Aion Rift - increasing the volume.

[milkypostman]

Built the AionFX Rift (https://aionfx.com/project/rift-octave-fuzz/) and while it has a decent amount of output, it could use more.

Best way to describe it is that when turning it on compared to my clean volume it sounds louder. But even with the balance cranked and the expander and tone knobs at 12:00, it doesn't cut above the loudness of other OD/Distortion pedals.

I fired up the ol' web browser and did some searching and it seems like this is a problem with the original Super Fuzz. I just wanted to confirm here if anyone else encountered this or if it's something I should go hunting down a potential problem I did when wiring it up.

[antonis]

1. Replace Ge diodes with Si ones..

2. Make R26/R27 220k/33k or better 470k/68k..

[milkypostman]

1. Replace Ge diodes with Si ones..

2. Make R26/R27 220k/33k or better 470k/68k..

I'm preferring #2 because I would guess that replacing the diodes will affect the tone differently, not that I'm opposed to this I should probably just socket the diodes there. But I am curious about the resistor suggestion.

Would you be willing to give a brief explanation for how the capacitor and resistors (C14, R26, and R27) are interacting here and why preserving the ratio but increasing the values leads to more output?

I need to just sit down and learn the properties of signal circuits in general but that's a large learning adventure. I need a crash course on guitar pedal circuits but haven't found one yet.

EDIT: Found https://www.diystompboxes.com/smfforum/index.php?topic=47572.0 which will hopefully help. Although the reverse polarity on C14 is odd here.

Thanks again, I'll give this change a shot!

[antonis]

Although the reverse polarity on C14 is odd here.

If by "here" you refer on Aion Rift fuzz, C14 polarity is correct..

Its positive leg sits at about +1.17V while its negative leg is grounded (0V) via Balance pot wiper - lug1..
(lug 3 is DC "floating" due to C11 blocking capacitor..)

[r080]

Would you be willing to give a brief explanation for how the capacitor and resistors (C14, R26, and R27) are interacting here and why preserving the ratio but increasing the values leads to more output?

It looks like this would increase the input impedance of the last stage better matching the impedance of the 50k pot, leading to more power transfer.

Another option would be to increase R28, but this would increase the output impedance of the pedal.

[antonis]

Another option would be to increase R28, but this would increase the output impedance of the pedal.

Not only..
I would also misbias (bottom) Q6..

Suppose Q6 Collector stands at 4.5V.. This calls for 450μA Emitter current.. By making R28 15k say, Q6 Collector would sit at 2.25V and would be  fully bottomed for R28 = 18k (taking into account Emitter voltage and V_CEsat)

[pacealot]

I have used the Wattson values for R26 through R29 on several Super-Fuzzes now, with excellent results for increasing the output without changing the pedal's basic response or tone:

R26 — 750K
R27 — 75K
R28 — 24K
R29 — 1.2K

[MG]

Built the AionFX Rift (https://aionfx.com/project/rift-octave-fuzz/) and while it has a decent amount of output, it could use more.

I think others have covered your question about output, to the degree that the current circuit can be adapted. (You could always add a low gain stage to the output)

Just wanted to comment on aionfx's demo track.  That's a great demo for their pedal.  It's a sound that I normally don't go for (Purple Haze aside), but the player finds the best ways to use the odd pedal sounds.  There are some really interesting moves; no painfully bad guitar cliches. All pedals should have demo tracks like that.

[antonis]

I have used the Wattson values for R26 through R29 on several Super-Fuzzes now, with excellent results for increasing the output without changing the pedal's basic response or tone:
R26 — 750K
R27 — 75K
R28 — 24K
R29 — 1.2K

No problem for Ge clipping diode pair, marginally Ok for Si but potentially bad for any LED..
(IMHO, happines of Q6 as a transparent booster with 820mV Base bias is strongly dependent on particular BJT specs, working temperature and particular Collector current..)

[pacealot]

Yes, in my case I've only ever tried germanium clippers in the circuit, and the transistors have mainly been low-hFE PNP silicons like the 2N3703 (I had a ton of those, and having a surfeit of trannies around 70-90 hFE gave me the idea to whip up a couple extra SFs for friends)....

[milkypostman]

WOW, thanks everyone I'll give some new resister values a shot. Probably try R26 and R27 first.

What I meant about C14 is I'm a complete noob. I was just trying to understand how changing the resisters affects the circuit. I understand the concept of a voltage divider but then trying to also understand how as signal from the guitar passes through this voltage divider stage into the last boost stage.

Conceptually the way I think about it is that by increasing the resistance to ground more of the guitar signal -- after the clipping stage -- goes to the output. But even after reading about impedance a bunch I still don't fully understand it.

Anyways, thanks again for the great discussion and help!

[antonis]

What I meant about C14 is I'm a complete noob. I was just trying to understand how changing the resisters affects the circuit. I understand the concept of a voltage divider but then trying to also understand how as signal from the guitar passes through this voltage divider stage into the last boost stage.

In brief: C14 forms a High Pass filter with ANY followed shunt resistance..
That is the parallel combination of R26, R27 and h_FE times R29..
(actually it's a bit more complicated but the above is a good aproximation..)
R27 obviously goes to GND..
R26 also goes to GND for AC 'cause power supply is considered ground for AC..
R29 obviously goes to GND but its "reflected" value to Base is h_FE times greater 'cause Base current h_FE times lower is needed to "drive" respective Emitter current..
So, all the above resistances should be considered in parallel from C14 positive leg point of view..

But even after reading about impedance a bunch I still don't fully understand it.

Just consider "impedance" as frequency dependent variable resistance for AC..
(0.159/C*f for caps and 6.28*L*f for inductors..)