the discussed 'mids' mod and JS's suggestion of an HF exciter (read clipping) element.

As I've mentioned in-numerous times already I'm new to electronics therory generally so any tips/pointers/warnings will be much appreciated.  I do feel like I'm learning loads though!

One direct question - is the 51x/500 card offset in the rack compared to it's face plate? Or does it sit directly in the middle? I'm guessing offset, and hopefully to the left of the panel as you look at it.  ;)

Cheers,
Ian

 

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Hi Ian,

The Radial Workhorse open source document has the answers to all of your 500-series mechanical questions. Pretty cool that they provide it for free.

http://www.radialeng.com/whbeta/re-workhorse-whos.php
 
Gemini thanks, that IS very cool of them.  8)

And you for pointing me to it! 8) 8)

Thanks.
Ian

Edit - thanks Meathands too
 
Cool project!  I love what you're doing.  Keep at it.  I will build one if it ever gets confirmed as working.

You asked about relays earlier.  They should be non-latching. Constant current to the coil keeps it switched. Cut the 16v and the switch opens.

I had similar thoughts as expressed earlier - millenium bypass has no real advantage here - already pointed out.
But you could even do true bypass without the relay using only the F2UEE if you didn't care about LED indication. But what you've got works, so enough mucking comments from the cashew gallery.

I wouldn't even bother with midrange in the context of a 51x rack which more than likely already has EQ inline, or would be better saved for ITB mixing. I love the idea of that tape saturator simulation in theory, provided it does something interesting in practice.

However, I mostly wonder about changing the focus of the EQ points on the bloviator.  Bajaman mentions you can change the 3n3 ( try 2n2 - 10n) capacitor for changing the process (high frequency) turnover point. The original harmonic saximizer centers it's high processing around 10k which makes sense for program material through one's home hi-fi. But for guitar, it would seem a lower frequency, like 1k - 2k where it's fighting with the vocals, might be more effective.

Always meant to build a bloviator, and try this mod.  Just never got around to it.  Let us know how it goes!
 

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