English Channel and squealing

[Unclerny]

I just built my first English Channel and once I dialed in the voltages, the 4.5s and the 1.6, the pedal took right off.

My problem is that it doesn't take much to get this thing squealing.  The Cut is particularly bad.  If I try to have the gain and volume both up high it's going to squeal and not like guitar feedback but circuit overload kind of squeal.

Any ideas what I may have done wrong?

Thanks UE

[dano12]

My English Channel had the same issue. Have you tried an MPF102 in place of the first J201? That tames it down quite a bit. The other thing that can make high gain pedals squeal is lead lengths that are too long. You can shorten the leads as much as possible or use shielded wire. (The MPF102 swap is easier though and worked for me).

[R.G.]

Welcome to the wonderful world of parasitic oscillation.

High gain devices and high input impedances stuffed into small spaces are the classical setup for oscillation. Grounding and power supply bypassing need to be immaculate for this to work well, as well as using short leads and separating inputs and outputs thoughtfully or with shielding.

[markm]

My English Channel had the same issue. Have you tried an MPF102 in place of the first J201? That tames it down quite a bit. The other thing that can make high gain pedals squeal is lead lengths that are too long. You can shorten the leads as much as possible or use shielded wire. (The MPF102 swap is easier though and worked for me).

Was there a major loss of drive when swapping in the MPF102 or was it unnoitcable?
I am thinking about building one real soon.
   MarkM

[Unclerny]

Thanks for the replies, I do have a couple MPF102s that I bought for the Tweed.  I'll try one in the first position.  My leads are a bit long right now as I haven't mounted it up yet.  I'll get those trimmed and I have some shielded wire from Small Bear I'll try if the problem persists.

Have any of you tried the Cut mod listed on ROG?  I'd like to know if it's worth the effort as I'd have to say the one in there is pretty sorry.

Thanks UE

[Ge_Whiz]

The cut mod was mine, but, if I were building another EC (and I will - the first was for a friend), I'd leave the cut control out. Even when modified, I didn't consider that it did anything that the treble control itself wouldn't achieve if turned down.

Incidentally, I built mine with 2N5457s throughout, and had no squealing problems.

[Unclerny]

Thanks Ge_Whiz.  I have 2N5457s as well.  I think I should be able to get it with this amount of advice.

Thanks Forum, I love this place.

UE

[dano12]

My English Channel had the same issue. Have you tried an MPF102 in place of the first J201? That tames it down quite a bit. The other thing that can make high gain pedals squeal is lead lengths that are too long. You can shorten the leads as much as possible or use shielded wire. (The MPF102 swap is easier though and worked for me).

Was there a major loss of drive when swapping in the MPF102 or was it unnoitcable?
I am thinking about building one real soon.
   MarkM

With the MPF102 it has tons of gain on tap. You won't lose anything. Good luck with the build!

[markm]

Thanks Dano!

[markm]

The cut mod was mine, but, if I were building another EC (and I will - the first was for a friend), I'd leave the cut control out. Even when modified, I didn't consider that it did anything that the treble control itself wouldn't achieve if turned down.

Incidentally, I built mine with 2N5457s throughout, and had no squealing problems.

What do you leave out to eliminate the Cut control?
Just leave the pot out entirely?
Do any changes have to be made to the board?

[dano12]

The cut mod was mine, but, if I were building another EC (and I will - the first was for a friend), I'd leave the cut control out. Even when modified, I didn't consider that it did anything that the treble control itself wouldn't achieve if turned down.

Incidentally, I built mine with 2N5457s throughout, and had no squealing problems.

The cut control on mine seemed to bleed off some of the very high end that I couldn't control with the tone control. I wonder if the different trannies had anything to do with it?

[Ge_Whiz]

Could be. You can leave out the pot and the capacitor to ground, or just the pot. Whatever, socket the capacitor if you might want to experiment with it.

[Unclerny]

I have another ? about the Cut.  Okay, I know I should remember the formula for determining the frequency but I don't remember last week.  I used to know it.

How should I determine, besides trial and error, the frequency of the cut and for that matter the Treble frequency so I don't have two controls doing the same thing?

Also, the cut should have a more noticable effect.  Or at the high frequency it's set at it will only really effect the highest notes on the neck.

What's the difference between what this Cut does and what a Presence would do?

I hope these are all valid questions.

Thanks UE

[Unclerny]

Okay All, here's what I've done that seems to have tamed the beast.  This may sound unorthodox but it's working.  If there's a reason why I shouldn't do this please let me know.

I replaced the first fet with a 2n5457, it helped very little.  It sounds better but the squeal is there.

I noticed that the total output is MUCH MUCH greater than bypass so I put in a 50K pot with a 51K resister between the pedal output and the pot.  The pedal still turns all the way down and now it can't get so loud at any settings to cause the squeal.  It's also still has plenty more output than bypass.

As for the Cut I used a 50K pot with the original cap value and it seems to work better.  The frequency is still slightly above the treble.

What do you think?

UE

[markm]

I think you may have some other issues with your build as I fired mine up yesterday for the first time
and after about 5-10 minutes of setting the trim pots, it worked fine.
No occillation or squealing.
In fact, it sounds just like my old AC30 that I owned many, many moons ago.
I don't know what else you could try but, I think perhaps there's some other issues in your build.

[Unclerny]

Hi Mark I'm certain of that.  The unit isn't mounted up and is very touchy.  If I bypass it I have a small whistle so I know there's some serious interference or noise hanging around this thing.  I'm pretty certain that will go away once everything is grounded and shielded in a chassis.  I can undo the master volume solution latter but I don't think that will be necessary.  I've checked the circuit over several times and can't find anything obvious.

Some of these guys here in my area do solo acts and play direct.  Half of them use pretty crappy mixers and too much signal from this thing will certainly fry those inputs.  I'll have it figured out before it leaves my hands.

The circuit sounds great and there's no noise at all with the guitar turned down, no strange noises.  I wouldn't know what an AC30 should sound like but this thing has a beautiful breakup and it doesn't go over the top at all.  The voltages are very nicely on the built although the first two fets have slightly high sources.  Is that a concern?

I should begin the Tweed circuit tonight and get it worked out also.

Let's see what happens. UE

[Unclerny]

Now that I have it all mounted up it's working perfectly.  I left in the 51K res + 50K pot because the english channel is so much louder than the Professor Tweed it helps balance them.

The finished product:


Details here:
http://www.uncleernieseffects.com/Projects.html

Later UE

[lucaneo]

Hi!

I've finisched the english channel taken by Runoffgroove, but I've some problem...I'm not a great diyer and I've some question: What is the voltage for setting the trimmers? I've used all j201 transitor. I like a crunch, but also a clean sound from this pedal...

[Unclerny]

I usually set my Jfet bias between 4 and 4.5 volts.  If you contact me through my site email I can send you the schematic I used for the Honeyboy.  It should have those details on there.  I thought the ROG schematics had the 4.5v note also but I haven't looked at them in a while.

Unclerny

[stumper1]

There is a voltage chart on the runoffgroove website.

http://runoffgroove.com/englishchannel.html