Compression Sustainer

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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mictester
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Post by mictester »

This is a cheap and simple circuit that was developed a few years ago for a series of commercial products. Unfortunately, the manufacturer got out of effects just as this was to go to production...
CompSus.GIF
The prototypes of this sounded truly amazing, and the range of control was better than many similar products. This was to be just part of an effects system - the output of this module would (for example) feed a three-band tone control.

We compared this unit against the MXR Dynacomp, the Orange Squeezer and the EH Soul Preacher. It didn't have quite as much "squish" as a Dynacomp but in "compress" mode, it was quieter and less distorted. It beat the Soul Preacher and the Orange Squeezer in every way!

You'll notice that component values are frequently repeated, and in some cases are used in parallel to get the values we wanted. Obviously, you can replace (for example) the 1uF // 1uF in the timing filter by a 2u2, and the 2M2 // 2M2 with a 1M. It's just much cheaper to bulk-buy a smaller range of components!

I've got a PCB layout somewhere - I'll post it here in a day or two. There's also the prototype Veroboard layout which I'll post too.

Have fun!
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Post by Brink »

Looks interesting.
Are the top left two 1uF caps supposed to be oriented that way?
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mictester
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Post by mictester »

Brink wrote:Looks interesting.
Are the top left two 1uF caps supposed to be oriented that way?
Yes. The rectified DC from the uppermost diode is below zero Volts (to drive the FET into conduction) so those filter capacitors have to have their positive plates to the ground rail!

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Post by Brink »

Here's my current vero, which is untested.
I'm somewhat unsure about which which pot lugs to use.


admin edit: see updated version viewtopic.php?p=90578#p90578
Last edited by modman on 20 Apr 2010, 17:56, edited 2 times in total.
Reason: deleted preliminary schematic
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Post by Brink »

I built up that vero of mine. It doesn't work. It could be my soldering skills, or I'm wondering if I got the transistor orientation correct.
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Post by RnFR »

well i see 7 1u caps in the schematic, and there are only 4 in your layout. also i don't see a 2u2 cap in the schematic, and you have one in the layout.
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mictester
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Post by mictester »

Brink wrote:I built up that vero of mine. It doesn't work. It could be my soldering skills, or I'm wondering if I got the transistor orientation correct.
I'll post a vero and a PCB later today!
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Post by Brink »

RnFR wrote:well i see 7 1u caps in the schematic, and there are only 4 in your layout. also i don't see a 2u2 cap in the schematic, and you have one in the layout.
The 2u2 was to replace 2 1u in parallel (same with a 1m vs 2x 2M2). That only account for 6, though. Looks like I forgot some components.
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Post by Brink »

Let's try this again. Here's version 2.
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MictesterComp2.PNG
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Post by John3 »

So could I use 1uf Film caps here or is there a reason to go with Electrolytic?
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Post by Brink »

John3 wrote:So could I use 1uf Film caps here or is there a reason to go with Electrolytic?
Film should be fine. Electros are often smaller/cheaper in those values.
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Post by beatles-1964 »

Bump.

Verified as of yet

:?:
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Post by Brink »

beatles-1964 wrote:Verified as of yet :?:
No. Mine still doesn't work, but that doesn't mean that the vero is wrong.
I'm wondering about the transistor orientation.
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Post by jstbrowsin »

Hi there I'm really interested in this circuit.. . when will you be posting the PCB please?
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Post by jstbrowsin »

Bump
kev01 wrote:This one wins the gooooooooooop award. That has more silicone than Pamela Anderson.
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Post by cpm »

jstbrowsin wrote:Hi there I'm really interested in this circuit.. . when will you be posting the PCB please?
well, in the meantime, you could do your own pcb and share with us?
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Post by jstbrowsin »

Yeah I'd love to, however although I have completed successfully a few projects from this site (Orange Squeezer and two xotic boosters) I'm relatively new to this game. Sort of a paint by numbers guy if ya know what I mean. I have just started L2 & L3 electronics engineering if that's any consolation so I hope to be able to contribute quite a lot more towards the end of the year but for now I'm a noob. :-) I didn't mean to ruffle any feathers. I noticed in the previous post that a pcb was going to be posted that day and just thought I wonder what happened to it? :hmmm: This post wasn't intended to put pressure on anybody here sorry if it came across that way. :oops:
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Post by John3 »

Before I dive into this, has anyone verified the vero layout? Since my skills are still in the newbe stage and all I have for 1uf caps is film just want to have a reference point to say this should work.

Thanks,

John
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Post by livingnote »

Wow - do I get this right? The compressor works by varying bias between the signal amplifier's +/- inputs rather than fetshunting the signal itself?
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mictester
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Post by mictester »

livingnote wrote:Wow - do I get this right? The compressor works by varying bias between the signal amplifier's +/- inputs rather than fetshunting the signal itself?
No! The FET varies the resistance "to ground" from the non-inverting input of the op-amp.
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