EH - Low Frequency Compressor  [schematic]

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
gigelmargel
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Post by gigelmargel »

Any chance for a PCB?

I am very curious how it sounds :)

Thxa all for your work!

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Post by gigelmargel »

No news?

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Post by mictester »

PierreBPSFSB wrote: - BlackFinger: also, following the post, i have seen the Morley (ProComp PCBmod), and it has the same clever use of OTA (attenuation inside the feedback loop, to keep the S/N # constant), but the CA3080 both inputs was "grounded": here the input are signal feeded, so it is more a signal "negative feedback" (with careful phase e- pin2 on µA741) than an output variable conductance.
It is just a remark :wink:
The use of the OTA in the feedback loop actually improves the S/N and bandwidth of the op-amp as the attenuation is increased, because you're increasing the negative feedback! It's quite a good approach to a voltage (or current) controlled amplifier, but has a few problems - limited range of control, small range of input voltages before it runs into distortion, and so on.
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gigelmargel
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Post by gigelmargel »

Anyone has a PCB for this compressor?

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Post by Duckman »

So... what about the "Boris schemo"? :hmmm: Looks like a discrete earlier version, don't you think?

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Post by seedseed »

Is there a vero layout somewhere for this one? I think it would work fine with a lm13700 also just use half the ic or make a blackfinger and a low frequency compressor with one ic on the same board would be cool also. Depends how keen you are on this pedal i guess. What is the software called that everyone makes the vero designs on and where can i get it? i usually do mine on paper and pencil but a program would be good also. Thanks

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Post by pedalgrinder »

Hi everyone,

I am new to this whats the easiest way of cloning a pcb picture. do you invert the picture or is there software you can use. obviously there would be a few of you guys who have done this. I was trying to save myself some pain and learn the easy way of doing it through someone else's experience. Thanks any advice would be much appreciated.
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Post by JiM »

pedalgrinder wrote:Hi everyone,

I am new to this whats the easiest way of cloning a pcb picture. do you invert the picture or is there software you can use. obviously there would be a few of you guys who have done this. I was trying to save myself some pain and learn the easy way of doing it through someone else's experience. Thanks any advice would be much appreciated.
Do you want to etch a PCB, or to draw a layout ?
You may want to look into those forum subsections :
http://www.freestompboxes.org/viewforum.php?f=45
http://www.freestompboxes.org/viewforum.php?f=51
http://www.freestompboxes.org/viewforum.php?f=21
Your questions are very likely to be answered there already. And don't forget to use the search feature!

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Post by Scruffie »

seedseed wrote:Is there a vero layout somewhere for this one? I think it would work fine with a lm13700 also just use half the ic or make a blackfinger and a low frequency compressor with one ic on the same board would be cool also. Depends how keen you are on this pedal i guess. What is the software called that everyone makes the vero designs on and where can i get it? i usually do mine on paper and pencil but a program would be good also. Thanks
Alot of people (my self included) use DIY Layoutcreator for Vero layouts, there are a few other options but i'm not sure what there names are.

It probably will work with an LM13X00, it might need an adjustment or two though... i'd be more interested in getting it to run off a single supply or atleast adding a charge pump on board if you want the extra headroom.

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Post by phibes »

pedalgrinder wrote:Hi everyone,

I am new to this whats the easiest way of cloning a pcb picture. do you invert the picture or is there software you can use. obviously there would be a few of you guys who have done this. I was trying to save myself some pain and learn the easy way of doing it through someone else's experience. Thanks any advice would be much appreciated.
I use to redraw them into Illustrator but shit, that would take all day. Just download ExpressPCB and redraw it in there. You can adjust lead spacings and what not in the program so you can end up with a pretty close layout. I also like ExpressPCB for exporting the file as a vector image for printing. Better traces and pads. I know I should learn eagle but I've really never been let down with ExpressPCB. Once you fuck around with it enough it becomes second nature.

This would be a fun one to convert to single power supply though. Everybody and their brother has built a Ross and Dyna already.

Mictester, anything you'd improve on the design?
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Post by pedalgrinder »

Does anyone know in this compressor which resistor or capacitor's in the the first low frequency compressor where it's using the transistor as the attenuator which resistor or capacitor would be the time constant's for the attack and release??? It would be good candidate for playing with these particular options. Cheers
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Post by seedseed »

i'd love to build one of these also. has anyone done one. Would be good for a nice vintage sound. I would think it would clip a bit using a transistor as the attenuation method. But thats not always a bad thing anyone cloned one??????

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Post by phibes »

I think there's a layout in this thread. The Black Finger is the same as the LFC from what I remember. Try er out.

https://www.diystompboxes.com/smfforum/ ... ic=25952.0

I don't think anyone has ever really dived into due to the power supply. A bipolar power supply can easily be integrated.
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pedalgrinder
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Post by pedalgrinder »

Here we go threadjacked hahhaha [smilie=threadjacked.gif] [smilie=threadjacked.gif] [smilie=threadjacked.gif] [smilie=threadjacked.gif] [smilie=threadjacked.gif]
electro harmonix the black finger schematic.gif
black finger layout pcb.gif
black finger pcb.gif
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Post by pedalgrinder »

is there any track side pics of the low frequency compressor using transistor attenuation rather than the ota. The schematic is there but has anyone got some gust shots of that particlular one especially the track side. I reckon the transistor one would sound better than the ota one. Cheers
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Post by mictester »

pedalgrinder wrote:is there any track side pics of the low frequency compressor using transistor attenuation rather than the ota. The schematic is there but has anyone got some gust shots of that particlular one especially the track side. I reckon the transistor one would sound better than the ota one. Cheers
I can assure you that it doesn't! The transistor attenuator introduces a lot of distortion, and completely destroys any dynamics that the guitar has!

The 3080 version is MUCH better and has a better frequency response and lower distortion than the MXR. The minor problem of dual rail operation shouldn't really put you off!
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Post by pedalgrinder »

it's not that at all dual power supply i prefer. i disagree with you i think it sounds better on a bass maybe a guitar you may find that but for a bass the transistor would give better attenuation sound even with the bit of distortion than the hissing ota. I can't say iam a big fan of transconductance amplifier compressor they just don't do it for me. So if anyone has a track side to the transistor version i would love to see it. Cheers
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Post by AnaSoundsFr »

Hi,

Thank you very much for your schematic, this is a good work.
But, I don't understand, were are the tubes on the scheme? I thought that this model is a tube compressor and that's what I am searching.

Regards,
Alex.

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Post by lietuvis »

Hi, I have this if this makes any help:
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