All about buffers and a dual compressor build.

[thegnu]

Howdy.

I'm going to be building a few things, but #1 on my list is a dual compressor with a buffer to go at the beginning of my signal chain.  The plan is to just get the OSQ and Ross boards from GGG for simplicity's sake, and house them in a single enclosure with a buffer.  The signal chain will be: guitar > buffer > OSQ or Ross > buffer? > out.  I'm going to have an on/off switch, and a mode switch for Ross/OSQ.

I was thinking of the AMZ IC buffer, as it's super simple.  As for the blending, I notice the B. Blender is just 4 of these, one on the input and output of both dry and wet.

My questions:

1. If I forgo the blender, should I put the buffer at the end of the compressor?  I figure this will give me low impedance for whatever pedal comes next, and I might as well use the other side of my opamp.

2. If I decide to do the blend, is it really necessary to buffer the output, or could I just buffer the beginning of the dry and wet signals, then blend them together?

3. Would you recommend a different buffer?  A different opamp from the TL071?  I've got super bright pickups, though I can always just use my tone knob or the tone on the amp.  In fact, I did that today.

4. Any upgrades for the OSQ/Ross you recommend?  I'm not looking to add a million switches to my pedal, and I'm already going to be using metal film resistors and good caps where possible.  But maybe you've found some sweet tone differences with some small changes in certain places.

5. I don't know anybody with a bicomprossor.  Would you recommend cascading them into one another instead of doing either/or?  Or whatabout blending them?

I apologize for the noobish questions, but I'm about to spring for parts, and I'm pretty broke at the moment.

The plan is to put this compressor at the beginning of my signal chain, rebuild a TS clone I built last year without all the sludge and with a buffer on in/out, and throw an SHO clone on the end to drive my amp.  Those are going to be my buffers/line drivers in an 8-pedal signal chain, save perhaps for my Pearl Octaver.  Is there anything else I should consider before I jump in up to my elbows in this crap?

Thanks in advance.

[merlinb]

1. If I forgo the blender, should I put the buffer at the end of the compressor?  

It would be the professional thing to do, yes. Especially if you have a free opamp just lying around...

2. If I decide to do the blend, is it really necessary to buffer the output, or could I just buffer the beginning of the dry and wet signals, then blend them together?

You don't have to buffer the output, but it's good practice.

3. Would you recommend a different buffer?

That buffer is perfect, and the TL07x is a low current, FET opamp. They don't come much better for guitar work.

5. I don't know anybody with a bicomprossor.  Would you recommend cascading them into one another instead of doing either/or?  Or whatabout blending them?

It is a bit weird, having two basically-identical effects in one box. Seems kinda like a handicap to me when you could build two compressors (i.e. separate boxes).

[thegnu]

Thanks for the advice on everything.  It's good to get a second opinion, as I've made some odd decisions in the past, to say the least.  

It is a bit weird, having two basically-identical effects in one box. Seems kinda like a handicap to me when you could build two compressors (i.e. separate boxes).

Well, the intention is to have two flavors of compressor that i like in a single box that can fit on my pedalboard, replacing my godawful CS-3, and provide a buffer for the beginning of my signal chain.  I suppose i might be better off with the DOD 280a circuit from GGG paired with either the OSQ or the Ross, though I haven't heard it before.  

If I had money, I'd got a Strymon OB-1 to play with, but that might just be GAS.

EDIT:  though i suppose you've got a point about just building two separate pedals.  it would be much simpler to just build a kickin' osq in a small box, and just live with that.  i'm in line to receive an old block font dynacomp, so other than not wanting to throw it on my board, i'll be pretty set there.

[eddie_bowers]

I would buffer both if you are going to blend.  Essentially if you don't have a buffer on the output you are relying on the buffer of the next device in the chain, so your effect may sound different depending on the next pedal (maybe not a huge deal).
One thing that you need to consider is that the OSQ (not sure about the ROSS) is very sensitive to input impedance.  When you use a buffer your input impedance is going to be MUCH lower than when a guitar is plugged straight in.  You can add a resistor in series (10-15k) after the buffer to simulate the guitar impedance.

[Processaurus]

I made a pedal like you're thinking of.  It's great.  Putting two similar pedals in one box is great, when you like both flavors but it would be prima donna to have two separate compressors on a pedalboard. 

I just ran mine serially, with true bypass footswitches for each, Ross --> OS, but never found the sound of them on at the same time to be anything magical, it's just really noisy.  I don't think you need to buffer the input or output of those effects.  Actually I did buffer the input of my Ross, because it had some tonesucking, but I think in retrospect that was because I had a cap value wrong on its input.  If you're into having a buffer, maybe buffer the pedal output, after the bypass switching.

What you mean by blending?  I wouldn't blend the OS and the dry.  The Ross and dry is nice, I made a circuit to work with the quirks of that circuit, if you're interested.

[brett]

Hi
JFET buffers are much simpler, smaller, lower current, but same effect as IC buffers.
cheers

[petemoore]

 Know what impedance mismatch is, and how to recognise it.
  There are ways to avoid, work around, or supply sufficient drive current so that the current load doesn't matter.
  Otherwise a buffer/low impedance/plenty of current driving capability is usually just nice to have on an output that doesn't know what the input it will drive is. It is a convention followed by convention creating pedals.

[frequencycentral]

I've done a couple of dual compressors, Flatline and Dyna in the same box. Switchable, not cascaded. Flatline for dynamic control, Dyna for compression as an effect in itself. Pretty useful, and the two circuits react so differently that it's valuable. It's useful to be able to switch between two sets of settings. I did consider cascading but it seemed to me that compressing an already compressed signal was a little pointless, whereas toggling between the two was worthwhile and desirable. YMMV.