DIYstompboxes.com

...for a simple mind.

Hello all, I'm hoping you can help me.

I need a very simple FX loop switch that is controlled via signal from a cable (the source of which will be "Amp Control" output from a Boss GT8). Powered by a 9V source, preferably with a ground loop isolator if you think it's needed.

The basic idea is below, although I don't know what I need to make it work.

if anyone knows of a unit like this on the market then please let me know - I as yet can not find one, hence my presence here.

Thanks!  :icon_mrgreen:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/AmpControlSwitch_zpsb5c2cd2a.jpg)

Hello all, I've found the exact wiring diagram, except I want to run this at 9v, will this change the component values?

(http://www.geofex.com/article_folders/rmtswtch/rmtsw3.gif)

The values are fine, the only thing you need to watch out for is the relay.

9V relays are kind of uncommon.

A 12V relay might still work at 9V, depends on what it says in the datasheet. A more consistent option would  be to use a 5V relay and wire in a series resistor, the drop the voltage from 9V down to 5V so you don't burn up the coil (use a multimeter to measure the relay coil's resistance and work out how much you need to add).


I'm not sure how the Boss GT8 runs it's amp control output but I'm guessing it's not a voltage signal, but rather it shorts out the input to ground (either with a relay or with a transistor). To make this circuit work with that you'd need to add a pull up resistor (about 10kiloohms should do) from left side of R1/D1 up to positive supply.

Hello Seljer. Thank you so much for taking the time to help me here. I am talking with CG who might be making one for me (with a ground loop isolator), but in case that falls through for any reason I'll continue with this conversation;

QuoteThe values are fine, the only thing you need to watch out for is the relay. 9V relays are kind of uncommon.

Will THIS (http://uk.rs-online.com/web/p/product/7181724/?grossPrice=Y&cm_mmc=UK%7CShopping-_-Google+PLA-_-TE+Connectivity%7CNon-Latching+Relays-_-7181724&kpid=&istCompanyId=f7e7b05b-2daf-4c0e-8825-3633baf8113b&istItemId=xwillarmq&istBid=tzit&gclid=CPTi2fLXqL8CFUTItAod90kAbw) Work?

QuoteI'm not sure how the Boss GT8 runs it's amp control output but I'm guessing it's not a voltage signal, but rather it shorts out the input to ground (either with a relay or with a transistor).

Yes, I've checked with the Boss manual and it just closes the circuit between the Tip and the Sleeve of the jack plug.

QuoteTo make this circuit work with that you'd need to add a pull up resistor (about 10kiloohms should do) from left side of R1/D1 up to positive supply.

Like this?

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/ExtraResistor_zps195b261c.jpg)

Yes on that relay and yes on how you wired it :)

That's excellent!

Thanks for your help Seljer. If I end up making this myself for any reason, I'll post some results.

Hello again.

I'm ready to order the components and I have a couple of questions on Capacitors:

1. is it important what type (if so, what type should it be)
2. is the voltage important? I'm struggling to find a 0.1uF at 10v

Thanks!

C1 will be an (aluminium) electro, being a value over 1uF. usually, but not always. when using electros, you need to watch the voltage ratings, as they are usually very much lower than non polarised types. for your 12V supply circuit, you'd want 16V or 25V types, but 35V and 50V and 63V are all just as good. in fact, smaller values, like less than 10uF, will mostly be 100V rated. also fine.

you can also use a tantalum there, again 16V or more. as for the 0.1uF, 100nF cap, these will be "box", "green", "poly", "ceramic" caps, there are others. ceramics might be as low as 25V, polys etc will generally start at 50V, 100V is v. common. they will all be fine. you will be hard pressed to find a 100nF cap that won't go in that circuit.

Excellent, thank you for the quick reply.

This is actually going to be a 9V supply.

I was worried (not properly understanding caps) that a higher rating (such as 35v) would require a supply of 'at least' 35v in order to function properly.

This is brilliant, thanks for the help.

:icon_smile:

> worried (not properly understanding caps) that a higher rating (such as 35v) would require a supply of 'at least' 35v in order to function properly.

In capacitors, "35V" is a BLOW-UP number.

Actually I've put 36V on "35V" caps and they didn't blow-up in hundreds of hours; also 490V on "450V" caps for a few seconds. OTOH if it did blow-up at 35.001V the maker could say "We told you so!" and laugh.

Say I need engineering plans for a porch for my 9 dogs to lay on. Maybe Molly gets fat, or my lumber is crappy, so I should allow a little extra. A 16-dog porch is plenty strong for my 9 dogs. And also when 7 dogs are chasing cars and there's only a 2-dog strain. If it turns out that the smallest (cheapest) lumber will support 50 dogs, that's the way I'd go. (And no, it's only 2 dogs here, that was just example.)

There are old stories about using 450V electrolytics in 15V circuits, that they "decay" fast. This was true for some caps made 1950-1970. Cap technology has changed, and it does not seem to be true today. However simple price difference will encourage you to use 16V-100V caps instead of 450V electrolytic caps. (Price and size goes UP with voltage rating.)

Thanks again.

I'm sorry, I've more questions, based on the below diagram now including all jack socket connections:

QUESTION 1
Which of the jack connections should the signal carrier be connected to (I'm guessing the 'tip' - i.e. bottom terminal)?

QUESTION 2
"From FX Output" - should the relay be connected to the "Tip" of the jack (this appears to be connected to the sleeve (ground)?

QUESTION 3
This is the Jack socket that takes the signal to the GT8 "amp control" (i.e. the switch) - again, should this be the connected at the 'tip' - and should the return path be the sleeve? (I suppose it has to be).

Thanks for your patience!


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/JackQs_zpsb163e3ff.jpg)

remember when you're wiring up all those dogs, the collars have to point to the most positive end of the porch.

A1 - signal always to the tip connection, unless you have a very good reason for wiring otherwise. ground to sleeve, always.

A2 - see A1

A3 - see A2. the volts needed to turn on the base is more "signal" than the ground, so it goes to the tip.

always the signal to the tip. and if you have a socket with 2 dingers, the longer dinger will contact the plug-tip ding. the shorter dinger can be used for stereo signal, or for short-to-ground battery connection switch.

now you've spotted those errors, you'll need to redraw the corrections.

Awesome! Thanks. I do have more questions (regarding rounding of the signal and the return of the 9v) I'll redraw first.

Cheers!

Updated drawing below. My next questions are:

Signal grounding
G1 - G2 - G3 - G4 are all signal based, can these all be grounded together?

9v Grounding
G5 - G6 Guessing it's a bad idea to ground 9V and the signal together, so this needs to be isolated (The project box I have is aluminium) where do I send this?

GT8 Amp control 9v return
Since the sleeve of the this Jack socket will be carrying a 9v return when the circuit is closed, am I correct in saying I somehow need to isolate this?

Thanks again!

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/GroundQs_zps67b073c8.jpg)

you will need to isolate something from something else. all the signal grounds on the G1-G4 need to be connected, yes. they can connect to the box if you isolate the switching grounds from the box. otherwise, the other way around, isolate all the (still connected) audio grounds from the box, ground switching to the box.

erm, the "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V. what is the "-9V" you have marked, where does it originate frumm? is it a real -9, or a mislabelled 0V?

Quote from: duck_arse on July 18, 2014, 09:46:02 AM
you will need to isolate something from something else. all the signal grounds on the G1-G4 need to be connected, yes. they can connect to the box if you isolate the switching grounds from the box. otherwise, the other way around, isolate all the (still connected) audio grounds from the box, ground switching to the box.

So, G1 - G4 can all be connected together?

Quoteerm, the "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V. what is the "-9V" you have marked, where does it originate frumm? is it a real -9, or a mislabelled 0V?

In honestly, I'm not actually following this one. especially this bit

Quotethe "+9V" needs to be referenced to the ground of the switching circuit. the switching signal also needs to be referenced to the same ground/0V

+9V is from the positive terminal of the power supply
-9v is the negative terminal (should this be "ground")?

As I understand it, the GT8 doesn't ground the current itself, it just acts as a switch. Or am I wrong about that? (I'll get the multimeter on it this weekend).

I've since learned that the project box is actually plastic, with an aluminium 'lid' so that makes it easier.

G1 to G4 connected together, yes.

to measure your +9, you need somewhere to put your black meter lead. we therefore say the +9 is referenced to ... (whatever your black lead is on). if you have a 9V battery, and you put black on the (-) terminal, red to the (+) you will read +9V, because you referenced to the -, or 0V.

so, for your signals to talk from one end to the other, they all need to reference to signal ground. your switching section needs a source of power, something above zero volts. it needs to still be referenced to zero so it knows how high it is (9 volts, positive). anything (signal-wise) that is to switch it will also need to know how high it is, referenced to the power ground. so the signal to switch the power, and the power the signal is switching need a common ground or reference point. we call it 0V, and the voltages are positive.

hopefully prr will come by soon and explain this clearly.

Ah, I think I got it - where you said "referenced to" previously - I'd never heard that terminology before.

Man, you've been so helpful.

Just to finalise, the finished diagram is below, and if I understand this properly, the two ground symbols at the bottom (off C1 and Q1) will be connected to "0v"?

..also, if I want to put two LED's in there instead of 1, would this affect the rest of the circuit? Series/parallel?

Thanks again!

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit_zps9477b4d5.jpg)

C1, Q1, 0V, yes, all connected.

two leds. well, you KNOW how to calculate the series resistor for a led, yes? well, instead of "1 led forward voltage", you will have, in series, 2 led forward voltage(s). if you used 1V6 for your one led calc, you would use 2*1V6 = 3V2 for two leds in series.

and if you put 2 leds parallel, it will be easier, because they both need their own series resistor. so, whatever value you had for one led (R3=4k7) goes in series with the second led (of the same colour: R3A=4k7), and that R3//LED1 string goes parallel the other R3A//LED1A string.

Quote from: duck_arse on July 19, 2014, 08:51:30 AM
you KNOW how to calculate the series resistor for a led,

Actually I'm afraid not. Sorry, I've not done any of this since school.

Quoteand if you put 2 leds parallel, it will be easier, because they both need their own series resistor. so, whatever value you had for one led (R3=4k7) goes in series with the second led (of the same colour: R3A=4k7), and that R3//LED1 string goes parallel the other R3A//LED1A string.

So:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led_zpscf155be3.jpg)

exactly. correct. 100%.

I won't type out the led resistor calculation, because I will make my usual long-winded botch/confusion of it. you can probably find an explanation hereabouts if you search "led series resistor calculation", or similar. (sometimes googoo searches this site better than the search button.)

OK thanks!

I've researched it and understand the theory, and there's plenty of calculators out there, although using this information says that the resistors I have are way over rated (N.B. the LED ratings aren't from the supplier, these I've found elsewhere online. The LEDs I bought are both "Bright Purple/Pink"):

Supply: 9v
Forward Voltage: 3.2v (each)
DC Forward Current: 30mA

The calculator I used tells me I need a total of just 100 ohms resistance, whereas I'm using 2x 4.7K.

Am I missing something obvious?

numbers. ok. first, 30mA is the max value, probably. it will burn the paint on your ceiling at that current.

for a superbright led, you can run at say 5mA andblind the neighbours, attract low flying planes, etc. at 0.5mA, or 500uA, you will have a status indicator instead.

so, V+ = 9V; Vf = 3V2; I(led) = 500uA, R3 = xR.

V+ - Vf = V(R3). VR3 is the voltage we want to "drop". 9 - 3.2 = 5.8. R = V(R3) / I(led) (Mr Ohm). xR = 5.8 / 0.0005 = 11,600 or 11k6. you can use 12k or 10k, and probably not tell the difference.

the led brightness varies with the led current. you must ALWAYS use a current limit resistor with leds (unless they are audio clipping). you can do all the calculations each time if you like, or just use something between 4k7 and 22k for a 9V supply, scale between depending if you want to indicate or room lighting.

you can and should look up the part number and see the manuf datasheet, for parts you know and parts you don't. there will be surprises.

> DC Forward Current: 30mA
> using 2x 4.7K.

30mA is a burn-up rating. Do you drive your car a constant 113MPH? Usually we poke around at 25-60MPH, which is fast enough for some and too fast for others.

6V drop in 5K is a large milliAmp. Working indoors, especially dim stages, you don't need "113MPH" light output, but a small fraction of a typical LED's MAXimum output. 10%, even 3%. (So a resistor 10 to 30 times bigger than calculated from the MAX rating.)

If it is bright enough for you, do it.

The only reason to know "30mA" is when you need it brighter and brighter and.... don't go (much) over 30mA or the LED becomes a DED (dark-emitting diode).

Thanks again for your valuable time/knowledge.

I've clearly overestimated even my humble perspective of my grasp of basic electronics  :icon_lol:

I've got everything but the box to put it in now - just waiting on the delivery. I'm sure I'll have some feedback soon enough, be it excited or with burnt fingers.  ;)

Ok, I think this is making sense now.

xR in this instance is 4,700 ohms, therefore I = 0.001234 [I = V/R]. This is greater than the 0.5mA you recommend....but how much greater in practice?

My lack of appreciation of how much current is actually required here has hampered my initial understanding. PRR's comments on driving at 113mph is an excellent metaphore and I am now grasping the logic.

Will 1.234mA be too much here, or should I be thinking about replacing these with 10k resistors (I have a surplus of them).

> Will 1.234mA be too much here

31mA is too much for the LED. Like tipping rocket-fuel in your 113MPH car to go 119MPH.

Any lower value is safe for the LED, but you get less light.

Whether 1.234mA is too much or too little pretty much depends on the neighborhood, no? On older LEDs, we "had" to run 5mA to see them in a bright lab. Modern/better LEDs in dimmer rooms, much less may be ample.

Great, thanks.

Well, I have another issue now:

I had used the internet to determine the power supplied by the Boss GT8 transformer (with an aim to branch off this to the other parts). Vendors on the internet list them as 9v 1000mA.

I've checked mine today, and it's 14v 800mA. So, here's the bigger picture question:

I want to split this supply so that it powers the GT8, The RAT Pedal (which requires 9v) and this switching unit.
GT8 draws 650mA
RAT pedal no more than 5mA (and no more than +120VDC) RAT DATASHEET (point3 = powersupplies (http://ratdistortion.com/pdf/RAT2_Sheet.pdf)
This switching unit? Don't know, but I need to put an inline resistor on the relay now, for sure? HERE IS THE RELAY DATASHEET (http://www.datasheetlib.com/datasheet/145434/v23105-a5006-201_m-a-com-technology-solutions.html?page=4#datasheet)

Have I totally fudged this, or am I still OK?

Here's the relevant Data on the Relay:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/RelayData_zps909bb3f9.jpg)

What do I need to do here to use the 14V supply?

nothing but ohm's law.

the relay max V shows as 21V, so 14V would be safe. seeing as the relay coil is 540R, and you want 9V across it, the other 5V you want to drop, (being near half 9V) suggests a resistor half the value of the relay coil, say 220R. now you get to draw the diagram, add the numbers, and work out what the voltages are and current is.

I think you could put that value resistor between your 14V supply and the point on your switcher marked "+9V", and not worry about anything.

I'll redraw this as soon as possible. Thanks again!

Any thought on the RAT pedal? That too needs a 9v feed (from a 14v source). I am willing to modify that if needs be.

the rat sounds like the perfect opportunity to learn about three-terminal regulators. 14V is just right as input to a 7809, and the regulator will supply enough 9V to run your relay section as well. no need for the 14V dropper resistor then.

OK, so, here's the new diagram,

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led14v_zpsb1be8156.jpg)

If I'm reading this correctly, then:

V = 9, R = 540, ThereforeI = 0.0166A (16mA)? Sounds a lot for what it is?
Also, the 2 LEDs in there are drawing 1.25mA each. So in total, 18.5mA?

..I'm guessing I'm wrong here?

And so, the RAT pedal too. Apparently 9v and no more than 5mA - so what to do here?

"R6=0.22K" this will confuse you. 0.22k is 220R.

your calcs are correct, mr ohm is very seldom wrong. your rat will be happy and clean with a regulator, as will your relay and switcher, and you will be happy not needing to calculate current draws and voltage drops. as for whether or not you are clean, well .....

Ok then. 220R it is.

On the regulator, this would be my second choice right now as I've gone quite a lot further than I had planned already, but - if I do go down that route, I'm guessing this is my diagram?

(http://www.usbekits.com/uploads/1/0/1/8/10185060/6810806_orig.jpg)

Let's just say I don't do this, and I want the rat to have a 14v feed. What's the process?

Don't worry about the last enquiry,

I've just bought a 7809 and heatsink, I got the 0.1uf caps anyway.

I also bought a bigger project box to put all of this in  ;)

Quote from: Minty on July 23, 2014, 09:19:13 AM
OK, so, here's the new diagram,

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led14v_zpsb1be8156.jpg)

If I'm reading this correctly, then:

V = 9, R = 540, ThereforeI = 0.0166A (16mA)? Sounds a lot for what it is?
Also, the 2 LEDs in there are drawing 1.25mA each. So in total, 18.5mA?

..I'm guessing I'm wrong here?

And so, the RAT pedal too. Apparently 9v and no more than 5mA - so what to do here?

I have an alternate wiring suggestion for the relay and jacks;

in: pin 8,11
send: pin 4
ground: pin 6
out: pin 13
return: pin 9

(I'm assuming that pin 4 and 6 are connected by default and when switched pin 4 connects to 8 leaving pin 6 out of circuit)

This properly grounds your effect pedal when NOT in use, which can be very helpful. If you had a high gain pedal in the loop then NOT wiring how I suggest would be like unplugging the cable from the guitar and thowing it on the floor.

Ok, so there's the updated diagram.

Honestly, I can't tell you all how much I'm enjoying this!!!!

Trix, thanks for your suggestion, I've reconfigured the relay.

Does this all look good to everyone?

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led14vRL-ARLY_zps745bb912.jpg)

nearly. a bit more has come to mind.

the relay will make noise, the rat may well not like it. we seperate the relay supply from the clean, minty-fresh 9V. take the tops of R4, R5 and R3 to the (dirty) 14V (after you've recalculated their value if you like). take the top of the relay and D2 to that 220R you calculated before, and the top of the 220R to the 14V line.

keep C3 and C4 as 100nF, but you'll probably want to add another electro, 47uF~100uF to the 14V line. it will help clean up after the relay and the connecting wires.  that should do for today?

I thought that the whole of the original V supply circuit was to take out the noise when switching?

Or are you talking about hum?

...and yes, that'll do for today!  ;)

so you're stealing power from the gt8 for this? being digital, it will be creating ALL SORTS of awful hash, and it won't care much about how dirty its 14V is. the relay driving bit doesn't care much about dirty supply, and the relay will produce some hash of its own when it switches off.

the regulator will clean nearly all the junk for the 9V. the rat will thank you. but the extra caps will help keep some of the gt8 junk in the gt8, instead of the newly minted 9V. they can't hurt.

Not entirely sur I followed this one correctly, what say you?

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led14vRL-ARLY2_zps781f56bf.jpg)

C5 as connected will block DC, that is, nothing will get past it. wire it (+) to 14V, and (-) to 0V. it will then be in parallel with C3, and you're cooking with gas. hopefully.

Like this?

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led14vRL-ARLYC5_zps62d85e4b.jpg)

I'd say, yes, like that.

Ok, just wait a couple of days for the 220r and the 47uf to arrive and I can start.

Is there any well practiced method I should think about when "mapping" this out on the matrix board?

well, if you have 180R or 270R you can sub, or if 22uF or 33uF or 68uF or 100uF .... if you can't wait. if they are on the way, doesn't matter.

matrix board? great! I only so far use vero, so I can't help.

really, I start from the left, input, work to the right, output. it makes sense to me to have the positive supply rails topp-er, and the grounds bottom-er. most of the time, all this goes out the window, whatever fits where w/ least # of cuts and links. there is 3 ways to work the laying out, pencil and squared paper, the perfboard and a stack of parts poking in, and diylayout creator, seen elswhere hereabouts.

keep in mind the layout of your enclosure, jack placements and controls. try and keep your leads straight up and down, don't stretch electro legs across 6 traks f'instance. sit resistors flat on the board, bend their leads to fit across 4 or 5 holes, keep all yr parts north-south or east-west (no slanty, no 2 leads one hole). or come up with your own layout rules to suit yr mood.

and it is easier to wire a board iff all the off-board connections run from one edge. not often possible, but something to work towards. post your 3rd or 4th try, we'll have a look.

Thanks for the heads up on the DIY creator.

I did this with it - look good?

I didn't run the 'wire' around the common grounds on the guitar signal, but they're there.

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/WiringMap_zps8c794684.png)

Simple question, but having a hard time finding an answer:

Is the relay coil directional? (does it have a polarity?)

a relay coil is just wire, it won't usually have polarity. some relays have a squelch/flyback/clamp diode internally connected across the coil to squash the off-switching collapsing-current back EMF spike. (D2 is your external diode performing this function.) your datasheet will clearly show a polarity if it HAS the diode fitted, otherwise it's open slather.

your datasheet.

Ok then - the last item (47 uf cap) should be delivered today, so I'm good to go.

Sadly, I can't attempt this until Sunday.

minty - try as I might, I couldn't see any error on your "matches diagram v0.8". (I was only guessing those version numbers, by the way.) so, nothing to stop you now ......

Brilliant!

I promise, I'll update the drawings with version numbers so that anyone (including myself) can follow this thread.

Manufacture of the unit this weekend.

Will report back asap.

ahhh, the debugging thread, something to look forward to.

good luck. oh, and nice work colour-coding those jacks on the layout.

Google image search, no credit for me there.

Well......DISASTER?

Turns out that the GT8 power supply is....AC, and on a meter is giving 16.8v

Where to go from here?

disaster averted, if you've read the AC before plugging it into the DC wanting parts. now you are looking for a rectifier and filter circuit, and we redo some parts o' yr last.

I hope your meter is set to AC volts. when the GT8 is attached, it will load down the supply some and the voltage will dip.

Yip, I decided to test the voltage/polarity of the supply prior to starting the project. It was at that point I found 0VDC. A little head scratching later I checked the label again, it said AC14V.

bugger!

Switched the meter to AC and there it was 16.8 half fat.

I'm going to build this and use a straight 9v supply for now, so - no power regulator and no 220r resistor - ALTHOUGH, once proven, I will seek to add this rectifier/filter you speak of and feed it with AC14V (or, AC16.8V as the case may be.)

I've connected the power part of the circuit as per the below diagram (no guitar signal circuit yet).

The relay engages without closing the GT8 amp control switch. That is, it's 'always on'.

Any ideas?

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/FinalCircuit2led_zpscf155be3.jpg)

well now, if the GT8 is meant to short the "amp control" line to ground, short your amp control line to ground, without the gt8 in-plugged, and see if the relay clacks. follow from the base of the transistor, see what DC it connects to. it needs V+ to the base to turn the relay on. I've meant to ask how the gt8 control controls, does it just short across those contacts?

I'da thort there is 3-ish ways to go from here:

add a mains (hi volts) transformer (lo volts) and rect (now DC) and filter (now clean) in your box. we are NOT doing this for a first project.

add the rect and filter in the box, steal (low volts) AC from gt8. ..... hmmmmm ......

or, find any DC! plug pack from 12V to 18V, and feed the box dc, as we'd originally figured.

how much lern'n and build'n do you wanna do?

Ha!

Why had I not thought of that!!!!!

Yes, it works. I was expecting it to be "off" by default until the GT8 shorts to 0v. It is infact 'always on' until the GT8 shorts it. (the GT8 simply closes the circuit)

This is ok, because I can set the GT8 to suit.

Power...well, I'd still like to use one power source, so your recommendations on that would be appreciated. As mentioned before, the GT8 supply gave me 16.8 on the meter, so a V loss can be tolerated by adding a rectifier.

But, for now - I'm happy feeding it 9VDC, I have a supply ready and willing.

NOW, to test this 'in situ' and hope for no strange effects to the signal..


Stand by.....

Would you believe it. It works!!!!!   ;D ;D ;D

Although, as I initially feared, there is a lot of buzz, not sure if it's ground loop (I'm using a 9V battery to power it).

Suggestions?

a buzz? not the relay buzzing I hope.

is there buzz when signal goes straight thru, and when sent to fx, or one or the other? and did you isolate the gt8 control from the signals ground?

nearly time for photos of the work (but it's bedtime for me now).

Yes, there is a lot of buzz (loud too).

I was careful use two seperate common grounds (one for power/relay, the other for guitar signal).

My soldering is atrocious (it's been many, many years. Pics below.

The buzz is there even if only this is plugged alone in to the amp - no RAT pedal attached. the relay position makes no difference. There is no buzz if I remove the power supply.

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204557_zps4d81654f.jpg)

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204537_zpsceb12e58.jpg)


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204455_zpsbce5d3d4.jpg)


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204411_zps49543f8e.jpg)


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204359_zps8e840b68.jpg)


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/IMG_20140803_204144_zps95347b4d.jpg)

well, let me say, you need soldering practice.

it is best practice to stick a single wire through a single hole, and link all the pads of joined wires together with tinned copper wire. then you at least have a chance of removing a single incorrect wire withoutout destroying the board. stip the wire, give the bare ends a twist to keep the strays together, then tin with solder so they can't fray. then stick them through the hole and solder, you can bend them over to buss them together if they are stripped long enough.

and it might be easier to make those busses with bare tinned copper wire instead of insulated. there is no shortage of space on your board, so they shouldn't bump together anywhere.

as for the buzz, I think you answered the question. "no buzz if I remove the power supply." you can't be connecting your AC supply to this without the rectifier/smoothing you don't yet have. and the battery is DC, no buzzing there. and the circuit shows (well, we know) that there is NOTHING common between the audio and the power needing parts. the relay contacts are in a world of their own, that's why it's there.

something from the relay powering part is connected to the audio part. are those panels metal? your dc jack is wired .... ? backwards?

At the moment, it is only a 9V DC supply and those end panels are plastic.

Should I try a meter on the relay to see if I got voltage or continuity with the power circuit?

DC Jack (backwards?) Not following you 100% here. The socket is wired with positive centre (to match the supply I'm using).

If you think it's best I start this over, let me know - I'll try strip board instead.

well, you can meter it (everything, just about), or pull all the wires off carefully, then add the flyings through the top and the bussings on the bottom. it should then be a little easier to see. you need to find where the common between audio and switcher is.

if you are meter-demonstrated sure that the centre pin of your supplies plug is positive, and dc, ok. it is backwards to the general plug wiring, I believe, and will cause smoke on other brands of pedal. seeing your relay works, your box must be wired right.

get the lead that plugs to the next stage. unplugg everything else. power on, and plug that next stage plug into each of the audio sockets. do it buzz in all? when the relay switches to other, still in all?

I'm baffled.

This is likely to be just bad workmanship on my part.

I'll order some stripboard and rework it, at least with stripboard I don't have to bus anything. Sounds a lot easier.

no! no stripboard, you've got plenty space there to shift wire runs, the parts are in (and working, remember), just the wires the problems. in my opinion. perhaps if you restrict black wires to DC ground, red wires to DC +, and green wires to audio grounds.

I use vero, and it's no fun.

What is Vero - is that strip board?

I've already bought it (it's on the way). THIS (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=221040847193&ssPageName=ADME:L:OC:GB:3160) is what I bought.....and I already did a new plan in DIY Layout Creator (before seeing your response). Is it really that bad? it looks far simpler to me, neater too.

You'da boss here so I'll go with your direction, I'll have to see if I can get more green wire.

Just FYI, I drew the stripboard layout including the power regulator, and then removed it, ready for when we are OK to add the recitifier and filters. The regulator would go on (what is below) the 9V rail, whiel we could add the rectifier and filter in the space above:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/WiringMapStrip9VDC_zpsf1e307b1.png)

well, that is indeed vero/stripboard. you understand the track-cuttings priciple then? I suppose for a circuit like this it will be alright, but I hate all the wasted holes and space when doing larger than 1 transistor.

anyway, if it were me, I'd cut that sized vero in half, maybe thirds even. I'd place the relay, contacts outermost, either top or bottom of the board. this means there is nothing but audio connections above/below the coil connections, less chance of wiring trouble. then I'd re-arrange all the resta the stuff to fit, with maybe the red lines "upper" and the black lines "lower", as fits. (and those slanty caps!)

did you find anything w/ the meter, or did you pull all apart? there must be some audio connection not being made, or some non-audio section (can we agree on a name for all the stuff driving the relay coil?) connection that is being made.

I haven't had the chance to  test any connections on the existing unit yet. I will tonight.

I suppose we can call the connections driving the relay coil the "Power Section" and the Audio connections "Audio Section"?

...and, is there anything wrong with slanty caps?  ;D

"well if you don't know, I'm certainly not going to tell you" I think is a quote from becker, or women in general. ocd affects us all differently, I'm finding. for me, things go north-south or east-west.

power section it is. what will we call the voltage regulator part?

The Regulation Section I suppose., and then the rectification section.

Ah, yes, OCD. I have it in some ways but not all. I understand your concern.


OK, I've run the meter across all relay terminals, and jack socket tabs. I have continuity only where I should. There is no power bleeding in and there is nothing grounding to earth where it shouldn't.

Step by step:

• Amp on - no noise
• plug in guitar lead to amp - standard hiss (as - no guitar connected)
• plug lead into "to next stage" - hiss increases
• touch lead jack shroud - hiss decreases but still apparent
• plug in 9VDC but wall switch OFF (no power) - buzz begins
• switch on power - buzz hugely amplified
• switch off power - buzz returns to quieter state, squelchy noises as caps discharge

Sound like a grounding issue? Should I try running the negative terminal off the relay direct to 0v to eliminate the "quietening" part of the power section?

...and here's a condensed version of the strip diagram:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/WiringMapStrip9VDC2Small_zps859a80ac.png)

Better?

I'm completely baffled now. do the plugging in test again, WITH NO POWER. just plug the lead to the amp into each of the 4 jacks, I know it won't make any humming, but ....

can you hack up a battery to the dc in socket, instead of wart power? it looks very much like your supply is the problem, but when it's off as well?? try wiring an electro, 22 or 47 or 100 or 10uF, whatever you have, cap (+) to board V+ and cap (-) to power ground. see if that improves the humm w/ wart.

that's a much nicer layout. how come C1 is so small now? all those tracks below the Q and left the relay are spare, you can run those scrunched parts up and then link back if you like.

Before I try adding the electrocap, here's a vid of the issue.

The unit (I'm calling it the Rat Trap, by the way) fully connected with the exception of the rat itself, I've run a patch lead from "FX out" to FX Return". Before connecting the power, the unit doesn't add any hiss to the standard 'amp noise, but a quick swap shows that it does change the pitch of the hiss slightly.

Anyway, at the start it's all connected for audio signal only (no power, no GT8 switch cable). With the GT8 off, it's 'normalish'
Power on GT8, noise gets worse (still no amp control or any other connection from GT8)

@0:12 - I connect a 9V BATTERY
@0:20 - I connect the GT8 switching cable
@0:24 - I cycle the amp control button on the GT8 to illustrate the difference in noise between 'on' and 'off'.

I'm thinking this is a grounding issue, the amp and the GT8 are both fed from the same power extension. even before I connect the GT8 amp control lead, the noise is greater when I simply switch the GT8 on. Ground Loop?

None of this is representative of the racket that happened when I connected 9VDC from a transformer. That was insane!



Regarding that condensed circuit, C1 is smaller so it'll fit across 2 tracks (no more slanty caps!)

hughes&kettner? you're not the bloke that was going to bring his floorbox around to get fixxed, and has never shown up are you? what model is that? his was a triamp mkII.

my connection does not lend itself to the watchings of utubes, I'm happy to say, but yours was so funny instructive I watched it twice.

the problem, as I see from your circuit diagram (not your real life rat trap, excelllent name, full points there), is that there is NO connection between the audio section and anything else to cause a loop. so, it seems the loop, if that's what it is, is being generated by the other stuff. and it all starts with the gt8, from all your sequence postings.

so. put the gt8 in another room for a minute. make it so you can CAREFULLY short across the rat trap gt8 jack to un-switch the relay, open to switch. a push-button switch, or a patch-lead and paperclip, like that. and the 9V battery to power the relay. add the fx patch as before and an in something and an out something. what happens? humm?

and did you add the electro? I'm off to look for a gt8 schem.

No, not added the electro yet, won't have a chance now until Saturday.

I'm not the other H&K Guy, mine's a Tubemeister 36.

Forgot to mention, without adding the GT8, even without the GT8 on, I've already did the shorting exercise. lots of humm/buzz, different pitches when open/closed. But I did that with the Rat Trap sitting on top of the amp. I'll try it with 6 metre leads and see if it makes a difference.

Thanks again for your constant attention here, glad my video amused ;)

how to do perfboard:
(http://sound.westhost.com/bal2-bd-b.jpg)

!!. after some many years, maybe.

I went looking for a circuit, saw a picture of a gt8. bloody hell! and then started swearing at the innernets connection, because I couldn't get the .pdf to download (don't even know how big it is) before my patience expired.

interesting results from your shortings.

I placed a 47uF electro across V+ and 0v. Not much, if any difference.

longer audio leads, no difference.

I did note one thing though, even with wart power, when turning the volume knob on the guitar down the noise changed (kinda like a wah or tone control), and when the guitar volume knob was in the 'completely off' position, no noise.....no noise at all.

let's assume I know nothing of gt8's or channel switching amps for a moment. can you draw me a block diagram of your connections, guitar to ?, ? to gt8, amp to ? include jack names please.

do you have a different amp you  can try? have you tried different cables?

the next step is to start with nothing but the guitar and amp. any noise? now plug the guitar into the rat trap, the rat trap into the amp input. use the battery and shorting method for switching the rat trap. any noise? if no - and no - then - guitar into amp, rat trap in/out amp fx loop. move it from the top of amp to the floor. any noise? if no - then - try bringing the gt8 back into the room, and apply power to it. any noise? move things about, any noise?

I think you can see how this is developing, I'll leave you to your in-pluggings.

...steps ahead....

Tried:

Different cables - same
Moving Rat Trap to floor, 6m away - same
Guitar to amp, no noise
Guitar to Rat Trap, Rat Trap to Amp - slight hiss introduction
Add 9V (battery) - noise
Add 9V (wart) - mega noise
Add shorting lead - more noise
Change shorting status (open/closed) - noise change

Not tried another amp, haven't got access to one I'm afraid.

Block diagram:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/RatTrapBlock_zps04ed341c.jpg)

"Guitar to Rat Trap, Rat Trap to Amp - slight hiss introduction"

can you try this again, add the rat itself (with a battery of its own) to the trap, and then work the relay? I can't remember if you said the switching actually passes audio in an appropriate manner or not.

also, different guitar? different mains socket? is the mains earthed, and earthed properly (can never tell with you americans, seems you people do odd things w/ mains power)? we have 50Hz here, so our earth loops sound bassier.

I'm about all tapped out for ideas. if built like shown, I can't see where the problem would be. I guess you'd be having to strip all the wiring from yr original, and re-do it nice and neat, see if any change.

American? Nah mate, I'm from UK.  ;D

All of our plugs are three pin with an earth - but there is an extension lead in the mix so I'll check that it has an earth.

I'll try a different guitar too.

All test have been executed without a Rat connected (just a patch cable going from "to FX In" and "From FX Out").

Could it be that this relay is just not suitable for this function?

OK, so, here's another thing.

I've gone back to the original publication which gave me the first diagram I had and found the author's suggested diagram of a PCB print trace, things I note are:

- He's already placed a 47uF across v+ and 0v (C3)
- There is no D1 running parallel with R1



(http://www.geofex.com/article_folders/rmtswtch/rmtswlay1.gif)

What do you make of that????

the uk? wit de funny fuses in the plugs?

the C3 addition is simply good practice, in any supply. it provides a "local bucket" as the experts call it, from which the circuit can get juice when it needs, and it also provides a low-impedance, smoothing path to ground for all the hash and noise long cables like to pick up.

from what I can see, without having built this myself, the D1 provides a bypass to the resistor in one direction only, so the resistor will allow a slow charge, but a fast discharge (I don't have the circuit in front me the moment, so this may be the other way round).

as for the relay, and as I keep hinting at, if it is wired as circuit-drawn, the switch contacts-ing has no common to the power section, so there should be no way the relay contacts can contribute hum. if the relay is chattering, it might make a hell of a noise, but it isn't, is it? and if there was a load of digital junk in the amp, the leads might pick it up, but there isn't any. with the gt8 in the next room, all the digital hash its internals will and do generate are too far away, and not connected anyway.

turning down the guit killing the noise may very well be a pointer to the rooot cause, but I'm not smart enough to know what that might be. so, all I can suggest is doing a nice tidy re-wire, so we can look in and say "yes, it's all wired as per the diagram". and then, if it still makes the noise, probably start a new thread, with a new title, to draw in some of the more knowledgable types. we'll get there in the end.

Sorry for the delays, having some auto trouble so this has taken a back seat - will test more asap.

Make sure your audio ground connects to power ground somewhere. I think that's your issue, is that it does not.

welcome aboard, trix! geeze, I hope that's not the problem, because I've been telling him exactly the opposite, all this time.

As the small-signal stuff is handled by relays, there is no 'electronic' need for mixing the signal with the switching.  In cases like this I'd say that the audio ground and the power ground can (and likely should) be isolated.

david

I made a new Rat Trap yesterday using the strip board - I took pictures (upload asap).

All tests with a meter were as they should be.

Results through the amp.....still the same.

Photos:

(http://i403.photobucket.com/albums/pp117/Minty_Cymru/StripComp_zps470672f2.jpg)


(http://i403.photobucket.com/albums/pp117/Minty_Cymru/StripSolder_zps0e4176eb.jpg)

I notice on the original pcb that there is a ground looping around the switch contacts, but isolated from the switching section.

really, if the second one is  the same as the first build, we can draw one of 2 conclusions: either you've done the same wrong twice, or, there is something lurking in the rest of your gear. possibly the rat trap is allowing the something to show itself, but not actually causing the prob.

perhaps if you tried the rat trap and none of your other gear on a mate's guitar/amp/leads/room, and see if he's still your mate after.

Quote from: duck_arse on September 02, 2014, 10:51:30 AM
I notice on the original pcb that there is a ground looping around the switch contacts, but isolated from the switching section

...and what might that do?

Quote
really, if the second one is  the same as the first build, we can draw one of 2 conclusions: either you've done the same wrong twice, or, there is something lurking in the rest of your gear. possibly the rat trap is allowing the something to show itself, but not actually causing the prob.

Same wrong twice is possible since I'm following the same diagram with my same interpretations.

Quote
perhaps if you tried the rat trap and none of your other gear on a mate's guitar/amp/leads/room, and see if he's still your mate after.

Good idea, I will.

I'm thinking about trying one more thing. taking out all of the switch quietening circuitry and the LEDs. Just test the relay on it's own withpower and  audio leads. Can't really go wrong with that. If it's still the same then I know it's not my bad workmanship.

ohh, and I forgot one thing: if you reused your sockets without rewiring them, they may contain the lurker.

the earth around the relay may provide some small protection to/from very high impedance circuits being interfered with/to, but mainly it just demonstates the isolation-ing principle.

you could do your test idea using your wired sockets and a double pole double throw toggle, or a stomp switch, anything you can solder as replace the relay contacts. this would flush the socket-wiring devils out. (don't forget your audio earths.)

Well, it's been a while!

I had a family tragedy and everything had to be shelved.

I'll be looking into starting this project again, maybe from scratch. Not sure yet.

I think the DPDT stomp switch is going to be the first thing I try - this will isolate the noise to either the audio or switching circuits anyhow.

welcome back. sorry to hear the bad news.