[mybud]

HI Cybercow: Tried the series mod on a temporary basis, but found it limited the range of the rate pot quite drastically. Could of course be that I miswired it, took the connection from the bottom of R8 to the symmetry pot and then onto the rate pot. However, the mod you listed works nicely. Thanks goodness for croc clips.

I’m interested in the diode SPDT mod, but no rush. When/if you have time …

Best and thanks again.

[mybud]

HI Marcus and welcome. The EA is a very nice sounding tremolo and an enjoyable build. Go for it.

[mybud]

‘Electronics is a fickle mistress and she can be devilishly playful.’ Well put, Cybercow.

[mybud]

Ok, resistors aren’t polarised, but it helps for troubleshooting to line up the tolerance bands similarly (gold or brown). If you follow the principle of building shortest to tallest, start with resistors, followed by diodes (which are, match the stripe according to the PCB), then sockets, caps and elcaps last. These are polarised too, so match the positive side to the plus sign, which implies that the negative stripe will appear on the other side. You can often bias a circuit by ear, so hold off on the multimeter for now unless you absolutely have to have one. That said, they are useful gadgets, especially if you get one with capacitance, continuity, and diode measurements. Hope this helps meanwhile. Best

[mybud]

Three suggestions that might be helpful, which you might already have gathered from the various guides: Socket your transistors as a basic principle. Apart from the fact that they don’t like excessive heat and shouldn’t strictly speaking be soldered straight to the PCB, socketing means you can swap them out for others as needed without harm.

Second, try to leave some slack in your off board wiring (pots, jacks, and so on). Have a look at Cybercow’s post regarding the Apollo tremolo (Shiver quiver, he calls it) which has a pictorial guide to how he does it. That extra couple of centimeters in the off board wiring makes troubleshooting or mods just much easier and doesn’t strain them or the PCB unnecessarily.

Try to get hold of a temperature-controlled soldering station. Ok, they cost a bit more but it’s worth the expense if you’re going to build more than one pedal, which I’m pretty sure you will 😉 The cheaper options don’t maintain a constant temperature, which can make one’s soldering less than reliable. A friend of mine advised me to do this when I started out (three or so years ago) and I’m very glad I did.

There’s a great sense of achievement when the build works, not to mention adding something new to your musical palette.

The Sunn-T is a classic and great circuit. You might be able to get it direct from Barry in due course. Again, very best of luck and keen to know how it goes.

[mybud]

Welcome Tom and enjoy the build. Have a look at the soldering guide meanwhile, in addition to the resources Billy mentioned, and there’s quite a bit of info on the circuit available on the web. Best of luck.

[mybud]

Deep Southerly (African) greetings to you all.

WRT the Apollo I’m curious as to whether the symmetry mod combined with the speed switch can achieve a slow ramp as Cybercow suggested, in which case it’s almost obligatory for my purposes (mostly nefarious, I have to admit). This would cause it to behave more like a VCA if I understand the mod correctly.

My observation is that the EA doesn’t provide the choppiness of the Apollo. It’s more like a straightforward sine wave to my hearing; I don’t have a ‘scope to verify this. But it’s a ‘musical’ circuit nonetheless, undoubtedly less versatile than the Apollo but still very usable. My only reservation is that it’s not slow enough for my taste and I was wondering whether a similar mod to the Apollo speed switch might be doable.

I assume (on the basis of no evidence at all) that the timing cap is C5, in which case one of Barry’s DPDT switch mods to add a cap in parallel to the 470uF there might do the trick.

Thanks as always for the interesting thread. Your thoughts and comments in due course will be greatly appreciated.

 

[mybud]

Looks fantastic, Cybercow. I’m inspired to try the symmetry mod on my next build.  Great stuff.

[mybud]

Because the waiting period for boards to reach here is normally quite lengthy, I print out the build guide first and spent time trying to figure out how the circuit operates. At this stage I can more or less trace the audio path, figure out which elements are power supply and which not, but deeper than that I dare not go. ‘A little learning,’ I have found, ‘is a dangerous thing.’

Next I prepare the off-board components (pots and jacks) and try to colour-code them consistently, so that white is always the tip of the in jack, yellow likewise for out, and the pots are likewise same colour wire for corresponding terminals. Red for positive, green for ground, and so on.

I then gather all the components together as per the BoM and once the PCB reaches here, I work much like Barry, shortest to tallest, ticking the parts off as I go. This all sounds fairly OCD, I guess, but these methods work for me.

Nowadays I seldom try to finish an entire project in a single sitting. Onboard parts first, double-check solder joints, then maybe sleep on it and re-inspect the next day.

Next the off-board parts, and this where I sometimes come unstuck. Stranded wire seems to be my particular nemesis.

What I have learned from this newish hobby (three years or so into it) is that mistakes are not the end of the world. They sometimes teach one the most valuable lessons. This insight, combined with the collective help and wisdom of the forum’s elders and newbies alike, has made me less compulsive about perfection and success and more concerned with how things work, and getting them to work when they don’t.

The fact that electronics is unforgiving (either right or wrong) becomes then one of its more welcome aspects, and failure (in relative terms) a source of curiosity rather than something to fear.

I raise a virtual glass of cheer to you all from the deep South (of Africa) and hope we will meet face to face at some stage in the near future.

[mybud]

I will surely let you know what develops, gentlemen. Thanks again and all best, mybud

[mybud]

Gentlemen: Your sound advice (pun intended) is greatly appreciated. I’ll try out Cybercow’s mod on a new build (from scratch) in due course. Just waiting for the quad 2N5952s to reach these shores. Thanks again, I have learnt a great deal from these exchanges.

Best regards, mybud

[mybud]

Yes indeed, Cybercow, there are at least seventeen ways, but first my apologies because I did phrase the question rather poorly. My intent was not to use both phase circuits simultaneously, but one at a time.

LFO’s or ADSRs both seem to work as CV sources, but not connected across the pot as I’d originally thought. Thanks for the tip to try R23 on the Phybes (correspondingly on the Vibe). This works in both applications (i.e. LFO or ADSR).

With the LFO at audio rate, one gets a ring modulation type effect. Bizarre, even by my standards.

Thanks again, I’ll see if I can get some musically useful results from fiddling with R23 meanwhile.

 

 

[mybud]

Now that’s a serious testbed. Thanks as always for all the wise guidance.

[mybud]

I approached the biasing issue (which I’ve found quite problematic in previous builds) by breadboarding the circuit first and using trimmers for R3, R6 & R7 as per your suggestion. I did not start with the charge pump but reversed the battery connections on the breadboard to get the correct polarity.

The Hfe and leakage figures follow: Q1 = 64 and 0.1mA, Q2 = 79 and 0.2 mA, and Q3 = 123 and 0.8 mA. R3 measured at 9.98k (fairly close to 10k) but after measuring the others I adjusted R6 to 24k and R7 to 20k so as to obtain -4.5V between ground and the collector of Q1. Once this was obtained the others fell into place really easily and I committed to the PCB with charge pump as per the schematic.

The circuit functions according to plan, with sustain operating as it should from the build notes. I used two Russian Ge transistors for Q1 and Q2 (GT402Bs) and a NOS OC75 for Q3.

Thanks Cybercow, I really appreciate the advice.

BTW according to Internet folklore, I believe the original was a favourite of Robert Fripp, of ‘Court of the Crimson King’ era.

[mybud]

Genius.

[mybud]

Thanks Cybercow. I’ve noted all your suggestions. Since I don’t have access to anything close to an Hfe of 220, I’m going to try a silicon PNP for Q3 as an experiment. I’m assuming by bias resistors you mean those connected to the base of Q1 and Q2, so R1 and R2 (voltage divider?) and R4? I’ll also check out the Buzzaround info on the web.

Thanks again and all best, mybud

[mybud]

Hi : Here are some voltage measurements from my circuit (averaged because they fluctuate quite a bit).

Q1: D                                              S                                              G

8.44                                         5.72                                         4.04

Q2: C                                              B                                              E

4.55                                         2.17                                         0.97

Q3: D                                              S                                              G

-1.75                                        0.001                                       -2.0

Q4: C                                              B                                              E

1.75                                         0.6                                           0.0

Perhaps these’ll help, hope so.

 

[Author]

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