Bass Ruby Tuby?

[Mabonimus]

Hi all, and happy new year!

New to the Forum, and am currently on my fourth build in as many weeks. Got the bug!

As I am new here and to pedal builds in general, I hope I don't make a total hash of the conventions - call me out if so!

I am looking for suggestions on modding Ivlark's Ruby Tuby build (http://tagboardeffects.blogspot.co.uk/2014/10/ruby-tuby.html) to be suitable for bass guitar. After some initial googling, I found someone who did this with a more basic version of the build.  They changed up the "DC blocking capacitor" on the LM386 from 0.047 nF to 0.47 nF, which seemingly benefited the bass response. Could anyone suggest a simple capacitor change such as this for Ivlark's vero, or any other potential changes? This build may even be entirely unsuitable (too high gain?) for bass, in which instance; is there any better simple low-watt bass tube(ish) amp alternative?

Cheers!

[Neil mcNasty]

My logic tells me to increase the 10nf caps to around 100nf, and the 100nf to about 470nf, or even 1uf.
IOW: Increase the values of the film caps that are in the audio path, in order to let more bass trough...

This kind of Tube circuit (because of the low voltage bias) has a tendency to be quite full and rich on low frequencies, so you often see quite small caps compared to other circuits in cases like these.
The low voltage bias might make it muddy and untidy in the low end, but can be fixed by giving the tube more voltage (B+ point, but keep heaters at 12v), so that you get more headroom and tidier bass frequencies.

In you want to do this, you feed the higher voltage via the 220K resistors going to pin 1 and 6 of the tube, and this will require a new layout with these having their own power input (or charge pump) besides the 12v input on the layout.
DO NOT FEED THE WHOLE CIRCUIT WITH HIGHER VOLTAGE THAN 12V!
The Opamps and Tube Heaters will be burned/destroyed!

[Mabonimus]

Hi Neil,

Thanks a lot for this!

I'm going to build a guitar version first then give it a go with bass implementing your suggestions. I'll let you know of the results!

Cheers!

[sevrien]

Hi,

have you built the bass version yet?
I'm planning to do the same.

greetings