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Solid State Amplifiers => Preamps and Effects => Topic started by: phatt on December 23, 2010, 09:24:55 AM

Title: Compressor Mods
Post by: phatt on December 23, 2010, 09:24:55 AM
Hi fellow tone tweakers,
 
It seems it's a love/hate thing with Compressors, some like some don't.

My main experiences are with the dreaded CS2. (hated it and sold it,, noisey as hell)
Also still own a Quadraverb GT. (poor me) It's preamp systems where also a horrabillas experience.

My CS2 was a long time ago and I have learnt a lot since those days so I thought I
should at least test some ideas and see what really goes on inside these circuits.
Heck why not,,I've got an LM3080 chip in the junk pile somewhere.

I've always found Compressors more trouble than they are worth but after hearing a neato trick using a CS2 in front of TS9,,,
Wow really did improve sustain and bingo it sounded a lot less like a compressor.
Well you learn something new everyday.
Obviously it got me thinking about Comp circuits again.

Now I'll cut to chase.
Needless to say out came the breadboard and after a few weeks of breadboarding many
ideas I've found a few things you might like to know. None of these tricks will fix the clean sound of these comps but may improve the OD sound if used *IN Front* of Distortion units,, Obviously after Distortion won't work as well.
If you are into a lot of funk rythums then I admit clean comp is a usefull tool
but Still Noise is usually the enemy.

The Pumping action.
After much headscratching it dawned on me that the clamping action is not a matter of speed but *DEPTH*, it's far too much.

I Fixed Pumping action by *Changing diodes to LEDs*.
A switch could be used here for standard (hard) and led (soft) comp.

This raises the comp point and although you loose a bit of clamping it still retains a fair amount of sustain which helps to overcome that dreaded humph mumph you get with most Comp circuits. (Very nice I like)

The switch on the caps changes the recovery time.
2u2= fast, 10uF= slow. Can't make up my mind about that part yet.

**NOISE**,, As said a huge issue. (on all but the rare expensive studio racks
systems)
It seems that everyone just copys the other's ideas with a few changes and throw it on the market. Even Bootweakers don't seem to try hard to solve some of the noise issues found in some classic circuits.
Heck,, maybe I'm alone in my quest to build quiter circuits.  :lmao:

So lower noise was the priority, the *must fix* otherwise it's just going to end up
landfill and I'm wasting my time. ::)

Now being this unit plays around with a lot of gain I can't say I've made it *Noiseless* but I believe I've dramatically improved on the CS2 styled Compressor circuit.

Tokai made one similar to Boss CS2 unit and it apparently had a better S/N so I mixed up some ideas from a whole pile of schematics and then I just kept tweaking things.

So yes I'm very impressed,, With the Sustain full up and Attack slow it works well
with my distortion units.

With the Leds engaged it has already fooled me a couple of times so it would be hard to tell if it colours the sound. Obviously run clean it still retains the classic CS2 comp sound if that is your thing but I'll hazzad a guess and say it will NOT be as noisy and hissy.

Of course if you wind up the level it will still deliver some hiss but I'm assuming you all know not to use the Compressor output as a master volume,  :trouble.
I doubt you would need to turn up the level much as this unit still has heaps of headroom. (A 50k level pot may work just as well here)

So if you wish to get more from your distortion units this may be an improvement.
At the least I've created a working circuit that may give others with better insight some ideas to work with.

When time permits *I will* be building this circuit. The Danger is to keep on tweaking but I doubt I could improve it further without resorting to much more complex circuits.
Have fun with it, Chrissy Cheers from Phil.
Title: Re: Compressor Mods
Post by: joecool85 on December 23, 2010, 10:16:13 AM
Keep us posted after you build it.  I've not used many compressors but this looks like one I might like quite a bit.
Title: Re: Compressor Mods
Post by: J M Fahey on December 23, 2010, 10:21:20 AM
Looks very good.
I *think* I have a 3080 too.
Where? ... God knows !!!
As a first step, the schematic was duly saved into the special "Phatt" file, together with Phatt-tone, Phatt-Dist , Phatt-presence and last but not least, the glorious Phatt-Reverb.
Yes, I've dabbled into Compressors too (still do) and agree that the *biggest* PITA is getting the correct control signal.
Pumping is deadly.
Congratulations.
EDIT: dear Phil, can't you please save your schematics as .gif or .png instead of .jpg?
The last format is useless here because it was invented for colour pictures and *on purpose* blurs images to hide pixelization.
See that lines, circles, etc. have a "ghost" image around them because of this.
Try it, you'll see a big improvement.
Title: Re: Compressor Mods
Post by: joecool85 on December 23, 2010, 10:38:01 AM
EDIT: dear Phil, can't you please save your schematics as .gif or .png instead of .jpg?
The last format is useless here because it was invented for colour pictures and *on purpose* blurs images to hide pixelization.
See that lines, circles, etc. have a "ghost" image around them because of this.
Try it, you'll see a big improvement.

Or try a better jpg compression.  As a webmaster and developer, I appreciate the jpg for all it's worth and agree it can be ugly if poorly compressed, but when properly made they look great.  I don't know what he's using for software though and if there aren't any settings, normally jpg gets the shaft and you have to use a .png for high quality work.
Title: Re: Compressor Mods
Post by: phatt on December 25, 2010, 08:56:08 AM
Hi folks,
         Yep I've never been able to get my head around all these different formats so Time for me to look into it further.

Sadly coming from an industrial background I missed out on basic Computer skills so a lot of this technoligy goes over my head I'm afraid.
Floppin hang it all ,,I'm Sooo old school I've still got Cassette players and Turntables.
I doubt I could even switch on an iPud. HaHa.

My first few Schematic's from the net took up about 10 pages of an old dot printer for
one schematic which had to be joined together with sticky tape.  :grr
But I've been using IrfanView since some enlightened person put me onto it which
allows one to resize things to fit on normal A4 paper.
That was a big big help. <3)
I've been using IView ever since but now I'm *up-loading* files I obviously need to
look deeper into the finer points,,,So thanks those helpful tips there maybe some improvement in the new year.

I've posted what I hope is a better effort.
Please note a small booboo. ***R13 should be 5k***
I paralelled two 10k as 4k7 is not quite right. The offsets are obviously quite touchy and
without knowing exact DC offsets it's hard to know exactly where to set bias points
so a trial and error working up and down until you find it.

The input to the LM3080 is about as low as you go for SNR but the output may still
need work as the sustain knob still presents a fair amount of hiss when the Amp is
cranked up to live gig levels.
(not bad but enough to be annoying,,
I'll except a Compressor but I'll burn in hell before I use a noise gate)

I might throw it all in a make shift jiffy box and give it a test run at the next Club gig.
Phil.
Title: Re: Compressor Mods
Post by: joecool85 on December 26, 2010, 10:54:46 AM
Phil, that file looks MUCH better.  Thanks for posting it.
Title: Re: Compressor Mods
Post by: J M Fahey on December 26, 2010, 03:26:34 PM
Hey !! That's cleaner , *and* smaller (40K vs 70K)
Congratulations.
Anyway I knew you were the nerdy type: cassettes !!! , what's wrong with 8 channel tapes , huh ?? :grr
And when we go dancing on the beach with all the guys and gals together, we have a portable, battery powered 45 RPM record player .
How's that ??  :tu:
And we sneak some beers too, although we're under 21.
Naughty boys. :trouble
Title: Re: Compressor Mods
Post by: phatt on December 29, 2010, 08:31:00 AM
Hi JMF,
A bit of trivia for you,
Did you know that 8Tracks never caught on in the land downunder whereas cassettes where a huge hit.

My LM3080 has died  :'( so that brings all progress to a grinding halt.

For the time being I relented and purchased a cheap S/hand Marshall pedal.
The *Ed 1 compressor* as it's called.
Same chip and very similar circuit that I've posted which of course still has the inherint hiss problem if you up the sustain and level.
With the level held low it's useable,, so will see how long I can stop myself from tampering with it. :lmao:
Hum?? I wonder how a couple of leds would work in that circuit.

Did find some interesting circuits while searching the net.
As to your comment about *Control Voltage* being an issue,, well 2 stood out and looked rather interesting.
*Pearl* Make one and the *DOD 525* looked trick.

Also *DOD Attacker* I did partly test but that is about the time the chip lost its magic smoke. I have a feeling that the control pin5 is a problem if you short it,, but I'll never know exactly what happened :grr
Cheers Phil.
Title: Re: Compressor Mods
Post by: J M Fahey on December 30, 2010, 01:06:09 AM
Quote
the land downunder
:o :o
You mean ... Argentina ??? ;)
We have the southernmost city in the World  8)
Just Google Ushuaia :o
Title: Re: Compressor Mods
Post by: phatt on February 06, 2011, 06:48:39 AM
Well guys,, it's bin a hard road :'(

A lot of the circuits floating around are really dud,, but light at the end of the tunnel.

I will never visit *Ushuaia* but I just may end up buliding a compressor,, Winky.

After thinking I blew up the LM3080 chip it came back to life after I found the *Blackfinger Schematic by EH*

Wow it works though it has no real controls except for comp.
It's very quite compared to other circuits and I've built a few in the last few months.

Will have a modded schematic in a few days if all goes well.

there are obviously a few *black finger* schematics floating around and they are different but we will see which ones works well after a bit more testing.

*Mictester* at FSB is a rather clever chap and has helped me get a grip on how these things work.

This one although it has limitations does not use the LM3080 chip in the signal path.
Helps keep the noise down by a big margin.  I liked it before I even BB built it.

Have been playing it all day and it's kinda nice,,, not as much Comp as the ED but far less noisey.

Now the trick is to see if I can get it to work from a single supply ,, another task,,, oh well life goes on.
Phil.
Title: Re: Compressor Mods
Post by: askwho69 on February 07, 2011, 12:54:02 AM
I think i will stop looking for compressor :tu: digging this up:D
Title: Re: Compressor Mods
Post by: phatt on February 07, 2011, 08:04:14 AM
I finally got a working schematic.
Bear in mind this is all on the BBoard and still siffting through some ideas but this at least will work as shown.

It was Glitching or clamping hard off in a cyclic LFO kind of way but added R7 (1m2) seemed to sort the random hickup problem.

The Aim is to get this working very well,,,understand it enough to then be able to establish if it could be modified to run on a single supply.
So wish me luck.

Note for Askwho,, be aware these are tricky circuits and I strongly recommend you test these circuits before building them.
Cheers, Phil.
Title: Re: Compressor Mods
Post by: askwho69 on February 08, 2011, 12:13:36 AM
Thanks Phatt  :lmao: you have Phatt heart  ;D
Title: Re: Compressor Mods
Post by: J M Fahey on February 17, 2011, 06:30:02 PM
Looks good, but I was dismayed when asked for LM3080's.
Looks like they are not made any more; NOS omes command from $15 to $30 each !!!!!!!!!!!!!  :duh :loco
Which is the modern replacement? (there must be some, although the ones I found so far were miniature SOIC and the like)
Title: Re: Compressor Mods
Post by: DJPhil on February 17, 2011, 07:29:18 PM
Looks good, but I was dismayed when asked for LM3080's.
Looks like they are not made any more; NOS omes command from $15 to $30 each !!!!!!!!!!!!!  :duh :loco
Which is the modern replacement? (there must be some, although the ones I found so far were miniature SOIC and the like)
I poked around a bit and it seems there's not many OTAs made anymore. You might consider the Japan Radio Corporation's version of the LM13700 (Mouser link (http://www.mouser.com/ProductDetail/NJR/NJM13700D/?qs=sGAEpiMZZMtCHixnSjNA6PNeOmaxGblUaxC6OFl8Epo%3d) and datasheet) (http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=4702). It's a dual, but it's only a dollar (here in the US anyhow). At that price you could leave the second half of the chip idle and still win out. I haven't done a detailed peek at the specs, but the original 13700 was used in synths, compressors, and LFOs for phasers for many years.
JRC has saved my bacon a few times, as they make more than a few older chips that aren't really easy to find. I'm a big fan of their LM386 clone (NJM386) as it comes in DIP, SOIC, and SIL (!).
Hope that helps. :)

Edit: Fixed a typo
Title: Re: Compressor Mods
Post by: J M Fahey on February 17, 2011, 11:19:53 PM
It sure does.
Thanks.
Title: Re: Compressor Mods
Post by: phatt on February 18, 2011, 07:25:42 AM
Hi chaps,,,
head over here>  http://www.freestompboxes.org/viewtopic.php?f=1&t=2086.

I like what *mictester* has to say re these comp circuits.

The trick seems to be use the  LM3080 in the FB of another circuit.

Much like the Morly circuits,, look for those on page 2 links kindly posted by
*Tonetweaker*.  (I don't thjink you need to sign in as it's a link?)
I tend to think there is little chance of getting a *Low noise version* while working with 9Volts and it seems that the LM3080 was not intended to pass serious audio anyway so it may turn out to be a no brainer.

I have one LM3080 chip and I've made a discrete version of the CA3094.
(suprised myself ,,, it worked first go :lmao:)
Now between those two I will at some stage try to replicate the famous Moog Lab series compressor circuit which of course needs a split supply.

Sadly a lot happening at the moment and these things are labour intesive so it will be a while.
I'll be back,,, Phil
Title: Re: Compressor Mods
Post by: phatt on February 18, 2011, 07:52:55 AM
Looks good, but I was dismayed when asked for LM3080's.
Looks like they are not made any more; NOS omes command from $15 to $30 each !!!!!!!!!!!!!  :duh :loco
Which is the modern replacement? (there must be some, although the ones I found so far were miniature SOIC and the like)
I poked around a bit and it seems there's not many OTAs made anymore. You might consider the Japan Radio Corporation's version of the LM13700 (Mouser link (http://www.mouser.com/ProductDetail/NJR/NJM13700D/?qs=sGAEpiMZZMtCHixnSjNA6PNeOmaxGblUaxC6OFl8Epo%3d) and datasheet) (http://semicon.njr.co.jp/njr/hp/fileDownloadMedia.do?_mediaId=4702). It's a dual, but it's only a dollar (here in the US anyhow). At that price you could leave the second half of the chip idle and still win out. I haven't done a detailed peek at the specs, but the original 13700 was used in synths, compressors, and LFOs for phasers for many years.
JRC has saved my bacon a few times, as they make more than a few older chips that aren't really easy to find. I'm a big fan of their LM386 clone (NJM386) as it comes in DIP, SOIC, and SIL (!).
Hope that helps. :)

Edit: Fixed a typo

Best I can make out is the *LM13700* might be a better idea anyway.

So far I've not been able to improve over the basic CS2 type copmpressors.
My ED Compressor is only just useable.

What may suprise those who've not had much to do with compressors it does alter things in a subtle way.
i.e. your Volume control on the guitar won't work quite the same while effect is on.

As you turn down the comp just keeps raising the gain up higher and higher until the last few notchs where it starts to shut off sharply.
By then the gain is so high the dreaded hiss will likely be quite evident.

I'm at a point where I'm starting to think it's all getting to complicated and I maybe better served by utilizing other drive circuits to make the sustain longer.

The only reason I got interested was because it extended the sustain of the OD sound.
As I have no use for clean Compressor type sustain then I might be better served by simply implimenting another OD circuit.
But we will see,,, oh all the things to ponder,, drives one round the twist at times :loco
Phil.
Title: Re: Compressor Mods
Post by: tarahall on August 15, 2017, 09:03:57 AM
I finally got a working schematic.
Bear in mind this is all on the BBoard and still siffting through some ideas but this at least will work as shown.
It was Glitching or clamping hard off in a cyclic LFO kind of way but added R7 (1m2) seemed to sort the random hickup problem.

I know this was a long time ago Phil, but I found this pic of an SS EH blackfinger. Your R15 1.5m looks like it was a 2.2m on the EH pcb. and R5 & R6 could possibly be the 390k & 680k that are on the pcb but not found on the blackfinger schematic where they are marked as 120k but no 120k's are visible on the pic.

If it's of any interest I do have some 3080's. I could always post you a couple (I'm up near macedon), are you down in gippsland or still in nambour?
Title: Re: Compressor Mods
Post by: phatt on August 16, 2017, 08:29:47 AM
Yes it was a long time ago but I gave up on the compressor circuits as most of the circuits I messed around with never really got the sound I wanted. So thanks for the kind offer but not needed now. :tu:

For a while I'd given up on comp circuits but then that clever chap mictester at FSB posted his RSC (really simple compressor) circuit only using a dual opamp and a couple of LEDs.

I've learned enough about electronics to recognize which circuits have merit, You also pickup that some members are very talented people and worth testing there ideas.
Well I'm glad I followed my nose because Mictester's RSC circuit is just so simple and does exactly what I've always thought was possible. :dbtu: :dbtu: :dbtu:

There may well be better comp circuits around but this is all I needed.
The black finger circuit like a lot of others that use LM3080 the parts count is often high and IME a fair bit of trimming to get them to work well. :duh

While the RSC circuit is dead simple, requires no special parts no trimming needed, then add that it's also DEAD QUITE,,, it's a no brainer. The hardest part is making the LDR and LED package.

I've built 3 so far and one was was for me, incorporated into a 3 in 1 unit consisting of the comp, OD and cab sim with a simple passive boost at the output. I posted this whole circuit a while back so rather than repeating it all it's here;
https://www.ssguitar.com/index.php?topic=3923.msg30915#msg30915

Oh yes,,  I was in Nambour Qld but moved to Bairnsdale Vic,, long story.
Basically the music was great, lots of open mic gigs in East Gippsland, meet some great people but it's just far too cold and I'm an outside kinda bloke so I came back to the Sunshine Coast so I'm in Morayfield ~40 Khm's north of Brisbane.
I just looked up Macedon,, ouch mate that's probably even colder than East Gippsland,, you Victorians are obviously a tough bunch. Ice on the window is hard enough for me and if I never see Snow in my whole life I've missed nothing. I likes me sunshine a lot higher in the sky in winter. <3)
Phil.
Title: Re: Compressor Mods
Post by: tarahall on August 17, 2017, 03:24:03 AM
For a while I'd given up on comp circuits but then that clever chap mictester at FSB posted his RSC (really simple compressor) circuit only using a dual opamp and a couple of LEDs.

The black finger circuit like a lot of others that use LM3080 the parts count is often high.

While the RSC circuit is dead simple, The hardest part is making the LDR and LED package.

Oh yes,,  I was in Nambour Qld but moved to Bairnsdale Vic,, long story.
Basically the music was great, lots of open mic gigs in East Gippsland, meet some great people but it's just far too cold and I'm an outside kinda bloke so I came back to the Sunshine Coast so I'm in Morayfield ~40 Khm's north of Brisbane.
I just looked up Macedon,, ouch mate that's probably even colder than East Gippsland,, you Victorians are obviously a tough bunch. Ice on the window is hard enough for me and if I never see Snow in my whole life I've missed nothing. I likes me sunshine a lot higher in the sky in winter. <3)
Phil.

I must bboard that RSC up - standard 5mm green LEDs I think you said. The high parts count is not so much of an issue in lieu of my research into comp ideas. I noticed that you used LEDs as a switchable option in your LNC version of the ROSS. I thought of trying that whole CV section from Q1,2,3 & 4 in the LNC as the CV section for the 3080 in your slackfinger circuit. At the moment I'm really just compiling ideas.

I lived up at Noosa in the mid 70's - we played up there for a couple of years. Barry still lives in Yandina and he and I still keep in contact regularly. One of my old schoolmates lives at Mooloola and the band's ex roadie is down near Caloundra. It used to be a great place until they Sufferers Parasited it.

Gavan

Title: Re: Compressor Mods
Post by: phatt on August 19, 2017, 04:51:16 AM
Yes standard 5mm Green LED's (wired back to back) hard up against the LDR inserted into a short length of black shrink tube. The LED's I had on hand were water clear green but the frosted ones work the same. I have no doubt many types will work as long as they are not those high brightness units.
I filed the tiny flange at the base flat so they could sit together tight and parallel then a dab of super glue. A small black plastic plug or some black foam holds them in and keeps light out. see pic attached :tu:

Well small world, I used to frequent an open mic gig at Yandina (old Bowls club house on the main street) about 7 years ago. I was told it had run for many years but it's folded now. Your mate Barry likely remembers it?
I agree the Sun coast is not the same now.
Phil.
Title: Re: Compressor Mods
Post by: tarahall on August 29, 2017, 07:18:40 AM
Well small world, I used to frequent an open mic gig at Yandina (old Bowls club house on the main street) about 7 years ago. I was told it had run for many years but it's folded now. Your mate Barry likely remembers it?

Yes Phil. Barry vaguely remembers that there was an OM night but he never went to it.

As a matter of interest (to me at any rate) how did you find the noise floor in your Slackfinger circuit and how useful was the compression factor in it. I notice that the EH Blackfinger and the Morley Tel-Ray VCO pedal use similar implementations of the CA3080 in the FB network of an IC stage to achieve their comp setup as indicated by mictester as the preferred way of utilizing the OTA.

I never got a chance to use those 2 pedals live. I used to use an MXR Dynacomp many many years ago (back in the 70's). After using it on an album session at TCS in Melbourne I hated the sound of it when I listened to the playback and stopped using it after that. However as I have a few of these chips I thought I would experiment with them especially after playing with Rod Elliots Proj 27 and adapting it to use loudthuds JFET bender idea. I was impressed with the results.

Cheers Gavan
Title: Re: Compressor Mods
Post by: tarahall on August 29, 2017, 10:08:47 PM
Yes standard 5mm Green LED's (wired back to back) hard up against the LDR inserted into a short length of black shrink tube. The LED's I had on hand were water clear green but the frosted ones work the same.
Phil.

I haven't been able to see mictesters circuit, so did he use a vactrol and did you use your green leds with ldr instead of the vactrol.
thnx mate.
Title: Re: Compressor Mods
Post by: phatt on August 30, 2017, 07:54:57 AM
Hi Gavin,
          Re CA3080,, I'll roughly quote Mictester's comments and help from FSB feedback and comments about compressors in general.

IF you use the CA3080 directly in the signal path like Boss CS2 and many others then you have to put up with the noise.

The better way is like the Morley, Telray and some other rare ones, where the signal does not pass directly through the CA3080.

If you want a really good CLEAN Comp then hard to go past the Boss CS3 which uses  the "THAT" chip. wacky name but that is what it's called.

I had a Boss CS2 and a CS3 and a Marshall ED compressor as well as one of my ideas on a bread board all lined up and switching between them all the Boss CS3 was the Clear winner at low noise at high sustain levels.

It was around that point I found comments by Mictester who put me onto those other circuits. But by this time I'd lost interest in pursuing Comp circuits as none of them could deliver the combination of compression with distortion.
I then went into running a small power chip into a light bulb and re-amplifiying the result which worked ok but a lot of circuit for no real benefit.
Then I BBoarded the RSC and that worked. So yeah I'm happy with what I've got so end of story for me,, heck I do actually want to play the god damned guitar lol.

If you want the best the CA3080 can do then look at the Compressor circuit from the Lab series L5 amplifier. From what I've read and been told by people that know that Amplifier it can do the comp as well as distortion. BUT that's a lot more work than Mic's RSC. (hint)

There is a posting here somewhere on the L5 circuit but I can't find it right now

In answer to the Vactrols Q
No Mictester's circuit worked with green LED's and an LDR. Some may have tried the Vactrols but I doubt it would improve the result. I built all mine with the picture shown ,, 2 green LEDs and the LDR came from Jaycar Cat Number RD3485. You can build the LED LDR setup for less that $5  I doubt a Vactrol would be that cheap ;)

The only problem you may have with the RSC is if the input signal is too big and has too much bass it may fart out a bit,, but heck that is exactly what many $$$ Famous $$$ Valve amps do if you wind up the volume too far. Go figure 8|

If that is an issue then lower the input cap value and maybe raise the 220k series resistor to 330k~470k.
Cheers Phil.

ps; Mictester was there when the first Tube screamer was built,,,worked in the same factory,, I figure he knows his circuits  :dbtu:
Title: Re: Compressor Mods
Post by: phatt on August 30, 2017, 08:47:33 AM
Here is the Really Cheap Compressor circuit as posted by Mictester at FSB
The circuit inverts the signal so I used a TL074, adding a simple input buffer and the 4th part to flip the phase back.

I know some might think I'm picky but it's disconcerting when you stomp on a pedal and it flips the phase as the ears hear the phase flip as well as the effect which plays tricks on the interpretation of the actual effect. :grr
On stage it would never be noticed but makes it hard to define the change when you are A/B testing circuits. :duh

I've found that buffer stages are in all the high end gear and for good reason so I tend to use them a lot in my builds as you never know what you may end up plugging into.
Phil.
Title: Re: Compressor Mods
Post by: tarahall on August 31, 2017, 09:00:33 AM
Here is the Really Cheap Compressor circuit as posted by Mictester at FSB

Thanks Phil,

I have looked at most of these circuits on this forum and I feel grateful that others within it have done an amazing amount of work and research into ss guitar preamp. I don't really use guitar pedals much. I have a BOSS RE-20 reverb unit and a BOSS CE-20 chorus unit which both run in their own separate aux send and returns which I built into my amps.

I guess I should explain my interest in the CA3080 and compressor circuits in general. I'm not really interested in compressors for compression sake itself though. I have been impressed with the JFET bender idea of “Loudthuds” after patching it into Rod Elliot's Project 27 preamp. I'm more interested in the research into the use of that chip as per “Mictesters” spiel on its use to control the gain in the FB network of an IC.

First a little background:

Back in the Tinbeerwah Hall days with Barry & the Rockets I was using a VOX AC-30 Top Boost. When we moved into playing the Maroochy Pub I swapped it for a Blackface Super Reverb as I wanted a brighter edge with less mid-range hump than I was getting with the VOX. When I eventually moved back to Melbourne in 76, for the next 8 years or so used a Mk 1 Mesa Boogie up til about 85 when I started to use my original 2SK117 FET based Roland Cube 60 (original model - even the terminals are Wire-Wrap) which I bought as a practice amp. I replaced that horrible Roland speaker with a Celestion and it virtually fixed the whole sound of the amp in one fell swoop. I took it to use on a couple of small bar gigs and I've been using it (sometimes 2 for large concerts – I have another model of the same sort of vintage) ever since then after making some minor mods to the circuit. Thanks to Qantas dropping it last year on a flight to Brisbane to play the GO Show concerts it has not been working optimally (the bastards f..kd it) and owing to the number of times the PCB has been removed for minor mods & repairs I doubt that it will ever be the same as it was or as reliable.

The Cube was great using guitar straight in (no pedals) to the firstt stage (OD channel and driving the second stage (Normal channel). Responded similar to a Fender Deluxe or Super Reverb and cleaned up after backing off the guitar vol pot. It also had a similar punch factor like the AC30.
After 32 years of never having to replace a tube I figure it doesn't really owe me anything :) besides which I can always get backline hired for major concert gigs. But I still need a decent reliable amp.

However I'm now interested in moving into the SS IC-based guitar arena. I like Rod's guitar amp project and as part of my checking out of IC systems I've just built up the L5 preamp but I've yet to test it. I rather liked mictesters idea of using the CA3080 to control the gain in the FB network so I was curious as to how you found the EH Blackfinger circuit both noise & response-wise.

I would dearly love to get an IC based front end that responded similar to that Cube 60 or the Fender Deluxe & Super Reverbs with the punch of the AC30 to use with a decent power amp like Rod Elliots.
Title: Re: Compressor Mods
Post by: phatt on September 01, 2017, 09:36:09 AM
Opp's,, yeah sorry I now see that I did not answer your Q re the slackfinger Comp.

Well it's a long time back and I honestly can't recall all the circuits I tested but I can
remember that everything I tried seemed to need a lot of tweaking to get things to work.
As JM Fahey noted on page 1 of this post **getting a good control signal is a nightmare**. :duh :duh :loco :loco :grr :grr

The dreaded pumping as they call it is due to that control voltage and with CA3080 in the signal path Hiss is unavoidable.

I also had a *Moen compressor* for a while which was quiet, (due to no CA3080) it was an LDR/LED setup but still the control was not great and it pumped too much and was to aggressive on the

signal. I ended up slipping a shim of plain white paper between the LED and the LDR (can't do that if you use a Vactrol) which helped to back off the aggressive behavior.
As I don't own a scope and sig gen and, and, and all the other fancy gear I can only go on what I hear coming out the speaker. At my age I'm not about to start up a teck repair workshop,, I'm just a guitar player with a reasonable grasp of the workings of amps and associated electronics.

As to your wanting a good amplifier,, you could just build another Cube 60.
Or keep going with “Loudthuds” Fet idea? :tu:

My observation after many years of messing around with electronics,,, There is no right way to get the sound you want as there are so many ways that may well achieve the same outcome,, or close to it. Just find one that works for you.

Like you I've always hated pedals but I've ended up with my main rig being an old Laney amp (A keyboard amp in fact,  :lmao:) which is about as basic an amp as you can get.

The power section of most guitar amps is a world away from a valve power stage and although you can tweak a SS Pwr stage I doubt it will ever respond the same way as a Valve unit. I believe you will find some of JM Fahey's SS Amps use output transformers. (He runs his own manufacturing of top rate gear)
There is much debate about the benefit of using *Defined output Z* on SS pwr stages,, some rave about it while others not so much. I messed about with some of those ideas but could not find any real benefit. Peavey uses some clever SAt circuitry but all the Peavey amps I've used don't impress me.

Your comments about the sound you want do seem a bit contradictory as those amps are very different.   xP

But if you want the punch of an AC30 just use a cab sim circuit (it's built into my pedals, I could not compete on some stages without it. With the help of my tone control setup, cab sim and Compressor I can dial up country pickin clean with a nice edgy rattle and two stomps away I can do a ZZtop rip off.
I also have a builtin *Level shift* button on the master volume of the pedal board output which is way better than stomping on another dirt pedal as you often sound worse as most alter the tone shape as well as more distortion and everything turns to mud.

My advice to anyone wanting to build a great guitar sound is *Limit Your Bandwidth*
The problem with a lot of modern rigs is Waaay too much bandwidth.
you noted above that changing the speaker in the Cube amp worked wonders to an average amp.

I once swapped a really fancy speaker in a Trademark 60 for a $10 2nd Hand old Etone and the owner could not believe the night and day difference in tone and usability of the amp. That original speaker had extended bandwidth which turns OD into harsh crap and makes it sound like a cheap SS Amp. :-X

Rod's ESP amp is fine but for what you want you will need more than just the ESP preamp tone control to get the sound to cut through.

Distortion is not that hard to achieve but for any serious OD,, TONE SHAPING is CRITICAL for a convincing result.
Hope I've covered most of you questions,, Phil.
Title: Re: Compressor Mods
Post by: J M Fahey on September 05, 2017, 07:48:24 AM
 :dbtu: :dbtu: :dbtu: :dbtu: :dbtu: :dbtu:
Title: Re: Compressor Mods
Post by: tarahall on September 05, 2017, 09:20:11 AM
As to your wanting a good amplifier,, you could just build another Cube 60.
Or keep going with “Loudthuds” Fet idea?

I have given some thought to just cloning the Cube's PCB but I did like what the JFET bender sounded like when patched into Rod Elliots IC based guitar preamp.

Thanks for all your thoughts & ideas Phil plus the benefit of your research into the electronics of ss guitar.

Cheers
Title: Re: Compressor Mods
Post by: tarahall on October 17, 2017, 01:44:49 AM
Yes standard 5mm Green LED's (wired back to back) hard up against the LDR inserted into a short length of black shrink tube.
[/qu ote]

Hi Phil,

I breadboarded up the oscillator Rod Elliot's IC based tremolo circuit (http://sound.whsites.net/project29.htm) which works really well. So as an adjunct to making these LDR/LED units, which LDR did you use? Both Altronics and Jaycar carry the same 2 versions of these CdS cells

One is a ORP-12 equivalent: Dark 10m   to   Light 48k - 140k,

while the other one is: Dark 500k   to   Light 2k8 - 8k4,

I think the ORP-12 was what was used in the old Goldentones and the EA Playmasters 116/117 tremolo circuits

Gavan

Title: Re: Compressor Mods
Post by: phatt on October 17, 2017, 11:56:32 PM

This is the LDR I have used in 2 builds
https://www.jaycar.co.nz/large-light-dependent-resistor-ldr/p/RD3485
As you noted,, Jaycar sells 2 types,, while testing I found the larger unit seemed to work better.
Both types will work and they are not expensive,, I can't recall why I went with the RD3485 but it felt better to my ears.

I tested the circuit with TL072, LM883, LF353 and some 4558 chips that I had in the bitz box. They all seem to work the same with no notable difference.
Green leds have a special quality which is beyond my ability to explain,,, some time back there was a whole posting on the subject of LED colour differences and why some are better than others. Something to do with doping If I recall?
Phil.
Title: Re: Compressor Mods
Post by: tarahall on October 18, 2017, 01:36:27 AM
The super bright leds will drop the resistance to virtually zero from my tests so far with an old LDR from that original Playmaster 116/7 parts list, but that is probably not really what is required I suspect.

Varying between a few K up to 1/2 meg seems to make more sense too especially with that tremolo circuit where you want to vary the volume level up and down but not turn it completely off. I guess the same goes for that compressor circuit of mictesters that you utilize.

Standard green, yellow, orange and red leds gave varying degrees of resistance with that LDR with red & yellow dropping lower than orange and green. That LDR varies from 10m+ (Dark) down to virtually zero (Light) using a white led.