Hooooooooray! After a two weeks of working on it, my Maestro Ring Modulator works like a charm! Thanks to Jsleep and Zero the Hero for making this one possible.
It sounds quite evil and is a LOT of fun. I found the layout to be a little too compact for my tastes, but it needed to be tight to fit all of the components on such a small board.
I built a different power supply from the one on Jsleep's site. I couldn't get the +/- 12 volts using the schematic (it dropped down to about 7 volts using the resistors as show), so I got one each positive and negative 12 volt regulators and made another circuit just like the +/- 15 volt one.
It has a bit of modulation bleed through, which has me thinking about how to reduce it. I was wondering how it would work out if I took a copy of the modulation signal, inverted it so that it is out of phase, then mixed it into the final signal as the last stage prior to going out of the box? Wouldn't this remove the modulation bleedthrough and leave the original signal, sum and difference signals?
Now to wire up all the external jacks and put it in a box!
Ry
Quote from: RyHooooooooray! After a two weeks of working on it, my Maestro Ring Modulator works like a charm!
Sweet! I would love to tackle this one someday, but I'd really want an electric piano to go with it 8) One of my favorite sounds!
Kerry M
Quote from: RyIt has a bit of modulation bleed through, which has me thinking about how to reduce it. I was wondering how it would work out if I took a copy of the modulation signal, inverted it so that it is out of phase, then mixed it into the final signal as the last stage prior to going out of the box? Wouldn't this remove the modulation bleedthrough and leave the original signal, sum and difference signals?
Maybe, but you might find, depending on the origin of the bleedthru, that there is a different amplitude and phase of the bleedthru at different oscillator frequencies. If you are REALLY unlucky, it will vary with temperature as well! Plus, it likely contains harmonics as well, esp. 3rd.
But, a heroic effort to get this sucker going, I dips me lid!
Cool, man! 8)
Did you find it difficult to set all those trimpots?
QuoteDid you find it difficult to set all those trimpots?
It was easy to set the ones that actually worked. I used a cheap o scope that a friend gave me and a multimeter. I replaced TR1 and TR3, thinking that they might be broken, but they still didn't do anything to the signal. I'm not sure why because I measured the output after replacing them and it is varying as you'd expect (from -15 to ground for TR1). TR2 also did not have any effect on the sound, as you wrote in your instructions.
I eventually changed out the 100k resistor off of the wiper of TR1 with a 56k, expecting that it would bring the signal closer to ground. Nothing changed. I will continue to look at it.
Thanks again!
Ry
please wath´s replace 2n4360??
help me!!!
2N3820
When I'll be at home I'll look for other suitable FETs.
I bought the Ready To Solder Board from GeneralGuitarGadgets.com and I have a few questions regarding a few components.
First off, what the hell are these things:
PT1 50k audio
PT2 50k linear
PT3 150k dual gang audio
Actually that's it for now, but the site I got it from is taking too long to e-mail me back with an answer.
Those are the pots.
Hi Brunetto,
QuoteActually that's it for now, but the site I got it from is taking too long to e-mail me back with an answer
I emailed you back the answer to your question almost immediately. I'm not sure why you didn't get my reply.
JD Sleep
http://www.generalguitargadgets.com/v2/diagrams/maestro_ring_mod_ps.gif
I PMed jsleep about this but I'll take anyone's suggestions on this one.
I'm at the stage of building a power supply. What I've been looking for is a 35V transformer with somewhere between 2A to 5A. I just got a PM back from jsleep stating this:
"Where did you get that specification? This unit takes 9 volt bipolalr power I think. 5a is way more than you need also. 35v?"
How are we supposed to get +/-15V and +/-12V from a 9V bipolar supply?
I already bought a 20VCT at 2A. I'd love to be able to return this and get something cheaper...more importantly I want the right one, so what did you guys use?
Is that power supply circuit correct? I would expect that the 35v center tapped transformer would be connected to ground from the center. That gives you 17.5v to be rectified.
In my Blue Ringer, I just use a 15 or 16v AC tranny (not tapped). I ground one side of the AC & have half wave rectifiers (single diode) for the raw + and - lines, which go to 15v + and - regs. I expect the Maestro might have slkightly more current draw, but mine is only 200ma or so, so I can't see the need for a HUGE tranny.
I used a 16v, 1A AC wall wart from Jameco. It works very well. I couldn't get the circuit to work per the schematic, so I used +/-12 volt regulators to get the correct voltage directly from the transformer (just like the +/- 15v circuit) rather than putting resistors directly in line with the 15v supplies to get 12v.
I actually used the power supply schematic for the infinitphase (I don't have the link readily avalible right now) because I knew that it was dead quiet.
Hope this helps.
Ry
MY FAULT!
People, that Poewr supply is not the one I used in my Maestro.
Sorry for that, I'll re-design a new one when I'll have a bit of time.
Use this one instead: http://www.diystompboxes.com/sboxforum/viewtopic.php?t=23268
Use 15v transformer and 7815, 7915 regulators. For +-12v use the resistors of the old power supply schematic or (as Ry suggested) another couple of 7812 7912.
Quote from: Zero the heroMY FAULT!
People, that Poewr supply is not the one I used in my Maestro.
Sorry for that, I'll re-design a new one when I'll have a bit of time.
Use this one instead: http://www.diystompboxes.com/sboxforum/viewtopic.php?t=23268
Use 15v transformer and 7815, 7915 regulators. For +-12v use the resistors of the old power supply schematic or (as Ry suggested) another couple of 7812 7912.
Do really need +/-15V?
I see on the schematic that the 741 chip requires 15V. We looked up the specs on the 741 chip, it only needs 12V. Of course, there are other chips on the board that require 15V, and we haven't looked those up yet, but are teh specs on the 741 a typo?
One other thing is that the new power supply you've linked me too only has an output 12V. So how is this useful for us when there are several components that require 15V?
O yea and one more question:
the trimpots TR1-TR5, once they're tuned they won't be touched again? Or will they be constantly messed around with? I'm thinking only PT1-PT3 will be used for constant adjustment.
The trimmers will be set once and then not touched. On that note, I HIGHLY recommend using 25-turn multi-turn pots. I just got mine tuned correctly. It was very difficult to zero in on cancelling out the modulation signal even with the multi-turn pots. I can't imagine getting it right with single turn trimmers.
A word of advice about the trimmer procedure: I did everything according to the factory instructions (with a multimeter and a scope). I found that trimmers 1, 2 and 3 didn't do anything. Trimmer 5 is very helpful in setting up the oscillator level. I adjusted trimmer 4 by ear to cancel out the oscillator signal on the output.
As far as the voltage circuit goes, the schematic that Zero the hero posted is for +/-12V, but the same schematic can be used to get +/-15v, just replace the +/-12v regulators with +/-15v ones. I think you need all four voltages to get this pedal working correctly. I built two power supply circuits, one each for +/-12 and +/-15. Just connect the transformer output to the input of each.
It sounds fantastic. Build it, you won't be sorry. Yell with any more questions.
Ry
I just asked for 5k multi-turn trimmers at teh shop. I hope they facilitate this tuning procedure. It sounds like a real bitch to do.
So that schematic I was originally looking from teh GGG site, isn't necessarily incorrect is it? I just want to know if there is a way to build only one power supply for all four voltages.
About the 741 chip, though. Was that a typo?
I'm trying to look up specs on the other ICs, namely the IC741 and IC1458 and they all say they require 12V and not 15V.
http://www.emba.uvm.edu/~oughstun/pdf/lab-07.pdf
It also says in the instructions that the MC1495 uses 12V.
I'm obviously having problems finding a 15V transformer, so I'm doing all I can to get this thing done with a 25VCT tranformer.
I am not getting what thes imput/output jacks are. I know there should be one input for the instrument(J1), a quarter inch plug, and the same for the output to the amp(it must be the one at the top, right hand corner in the schematic).
So what is this stuff about an Oscillator Output(j5), Pitch pedal input(j4), External Carrier(j3). and Modulation Pedal input(j2)?
Are they just for trimming? Does this mean I have an expression pedal for this thing?
I hope everyone's not taking their vacation just yet.
Woah, I didn't see your last couple questions. Sorry about that.
I'll try my best to answer your questions here (let me know if I'm not understanding what you are asking):
You do need all four voltages, it works according to the circuit schematic for the pedal. The 1458 and 741 op amps use 15v and the 1495 uses 12v. The power supply schematic at GGG was wrong, look at the one at:
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=23268
for an idea of how to make all four voltages.
As for the jacks: J1 is input, and the output is the one on the top right hand side of the schematic, you are right about that. The other ones are not absolutely necessary to the function of the circuit, but they are neat to have. J2 is the modulation input, it is a stereo switching jack that will allow you to input a different modulation source. J4 is a pitch pedal input, which is also stereo switching. It allows for an expression pedal input (I think, I haven't wired these up yet). J3 is a mono jack. It is an input for a carrier signal (from another instrument, for example). J5 is a mono jack that provides an output of the 741 oscillator.
They don't have anything to do with the trimming other than what the instructions say to do with them. I just jumpered them according to the instructions.
Ry
Another problem is with the Parts Layout diagram. It doesn't seem to tell us where to hook the power up to. It doesn't look like the power is connected to all the components that require it, on the parts layout diagram that is.
The instructions also mentioned empty pads that were marked "A" and "B" but I haven't seen anything marked yet.
I have no info on these switches, sw1a and sw1b. I'm assuming there a part of the mods done to this for true-bypass; but what kind of switches do we have to buy? Where to put them in? They are only mentioned in the schematic but nowhere to be found on teh parts layout.
The Part Layout picture doesn't show any external connection cause I draw another gif file with these important info. I don't know why there is no link to this picture in the GGG site.
I'm going to send it to you via mail, and I'm going to ask JD.
I've drawn another power supply shematic, i hope to draw the PCB as soon as possible.
Quote from: Zero the heroThe Part Layout picture doesn't show any external connection cause I draw another gif file with these important info. I don't know why there is no link to this picture in the GGG site.
I'm going to send it to you via mail, and I'm going to ask JD.
I've drawn another power supply shematic, i hope to draw the PCB as soon as possible.
Is this new power supply schematic significantly different from the new one that's been linked in this thread?
I found a 18V transformer, non VCT, lying around and just decided to give the dual power supply shit a shot. Of course, if the schematic you're working on is a lot easier, I can wait.
I hope you mean e-mail heh
No, it's not that different. It's the same as the one I posted days ago, but it gives both +-15 and +-12.
Ry, as far as I know ALL the trimpots influences the sound of the unit. People, I'm overwhelmed by things to do, I hope to finish all the jobs I'm carrying on so I'll be able to correct everything in this circuit.
I've read 1458 and 741 datasheets, and +-12v are suggested supply values. 741 will work even with +-22v.
I don't exclude that the Maestro will work with +-12v.
Quote from: Brunetto LatiniI'm obviously having problems finding a 15V transformer,
Most domestic burglar alarms use 15 or 16v AC transformers, so that is one source.
The power supply circuit that Ry referred to, is exactlyu how I do it in my commercial (Frostwave) Blue Ringer, except I use +- 15v rails.
http://www.rk-elettronica.it/
looks like a source of transformers (and other stuff) in Italy, they appear to have a tranny with dual 15v windings, might be a bit large though.
The thing about the connections of the pots, jacks, switch, etc is that you can take the schematic and the layout, put them side by side and figure out where the connections go. Just look at what components are near the part you're looking at...having two resistors or a resistor and capacitor connected to the same point as the lug of your pot is a dead giveaway. This is how I figured mine out.
Ry
I have uploaded in my photo bucket account the missing pics for the maestro ring mod.
http://photobucket.com/albums/v368/zero_thehero/
under the "electronics" album you'll find the power supply schematic, PCB and parts placements diagram. I uploaded a pic showing the connections too: That's a missing pic from the GGG site.
I forgot to say that thePCB for the new power supply is still UNTESTED. I'm going to build it as soon as I can.
Hello all ....
Ive just finished the maestro ring mod from the GGG site .
The power supply i used was a 7660s booster n voltage inverter , which gave enough current to run the ring mod.
Its definetly the most compact ive come across .
Posting a link below .
http://tagboardeffects.blogspot.in/2014/01/providence-stampede-od-sov-2.html?m=1
Just used 7815, 7915 and 7812 ,7912 regulaters aft the 17v out with 420 uf caps . ( any reservoir cap values)
Thought it might help future builders
Cheers
Does anyone know where "test point A" and "test point B" is on the GGG schematic? The service manual (the part that I can find) talks about these test points but I don't see them indicated anywhere on the GGG schematic or PCB/parts layout.
http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif (http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif)
http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif (http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif)
Quote from: Paul Marossy on September 16, 2020, 02:11:56 PM
Does anyone know where "test point A" and "test point B" is on the GGG schematic? The service manual (the part that I can find) talks about these test points but I don't see them indicated anywhere on the GGG schematic or PCB/parts layout.
http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif (http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif)
http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif (http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif)
I can see Test Point A on the schematic (just to the left of Pin 9 of the 1495 chip)
No sign of Test Point B. Maybe it was 'written over' when the component ID numbers were added??
EDIT: Test Point A appears to be Pin 9 of the 1495 IC. Test Point B is Pin 7 of one of the 1458s
http://files.effectsdatabase.com/docs/schematics/maestro_ringmod.gif
Quote from: Govmnt_Lacky on September 16, 2020, 02:23:44 PM
Quote from: Paul Marossy on September 16, 2020, 02:11:56 PM
Does anyone know where "test point A" and "test point B" is on the GGG schematic? The service manual (the part that I can find) talks about these test points but I don't see them indicated anywhere on the GGG schematic or PCB/parts layout.
http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif (http://www.generalguitargadgets.com/wp-content/uploads/maestro_ring_mod_sc.gif)
http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif (http://files.effectsdatabase.com/docs/schematics/maestro_ringmod_trim.gif)
I can see Test Point A on the schematic (just to the left of Pin 9 of the 1495 chip)
No sign of Test Point B. Maybe it was 'written over' when the component ID numbers were added??
EDIT: Test Point A appears to be Pin 9 of the 1495 IC. Test Point B is Pin 7 of one of the 1458s
http://files.effectsdatabase.com/docs/schematics/maestro_ringmod.gif
I see it now. Test Point A would be Pin 4 or Pin 9 of 1495? I just found Test Point B on the schematic, I believe. It's at junction of Pin 7 of IC-2B, R18 & R19. No circle around it.
Quote from: Paul Marossy on September 16, 2020, 02:54:14 PM
I see it now. Test Point A would be Pin 4 or Pin 9 of 1495? I just found Test Point B on the schematic, I believe. It's at junction of Pin 7 of IC-2B, R18 & R19. No circle around it.
Check the schematic link I sent in my previous post. Shows where both points are located.
Quote from: Govmnt_Lacky on September 16, 2020, 03:03:57 PM
Quote from: Paul Marossy on September 16, 2020, 02:54:14 PM
I see it now. Test Point A would be Pin 4 or Pin 9 of 1495? I just found Test Point B on the schematic, I believe. It's at junction of Pin 7 of IC-2B, R18 & R19. No circle around it.
Check the schematic link I sent in my previous post. Shows where both points are located.
Got it. Thanks!