Looking to restore some highs in the signal . . .

RD

Generally, no - not without changing the character of the compressor (see Ross clones) or introducing a lot of noise. A compressor increases the gain on small signals, coincidentally all the noise is perceived in the high end as well.

If your compressor doesn't have enough high end, IMHO that's part of the design of the pedal. Time to get a new (more transparent) compressor!

What type of compressor is it? Sometimes there are things that can be done to help.

Head

The Tone Press blends in clean signal which adds highs. The BOSS CS3 has an EQ knob.

quote:

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Originally posted by Headshot:
What type of compressor is it? Sometimes there are things that can be done to help.

Head

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Hey Head,

This is my Atomic (Ross type). You may recall that I had asked you about this previously, and you were going to look into it. Any ideas?

Thanks as always!
RD

davei is correct. Most comps have a fair amount of high end filtering to reduce the line noise the comp amplifies.

The Blackbox Oxygen does not have all that filtering so your tone will stay intact. To combat amplified line noise, it has a built in noise gate that can be used to quiet things down when you're not playing.

Definitely can't do anything (or much) with a Ross type. The circuit kills highs before the compression circuitry to reduce noise, then boosts the highs afterwards to partially restore them. Try to "fix" that and you lose the character of the pedal.

As usual, you might want to try a $20 Dano EQ pedal for general tone shaping.

quote:

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Originally posted by davei:
Definitely can't do anything (or much) with a Ross type. The circuit kills highs before the compression circuitry to reduce noise, then boosts the highs afterwards to partially restore them. Try to "fix" that and you lose the character of the pedal.

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But can you mod the circuit before the compression circuitry so it does not kill the highs as much? Or can you mod the circuitry after the compression circuitry so the highs are boosted more?

The Atomic is very quiet now, so a little added noise would not be a problem.

RD

RD,

I have a Ross clone that I built that does kill a little high end, but not too bad. I'm not after a super bright sound, so it works ok for me. I built my pedal with very high quality parts, so it helps to avoid as much tone/high end loss. I would assume that the Atomic uses qualtity parts as well. Just how much high end are you losing? What kind of setup do you have, and what are you trying to achieve with a compressor?

Head

Hi,

It's been a long time since I had a ROSS or the
MXR.....never seen the Atomic
Anyway I believe I answered this once before.
Asuming this is dealing with the same circuit
below is what can be done
Perhaps Head will do the honours

Oh just one note: the transconductance varies the outputimpedance of the 3080 and that works into the load of 150K//1n0// Zi of phase splitter so this filter varies with gain.....

quote:
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Originally posted by Rockin_Dachshund:
I'm wondering if it is just a matter of swapping a cap or two in the circuit . . .
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Hi,
Yes it is. One could say the ROSS is an upgrade of the original MXR in terms of a coupple of transistors, but the circuit is the same more or less.
To swap out the noise that the CA3080 Operational Transconductance Amplifier has, a filter technique is used, that boosts the treble at input, as set by one resistor and one cap, and then a cap at the transconductance output.The way this noise reduction is applied in the circuit makes it impossible for the filters to align for minimum loss, but it serves the function to cut down wideband noise that would result if the filters were removed.
ONe can lessen the trebleloss in two ways: Either by connecting a resitor in series with the capacitor at output ( the one that is in parallel with the 150K) or one can adjust the value of this cap to a slightly smaller one.
In the original MXR circuit these caps were ceramic types of poor tolerance and losses may vary from unit to unit. This was the same in the ROSS. In the Keeley Compressor these are plastic types and consequently better match - still highend loss though.
One thing to bear in mind with this circuit is that the trade off for less trebleloss is noise.
To make this work real well one would have to change a few more things and rearrange the filter at output to swap out the noise but retain the treble, and then one could think of other things to do to extend the input range and the attack and release times.
Ah well the simplest thing to do is to connect a series resistor trimmer to the cap in parallell with the 150K and tune to something more 'T'
Just a thought
BJ

BJ....

Can you be more specific??

Just kidding. Thanks again for a very thorough answer. You never fail to impress me!!

Maybe I will mess with my ROSS clone, and see how this affects the circuit.

Head

Found this somewhere but it originally came from Jack Orman.

Now I am not a compression expert but the nature of the beast I'd say if you wanted to keep your highs don't use a compressor.

There are mods that can be done to compressors to make the highs and low come out more but from what I had experimented with they lessened the original squash of the pedal. I did a hi-fi mod to an MXR Dyna COmp and thought it sounded better when I got finished with it but it remains difficult for me to judge in that effects like these sound unnatural to my ear to begin with.

quote:

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Originally posted by Headshot:
BJ....

Can you be more specific??

Just kidding. Thanks again for a very thorough answer. You never fail to impress me!!

Maybe I will mess with my ROSS clone, and see how this affects the circuit.

Head

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Ditto -- great stuff from BJ!

I'm going to take a look at the Atomic circuit and try some of BJ's suggestions.

RD

quote:

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Originally posted by BJF:

ONe can lessen the trebleloss in two ways: Either by connecting a resitor in series with the capacitor at output ( the one that is in parallel with the 150K) or one can adjust the value of this cap to a slightly smaller one.

Ah well the simplest thing to do is to connect a series resistor trimmer to the cap in parallell with the 150K and tune to something more 'T'

BJ

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Any suggestions on the value of the resistor/trimmer?

Hi,

Hm, yes Head, I could be a bit more specific I guessPerhaps best results would be gained from connecting a small value cap like 220pF instead of the 1n0 and then connect 50K trimmer in series with the 1n0 and then trim highend.
This would put a limit to the wideband and shift corner frequency upwards to make loss less noticable. To cut down input noise a trimmer, of 1K0 could be connected in series with the 10nF cap - trim for a slight drop in
inputnoise.


The 2:1 compression as shown in the picture is what you can find in application note AN176 regarding use of the compander chip NE570/571/SA571.
If I remember correctly it was stated in the MXR catalouge of 1979 that the Dyna Comp had a compression ratio of 20:1, which is severe compression.
The most common problem with the early ic designs (transconductance type) is the noise
and especially at high compression ratios.
This is most often compensated for via noise reduction filters, similar to the kind used in dbx systems.
I believe Craig Anderton proposed this filtertechnique be used on raspy fuzzes in a GP article 1980- the principle being that you'd boostat the input with about 20dB 8Khz and a slope of 6dB/octave and thus flat at 800Hz.
Then treble level is kept high through processing.At the ouput treble is lowered by the inverse, thus starting at 8KHz 6dB slope and then flat at 800Hz. This gives a percieved noise reduction of 12dB. Variations of this filter technique is widely used so also in the MXR Dynacomp and it's siblings, only this time
a few parts have been saved and the filters made at strategic spots in the circuit. Now these filters do not align and therefore a portion of the treble is lowered. It would take presicion componets to make a noisereduction like this that perfectly aligns....

High compression ratios will drastically diminish the twangy quality of a guitar.
With a dynamicrange of 80dB or 10000 times difference between the lowest signallevel and peak a bit of compression can be used to make
the guitar more audible,and this may be necessary in recording and at liveperformance, though, as stated above shrinking the dynamic range will also change the caracther of the instrument. Sometimes one might need to do that to compensate for less sensitive spots on the neck.
In many ways compression is best used so that
it is not noted as compression but that you miss it when it is removed. While of course there is no wrong way.

I would agree George, this effect is hard to judge and even a compression ratio of 2:1 is
quite enough.
Still my major complaint with the MXR was that it messed with the treble and never was as bright as the bypass.
Compare with the Levelar, that retains the qualities of sound.
I am curious to what hifi mod you did on yours

Thoughts
BJ

i use a eq pedal and dial in just what i want.
(after the compressor)

Here's something interesting: I'm looking at the inside of the Atomic compressor and am comparing it to the Ross specs.

The Ross specs call for six 1uF radial electrolytic caps and two 10uF radial electrolytic caps.

However, at least SIX of the radial electrolytics in the Atomic are 10uF. There are only two or three 1uF. Plus, there is a 100uF radial electrolytic in there -- this is not in the Ross specs. Could these high cap values be the reason for the tone loss in the Atomic?

RD

Anybody home?

Hmmmmm... I don't think that's the cause of the high end loss. Most of the highs are lost where BJ talked about. Those higher values should actually "help" let more highs through, depending on how they are used.

Obviously the Atomic is not a direct clone of the Ross, but it could be similar. I've never played or even seen one, so I can comment.

What type of music are you playing, and what kind of gear do you use? What are you looking for your compressor to do?? (limiting, hard squash, sustain, more for an "effect" or for transparency?) Compressors are kinda finicky animals.

Head

quote:

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Originally posted by Headshot:

What type of music are you playing, and what kind of gear do you use? What are you looking for your compressor to do?? (limiting, hard squash, sustain, more for an "effect" or for transparency?) Compressors are kinda finicky animals.

Head

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I like to use a compressor to get a plucky, squished sound, not for transparency. The Atomic gives great squish, but is too dark -- even at low sustain settings.

I think I'll try BJ's advice -- hopefully I can find the right parts inside the Atomic!