EA Tremolo layout by Paul Marossy distorting

xnery · May 13, 2007, 10:21:55 PM

Hello everyone.

I have been working with tremolos lately. I originally built the EA Tremolo according to the circuit and layout at general guitar gadgets, but got tons of distortion. I then stumbled accross Paul Marossy's layout at http://www.diyguitarist.com/PDF_Files/EA-TremoloPCB.pdf Paul's worked immediately, and only distorts if you have humbuckers at full volume and strum full chords rather hard. Would there be a way to reduce the input a little? I tried moving the volume pot to the front of the circuit, but it seemed to buzz a lot. I was just runing the input to the pot, then the pot to the circuit board. I would greatly appreciate any advice, this tremolo sounds great otherwise, and it was so simple.

Threefish · May 13, 2007, 11:06:08 PM

I had the same problem with my EA trem distorting, and there is a easy fix. Have a read of my build report on a modified (ROG) EA Trem with the ROG layout, with the gain control at the input.
http://www.diystompboxes.com/smfforum/index.php?topic=45546.0
I didn't get any buzzing (you've probably got a dicky connection somewhere). It should solve your problem.

It's a beautiful Trem. I love mine.

Reid.

xnery · May 13, 2007, 11:13:35 PM

It looks like I have to put the volume control after the input capacitor. When I tried it, I had place it before the cap. I suppose that would make some difference.

Threefish · May 14, 2007, 01:40:50 AM

I think Pot Before Input Cap=DC Across Pot = Crackle, like the Crackle Ok? knob on the ZVex SHO. There's a couple of threads in the forum about it. Haven't seen the SHO schem, but I understand that's why that happens.

markm · May 14, 2007, 07:13:10 AM

I've never had a distortion problem with mine, although I have read more than one thread concerning this.

xnery · May 14, 2007, 12:35:19 PM

I tried runing the volume control right after the input cap, but it still gives me a lot of crackle. My layout and parts aren't the stock ROG pedal, so I'm not sure exactly what to do. Could someone please glance at http://www.diyguitarist.com/PDF_Files/EA-TremoloPCB.pdf and give me another hint

Thanks

Paul Marossy · May 14, 2007, 01:39:09 PM

I never had an issue with distortion, but as has been mentioned, some people do. It is a preamp, too, after all.

You could always use a fixed voltage divider to keep the signal level at a fixed setting.

xnery · May 14, 2007, 01:47:41 PM

How would I do that? It's new to me. Sorry to be such a noob

Are you THE Paul Marossy? If so, you're pics and site have been a great inspiration for me.

Paul Marossy · May 14, 2007, 05:05:03 PM

QuoteAre you THE Paul Marossy? If so, you're pics and site have been a great inspiration for me.

Why, yes, it is. Glad I could be of some use to you there.

QuoteHow would I do that? It's new to me. Sorry to be such a noob

I'm not quite sure how to explain a voltage divider with just words. It's basically taking a certain value resistor in series with the output and using a resistor of the same value to ground at the inlet to the resistor in series to halve the voltage. There's numerous threads discussing voltage dividers here at the forum.

A simpler way for you to do it is to use a trimpot wired as a volume control in a set it and forget mode. A 100K trimpot should work OK.

xnery · May 14, 2007, 07:32:05 PM

Where on the layout would I put the prongs of the trimmer? I'm so close to figuring this out...

markm · May 14, 2007, 07:37:57 PM

If you're putting in a trimmer to substitute the volume control, maybe it would help to take a look at my build?

Paul Marossy · May 15, 2007, 07:39:55 AM

QuoteWhere on the layout would I put the prongs of the trimmer? I'm so close to figuring this out...

I would probably place it after the preamp. Pin 1 would be from the output of the preamp section, Pin 2 would go to the next stage of the circuit and Pin 3 would go to ground.

xnery · May 15, 2007, 10:40:02 AM

I'm guessing that the preamp section includes the first 2n3904 that the signal passes through. I would then place the trimpot between the Emitter of the 2n3904 and the 180 resistor. Does that sound right?

Paul Marossy · May 15, 2007, 02:58:59 PM

You know, I think I would actually put a 1K trimpot wired as a variable resistor in place of the 180 ohm resistor on the emitter of the 2N3904 on the input. Then you can adjust it for a little less gain.

xnery · May 16, 2007, 10:01:06 PM

Does replacing the 180 ohm resister with a higher value reduce the gain of the 2n3904? Or is a lower value necessary?

Paul Marossy · May 16, 2007, 10:16:07 PM

QuoteDoes replacing the 180 ohm resister with a higher value reduce the gain of the 2n3904? Or is a lower value necessary?

A higher value will reduce it.

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EA Tremolo layout by Paul Marossy distorting