Red Llama mods - opinions?

[Al Heeley]

I'm just about to put together a Red Llama and wanted to build in a few modifications for it, be interrested in anyone's opinion on the following:
( Based on GGG schematic: http://www.generalguitargadgets.com/pdf/ggg_whrl_sc.pdf )
1) SPDT switch to C1 68nF input cap to allow switching between the 68nf and a 1uF cap for some fat bass
2) SPDT switch on R4 1k resistor to add in further 100k(?) for some voltage sag before the IC - according to Beavis Audio this should add more distortion and a little compression, but I don't know if 100k is big enough?
3) Add a 10k pot in parallel to C3 to allow C3 hi-pass filtering to be scaled down (=tone control)
That's it really, it's a plan but is it a good one?

[Processaurus]

Breadboarding is the best way to know if it's worth drilling a hole for a mod.

With the red llama/CA tube sound fuzz, I always wondered how it would sound to have two or three parallel distortion circuits (because there are 4 free inverters on the IC), with different gain on each, summed together, for a super soft sounding clipping threshold.

[earthtonesaudio]

Yep, breadboarding is the way to go.  I found this type of circuit to be very particular to the guitar you use.  Humbuckers vs. single coils, even neck vs. bridge pickup can make a huge difference.  For me a switchable input cap is the best bang-for-buck, but you might want even more values to choose from (rotary switch).

[Mark Hammer]

C1 is but one of the caps limiting low-end response.  Given that C3 is a smaller value than originally used by Craig Anderton for the TSF that the RL is based on, I'm assuming that Jeorge (Tripps) had some empirically-derived rationale for using it.  He's like that.  So, should you try futzing with the circuit to get MORE bass out of it than you currently get?  My personal opinion is no, unless you wish to radically alter its character (in which case why use this as a base?).

If you wish to explore sag with a 4049, go see this article at GGG:  http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=36&Itemid=27

The circuit described there uses a current regulator to deliberately adjust the sag of a 4049 buffer.  Looks promising.

As for the pot in parallel with C3, I am sceptical about that.  One generally wants some degree of DC-blocking between gain stages, and the parallel pot provides a direct path for DC.

Your objective seems to be achieving a bigger sound from the RL by accentuating the bottom.  Given how much output the RL is capable of (implying you can tolerate some passive loss), maybe the tactic to adopt is not to try and accentuate the bass but to de-accentuate the mids via some sort of scoop inserted between C6 and the volume control.  People forget that "big bottom" is simply yet one more EQ curve, and the same EQ curves can be created by adding OR by taking away.

[earthtonesaudio]

That's an interesting read, Mark.  Thanks!

Another interesting feature related to "sag" is that when you reduce the supply voltage, you increase the gain but reduce the bandwidth. At 15V the bandwidth goes to many MHz but the gain is perhaps limited to 30dB, but at 3V the bandwidth tops out around 5-10kHz while the low-frequency gain may go up to 50dB!

[WGTP]

http://www.aronnelson.com/gallery/main.php/v/WGTP/Red+Rooster.GIF.html?g2_imageViewsIndex=1

This may be of interest. 

[Al Heeley]

Your objective seems to be achieving a bigger sound from the RL by accentuating the bottom.

I guess that's part of it, and I appreciate your wisdom and experience on this, but the other part is just really exploring the whole learning process, to be able to hear the effects of tweaking certain things and swapping out various components to start understanding how they all interact.

Should you try futzing with the circuit to get MORE bass out of it than you currently get?  My personal opinion is no, unless you wish to radically alter its character (in which case why use this as a base?).

Just exploring the options really before I commit, a few people comment that the RL works a lot better for a bass guitar when C1 is bigger (0.1uF -> 1uF) and C3 is more regulated, so again part of the learning curve, whack it in and give it a try.
Seems as good a base as any to experiment on, thats what the main purpose of the forum is, after all. If the character changes, then I have an interesting pedal, I'm not too precious about the starting point, just that the RL is a classic.
WGTP: Thanks for the link, will have a good read thru this before I plug in my soldering iron.

[Mark Hammer]

Just exploring the options really before I commit, a few people comment that the RL works a lot better for a bass guitar when C1 is bigger (0.1uF -> 1uF) and C3 is more regulated, so again part of the learning curve, whack it in and give it a try.

You'll hear a lot of recommendations to change only the input cap.  And while that certainly influences bass response, often it is not the only bandwidth limiting cap in the signal path.  If the designer intended it to be the most bass-restrictive component, fine, but one can't make that assumptoin just because it is the input cap.