KENT EA-3 FUZZ TONE BENDER

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LucifersTrip
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Post by LucifersTrip »

I couldn't find a schematic, sound files or any great gut shots of this one...There's some decent pics at:
http://www.effectsdatabase.com/model/kent/ea3

Anyway, lemme know if this has already been traced or if there's any schemes or sound files out there.
If not, I'll open it up shortly.

I can tell you it's sounds like it's a Fuzz Rite topology. It blends a fuzz into a "clean" signal the exact same way.
The big difference is that the "clean" is louder, bassier (almost muddy) and a bit more distorted and at full ("increase"),
there's still a large chunk of "clean" still in the mix...like a Fuzz Rite at 50% fuzz.

Here's some clear outside shots with the instructions.

Image

Image

Image

Image
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Post by lowbrow »

Is that the same as the Walco?
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Post by LucifersTrip »

Probably, or at least very close...but when I posted this I couldn't find the schematic or guts for a Walco Fuzz either.

Do you have a schematic or gut shot?
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Post by lowbrow »

LucifersTrip wrote:Do you have a schematic or gut shot?
Wish I did. Keep meaning to buy one, but it just hasn't happened yet. Have never been able to find either on the net.
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Post by jreeves47 »

love the belt clip
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Post by jrod »

Attached is a schematic of the Walco unit I've had saved for a while. I have no idea if it is correct.
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Post by IvIark »

47pf output cap? There's not going to be much bass coming out of that.
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Post by mirosol »

IvIark wrote:47pf output cap? There's not going to be much bass coming out of that.
:hmmm: The pot will let the bass through from the first transistor. I think i'm interested...
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Post by IvIark »

Ha yeah I didn't even see that, I thought it was just the usual ground connection for the volume pot but it's a blend control isn't it
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Post by LucifersTrip »

Yes, a blend control...see my first post.

I opened it up, took some gut shots and just finished hand drawing the traced schematic last night.

jrod, thanx for posting the Walco scheme... When searching a few days ago I found the DIYSB link from 2006,
but the schematic link was dead:
https://www.diystompboxes.com/smfforum/ ... ic=52076.0

Cool that you saved it...I now know I traded it correctly...

The Kent is very close with a couple small changes.

I'll post the guts, scheme & voltages shortly...
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Post by LucifersTrip »

Ok, as promised, here's the rundown.

guts from afar:

Image

guts top side:

Image

guts top side labeled:

Image

guts bottom side:

Image

guts bottom side labeled:

Image

schematic with voltages (new 9.6V battery):

Image

transistors used:

Image

It's breadboarded and confirmed and sounds almost identical to the original.
If you want to hit the voltages in the original, use hfe around 350-400 for Q1 and
250-300 for Q2.

The 47pF in the Walco schematic posted earlier is most likely incorrect. If you use
the 47pF, you'll barely get ant fuzz in the mix.

Possible mods:
1) I could tell little or no difference with the 18K removed
2) Experiment with a smaller Q1 BC cap. The .01uF is kinda large. If you remove it
totally, it's noisy and the distorted clean/fuzz blend is not good.
3) Recommended: Increase the 12K for more volume & fuzz. Even better, place a
50K pot in series between the 12K and ground. Increase K for more volume & fuzz.
Note, if you lift the 12K completely, you will get more volume & fuzz, but the sound
(distorted clean/fuzz blend is not as good).

anyway, have a blast
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Post by mirosol »

The mistake with the 47/470 cap is quite understandable. The value marking with "470" and "471" mean the same thing on cheap ceramics and multilayered ceramics. I may have been baffled about this myself at one point...

Anyway. Thanks LT for photos and a trace!

Here's my stripboard layout for the circuit. I've added input pulldown to prevent popping and a series polarity protection. Currently unverified.
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Post by LucifersTrip »

^ looks cool...maybe someone will try it.

Since I already have the original sound, I decided to improve my "clone" to my taste.

There's one main thing I wanted to do.

As I wrote above, the dirty "clean" part of the mix is always WAY up in there. I wanted to be able to
knock that down a bit, just leaving the fuzz.

The stock is at unity volume or a bit higher, but what keeps it there is the dirty "clean" part of the blend. If
you knock that out and just leave the fuzz, you'll be below unity.

The goal was to keep it true to the original sound, but take it further...not turn it into a
standard Fuzz Rite.

After a bunch of experimenting, I'm going with this.

Image

If you have both pots full counter clockwise, you have identical to the original counter clockwise.
Slowly turn the 1M clockwise and at maybe about 25-30% you'll have what the stock sounds like maxed out.
As you turn the 1M further clockwise, the dirty "clean" slowly drops out leaving more fuzz. Turn the 100K
counter clockwise and the volume increases along with the fuzz intensity.

Now you can get a perfect mix of clean, fuzz and all at the volume you want.
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Post by LucifersTrip »

should say:

"Turn the 100K clockwise and the volume increases along with the fuzz intensity. "
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Post by wjmwpg »

LucifersTrip wrote: ↑03 Apr 2014, 06:50 Since I already have the original sound, I decided to improve my "clone" to my taste.
[ . . . ]
After a bunch of experimenting, I'm going with this.

Image
Hi LucifersTrip, I know that almost 9 years has gone by but I’d love to see this modded schematic of yours if you could re-upload it. Cheers!
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Post by george giblet »

Hi LucifersTrip, I know that almost 9 years has gone by but I’d love to see this modded schematic of yours if you could re-upload it. Cheers!
LT did a lot of work back-engineering old pedals then modding them to get to them work.

I hope he doesn't mind me reposting his old schematics.

Can I ask that:
- his LT signature is not removed from the schematics.
- if you modify LT's schematics make sure it's clear *you* modified it.
Put some text like "modified by <yourname>" and the date.

Original (drawn by LT):
kent-fuzz-schematic.jpg
Modded by LT:
kent-fuzz-schematic-mod.jpg
[end]
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Post by wjmwpg »

george giblet wrote: ↑28 Dec 2022, 23:55LT did a lot of work back-engineering old pedals then modding them to get to them work.

I hope he doesn't mind me reposting his old schematics.

Can I ask that:
- his LT signature is not removed from the schematics.
- if you modify LT's schematics make sure it's clear *you* modified it.
Put some text like "modified by <yourname>" and the date.
Absolutely George. Thank you very much for posting these.
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