Bluesbreaker Pedal Clone Lacks Drive (low output)

[GroverRock]

Hi all,

Perhaps a little background first:
I have some background in electronics, but that was a number of years ago, and I'm a tad rusty
I have good soldering skills some basic (very basic, until I do some more reading and "making")
knowledge of amplifiers. I have a lot of catching up to do!

I've successfully built a "Real McTube" tube preamp, an "Orange Squeezer" compressor and am working
on a power supply to power all my 9v effects. Future plans include a volume pedal.

Bluesbreaker Overdrive.
Using a board from Tonepad, I just built a clone of the Bluesbreaker Overdrive pedal. I love it,
love the tone (not harsh, nice and smooth) but the output is significantly lower than the output
of my lap steel. I had hope to use it to drive my "Real McTube" a bit harder, but to my surprise
the output is actually less than unity gain.

I've checked all components, all look ok. I've looked around the net for mods, but see only mods
for tone and higher gain. What I need is more voltage at the output. Plus, some of the gain mods
are apparently known to affect the tone, and one thing I definately don't want to alter, is the
tone. Apart from this problem I am thrilled with the sound of this effect.

If I'm unable to rectify this  problem (nice pun, eh?), I'll probably build "Jack Ormon's Mosfet Boost"
but I'd really like to keep as little components as possible out of my signal path from lap steel to
amp, you know?

I'd be grateful for any suggestions anyone might have.
Thanks,
Pete

[GroverRock]

Hi again,

I thought I'd better clarify my original post and also post the schematic.
I don't understand how this circuit works, so if anyone is able to tell me which part of the circuit
determines the signal output level, that would be great.

Any ideas as to why the output would be too low would be greatly appreciated. I have checked all
components and connections, and all looks fine. I do have a multimeter, just so you know.

My understanding, from what I've read, is that this effect should be able to boost signal and drive
a tube preamp. It's working fine, but the signal is less than unity, no signal boost whatsoever.
Sounds great though..

Thanks,
Pete

[duckpow]

Schematic 

[GroverRock]

Schematic 

Oopsy, let me try to get that schematic up again...
Forgive me, I'm a bit rusty and haven't "forumed" for about 3 years. Because, with dialup, it (and net in general) can make you want to pull your own head off. Looking foward to broadband that's coming in a few weeks :-)
Now let me find that schematic...
Pete

[GroverRock]

Here's the schematic. I built mine exactly per this schematic.

[twabelljr]

Link to download Tonepad's PDF:  http://www.tonepad.com/getFileInfo.asp?id=75
Edit: Good, GroverRock got the image to show. The Tonepad link has their layout, schematic, and offboard wiring.

Read this and see if you think it applies to your issue: http://www.diystompboxes.com/smfforum/index.php?topic=80761.0

                                       

[GroverRock]

Read this and see if you think it applies to your issue: http://www.diystompboxes.com/smfforum/index.php?topic=80761.0
                                   
[/quote]

Since I'm happy with the tone of it now, it seems to make sense to add a boost at the output, as did the
poster in the above link. Since the signal out is now less than the input, I thought I'd try a mosfet boost. Before I do that, however, I'm going to change the 220K feedback resistor to a higher value, and post results here.

Thanks Tommy,
Pete

[GroverRock]

Hi all,

I replaced the 220k feedback resistor with 270k and have settled on this 270k mod. This has noticably
increased the gain quite a bit, but not had a dramatic effect on the output level. I actually tried up to 320k, and things were getting pretty wild, not that that's a bad thing     If you wanted a lot of gain, but wanted to avoid the usual harsh mid-range tone of many overdrives, then you would
probably like this effect with the 320k mod - that would wail quite nicely.

Since I've improved the gain, but not really the output level (by just a tad), I'll see if have enough bits and pieces to put a booster together, and I'll post results here. I think keeping the sound I"m getting is worth
building the additional circuit (booster).

I hope some find this helpful!
Pete

[GroverRock]

Hi all,

I found the reason for low output, problem solved; there was a nearly invisible thread of solder connecting the + supply to one connection of the 25k tone pot. The pads are (obviously) adjacent on the pcb.

This connection to the tone pot was sending +9v to the pot, and, via a 1k resistor, straight to the
220k gain resistor. All good now, loads of output!

I found this error while connecting the circuit to a power supply bus. I learned that I'd be better
off working in better light, and that it'd be wise to use my magnifying glasses more
often

Also, I threw a DPDT bypass in it this morning (just a toggle switch for now) and all is well. 

Cheers, hope this helps someone,
Pete

[arma61]

Hi all,

All good now, loads of output!

I like fairy tale with an happy ending........ enjoy it