ea tremolo... something wrong

1878 · February 22, 2009, 06:12:45 PM

Hello Everyone.

I've been getting into tremolos recently, so I built myself the EA Tremolo from the perfboard layout on this page...

http://runoffgroove.com/eatremolo.html

I've used a BS170 for Q1, J201 for Q2 and a 2N5088 for Q3. I've also added the pulsing LED. Unfortunately, neither the LED nor the effect pulse at all. When the effect is engaged, It's basically a boost with a medium to high pitched wailing in the background. The LED is constant too.

Basically, whatever makes it pulse/tremulate/work is not working. I've checked and triple checked everything, but I can't find anything wrong. Any ideas anyone ??

Thanks in advance.

blanik · February 22, 2009, 10:48:57 PM

check pinout of the transistors, maybe you have one reversed...

on another note, i was on a search for the perfect tremolo (one that sounded as good as the tremolo on my twin and traynor but also able to do "machine gun-fast-square-waved" sounds), i made a couple of builds including the EA but the only one that ended up sounding like i wanted was the tremulus lune... it's a little more complex than other tremolos (it has a LED/LDR) but worth the trouble...

1878 · February 23, 2009, 05:57:26 PM

I've built a Trem Lune and I agree, It's fantastic. I'm building the EA for sh*ts and giggles basically. Something to experiment with and learn from. It'll probably end up on a 'jam session' board along with a couple of other effects I've built which didn't make it to my main boards.

Does anyone know what makes this circuit tick ?? I'm getting signal when the effect is engaged, just no tremolo effect. The volume control works, but the depth and rate don't. I'm getting a little annoyed 'cos it seems such an easy circuit to build

Thanks again.

EDIT: I've checked the pinout and they're all correct. I even reversed the J201 'cos I've heard this is the one that a lot of peeps make a mistake on. No change

Processaurus · February 24, 2009, 05:42:03 AM

sounds like your oscillator section isn't working. If you are sure your parts are correct (and the transistor is good, and in right) as a test try it without the LED and see if it works (short the led legs). The funny phase shift oscillator is somewhat tempermental, a few different variables can make it it latch up. Low supply voltage is one, and the LED drops the supply voltages seen by the oscillator by ~1.4v.

Another test is to disconnect the oscillator section from the top of the depth pot, if something is amiss there (a short or wrong part) it can load down the oscillator and make it latch up as well.

Otherwise, I and probably some other people here could steer you better in debugging if you post the voltages.

blanik · February 24, 2009, 12:09:24 PM

or your depth pot is shorted somewhere so it's always at zero depth, it turns the trem into a booster...

1878 · February 24, 2009, 01:51:50 PM

Multimeter !! Only got one a few weeks ago and I always forget to use it

The measurements are:

9v+ 9.2
9v- 0.0

Q1 (BS170)

D: 8.10
G: 1.19
S: 0.32

Q2 & Q3: NOTHING !!

There's almost no juice getting through to anywhere after the BS170. I'm gonna change it now and report back.

1878 · February 24, 2009, 02:05:19 PM

No.

Changed the BS170 all to no avail. Stumped basically !!

gez · February 24, 2009, 03:40:52 PM

Adjust the bias for the BS170 so that the drain of this transistor sits at around half supply (ideally, slightly above the halfway mark). There's probably something in the notes about this, but that's what the 100k trimpot is for.

As you're hearing a whine, your oscillator could well be working only you've used the wrong value caps (are you sure they're 1u and not smaller?) That would also explain the constant LED: oscillator blinks at a rate undetectable to the human eye so looks constant (similar principle to film/flick-book). It wouldn't explain the lack of DC voltage readings, though.

It's normal for no DC voltage to be on Q2 (it's AC coupled via the .47u cap).

Get your bias sorted first. Then work on Q3. Probably a dodgy joint, wrong pinout, transistor doesn't have enough gain etc.

1878 · February 24, 2009, 04:31:29 PM

I've set the trimmer to give 4.8v on the drain of the BS170. Still no change other than the volume of the whine decreasing. The 1uf caps are the correct value. I've used electrolytics, would none polarised also work ?? This layout uses them...

http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album19/album145/EA_TREMOLO_VERO.gif.html

gez · February 24, 2009, 06:02:20 PM

Q3 seems to be the problem. Check voltages again. If the LED is on, then there should be something registering at the collector of Q3. If not, then you have a short to ground.

Non polarised will work fine.

1878 · February 25, 2009, 05:44:11 PM

Just got it working !!

The 10k resistor from 9v+ to the collector of Q3 was dodgy. I may have done something to it whilst removing the LED. Anyway, I replaced it and it's working. The whiny screechy noise is still there though. It's less noticeable, but I reckon it'd start to annoy you through a big amp. I'll have a play around with it and see what can be done. I'm hoping putting it in it's enclosure will help.

Other than that, I think it's a very nice tremolo. Obviously not as tweekable as the Trem Lune, but it does it's job very well, and seems to add a bit of warmth (if that's the right word) to the signal.

Thanks everyone for your help !!

gez · February 25, 2009, 05:58:03 PM

Re the screeching. Are you using a switched PSU?

Are you working close to any electrical equipment/lighting that could be causing interference?

1878 · February 26, 2009, 03:37:16 PM

Thanks again !!

I used my Rocktron On Tap to power the pedal. It's 9v, 1670ma. I then hooked up a battery. Quiet as a mouse. I'm hoping it'll be ok when it's in the chain. Is there any sort of regulator (or something) I could fit ??

I'm REALLY getting into the sound of this pedal. I know the Trem Lune is the ultimate in tweekaliciousness, but I've been impressed with the way this little fella works. I've just hooked them both up, and I'd go as far as to say the EA has a better overall tone than the Lune. It 'lulls' you. Definately a keeper !!

Thanks everyone.

gez · February 26, 2009, 06:51:17 PM

Quote from: 1878 on February 26, 2009, 03:37:16 PMIs there any sort of regulator (or something) I could fit ??

With any luck the noise will go once boxed (screening should get rid of it), especially if all your other effects run fine with the PSU. If not, then an inductor in series with the +ve rail might help; although if the whine is within audio range said inductor might end up being a little on the large size (physically). Just box it and see what happens.

blanik · February 26, 2009, 09:13:24 PM

Quote from: 1878 on February 26, 2009, 03:37:16 PM
...I'm REALLY getting into the sound of this pedal. I know the Trem Lune is the ultimate in tweekaliciousness, but I've been impressed with the way this little fella works. I've just hooked them both up, and I'd go as far as to say the EA has a better overall tone than the Lune. It 'lulls' you. Definately a keeper !!

it does sound natural and good indeed, where it lost me it's when it's put after a distortion pedal (or any pedal with a high output, like a Klon, BD-2, SHO, etc...) it doesn't react well, the tremolo effect kind of disappear but it's a perfect tremolo for smoother organic (cleaner) sounds

gez · February 27, 2009, 03:42:18 AM

Quote from: blanik on February 26, 2009, 09:13:24 PMwhere it lost me it's when it's put after a distortion pedal (or any pedal with a high output, like a Klon, BD-2, SHO, etc...) it doesn't react well, the tremolo effect kind of disappear

If the EA's input stage/amp is clipping, then I suppose you would lose the trem effect. Try turning the level from your distortion right down and see what happens.

blanik · February 27, 2009, 03:25:10 PM

Quote from: gez on February 27, 2009, 03:42:18 AM
Quote from: blanik on February 26, 2009, 09:13:24 PMwhere it lost me it's when it's put after a distortion pedal (or any pedal with a high output, like a Klon, BD-2, SHO, etc...) it doesn't react well, the tremolo effect kind of disappear

If the EA's input stage/amp is clipping, then I suppose you would lose the trem effect. Try turning the level from your distortion right down and see what happens.

i tried it but it didn't made enough of a difference... (my reason for using a high output device is to push my tube amp into a natural overdrive so lowering the gain pedal kind of goes against it's purpose), i remember hitting a chord, the tremolo wouldn't be heard but as the chord decayed the effect appeared... the lune would trem and chop no matter how loud the input is... i also tried the EA in front of the gain pedal but the inherent compression of the gain pedal would also kill the effect

it still sounds good au naturel

gez · February 27, 2009, 05:35:23 PM

Drive (turned down) - trem - booster, would work.

Edit: That said, if the trem is clipping (and it is from what you've described), then the drive is putting out too much volume. The EA has quite a large output swing (as much as any booster run off 9V), so your drive signal is definitely too hot...or you like the sound of the MOSFET clipping as part of your distortion sound.

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ea tremolo... something wrong