Small Stone Phaser + AMZ Miniboost troubleshooting

[Getomonk]

Hi

I have an old Small Stone Phaser (version 4) that I love everything about except for the volumedrop it has when I engage the effect. My solution up until now was running it in a loop with a clean boost after it. But that takes up room on my board, so I decided to build an AMZ miniboost into the Small Stone box. So far so good. It works really well except for one thing.

When the phaser is engaged with the boost in the circuit I get a small amount of distortion on the signal. The phasing is there but with a little grit that I don't like. The weird thing is that I have another AMZ miniboost on my board as my overall clean boost and If I disengage the boost inside the SS and run it before the boost on my board I get phasing with no distortion.

Does anyone have an idea what causes this problem? And possibly how to solve it?

[Chris60601]

Is your on-board boost wired before the SS or after?
That may not make much difference but who knows.

[adapt]

isnt the AMZ booster also a buffer? wonder if that's an issue.

[Chris60601]

I have built the SS using the PCB also. I myself am considering the EH LPB1 to combat the loss.
I have not built the LPB1 but I opted for it for 2 reasons:

1. Really small footprint
2. Simplicity
3. Well, it's EH

No 3, 3 reasons.
1. Small footprint
2. Simplicity
3. Well, it's EH
4. Low part count...

No, 4, 4 reasons.....
Sorry - a little Monty Python humor there.

Then again, the Lotus Pedal Snowjob looks interesting as a boost too.

[rocket88]

And our fanatical devotion to the church.  

Among our weapons......

[Beaker]

Cardinal Fang... bring out the comfy chair!

Yeah, I would try the LPB-1 with trimmer.

http://tagboardeffects.blogspot.co.uk/2013/01/electro-harmonix-lpb1-with-trimmer.html

Tiny enough to fit in the tightest of places. I've used it in a couple of low output builds, and it does the job admirably.

[Muadzin]

There exists a mod to fix the Small Stone volume drop. I know this because I performed it on one of my Small Stones.


http://www.generalguitargadgets.com/wp-content/uploads/smallvlp.txt

UNMATCHED VOLUME PROBLEM:

Many people have complained about a small volume loss when the Small
Stone is switched on.  My Small Stone exhibits this behavior as well.
Here is a post from R.G. from Aron's Stompbox Forum on a possible
fix (modifications to the circuit) for this problem.

-------------------------------------------------------------------------
From R.G. Keen

The loss of volume when engaged is correctable in the Issue J Small Stone
by changing the gain of the two-transistor preamp at the input of the circuit.

There are two 4.7K resistors at the emitters of the input transistors. One
(R7) goes to ground from the emitter of Q1, the second (R42) connects the
emitter of Q2 to the emitter of Q1.  Those two resistors set the feedback gain
of the two-transistor compound.

Increase the 4.7K between the emitters (R42) to increase the gain. Start with
10K.  Be aware that this will affect the stage biasing, so the headroom may
be affected; I don't think this will really be a problem.

The silly thing *ought* to have included a JFET buffer in front of it for
buffered bypass and a bit of gain in the first place.

-------------------------------------------------------------------------

Dave Matelitz reported successfully fixing this problem by making these
part substitutions:

Changing R42 from a 4k7 resistor to a 10k resistor
Changing R11 from a 3k3 resistor to a 10k resistor

Tweak these two resistors until you get the volume right with no oscillation
in the signal.

[Getomonk]

Thanks for all your inputs.

@Muadzin - yeah I looked into that, but opted for the onboard boost circuit, because I really wanted not to compromise the integrity of the SS board. Also it seems more logical to me to boost the output than to add more gain at the input.

Anyway, I've done some more testing and it turns out that it's the boost circuit iself that distorts. Guess it's a bad component somewhere. I'm probably just going to build a new one.

Cheers
Getomonk

[Getomonk]

Just to let you know.

I tried the LPB-1 as onboard boost and it works really well. Definitely recommend this to others with SS grievances:-)

Again: thanks for the advice.