Stacking overdrives/ buffer issue?

[888guitars]

I am going to try to true bypass one of my Boss overdrives because I think the buffer might be the reason I get too much squish/compression when stacking overdrives. Tube screamers don't have this problem but, I don't think the buffer in the TS is as "GOOD". Maybe the downfall of the good buffer is whats keeping me from a good overdrive stack with the Boss stuff? Ideas?

[Richard]

So when the Boss OD is off you get strange response from a pedal further down the chain compared to removing the pedal and plugging straight in to the next pedal? If you list your pedals and the sequence it may make the discussion clearer. I don't know it if interests you but there are effects loop pedals that have many options for routing and switching and buffing. Some are pretty spendy though.

[888guitars]

Nope. When using 2 overdrives together. Say a tube screamer into a boss sd1. Crank the level of the screamer and see how well the boss will take the gain. Not great. If you swap the pedals, the screamer takes the gain quite well. So I am going to pull the buffer in the boss and see if it's better.

[Steve A.]

I am going to try to true bypass one of my Boss overdrives because I think the buffer might be the reason I get too much squish/compression when stacking overdrives. Tube screamers don't have this problem but, I don't think the buffer in the TS is as "GOOD". Maybe the downfall of the good buffer is whats keeping me from a good overdrive stack with the Boss stuff? Ideas?

When I stack dirt pedals I try to keep the volume at unity (or just a little bit higher for a slight boost) and the gain not too high. It works great even if some of the pedals are not true bypass although I haven't tried stacking any Boss pedals. I've mainly been experimenting with the more transparent low to medium gain pedals...

I've heard that germanium fuzz boxes do not like buffers so you either hook them up directly to your guitar, or from guitar->wah->fuzz if you want to do the Jimi Hendrix thing...

Steve Ahola

EDIT: After reading your second post I think that the SD-1 might not be able to handle the signal level from a cranked TS. Unity level plus a smidgen seems to be the key when stacking dirt pedals unless you are going for Mondo Distortion...

[Steve A.]

In comparing the schematics of the SD-1 (the first) with the Tube Screamer I see that the SD-1 has a 1M gain pot in the feedback loop of the 1st half of the 4558 op amp while the TS has a 500K pot. For the 2nd half the SD-1 uses a 10k resistor in the loop compared to 1k for the TS. That could account for more gain in the SD-1 which is why feeding the signal from the TS into it is causing it to "go bananas," to use the technical term.

Changing the SD-1 from buffered bypass to true bypass is not going to make a difference when both pedals are on as can be seen on the schematic.




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Steve Ahola

[Richard]

Yeah, I was thinking that when a pedal is turned on then it becomes a buffer. Different pedals will have different output and input impedances that can cause strange stuff. I try to keep my pedals at unity gain but when I run my Plush Cream distortion into my Bogner Ecstasy Blue it has a bump in level. It's actually nice having the boost. I agree, Steve, I don't think making the OP's pedal true bypass will solve his issue.

[888guitars]

But I'm thinking that if I get around Q1 it will not squish as much. Not a good squish

[J M Fahey]

1) I donīt think you have a buffer problem.

2) those pedals clip in a different way

a) the TS clips somewhat less *and* lets some clean signal go through and get mixed with the clipped one, so it does not sound *so* compressed, even if way overdriven. Thatīs the way it is.

b) the DS1 clips hard and does not let clan signal through,so it appears to compress more.
Ok, not "appears" , it does compress more.

If you drive it with the signal from another distortion pedal, it will compress even more, thatīs the way it is.

So what you hear is not surprising ... and buffers are completely unrelated to the way the respective pedals distort, which depends on where are the diodes and the way they distort.

[888guitars]

J M , the DS 1 definitely clips different. I was talking about the S D 1. Pretty similar to the TS. Anyway I will have my results later today.

[Steve A.]

Juan, what function does the initial transistor stage serve in the SD-1? I suspect that it amplifies and buffers the signal from the guitar and that without it the following stages would not be driven properly.

888guitars, some stacked combinations of pedals do not work as you would like them to, especially if you overdrive Pedal B with Pedal A hard.

Richard, I, too, like to experiment overdriving Pedal B with Pedal A, especially when Pedal B is a low to medium gain dirt pedal. BTW in many pre-stacked two-in-one pedals (like the Jetter Red Square) they put the lower gain pedal AFTER the higher gain pedal. But in general I like lower gain overdrive not unlike a vintage tube amp.

Steve Ahola

[Richard]

Yeah, the Cream into the Ecstasy is an over the top shred tone, I'm happy with it because I don't use that tone a lot so I don't have a pedal set up for that. No other combinations give me the volume boost, everything else is close to unity gain.

[pdf64]

Steve, re the 1st transistor http://bmamps.com/Schematics/Boss/Bo..._Schematic.pdf
Q5 is an emitter follower / unity gain buffer.

Yes, the SD1 is rather similar to a TS, the main difference being that the back to back clipper diodes have been made a series pair on one side, to add some asymmetry to the clipped wave.
As with the TS, the clipped wave will ride on top of the (buffered) input signal.