Build Your Own Clone Message Board

A look at Dan Armstrong's Orange Squeezer - vero style:



The components are labeled the same as the schematic found at GGG; I didn't include the true bypass switching part of the schematic as I'm pretty sure anybody building this will know how to implement bypass switching - if not, I'd be happy to include it in the next post.

There is one important addition - correct termination of the unused op amp, which doesn't appear on the GGG schematic. Adding the two extra resistors (R14 and R15) and connecting the inverting input to the output will:

Reduce noise in the circuit
Reduce the amount of current drawn by the op amp
Reduce the heat given off by the op amp.

The vero board:



The reverse:



And the finished product:



So the vero board is verified.

There are a few mods floating around the web that you can implement to the basic circuit. Recognition to R.G. Keen and Mark Hammer:

Change R9 from 220 kΩ to 200 kΩ
Change the volume pot (R13) from 10 kΩ to 100 kΩ
Change C6 from 4.7µF to 1µF
Change C7 from 4.7µF to 10µF

One very important point to note is the two JFETs. If your JFETs are at the limits of their parameters you will end up with no compression (took me a bit of head scratching to find this bug). With no input signal and Q2 removed you should be measuring around 3V or more at the junction of R5/C3/R7 by turning the trim pot fully. As much voltage as possible with the trim pot turned fully is desirable (I got 3.8V from a choice of twenty 2N5457s).

I've designed this vero board so that all possible mods (via switches and pots) can be added if wished, I will look at these in my next post.

Comments and crtique, as always, are welcome.

Sweet ... I've been putting off this build for some reason, now I know what that reason was.

Thanks for posting. I've got everything required apart from the trimpot, I'm gonna tackle this for my next build.

I'm still fairly new to building stompboxes from scratch; tonmann, your posts in this and other forums have been hugely informative and educating. Thank you sir!

thanks again tonmann.
another great layout. this is one for the layout vault.

Due to a lot of work commitments, I don't know when I'll be able to apply the following mods to the basic Orange Squeezer. I'll cover the mods now in case any brave soul wants to give them a try.

There are five basic mods (actually six - but I'll leave the sixth for the moment) that can be done with pots and switches. You can do as many of the mods that you want or as many as room on your enclosure will allow.

The modded schematic:



The first two mods concerns setting the gain of the op amp. This basically equates to setting the threshold level on a compressor (the point at which the compression kicks in). In the basic version of the Orange Squeezer the gain of the op amp was set at 23 (if you used a 220 kΩ resistor) or 21 (if you used a 200 kΩ resistor), by adding a pot, R9a, in series with the R9 resistor, you can adjust the gain from 16 to 26; if you also add a switch across R9 you can reduce the gain from between 1 and 11. If you want to make the gain transistion smoother you could change R9 to 110 kΩ, this will give you a gain structure of:

Switch closed: 1 to 11
Switch open: 12 to 22

The second pair of mods concerns adjusting the values of the capacitor (C7) and resistor (R12) combination, the values of these two components set the release time of the compressor (the length of time after the signal drops below the threshold level when the compressor stops compressing). The basic circuit uses a 4.7µF capacitor for C7, Mark Hammer suggested changing the value of C7 to 10µF which increases the release time. By adding a second capacitor (C7a) and a switch you can now choose between two capacitance values, switch open 5µF, switch closed 10µF giving you a short and long release time. If you want to increase the release time even further, make C7a larger - an example C7a at 22µF and C7 at 6.8µF will give you a total capacitance value of:

Switch open: 5.2µF
Switch closed 22µF (I suspect this might be too long a release time)

The second mod suggested by R.G. Keen was to change C7 to 10µF and replace R12 with a 68 kΩ resistor and a 500 kΩ pot.

If you have room on your enclosure, it might be worth adding both of these mods for greater flexibility.

The last mod is basically changing the trim pot R7 to a pot which is mounted on the enclosure. R7 equates to the compression ratio of a compressor (it sets the amount of reduction of the signal going into the op amp). The problem with just replacing R7 with a 10 kΩ pot is that there is a dead area at one end of the pot's rotation - no signal at the input of the op amp. Ideally the pot should provide heavy to light compression throughout its full rotation. This is done by adding a resistor, R7a, in series with the pot. The bad news is that it is impossible to calculate the value of R7a - this is due to the very wide differences in the electrical characteristics of JFETs. The following method will ensure you get the correct value for R7a:

Take a 10 kΩ pot and connect lug 3 to b19 of the circuit board and lug 2 to ground.
Power up the circuit, plug you guitar in and adjust the pot until you get a low-level signal that you are happy with.
Without disturbing the pot setting, remove the pot from the circuit board (very important !!!)
Measure the resistance between lugs 2 and 3 to get the correct value for R7a.

OK, enough talk - onto modding the board:



To add the gain pot to the op amp:
Change the b7-g7 jumper to a c7-g7 jumper and wire the R9a pot to b1 and c1.
Dont forget to connect lugs 2 and 3 of the pot together.

To add a switch to the op amp feedback resistor:
Wire one side of the switch to lug 1 of the pot R9a and the the other side of the switch to k1.

To add a capacitor selection switch:
Instead of connecting the C7 capacitor between j16 and l16, connect it between j16 and k16.
Add the C7a capacitor between k13 and l13.
Connect one side of the switch to j19 and the other side of the switch to k19.

To add a pot to R12:
Remove the jumper from l17 - m17.
Run a wire from m19 to lug 3 of the R12a pot and connect lugs 1 and 2 to ground.

To change the trim pot to an external pot:
Remove the trim pot R7 from the board.
Calculate the value of R7a, as described above.
Connect R7a between a17 and b17 (damn - there goes my completely flat layout)
Run a wire from a19 to lug 3 of the pot R7 and connect lugs 1 and 2 of the pot to ground.

And there you have five mods for the Orange Squeezer.

Great work. I was wondering why the other half opamp was never utilised. Couldn't we use the other half for a tone control? We could base it off the tube screamer tone and my guess would be to put it right before the output. I could be way off base but it seems like a good idea to me. ( )

Thanks Tonmann! I will be giving this a go real soon!

I really like your mods, and would like to build your version of the basic Orange Squeezer as my first DIYC project... I got confused about one thing though...



...I don't quite get how the trim pot attaches. Specifically... I don't understand what happens to the connection at a-19 of the vero-board. It looks to me like it does not go anywhere. Should it go to ground? Or am I missing something?

Thanks!

a-19, b-17 and c-19 are the three lugs of the trimpot. It's shows on this layout as a vertically mounted type. (I'm not sure if the DIYLC software has a symbol for a flat trimpot??)

The two circuits below are electrically identical:



The trimpot (R7) in both cases functions as a variable resistor, the only difference being that in order to get more voltage at the R5/R7/C3 junction, the trimpot is turned in one direction (the arrow has to move down) for the left hand diagram, while in the right hand diagram, it is turned the other way (the arrow moves up). The right hand diagram is how the vero board is wired.
The reason for this change is that it would have been difficult to do the modification (changing the trim pot to an external pot) without a major change of the whole layout. I spent a lot of time in designing this board so that people could do the mods they wanted by changing as little of the basic layout as possible.

Sorry for the confusion, I hope you are not confused now.

Thanks for the clarification. The right is the how I saw it...but did not know that it was electrically identical. Makes sense now that you explain it. I can see that the design is very flexible. A real contribution!

Are any of these switchable mods to make the OS for Bass?

Ok, I thought so. I've seen the mod for bass before, bet never a layout where it was switchable. I wonder if that is possible? Wait, I'm sure it is possible... but possible in a not-freakin-crazy-hard kind of way.

Yeah, Something like a Magic Van!

crbmoa has it correct all the way - I can retire now and let him take over !!!

All of the mods so far are to do with signal amplitude and not frequency.
There are actually four components that will increase the bass response:
C1, C5, C6 and the volume pot R13. You could double the values of the capacitors, C1 lets more bass into the circuit, C5 boosts the gain of bass frequencies and C6 lets more bass out of the circuit. If you increase the value of the volume pot (R13) this will also increase the amount of bass at the output. I don't think there will be much difference between a 47k pot and a 100k as both will extend the frequency response to sub-audio frequencies.

Which doesn't answer Anna's request for a switchable bass mod.

Good news ! There is one switchable bass mod that can be done to this circuit and that involves changing the value of C1. I would suggest the following:

If you haven't already cut the tracks for the board, change the cut from a12 to a13 and the cut from c12 to c13. If you have already cut at a12 and c12, don't worry as these cut changes are only providing a means of fine tuning later on (hopefully it won't be necessary).

Use a socket for C1 and try different value capacitors for bass and guitar, you will then have a minimum and maximum value for C1.

I'll take the optimal values of 47nF for guitar and 100nF for bass as an example.

Here's the change to the schematic:



and the change to the layout:



Don't forget to cut the track at a5 !!!

If you make C1 100nF and C1a also 100nF, the total capacitance with the switch open will be 50nF (pretty close to 47nF) and with the switch closed C1a is bypassed and the total capacitance is 100nF.

If you end up with different minimum and maximum values for C1, there will be some maths calculation and compromise needed to get close to the required values for C1 and C1a (with the possiblilty of a third capacitor between a12 and c12).

As a full explanation of how to calculate series/parallel capacitors is a bit long (plus I don't want to frighten people off with the maths), I'd be happy to do the calculation for you on request, please do this via PM as that will guarantee a quick response.

Hope this is of some use.

Wow! Thanks! So would you suggest not doing the other bass mods then? Just adding the switch for C1? Also, why move the cuts on a12 and c12?

Apart from the C1 mod, I'd probably change the volume pot to 100k - doing that makes changing the output capacitor redundant. If the output is a bit muddy, I'd either drop the value of the pot or the output capacitor.

I'd leave C5 as it is for the moment as you can't really make that a switchable mod, it's more of a general tweak.

Changing the a12 and c12 cuts to a13 and c13 allows me to get an extra capacitor (C1b) onto the board for more flexability. I'll give you an example of why you might want to do that (just to confuse you).

Let's say that during testing, you find that C1 at 47nF is good for guitar, at 100nF it's not really enough for bass and at 220nF it's too much for bass.

If you make C1 100nF and add a 47nF capacitor (C1b) between a12 and c12, the total capacitance in bass mode (with the switch closed) is 147nF - not exactly half way but it's getting there.

All that remains is to calculate the value of C1a, so that when the switch is open (for guitar mode) the total capacitance (of C1, C1a and C1b) looks like a 47nF capacitor. If you make C1a 68nF, the total capacitance with the switch open is 45.49nF - which is very close to 47nF.

Hopefully my explanation is not too confusing.

Ah! Great! So I'll probably just change the pot to 100k, add a switch, and C1a (maybe b too) and I should be set to go? I want to build a few of these for some friends who like to mess around on both bass and guitar... this way they'll be able to us it for both! Thanks!

If you are making a few, I would suggest the following:
Do the bass first
Socket C1, C1a and C1b, Install the switch and change the pot to 100 kΩ
Close the switch (you can leave C1a blank for the moment) and plug a 100nF capacitor into C1. If you need more bass response, add a capacitor to the C1b socket.
Once you have the compressor set up for bass, do the guitar.

Install a 68 nF capacitor in C1a and open the switch. Adjust C1a as nessecary - more bass increase C1a.

Thanks, Tonmann! I'll give your suggestions a shot once I get all the parts in... I'm just happy this is possible!

Tonnman used a TL 072, is that preferable to an NE 5532? I have also been hearing about OPA2134 and MAX412 ICs...

I seem to remember reading on GGG about the 4558d being essential for the Orange Squeezer sound?

I would encourage people to socket the op amp and try different types; actually I would encourage this for almost any circuit you build. The NE 5532 is slightly less noisy (according to technical specifications) than a TL072 with the 4558D lagging behind. As noise is probably the most important op amp parameter in this circuit I would probably choose the NE 5532 or TL072 over the 4558. I tried both an NE 5532 and a TL072 in the circuit and there was no perceptable difference.

I think using 4558s in the original Orange Squeezer had more to do with price and availability rather than component quality, still, it might be worth comparing a 4558 to an NE5532.