Mad Professor Ruby Red Booster

RnFR · Post by **RnFR** » 10 May 2011, 06:25

that's a lot of parts for a booster... intriguing.

coldcraft · Post by **coldcraft** » 10 May 2011, 07:00

well, its two things in 1. like me, I'm a man, and a provider...

MoonWatcher · Post by **MoonWatcher** » 20 May 2011, 05:46

RnFR wrote:that's a lot of parts for a booster... intriguing.

That was my first thought, too.

I guess that a booster now has to be more than just that, at this point. Buffers and tone shaping seem more and more common.

coldcraft · Post by **coldcraft** » 20 May 2011, 19:13

I have not really listened to this pedal before, but I'm pretty interested in whatever it might be.

Judging by the number of gain elements, I'm going to suggest that 1 transistor might be for driving/switching the LED, and that the switchable output buffer is opamp based.

That leaves 1 opamp stage for a boost, and 3 FETs. From reading about its operation, it sounds like turning the treble boost knob down removes the bass cut. That has me thinking that the Treble Knob is actually a blend between flat and treble boosted signals (50kB). We could assume that it is a FET based treble booster perhaps. Also, we probably shouldn't rule out the idea that some FETs could be used for clipping, as we've seen that before in the Sky Blue OD.

just my thoughts.

coldcraft · Post by **coldcraft** » 23 May 2011, 23:30

so thats a single opamp, the 5534?

WhiteKeyHole · Post by **WhiteKeyHole** » 24 May 2011, 01:11

coldcraft · Post by **coldcraft** » 24 May 2011, 01:58

ok, well that helps us narrow down the possibilities. Seems like it has to be 2 JFET Boosters with an OpAmp Buffer.

WhiteKeyHole · Post by **WhiteKeyHole** » 24 May 2011, 03:00

No need for speculation. I'm tracing it now.

WhiteKeyHole · Post by **WhiteKeyHole** » 24 May 2011, 04:53

So, yeah, definitely need some confirmations before I'll post the schematic but the buffer is very similar to the "Folk Buffer." The "booster" is a typical cascaded FET design in four stages.

coldcraft · Post by **coldcraft** » 24 May 2011, 13:37

WhiteKeyHole wrote:No need for speculation. I'm tracing it now.

but speculation is so fun! what happens when I'm right without ever seeing/hearing a ruby red! I will be da bwoss.

anyway, perhaps one of the FETs is an input buffer?

WhiteKeyHole · Post by **WhiteKeyHole** » 24 May 2011, 13:55

coldcraft wrote:anyway, perhaps one of the FETs is an input buffer?

Not strictly speaking, no. It's all traced, I just need some of the electrolytic and monolithic capacitor values and confirmation on the "Treble" control, as the relevant traces are hidden.

Anyway, like I said, four stage cascaded FET design. 1 > Treble > 2 > 3 > Boost > 4 > Master. The IC buffer, when engaged, is only active in bypass.

RnFR · Post by **RnFR** » 24 May 2011, 15:14

four stages for a booster? that thing must be loud and clean. either that, or it can get dirty as well. is this really just a booster, or a FET OD as well?

coldcraft · Post by **coldcraft** » 24 May 2011, 16:45

RnFR wrote:four stages for a booster? that thing must be loud and clean. either that, or it can get dirty as well. is this really just a booster, or a FET OD as well?

from the description, it does distort when the gains are up and the master is down.

WhiteKeyHole · Post by **WhiteKeyHole** » 25 May 2011, 02:12

Awesome, thanks. Yep, that confirmations what I have drawn.

WhiteKeyHole · Post by **WhiteKeyHole** » 25 May 2011, 02:29

As always, there may be revisions. The switching scheme I have shown may not be accurate insofar as specific methods are concerned (ground input in bypass, etc), but will provide the same basic functionality.

RBBR1.png

coldcraft · Post by **coldcraft** » 26 May 2011, 18:27

that's quite interesting. I have never seen FET stages like that, which more-or-less equal Drain and Source resistors for DC bias and then using Cap and resistor bypass to set the AC again. I will have to bread board those individually and evaluate the sound.

coldcraft · Post by **coldcraft** » 26 May 2011, 18:29

i forgot to ask, what's the verdict on this pedals sound? is it crunchy/grit at higher gains? smooth or harsh, etc?

Barcode · Post by **Barcode** » 26 May 2011, 19:53

coldcraft wrote:i forgot to ask, what's the verdict on this pedals sound? is it crunchy/grit at higher gains? smooth or harsh, etc?

I'll probably find out later tonight when I whip up a PCB for this (which of course I'll share) and build it to find out. Provided I have any fets in my stock.

Barcode · Post by **Barcode** » 26 May 2011, 23:58

does the 2n5952 have the same common pinout as j201 and 2n5457? I think it does...

WhiteKeyHole · Post by **WhiteKeyHole** » 27 May 2011, 00:11

Yes, though they need to be rotated 180 degrees.