Xotic Effects - Super Clean Buffer (SCB)

[matoni]

Hello,
I haven't seen anyone do this yet, so I thought I'd get one and trace it! Please let me know if there's anything that you see that looks obnoxiously wrong, or if there's anything that you think I may have missed.

[karul]

Are you sure about the value of C12 = 10nF ? Isn't that too big? It should be in pico range, if I'm not missing something.

Can we see some photos of the pcb's ?

[matoni]

you may be correct about C12 being smaller, it is very possible that I mismeasured. I didn't test the buffer section of the circuit, only the boost, so I couldn't tell you. I will try to remember to upload pics of the PCB if I get a chance.

[george giblet]

Without any info I'd be putting C12 as 100pF.

The buffer stage has some loose similarities to the Cornish buffer, which actually doesn't use an input cap.

[aion]

Can you double-check the value of C8, the bass boost cap? The Super Sweet is almost identical, but mine measured 112n and this one was 200n, both of which are on the very edge of a 10% tolerance of 100n and 220n respectively, so I am wondering if one or both of them could have been measured wrong. It could be a difference between the Sweet and Clean, but that's the only part of the schematic that I would wonder about. (C12 is definitely 100pF.)

[karul]

hi pass filters freq as per schematic (comparison if C8 is 220n or 100n)

159 Hz - mid boost (100n & 10k)
72 Hz - mid boost (220n & 10k)

98 Hz - low mid boost (62n||100n & 10k)
56 Hz - low mid boost (62n||220n & 10k)

318 Hz - high mid boost (100n & 5k)
145 Hz - high mid boost (220n & 5k)

I can't see any filter for bass boost, the C8 is bypassed when the switch for bass boost is on

and this is from xotic manual
the gray one is for the Buffer, the red one is for the Booster

the freq are not the same, so the capacitor will be different, if everything else is the same

[aion]

and this is from xotic manual
the gray one is for the Buffer, the red one is for the Booster

I didn't notice those on the site, but I would be really skeptical that they're accurate. Notice that the actual graphic of the frequency plot is 100% identical between the two, they just shifted the frequency & amplitude scales on the bottom and left for the Super Sweet.

The Super Clean looks more intentionally designed, so I would bet it was done first. The Super Sweet is just a lazy edit and should not be taken seriously. According to the graphic, most of the differences between the DIP switch settings are well above 16kHz!

[Ichabod_Crane]

I looked at the graphic in the past, and it seems a bit weird to me, too.
I'll try to emulate the schematic we have above.

[aion]

Can you double-check the value of C8, the bass boost cap? The Super Sweet is almost identical, but mine measured 112n and this one was 200n, both of which are on the very edge of a 10% tolerance of 100n and 220n respectively, so I am wondering if one or both of them could have been measured wrong. It could be a difference between the Sweet and Clean, but that's the only part of the schematic that I would wonder about. (C12 is definitely 100pF.)

I grabbed another Super Clean to verify and C8 is definitely 100n (measured 106n). If you measured it in-circuit, then C1 may have been directly in parallel depending on the DIP switch settings, but at the very least there is other capacitance in the circuit that would impact the measurement.

Finally finishing up the PCB design on this after resolving a few questions on my original trace. I'm hoping to fast-track the release for sometime in September assuming all goes well with the prototype. Once it's released, I'll post my schematics for both units here.

[aion]

Here's the SCB schematic. Only two components are different from the SSB: the Gain pot and a single resistor that sets the gain ratio and also the frequencies of all the DIP switch settings. It's a lazy cash grab splitting it into two pedals like this, but I can understand it's hard to market a single pedal and convince people that it does both jobs equally well. It's a good circuit.

Schematic:

Xotic Super Clean Buffer schematic

Some differences from the schematic posted earlier in the thread, just a couple of values which were probably measurement errors in that schematic. But I believe all the connections were correct, so good work!

Full tracing journal here: (SCB and SSB covered in the same article)
https://aionfx.com/news/tracing-journal ... eet-boost/

PCB available here: (SCB and SSB on one board)
https://aionfx.com/project/xanthus-buffer-boost/