Keeley compressor clone

[Jay Doyle]

Thanks Jay.  I owe you one.

Mark,

Not a problem, glad to get it in the 'Search' function, at least the stuff I know. But after all the times you've posted the same stuff, I think I'm still well in your debt.

Jay

[davph30]

I've still not decided on any mods or changes yet, any more suggestions would be great

thanks

Dave

[RobertKeeley]

You can post any of my PM's about this subject.
No problem.
Robert

[davph30]

Hi Guys, just to let u know Robert told me he now uses MPSA18 transistors in his compressor.

Anyone got any other usable mods or ideas?

Cheers

Dave

[markm]

Hi Guys, just to let u know Robert told me he now uses MPSA18 transistors in his compressor.

Interesting........

[davph30]

I really don't have any magic or other things I think make the compressor sound good or otherwise.  I can tell you that tonepad (think that is it?) has boards for the pedal.
I use MPSA18s for the transistors now.  I used to do half and half for about the last year or so...using the 2sc1849 units in two positions.  I've had people that have owned different compressors over the years say this latest version is the best.  SO the 2sc trannies might be vintage correct, the mpsa seems to make people happy.
The rest of the parts are metal film resistor, metal film caps by panasonic.

As said by Mr Keeley

Dave

[Gilles C]

THey say about the MPSA18 in the Fairchild specs... (The Motorola is the original).

NPN General Purpose Amplifier

This device is designed for low noise, high gain, applications at collector currents from 1m A to 50 mA. Sourced from Process 07. See 2N5088 for characteristics.


Is there a difference in sound when a 2N5088 is used? If so, maybe I would use a Motorola MPSA18 to make sure it is not a 2N5088 labeled MPSA18 by Fairchild or another company...

Gilles

[markm]

hmmm...Even more interesting.....
I used 2N3904 for my Dynacomp build from the USTOMP layout, (very nice layout BTW!) and I used 2N5088 for my
RossClone built using the TP layout (which is also a very nice layout!).
Check out FuzzCentral as Phillip used 5088's for his build of the Ross too.
He states in his notes that the 5088's are higher gain (we do know that) but that they would sound "cleaner" in that circuit.
Aren't the MPSA18 usually used in Hi-Gain overdrive/distortion circuits?

[Mark Hammer]

hmmm...Even more interesting.....
I used 2N3904 for my Dynacomp build from the USTOMP layout, (very nice layout BTW!) and I used 2N5088 for my
RossClone built using the TP layout (which is also a very nice layout!).
Check out FuzzCentral as Phillip used 5088's for his build of the Ross too.
He states in his notes that the 5088's are higher gain (we do know that) but that they would sound "cleaner" in that circuit.
Aren't the MPSA18 usually used in Hi-Gain overdrive/distortion circuits?

See my earlier posting. I used MPSA18 for the input and phase-splitter/driver transistors (before and just after 3080), 2N3904 for rectifier, and 2N5089 for output transistor.  Sounds nice and is pleasingly quiet.  I did this just based on the naive assumption that the input and output stages ought to be higher-gain low-noise devices, and happily this hunch was right.  Not sure if RK's decision to use the same device was an instance of great minds thinking alike or fools seldom differing!

(The switch to 2N5089 for output was because I ran out of MPSA18's)

[markm]

Mark,
an chance that you could label which tranny does what on the tonepad layout?
For educational purposes   

[Mark Hammer]

Q1 is the input transistor.  Q2 is the phase-splitter/output transistor.  Using a high-gain/low-noise for these two devices is helpful.

Q3 and Q4 can be cheap "garden variety" 2N3904 types that don't have to be anything other than within spitting distance of each other since they only carry control signal, not audio signal.  Matching them is not counterproductive, per se, but as some have wisely pointed out potentially a waste of effort given tolerances in other components.  So at least make sure you don't have one with hfe=124 and the other with hfe=840.  Q5 sums them and feeds the current-control line on the 3080.  Again, not an audio signal carrier, so hiss potential not that big an issue as near as I can tell.  However, it does supply the current that controls the gain of the 3080, so I gather higher-gain units are preferable here.

I will happily defer to others with more knowledge of transistors (which is a VERY large group of people).  I'm just telling yu what I used and what the different devices do.

[beatstrat]

Good thread for me.

I used 5088s for all 5 positions (out of ignorance, I guess).  I used metal film caps for all values 1 uf and smaller and tantalum caps for the 10 ufs.  (I would like for someone to point me to a source for high qual/low noise electrolytic caps).  I don't seem to have a noise issue - using this pedal with my live rig, it works fine and doesn't (seem to) accentuate/exacerbate any noise issues already present (Stratocaster!).

I would like for someone to comment on the overall intrinsic tone of this comp.  I've used a Boss CS-3 (tweaked) for many yrs and just recently built the Ross clone mostly to see if I could not hate it as much as I've disliked various Dyna Squash comps that I've played thru (incidentally) over the yrs.  With the various Attack/Release tweaks, I've not got a squash circuit, but it seems to impart a plastic quality to the gtr tone.  I suppose it's the nature of the beast (3080E?), but if there's one thing I'd really like to tweak/change about this circuit, it's this 'plastic'/whatever tone.  In thinking about it, it seems that this coloration is mainly present (audible, noticable?) in the upper mid and high frequencies.  Part of it is the squashing nature, I'd guess.  Is there anything that you collectively know to be able to change this?  The CS-3 doesn't give me this same type of tone issue.  (Obviously, I'm aware that if I don't dig the tone of the Ross, just use the one that I like - that's not really what I'm after here).

Any help/ideas/thoughts would be greatly appreciated.  Thanks.

Edit - I couldn't get rid of the itallics.. ?

[Mark Hammer]

Unless they deliberately include some circuit changes to compensate for it, just about EVERY compressor I've ever tried introduces some illusion of high-end loss as a result of the compression process.  I've never really understood it before, although now that I think about it, perhaps that's because the most treble occurs at the onset of the note, which is coincidentally where the most gain reduction takes place.

Note as well that the CA3080/LM3080 is not well known for its ability to handle hot input signals, compared to some other chips.  Here is Jim Patchell's comparison of the CA3280 and 3080: http://www.oldcrows.net/~patchell/archives/ca3280_2.html  If you look at the article on page 6 here - http://hammer.ampage.org/files/Device1-8.PDF - you'll see that the 3080 is being used for a voltage-controlled distortion unit.  This is NOT a "clean" chip except for some highly restrictive circumstances.

So, the readiness with which the CA3080 can inject harmonic content NOT found in the original, when pushed hard, plus the tendency of the compression process itself to subtract harmonic content found in the original, can result in a sound that some find a little artificial.  These are both reasons why some folks feel that optical compressors (LDRs will introduce no distortion), or compressors with much higher quality OTAs/VCAs (such as the THAT module found in the CS-3) are preferable, and why some folks like to have just a little clean signal (at least the high end) mixed in with compressed signal.  These two differences ahouls keep the "bite" in, and keep the harshness out.

[markm]

Q1 is the input transistor.  Q2 is the phase-splitter/output transistor.  Using a high-gain/low-noise for these two devices is helpful.

Q3 and Q4 can be cheap "garden variety" 2N3904 types that don't have to be anything other than within spitting distance of each other since they only carry control signal, not audio signal.  Matching them is not counterproductive, per se, but as some have wisely pointed out potentially a waste of effort given tolerances in other components.  So at least make sure you don't have one with hfe=124 and the other with hfe=840.  Q5 sums them and feeds the current-control line on the 3080.  Again, not an audio signal carrier, so hiss potential not that big an issue as near as I can tell.  However, it does supply the current that controls the gain of the 3080, so I gather higher-gain units are preferable here.

I will happily defer to others with more knowledge of transistors (which is a VERY large group of people).  I'm just telling yu what I used and what the different devices do.

Many thanks Mark a dozen times over!
Appreciate the help you always offer 

[Gilles C]

Edit - I couldn't get rid of the itallics.. ?

CTRL-I controls it.

I had the same problem when I was hitting "CTRL-I" instead of "Shift-I" until I realised what I was doing...

Gilles

[davph30]

Still waiting on some parts arriving hope to have the basics together by the end of the week and will let u all know how i get on.

Anyone got any other mods or ideas. A keeley schematic would be great

anyone got a keeley compressor and would like to mail me the layout?

Thanks again

Dave

[markm]

I think we'd all love to get a look at that. 

[davph30]

I know Mark someone must have one they can pull apart, my pedals usually get taken apart the first week

[nag hammadi]

Howdy!
Sent you a PM (after I figured out how to do one      )
The variable recovery or attack control, etc.  Those are things I got from the CP9 by Ibanez I had from living in West Germany, along with my Aria Pro ;-) .  Slightly interesting story, several years ago, really wish I knew when, I started doing them when a humbucker customer was going to return a pedal.  I wanted to figure out why they were having poor tone/performance, distortions, etc.  So I would do some 'back them',  again don't remember how many years ago.  I did experiment with different versions and found out that I didn't like the exact copy of the Ibanez one and that on some of the keeley comps it just plain didn't work because of significant distortion. So, I ended up finding out that the transistors I was using were different (duh!) and that I had to simply crack out the books and find out 'where they wanted to be' without distortion.
Sure, there was that cap mistake on the schematic and things to make sure were matched, that was the best part of the beginning of the ROSS CLONE ERA, people would send me their compressors that they bought from somebody and I would find just a simple copy of the schematic built, easy fix.
I also did tweak/diddle-stick/calculate/alter just about every part in the unit....just so that I had a decent understanding of it.
I have built them with different IC's, different rectifier circuits, build different input and output buffers for a variety of uses and to match other signals equipment (including one for a TV audio circuit/speaker....don't you just hate LOUD commercials, etc...
In this Late 2006 time frame, RoHS compliant matters force a change.  We are nearly complaint to the letter of the law on about 85% of our product line, so to be analyzed more strictly and technically.  So a true clone to Europe is not legal at all anymore.  At least that is my best understanding.
Take care folks,
Yes, decaf ain't to bad an idea.... 

Robert

that's funny - my wife and i have been talking about a compressor to get rid of the stoooopidly loud commercial thing.  MAN that bugs me.

also - let's here it for the aria pro II phase shifter!  the first pedal i got (in 8th grade - what, 20 years ago???), and i used it on every gig up until i built mine.

and just as a side note...

i build pedals for the customers in the shop in which i work.  they ask me if i "invented" any of the stuff.  the best way i have found to describe the majority of the DIY for $ scene is "i am not re-inventing the wheel, i am just making a REALLY good one".

good luck to everyone.  let's face it - the market is WAY large enough to support any of us who are willing to make a living from it.  the mustang belongs to ford, but there are MILLIONS of guys who know it inside and out enough to fix, modify, or reproduce it.  and they make a living from it.

good luck everyone. 

[davph30]

Got the pedal built today using the tonepad schematic but am not pleased with the sound. When the pedel is on the output level is much lower than my bypassed signal until the level pot is at about 3 oclock and lacking treble.

The only differences to the values are

the output cap is 0.047 instead of 0.05

MPSA18's instead of 5088's

and i didnt have a 50k pot so i put a resistor across a 100K whick gave me a 51.2K

any ideas guys??

Thank you

Dave