Marshall - ED-1 Compressor  [schematic]

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andreas
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Post by andreas »

First post, and already I'm asking for freebies :D

Anyway, I have an ED-1 compressor on the bench, and trying to follow all those mini connectors is doing my head in... Does anyone have a schematic for this pedal? I've e-mailed Marshall tech support about it, but haven't gotten any response yet. I suppose they'll get back to me eventually, but I'm itching... 8)

/Andreas
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The Rotagilla
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Post by The Rotagilla »

andreas wrote:First post, and already I'm asking for freebies :D

Anyway, I have an ED-1 compressor on the bench, and trying to follow all those mini connectors is doing my head in... Does anyone have a schematic for this pedal? I've e-mailed Marshall tech support about it, but haven't gotten any response yet. I suppose they'll get back to me eventually, but I'm itching... 8)

/Andreas
Try emailing them again. I've found them to be very helpful and responsive in the past.
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Post by Dirk_Hendrik »

andreas wrote:First post, and already I'm asking for freebies :D

Anyway, I have an ED-1 compressor on the bench, and trying to follow all those mini connectors is doing my head in... Does anyone have a schematic for this pedal?
[parrot mode]
Since you have the thing on your bench. How' bout you being the one drawing up that schematic? I'm aware that might be difficult but it's a great learning experience and, in the end, ego boost as well ;) It's the start of the weekend. Make fresh coffee, kick the family out and dive into this!
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Post by analogguru »

[parrot mode]
why he should draw the schematic when he already has the factory schem in his mail ? :roll:
[/parrot mode]

you want that too ?

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Post by Dirk_Hendrik »

only if it's not another variation on a dynacomp :roll:
Sorry. Plain out of planes.

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Post by andreas »

No word from Marshall yet - although I really can't expect them to answer over the weekend, so... In any case, analogguru came to the rescue. Thanks! :D
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Post by Herakles »

I stumbled upon this old post today and noticed that it wasn't resolved. I draw the schematics for the ED1 many years ago, with the Eagle freeware app. If someone is still interested, here it is. I can see that I missed some of the C and L values, don't remember why.
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Marshall ED1
Marshall ED1
ED1.png (24.45 KiB) Viewed 5174 times
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Post by Hides-His-Eyes »

Inductors?
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Post by IvIark »

Great first post! :thumbsup
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Post by mictester »

Hides-His-Eyes wrote:Inductors?
Yes. They're just ferrite beads with a few turns of enamelled wire through them. They stop getting RF into the pedal. I use them throughout my gear (especially in high gain circuits) to prevent the AM receiver effect!

Back in the days when I used to play USAF bases in the UK, we used to have to include lots of RF filtering in the gear to keep the radar out of the PA! The control tower AM or SSB would also cause interference, and they didn't care where their aerials pointed!
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Post by Hides-His-Eyes »

I take it that having a small cap across an op-amp will also filter out all but the most dedicated of radio stations? :)
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Post by Valve Head »

For anyone still interested in the ED-1, here's an updated version of herakles' Eagle schematic with the missing R & C values filled in.
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Post by Valve Head »

Sorry, I meant Herakles' schematic - and I'm usually quite good at CaPitAl lEtteRs.

I also forgot to mention that my ED-1 came with a BA4558 IC for IC1.
All transistors and IC2 are as per Herakles' schematic.
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Post by Duckman »

Lot of filtering caps at the power input... are all really necessary :?: It makes a big difference :?:
Even a cheap chinese wall wart usually got a 1000uF cap :scratch:
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Post by roseblood11 »

The smaller caps improve the filtering at higher frequencies. But I don´t understand why they use 4 identical caps. I read somewhere that it would give the best result, if each cap was 10 times smaller than the preceding one, say 100µF, 10µF, 1µF,...
---

I wonder if (and how?) the ferrite beads affect the sound.
Or what else could be done to improve the bypass sound? If a passive guitar is connected directly to the ED-1, the highs are tamed a bit.
I know that it´s quite simple to remove the small pcb with the jacks etc and make a standard true bypass switching (photo...), but if the ferrite beads don´t affect the tone, I would rather keep them where they are...

The pedal on the photo was modified by "tonesucker" and posted at musikding.de.
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Post by RnFR »

roseblood, your pic isn't showing up for me.
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Post by Valve Head »

C16 (.01) is across pins 4 and 8 of IC1, C17 (.01) is across pins 4 and 7 of IC2 - for maximum RF rejection I guess?

The ED-1 and the other pedals in Marshall's metal beetle series use something that they describe as "passive bypass", but it's not even close to true bypass. Definite tone-suck.
Maybe we could use the inbuilt DPDT switch to make something like Jack Orman's Millenium bypass, which would make these pedals really kick arse.
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Post by roseblood11 »

Here it is:

"Tonesucker" wrote that he made some changes after he took the photo: a) Changed the wiring to shunt the input to ground in bypass mode, b) added a 2,2M pulldown before the input cap.
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Post by Valve Head »

Thanks roseblood11. That true bypass looks good....might be easier than modifying the little PCB too.
Worth a try, methinks.

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Post by roseblood11 »

Valve Head wrote:C16 (.01) is across pins 4 and 8 of IC1, C17 (.01) is across pins 4 and 7 of IC2 - for maximum RF rejection I guess?
That makes more sense! ...and I found another version of the schematic that shows it that way.
Valve Head wrote:The ED-1 and the other pedals in Marshall's metal beetle series use something that they describe as "passive bypass", but it's not even close to true bypass. Definite tone-suck.
Maybe we could use the inbuilt DPDT switch to make something like Jack Orman's Millenium bypass, which would make these pedals really kick arse.
Shouldn´t be a problem...

I would also be interested in an improved bypass for the pedals with stereo outputs, for example the VT-1 Vibratrem or the SV-1 Supervibe Chorus.
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