Ruby Bassman w/bass mods vero help

Started by Baseman96, April 24, 2019, 05:16:37 PM

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Baseman96

I have just got back into pedal building after a 6 year hiatus (damn kids are a time suck) anyhoo... I am currently building a small practice amp for my bass so I can get back to playing again.  The circuit is a collection of 2 pedals (keeley 4knob comp with a trim on the output to set to unity into a rog tonemender with a 22k in place of the volume into the ruby power amp modded for bass with the bassman mods included).  I just finished with the layout for the power amp side and wanted a few eyes on it first before I wasted any components. 

I used the layout from here as a starting point
http://giftlike12.rssing.com/chan-7249295/all_p4.html#item80

And included the bassman mods suggested by runoffgroove.com plus the other mods to make the circuit more bass friendly found in this topic here:
https://www.diystompboxes.com/smfforum/index.php?topic=37152.0

This is my first time doing any layout designing so am not 100% confident in my work. 



Still debating the gain resistor.  I might make it switchable to add a "dirt" switch.  Depends on how it sounds really.  I am shooting for a bit of a vintage tube sound out of the little amp so it might work as printed there.  At first glance does anything look off with the layout?  Thanks guys.  Feela good to be soldering again!

PRR

> small practice amp for my bass

C1 0.2uFd and VOL 10k define a 83Hz bass-cut. That's an octave off from the nominal 42Hz low-note of Bass.

Of course a half-Watt chip and the small speaker normally used with it may struggle to reach even 83hz. But I'd have in mind that I *might* someday want a bigger cap there, and plan how to fit it (leave room).
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Baseman96

What value would you shoot for there or maybe how much room would it need?  Unless it's an electrolytic they all more or less take up the same amount of room from my experiance.  I will be running this into a 4ohm 12" subwoofer I just happen to have on hand initially.  Might buy an actual guitar speaker at some point.

antonis

Quote from: Baseman96 on April 24, 2019, 07:36:19 PM
What value would you shoot for there or maybe how much room would it need?  Unless it's an electrolytic they all more or less take up the same amount of room from my experiance.
At same voltage rating, yes..

Try a 470nF poly cap of 5mm pitch (up to 100V..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

bool

TBA820 is an infinitely better chip for bass compared to a LM386.

It even has a Hi-Z input so you can plug a passive bass straight into the chipamp, no buffers required.

duck_arse

as much as I stare at your vero, I can't see a connection between GND and the IC. also, many people have problems with the 386 which are often cured by fitting the supply bypass cap AS CLOSE TO the IC supply pins as possible. might be a good idea to shift your bypass cap and then work the rest of the parts around it.

and welcome back.
" I will say no more "

Baseman96

Quote from: bool on April 25, 2019, 07:00:42 AM
TBA820 is an infinitely better chip for bass compared to a LM386.

It even has a Hi-Z input so you can plug a passive bass straight into the chipamp, no buffers required.

I'll have a look at the data sheet but is it a drop in replacement or is the pinout different from the 386?

Quote from: duck_arse on April 25, 2019, 11:22:46 AM
as much as I stare at your vero, I can't see a connection between GND and the IC.

Pins 3&4 are taken to ground via a double link under the IC