DIY Stingray 3EQ Preamp

[delta7fred]

Originally Posted by eukatheude

Actually i started out using a 50/50, the only one my town's hardware store had, and i'm much much more comfortable with the one i'm using.

I ran out of wire Maybe i can find some if i dig around the garage.

By the way, in most pedal layouts i've seen, usually there's a ground wire going to the jacks. From where should i connect it?

Maybe the 50/50 you bought was plumbers solder without the flux cores.

If you are short of hook up wire look for old computer cables, parallel printer cables are a good source with lots of different colours, serial cables or old monitor cables are also good.

If you are fitting the preamp in a guitar then the jack socket is usually stereo (Tip, Ring, Sleeve - TRS) with the sleeve and ring being used to switch the battery negative when you insert the mono (Tip, Sleeve) jack plug. You just have to remember to unplug it when not in use.

The Battery negative is usually connected to the Jack socket Ring connection with the Sleeve going to the preamp Ground - Post #1, picture #1, Black wire on right hand side.

[eukatheude]

Nope, i'll put this one in a pedal. The battery ground is connected to the circuit ground, maybe connecting that to the jack ground could fix the hum? The friend's guitar was noisy as hell until i connected the main ground to the sleeve.

[eukatheude]

I tried connecting the spare pots i found - another 25k on the treble, a 250k on the mids - and the total output seems increased. I grounded the volume pot to the jack and it got better, while i must have done the connection badly as i needed to keep my thumb on it. Still, the signal i'm hearing seems clean as i didn't notice any change in the sound when turning the tone pots.

[eukatheude]

Would love some input on this, i'm kinda stuck.

[delta7fred]

Originally Posted by eukatheude

Would love some input on this, i'm kinda stuck.

Debugging stuff over the net is difficult at best. When all we have to work with is a blurred photo of the track side of a perfboard it is almost impossible. Add to that your own admission about bad solder joints and pot values not being what they should and it only gets worse.

This is how I would tackle the problem.

Buy a reel of rosin cored 60/40 solder, a solder sucker (or de-solder braid), the correct value pots (and any other components not as specified), a spare IC and an IC socket if you haven't already got one.
Ebay is great for stuff like this.

Remove all components from your prefboard.

Start again in a different place on your perfboard, follow the layout given in post #1 exactly. Don't leave pieces of bare wire floating in mid air. Check each joint as you make it and be slow and methodical. (My mentor when I was an apprentice always told me that the only thing made in haste is babies.)

Fit all the components, (but don't plug the IC in yet) checked and double checked that they are in the correct places, wired correctly and the correct way round where applicable.

Apply power and check for 9v between the IC socket pins 4 (black lead) and 8 (red). check for about 4.5V between pins 4 (black) and 5 (red). This can be done before the pots are wired.

Remove power, wire and check (and double check) the pots, insert the IC making sure you get it the correct way round.

Test with a signal from your bass and an amplifier.

The thing to remember is that this stuff isn't black magic. If all the components are correct and serviceable and connected correctly then it WILL work. One error, bad (or in some cases incorrect value) component or bad joint and it may not work or may do something but not what you are expecting.

Best of luck.

[eukatheude]

Originally Posted by delta7fred

Debugging stuff over the net is difficult at best. When all we have to work with is a blurred photo of the track side of a perfboard it is almost impossible. Add to that your own admission about bad solder joints and pot values not being what they should and it only gets worse.

I understand that, i was looking for general advice. As for pot values, i realise they're not the ideal pots but that couldn't possibly stop the entire circuit from working. The fact that there is some dry signal going through might mean there's something that is connected somewhere it shouldn't be.

Buy a reel of rosin cored 60/40 solder, a solder sucker (or de-solder braid), the correct value pots (and any other components not as specified), a spare IC and an IC socket if you haven't already got one.
Ebay is great for stuff like this.

Already have the socket and solder sucker
The solder would be hard to find here, and ebay is unfortunately not an option since i'm moving to another city in less than a month. In any case, i think the solder itself it's the lesser problem as i'm not that much of a noob, it's just the first time i'm working on a perfoard.

Start again in a different place on your perfboard, follow the layout given in post #1 exactly. Don't leave pieces of bare wire floating in mid air. Check each joint as you make it and be slow and methodical. (My mentor when I was an apprentice always told me that the only thing made in haste is babies.)

I was thinking of etching a pcb for this, as the track part is really difficult and frustrating. Is there really no better way than putting copper wire in there? I can't see a way to make GOOD connections with that. I might just buy all components again just to be able to connect them via their legs.

Fit all the components, (but don't plug the IC in yet) checked and double checked that they are in the correct places, wired correctly and the correct way round where applicable.

Apply power and check for 9v between the IC socket pins 4 (black lead) and 8 (red). check for about 4.5V between pins 4 (black) and 5 (red). This can be done before the pots are wired.

Interesting, why shouldn't i plug the IC?
I don't have a tester unfortunately, but i can borrow one. I think the first thing i'm going to do is check the connections on this layout without starting over - yet.
In any case, i wish to thank you for the time you're taking in helping me, i really appreciate it.

EDIT: Got the multimeter.

[delta7fred]

Originally Posted by eukatheude

I understand that, i was looking for general advice.

My advice is to build it right, that way you only have to build it once.

The solder would be hard to find here, and ebay is unfortunately not an option since i'm moving to another city in less than a month. In any case, i think the solder itself it's the lesser problem as i'm not that much of a noob, it's just the first time i'm working on a perfoard.

50/50 solder is used for soldering stained glass panels. It has a higher melting point than 60/40 and will be very difficult to use. Until you get the correct solder you are just wasting time and effort.

The old pre lead-free solders used different proportions of tin and lead. These are the main ratios, there were many more subtle variations on these. They have mostly been superseded by lead free solders now.

60/40 - Electrical and electronic work
50/50 - Stained Glass - Higher melting point than 60/40
40/60 - Plumbing work - has particular properties that made it good for pipe joints - even higher melting point.

In addition to the correct solder and flux you also need to make sure the copper wire and pads a scrupulously clean - you cannot solder to corrosion.

With clean materials, the correct solder and flux and sufficient (but not too much) heat you have to try hard NOT to get good joints.

I was thinking of etching a pcb for this, as the track part is really difficult and frustrating. Is there really no better way than putting copper wire in there? I can't see a way to make GOOD connections with that. I might just buy all components again just to be able to connect them via their legs.

Done correctly perfboard is a very good method for building up a circuit. Personally I prefer it to stripboard, that stuff annoys me no end.

Interesting, why shouldn't i plug the IC?

So if you have something wired wrong you don't stick reverse polarities on it. Resistors don't care, and capacitors usually don't mind especially with a 9v battery with limited current output. ICs are easily damaged by reverse polarity supplies.

Checking pin 5 makes sure the bias voltage divider is wired correctly.

I don't have a tester unfortunately, but i can borrow one. I think the first thing i'm going to do is check the connections on this layout without starting over - yet.
In any case, i wish to thank you for the time you're taking in helping me, i really appreciate it.

Multimeters are cheap and are essential if you are seriously considering building anything. (They are also very handy for checking fuses, verifying resistor values (especially 4 band resistors), checking batteries, suspect guitar leads (chords) etc. etc.)

I mentored a lot of apprentices and don't like to see anyone struggling with such a simple thing as soldering. If you are getting bad joints there is a reason and it is probably not bad technique on your part. I honestly believe that once you get the correct 60/40 electrical solder (with flux cores) and everything nice and clean you will have very little trouble with it.

[eukatheude]

Originally Posted by delta7fred

50/50 solder is used for soldering stained glass panels. It has a higher melting point than 60/40 and will be very difficult to use. Until you get the correct solder you are just wasting time and effort.

50/50 is the only i can find around here. On this project i used 97% tin, 2% flux and 1% copper, and while it might be harder to use it should work fine, and i really have no alternative as of now.

In addition to the correct solder and flux you also need to make sure the copper wire and pads a scrupulously clean - you cannot solder to corrosion.
With clean materials, the correct solder and flux and sufficient (but not too much) heat you have to try hard NOT to get good joints.

I should have paid more attention to this. The copper wire is probably dirty. The main issue though is not doing the basic joints (as in populating the perfboard and soldering the components' legs by themselves) but connecting adjacent ones with solder blobs and distant ones by copper wire, since it was hard as hell to keep it still. And having to put 2-3 wires on the same spot only made matters worse.
So the main problem is getting verything to stay still. I do have a little helper but it's of little use here. I used a screwdriver to help keep them in place.

So if you have something wired wrong you don't stick reverse polarities on it. Resistors don't care, and capacitors usually don't mind especially with a 9v battery with limited current output. ICs are easily damaged by reverse polarity supplies.

Checking pin 5 makes sure the bias voltage divider is wired correctly.

I see, thanks.

Multimeters are cheap and are essential if you are seriously considering building anything. (They are also very handy for checking fuses, verifying resistor values (especially 4 band resistors), checking batteries, suspect guitar leads (chords) etc. etc.)

I mentored a lot of apprentices and don't like to see anyone struggling with such a simple thing as soldering. If you are getting bad joints there is a reason and it is probably not bad technique on your part. I honestly believe that once you get the correct 60/40 electrical solder (with flux cores) and everything nice and clean you will have very little trouble with it.

I borrowed a multimeter and figured out how to test connections in continuity mode. I definitely agree with you on it being essential, but due to having to move (and most likely i won't be able to solder as i'll be living in a shared house) i wouldn't want to spend on it (can't find one under 30€ and i've been told the cheap 5€ ones stop working after a week) right now, but in the future that's a definite yes.
That said, i've tested most of the connections and they seem solid. Testing adjacent or directly connected joints gave me a reading of 0, while testing joints that were apart or had other components between them gave me different values. I suppose this wold be the way to see if there are connections that shouldn't have been made? Which i believe to be the issue in the first place, i think the signal is bypassing the EQ and going straight to the output. Anyway, i'll try wiring it with all 25k pots (found a couple more).

[T_Bone_TL]

Originally Posted by eukatheude

The main issue though is not doing the basic joints (as in populating the perfboard and soldering the components' legs by themselves) but connecting adjacent ones with solder blobs and distant ones by copper wire, since it was hard as hell to keep it still. And having to put 2-3 wires on the same spot only made matters worse.
So the main problem is getting verything to stay still. I do have a little helper but it's of little use here. I used a screwdriver to help keep them in place.

...

(and most likely i won't be able to solder as i'll be living in a shared house)

Soldering is not generally a kicking out of the house offense, if done intelligently. Clean up after yourself, don't burn the furniture (newspaper helps, damp if you are really out there) and your housemates will have no reason to complain. Soldering irons can be found used, and electronic solder can be mail-ordered (web-ordered, if you like.) See if you can find an amateur radio (ham) club - often a good source of knowledge and where to get materials in your area. Or go all current era and look for "makers" (a 200 year old job description that's back in style again.)

As for wiring, umm, how do I say, you're doing it wrong, in so many ways.

Solder blobs are a lousy way to connect at any distance. Use wire, though you can certainly use wire that happens to be excess lead over short distances.

Your giant mistake was not only cutting the leads off, but soldering components at all without getting the wiring done first. I facepalmed when I saw your first picture. Bend the leads a little so things won't fall out, and put connecting wires into the same hole (if you run out of space, use an adjacent hole and run copper wire between them before soldering it.)

Wires stay put very nicely if you put them THROUGH the HOLES in the perfboard - that's what the holes are there for.

Wire with insulation is much less prone to inadvertent short circuits than bare wire. More than one color of insulation will help you keep straight which wire is which (or not, depending on how you use it. Think.) Old telephone or internet cables (or new cable scraps from an installation) are a handy source of small multi-colored wire.

There's probably more, but that's a start. You want CLEAN wires and good MECHANICAL joints before you ever turn on the soldering iron. Wires held on by solder alone tend to fall off when exposed to real life. Not to mention trying to run away when you try to solder them unless you have 4 hands.

[delta7fred]

Originally Posted by eukatheude

50/50 is the only i can find around here. On this project i used 97% tin, 2% flux and 1% copper, and while it might be harder to use it should work fine, and i really have no alternative as of now.

Ok, I see now. I misunderstood you and thought you were using 50/50.

Lead free has a higher melting point than 60/40 I can't remember the figures now. It is also less forgiving hence the reason I don't recommend it for beginners.

(I can see the need for lead free in consumer equipment that may end up in landfill in 18 months but I would like to think that anything I make will be around for many years.)

I see T_Bone_TL has already covered some of your perfboard mistakes so I won't rub it in.

i've been told the cheap 5€ ones stop working after a week.

Not what I have found but YMMV.

Best of luck getting it working.

[eukatheude]

Originally Posted by delta7fred

Lead free has a higher melting point than 60/40 I can't remember the figures now. It is also less forgiving hence the reason I don't recommend it for beginners.

Yeah i noticed when trying to re-heat a joint, but when i'm applying it for the first time it flows on perfectly.

Originally Posted by T_Bone_TL

Soldering is not generally a kicking out of the house offense, if done intelligently. Clean up after yourself, don't burn the furniture (newspaper helps, damp if you are really out there) and your housemates will have no reason to complain. Soldering irons can be found used, and electronic solder can be mail-ordered (web-ordered, if you like.) See if you can find an amateur radio (ham) club - often a good source of knowledge and where to get materials in your area. Or go all current era and look for "makers" (a 200 year old job description that's back in style again.)

Eventually i'll get an iron, though i'll have first to see if there is space, what kind of housemates i'm getting etc.

As for wiring, umm, how do I say, you're doing it wrong, in so many ways.

Solder blobs are a lousy way to connect at any distance. Use wire, though you can certainly use wire that happens to be excess lead over short distances.

Ok. Blobs seemed like the quick way, and having managed to do it without accidentally connecting to other perfboard plates, they felt kinda safe.

Your giant mistake was not only cutting the leads off, but soldering components at all without getting the wiring done first. I facepalmed when I saw your first picture. Bend the leads a little so things won't fall out, and put connecting wires into the same hole (if you run out of space, use an adjacent hole and run copper wire between them before soldering it.)

Wires stay put very nicely if you put them THROUGH the HOLES in the perfboard - that's what the holes are there for.

I realise that, i only wish i found out about that before actually soldering the things in. I might just buy all resistors/capacitors again. It's a shame because i went to the electronics store just this morning, and it's 20km away, also be measured in 5€ in bus tickets.

[delta7fred]

Originally Posted by eukatheude

Eventually i'll get an iron, though i'll have first to see if there is space, what kind of housemates i'm getting etc.

Make sure that you find something of theirs that needs soldering and they will probably encourage you to get one.

[domdec314]

I'm really confused why anybody would have a problem with you soldering. It's a completely noninvasive activity, like sitting in front of your computer.

[eukatheude]

Originally Posted by delta7fred

Make sure that you find something of theirs that needs soldering and they will probably encourage you to get one.

Haha, yeah, i thought about that.

Originally Posted by domdec314

I'm really confused why anybody would have a problem with you soldering. It's a completely noninvasive activity, like sitting in front of your computer.

I was actually thinking more about space and the fumes i'd breathe in. The "having a problem" part might come into play depending on what kind of housemates i'll be getting. An engineering student is different from an old lady.



Anyway, i'd like an input on this:

I borrowed a multimeter and figured out how to test connections in continuity mode. [...]
That said, i've tested most of the connections and they seem solid. Testing adjacent or directly connected joints gave me a reading of 0, while testing joints that were apart or had other components between them gave me different values. I suppose this wold be the way to see if there are connections that shouldn't have been made?

By which i mean, if i get a reading of zero on two points that aren't an the same trace, they probably were connected erroneously. Still, i've yet to fit all pots. I'll try putting all 25k, it might even work.

[delta7fred]

Originally Posted by eukatheude

By which i mean, if i get a reading of zero on two points that aren't an the same trace, they probably were connected erroneously. Still, i've yet to fit all pots. I'll try putting all 25k, it might even work.

That is correct. If you get a zero reading then either it is the same trace or there is a very low resistance (a short circuit) connecting them. I would pull the IC out and set the pots to mid travel so it doesn't confuse the issue.

On this circuit there are no very low resistances, 1k is the lowest so you should never see less than that between any 2 pads that are not on the same trace. Most times you should see a lot more.

Resistors should measure no more than their marked value (within tolerances) but they can measure less in certain circumstances when other resistors are effectively in parallel with them. (Transistors can throw the readings out but there are non in this circuit)

Electrolytic capacitors can give an apparent resistance reading when you first put the meter probes on them but as they charge up the resistance should rise to approach infinity unless there is a resistor across them (like the supply decoupling capacitor).

Non electrolytic capacitors will probably charge up so quickly that you will hardly see the display move, but will show a resistance if there is a resistor connected across them (like the capacitors across the Bass and Middle pots).

Download/open/print a copy of the hand drawn schematic that domdec314 refers to in post #1 and measure across each resistor and see if the resistance values that you measure tie up with the schematic.

See if you can work out which capacitors will show a reading because of paralleled resistors.

If any component has a zero reading then follow the traces and see where they are shorted.

[eukatheude]

Thanks. Should i test for values when the circuit is powered? Also, i can test components by just applying the meter leads to their leads on the back of the board, right?

[FunkMetalBass]

Anybody here experienced with SPICE? I was hoping to get this circuit built up in it so that I could play around with a few component values before I buy parts, but I'm not experienced at all with the program and I'm really confused as to how to implement the opamps.

I can post my current .sch file if needed.

[delta7fred]

Originally Posted by eukatheude

Should i test for values when the circuit is powered? Also, i can test components by just applying the meter leads to their leads on the back of the board, right?

Don't power it up as it will upset the resistance readings and may damage your meter.

You can measure the components on their leads on top or on the solder connections underneath. The results should be exactly the same as long as you get a good connection with your probes.

Anybody here experienced with SPICE?

I use QUCS running under Linux (Quite Universal Circuit Simulator).

[FunkMetalBass]

Originally Posted by delta7fred

Don't power it up as it will upset the resistance readings and may damage your meter.

You can measure the components on their leads on top or on the solder connections underneath. The results should be exactly the same as long as you get a good connection with your probes.



I use QUCS running under Linux (Quite Universal Circuit Simulator).

I'm also in Linux. I might give that a shot, it looks pretty nice being all GUI-like. Any chance you've already got this schem put in? (I originally put it into gschem, and of course the .sch file isn't compatible, so I'll have to do it all over again).

Since I've already lain it out once before, doing it again is actually pretty quick. However, I'm stuck on crossing lines without a junction (as shown from the wiper of the EQ pots over to the TL072). Any ideas about how to implement this, or maybe just a workaround?

EDIT: okay, I've figured out that QUCS uses the dot to represent a junction, and no dot to represent a crossing.

EDIT2: I've set it up, but now I'm getting an error when trying to simulate that says ".DC action required". Any idea what that is? I'll get the .sch file up here for you. http://dl.dropbox.com/u/15430220/Stingray3Bandv2.sch

[delta7fred]

Originally Posted by FunkMetalBass

I'm also in Linux. I might give that a shot, it looks pretty nice being all GUI-like. Any chance you've already got this schem put in? (I originally put it into gschem, and of course the .sch file isn't compatible, so I'll have to do it all over again).

Since I've already lain it out once before, doing it again is actually pretty quick. However, I'm stuck on crossing lines without a junction (as shown from the wiper of the EQ pots over to the TL072). Any ideas about how to implement this, or maybe just a workaround?

EDIT: okay, I've figured out that QUCS uses the dot to represent a junction, and no dot to represent a crossing.

EDIT2: I've set it up, but now I'm getting an error when trying to simulate that says ".DC action required". Any idea what that is? I'll get the .sch file up here for you. http://dl.dropbox.com/u/15430220/Stingray3Bandv2.sch

See post #130 for correct file.