CS-3 Opto/Ultra Plus/Opto Plus Differences?

[hellbent_Nivek]

Though I've search this site for this answer, I figured I might post something for once.

I'm looking to mod a CS-3 for the fun of it and since I've managed to obtain 3 of them. I'd like to mod one since I'm always looking for a cheap easily replaceable compression for my stage rig.

So before everyone tells me I could do better than the CS-3, Ive tried a ton pedals and have read threw Bongo's threads "genius by the way". And really like the BBE Stomp and DOD Milkbox. So one being limited on controls and the other being hard to find. I need a work horse that works with a poor musician budget. And stage and tour really, where if one of them breaks it can be replaced quickly.

Expensive pedals are rad, but if broken... yer stuck.


So back to my question:


Can someone explain the differences between the CS-3 Opto/Ultra Plus/Opto Plus? And would it matter for bass? "Also to add, all my basses are active p.u's"

http://www.monteallums.com/pedal_mods.html#cs3opto

Just to add, I was running threw a friends rig at a show. And he has a LMB-3 at the front of the chain "all limiter settings" and a mod'd CS-3 with the Opto right after that. And it sounded f'n awesome for stage work. It blew me away.

We have similar styles hard to soft playing, so it worked out get.

So please don't bash the newbie for beating a dead horse. This has been a question on my mind for a while. And just want to get the right mod.

[Silent Fly]

Originally Posted by hellbent_Nivek

Can someone explain the differences between the CS-3 Opto/Ultra Plus/Opto Plus? And would it matter for bass? "Also to add, all my basses are active p.u's"

http://www.monteallums.com/pedal_mods.html#cs3opto

My understanding is the following:

CS-3 Opto Mod: general improvement
CS-3 Ultra Plus Mod: further improment compared to the CS-3 Opto Mod with (among other things) replacement of the ICs
CS-3 Opto Plus Mod: exacly like the CS3 Opto Mod but with new ICs

[hellbent_Nivek]

Cool, just general improvement then. I was curious as if this was a change in sound. Sweet, thanks a ton.

[cybersnyder]

I have the Ultra Plus Mod and I'm not sure that it's all that great for bass. Guitarists seem to like it a lot.

[bongomania]

Good point there--an "improvement" is not the same as a "mod so it works well on bass". You'll want to raise some of the capacitor values, for bass.

[hellbent_Nivek]

Originally I wanted to go this route:

http://www.ovnilab.com/articles/cs3modding.shtml

But I figured that maybe Monte Alum's would be the way to go? Also, does anyone have a Online one spot shop that could have all the parts I need for this mod? I have a local shop in my town, but I like to research.

[Silent Fly]

Originally Posted by hellbent_Nivek

Originally I wanted to go this route:

http://www.ovnilab.com/articles/cs3modding.shtml

But I figured that maybe Monte Alum's would be the way to go? Also, does anyone have a Online one spot shop that could have all the parts I need for this mod? I have a local shop in my town, but I like to research.

I would add the following mod to the ovnilab page:

C5 = 1nF (original value: 1.8nF)

It increase the frequency of the internal LPF from 8.8kHz to 15.6kHz.

[bongomania]

Cool, thanks for the tip. Just so I understand, what is the specific benefit of raising that LPF value?

[Silent Fly]

Originally Posted by bongomania

Cool, thanks for the tip. Just so I understand, what is the specific benefit of raising that LPF value?

It improves the high frequency response.

<technical explanation>
Essentially, with the LPF set to 8.8 kHz everything above 8.8 kHz is cut with a 6dB slope. Which is ok with electric guitar but it’s not so good with bass - especially if it is played slap with stainless steel strings.

From the circuit viewpoint, there is an op-amp in inverting configuration with a 10k resistor in parallel to a 1.8n capacitor as feedback network. f = 1/ (2*PI*10k * 1.8n) = 8.81kHz.

After the compression, the signal goes straight into the op-amp.
</technical explanation>

It is not a crucial mod but it can add a little bit of clarity to the signal.

[hellbent_Nivek]

Nice, thanks for the breakdown. I'll post my outcome as soon as Im finished with the mod.

[boomertech]

The schematics that I have (not factory schematics) for the CS-3, shows C5 as 560pF and R6 as 33Kohm resistor. However, with those values the HF attenuation still remains near 8.6KHz as Silent Fly points out. Boss may have increased the value of R6 to lessen the loading that the op-amp has to deal with… or my schematics just have the wrong values. There is also a +/-10dB HF boost/cut tone control following that stage that can be used to significantly brighten the signal to the output buffer.

One thing to consider is that the HF attenuation that C5 and R6 provide is part of the attack response in the side-chain. Since these “OPTO” modifications smooth out the attack with the VCA (slower response), increasing the frequency response or lessening the time constant for the integration may negate some of the benefit that the mods provide.

IMO, I wouldn’t change the filter cap for a higher frequency response. Since traditional OPTO compression is fairly slow in its response (with respect to a VCA), possibly decreasing the HF at this point (slightly larger C5 cap) may actually be beneficial in achieving a bit more of an “OPTO” type of response. The tone control has plenty of HF gain to make up for it.

Again, this is just my opinion.

-Frank

[NickInMesa]

Originally Posted by Silent Fly

I would add the following mod to the ovnilab page:

C5 = 1nF (original value: 1.8nF)

It increase the frequency of the internal LPF from 8.8kHz to 15.6kHz.

Interesting. I have done this mod already, maybe I could try this other one as well. I have one cap left.

I know, it's getting old for some but here is the internal view of the CS-3 modded following Bongo's specs:

[Silent Fly]

Originally Posted by boomertech

The schematics that I have (not factory schematics) for the CS-3, shows C5 as 560pF and R6 as 33Kohm resistor. However, with those values the HF attenuation still remains near 8.6KHz as Silent Fly points out. Boss may have increased the value of R6 to lessen the loading that the op-amp has to deal with… or my schematics just have the wrong values. There is also a +/-10dB HF boost/cut tone control following that stage that can be used to significantly brighten the signal to the output buffer.

One thing to consider is that the HF attenuation that C5 and R6 provide is part of the attack response in the side-chain. Since these “OPTO” modifications smooth out the attack with the VCA (slower response), increasing the frequency response or lessening the time constant for the integration may negate some of the benefit that the mods provide.

IMO, I wouldn’t change the filter cap for a higher frequency response. Since traditional OPTO compression is fairly slow in its response (with respect to a VCA), possibly decreasing the HF at this point (slightly larger C5 cap) may actually be beneficial in achieving a bit more of an “OPTO” type of response. The tone control has plenty of HF gain to make up for it.

Again, this is just my opinion.

-Frank

Interesting comment Frank.

I think we have a different schematic. In my version there aren't any 560pF capacitors.

I may be wrong but I think the LP filter is there to mitigate the noise of the circuit more than changing the attack time of the compressor. Even if this was the case, the time constant is 1/8.8kHz = 0.1msec. With 1nF capacitor it should be 0.064msec. I am not sure but I don't think it would make any audible difference from the compression viewpoint.

Personally, I would try anyway. The worst that can happen is that it sounds better with the original capacitor and it takes 5 minutes put back the stock value.

[boomertech]

Originally Posted by Silent Fly

I think we have a different schematic. In my version there aren't any 560pF capacitors.

You show me yours and I will show you mine… The version that I have matches a pic that I found on the GOOGLE. It is very possible we may have different versions of the same circuit.

Originally Posted by Silent Fly

I may be wrong but I think the LP filter is there to mitigate the noise of the circuit more than changing the attack time of the compressor.

I agree 100%. I initially thought the same, but I wanted to research it further. After posting above, I read several comments (again from the GOOGLE) from owners of these pedals that completely validate your statement. I believe the designers needed to put the corner frequency there for that reason. I’m not trying to be difficult… but I think that increasing the HF will only restore what the original design was trying to remove. That filter being located where it is also helps to reduce the noise in the side-chain circuit. I have great respect for Boss/Roland engineers and they seem to always have a very logical reason for their designs.

OTOH, the mod kits that the OP is interested in may reduce the circuit noise to the point that increasing this filters corner frequency would be beneficial. I would try it on a modded unit.

Originally Posted by Silent Fly

Even if this was the case, the time constant is 1/8.8kHz = 0.1msec. With 1nF capacitor it should be 0.064msec. I am not sure but I don't think it would make any audible difference from the compression viewpoint.

I agree about the attack response. Especially when the "OPTO" mods should slow the attack time elsewhere in the circuit. I have had the pleasure to work with colleagues that are VERY, VERY rigid with synergetic circuit design. So, I blame my knee jerk reaction on them…(their voices in my head are still saying nooooo--- if you need to change it, go the other direction!!)

Originally Posted by Silent Fly

Personally, I would try anyway. The worst that can happen is that it sounds better with the original capacitor and it takes 5 minutes put back the stock value.

Absolutely! That is what makes this work so enjoyable! I am totally on board if you want to put your 1nF cap in my CS-3 schematic.

-Frank

[Silent Fly]

Originally Posted by boomertech

(...) I believe the designers needed to put the corner frequency there for that reason. I’m not trying to be difficult… but I think that increasing the HF will only restore what the original design was trying to remove. That filter being located where it is also helps to reduce the noise in the side-chain circuit. I have great respect for Boss/Roland engineers and they seem to always have a very logical reason for their designs. (...)

+1

Thinking about it... you are probably right. If the filter is there, there must be a good reason.

(Don't worry about being difficult. As I see it, the best way to learn is being challenged with interesting ideas )

Originally Posted by boomertech

Absolutely! That is what makes this work so enjoyable!

+1

(I’m seriously thinking about buying a CS-3 and experimenting with some mods )

[hellbent_Nivek]

See the beautiful thing of the CS-3, they are cheap and a dime a dozen. Ya dont feel bad if they break and if you do. Another 50 bucks "parts+pedal on ebay" you have a road ready pedal!

Thanks to nickinmesa for the pic too and of course boomer, s.f., bongo. You guys really fill in some gaps. Thanks a ton

[hellbent_Nivek]

Also, should I use polyester caps? What do you guys recommend for the type of caps and resistors for audio devices? Or pedals?

[NickInMesa]

Originally Posted by hellbent_Nivek

Also, should I use polyester caps? What do you guys recommend for the type of caps and resistors for audio devices? Or pedals?

No you don't have to use polyester caps, they are just better for audio but you don't HAVE to. Also making them fit was a bit of an issue, hence the long terminals (which I had to wrap).

They use small caps like tantalum or eletrolytic because they are small and cheap and so can you.

[hellbent_Nivek]

parts are cheap, so that doesnt matter. I was thinking if I could use better parts and the price of which is really only a couple dollars. Why not, but as a over all question that seem to get left out of forums.

Yes, Ive done searches. But nothing ever shows what should be for low noise. Other than not to use ceramics... anything else should be cool? Like radioshack parts? I know they are all the same anyways, but Im a firm believer in doing things right the first time.

But I hear ya Nick

[NickInMesa]

Originally Posted by hellbent_Nivek

parts are cheap, so that doesnt matter. I was thinking if I could use better parts and the price of which is really only a couple dollars. Why not, but as a over all question that seem to get left out of forums.

Yes, Ive done searches. But nothing ever shows what should be for low noise. Other than not to use ceramics... anything else should be cool? Like radioshack parts? I know they are all the same anyways, but Im a firm believer in doing things right the first time.

But I hear ya Nick

Radio Shack is not your least expensive option but they do have nice assortments of electrolytic caps, resistors, leds which makes them cheaper than online vendors if you factor in shipping vs sales taxes.

If you want to get into that hobby, best option is to look on eBay for someone getting out of it.

Small Bear has a good assortment of parts, bulk everything into one big order, that way you save on shipping.

Fry's Electronics in the West has a lot of parts but they are not always stocked well. Their staff is not as knowledgeable as it once was and they now know more about computer parts than components.

Radio Shack is still a great American tradition that I hope they will keep alive, unless the big stores like Best Buy start selling components to take over this responsibility.

I think that a lot of what makes America unique is the hobby tinkerer who makes stuff out of his garage and if nobody sells components in residential areas anymore, this uniqueness may expire.