Some questions from inexperienced builder while copying a design...

[DaveBasser]

So, I was breadboarding the Ruiner by Devi Ever yesterday.  I had all of the components in the right place per the picture below.  It didn't seem to work well.  Now, I don't really understand what oscillation sounds like, but this might be it.  Or a biasing problem.  The sound of my bass would kind of get a volume spike followed by a dip and back and forth very slowly as I rang out an open string.  It wasn't acceptable, and I've experienced the same sound on my Whisker Biscuit build.  It was like a switch going on and off.

I was bummed.  Then I looked at other circuits where there were two basically similar arrangements in series.  I noticed that some have different collector resistor values at each stage. 

So I went into the dungeon and tried out all the resistor values until I found what worked.  But I changed the feedback loop resistor, not the collector to 9v.  I ended up with 2.2M for the first and 22k for the second!  And it did work.  But why so different from the diagram below?  I changed some caps to 1uf and others I left .1uf.  Is that enough to throw off the whole balance of the transistors?  And is the a correlation between 2.2M and 22k?  I also changed the 100uf to .1uf because i think thats wrong, maybe a typo, it cut so much middle and high content.  My Whisker Biscuit sounds the same so there might be hope for that project after all.
Thanks in advance!

[DaveBasser]

I guess what I'm asking is...

Will making the input, output and in between stages caps make a difference in the second transistors feedback loop resistor?  And is it a coincidence that the first transistor likes 2.2M and the second 22k considering the caps larger size from .1 to 1uf?

[R.G.]

...I went into the dungeon and tried out all the resistor values until I found what worked.  But I changed the feedback loop resistor, not the collector to 9v.  I ended up with 2.2M for the first and 22k for the second!  And it did work.  But why so different from the diagram below? 

Pardon me for some digression into my dim past. It is pertinent. I had a semester full of transistor circuit design, and one of the big issues in this was the process for identifying the sensitivities of the circuit's operation to changes in component values. The circuits we see in so many pedals fall into only a few types of connections, and for reasons that the sensitivities analysis revealed.

The bottom line is that (1) transistors vary - a lot - even for the same type and (2) components have tolerances and also drift in value over time. So to get predictable performance, you have to know how to arrange the circuit so that you have sensitivities that are small to these changes. The ideal thing is to have the gain (or impedance, or whatever it is you're looking for) vary with only the value of one component, ideally a stable and cheap one like a resistor. Having it vary with two resistors is OK if you can't get it to vary with only one, and worst is a multiplicative variation, where the results vary by the product or power of some part's value.

The circuit with a collector resistor, collector-to-base resistor and an emitter resistor which may be a value as low as zero ohms is sometimes known as the "voltage feedback" circuit. It relies on the feedback of the collector voltage to the base, effectively converted to a current by the large value of the collector-base resistor for stabilizing the transistor's operating point. This circuit works most stably when the voltage across the collector resistor is as big as practical, and the resistor value from collector to base is as large as practical. That is why changing the collector resistor didn't change much, and why the collector-to-base resistor did.

I changed some caps to 1uf and others I left .1uf.  Is that enough to throw off the whole balance of the transistors?  And is the a correlation between 2.2M and 22k?  I also changed the 100uf to .1uf because i think thats wrong, maybe a typo, it cut so much middle and high content...

Will making the input, output and in between stages caps make a difference in the second transistors feedback loop resistor?

Capacitors are open circuits to DC. They make absolutely no difference whatsoever in DC conditions as long as they are not defective. Circuit simulator programs calculate bias conditions by removing them entirely to do the DC conditions. If a cap affects DC, there's something wrong with the cap.

And is it a coincidence that the first transistor likes 2.2M and the second 22k considering the caps larger size from .1 to 1uf?

Yes.

[StereoKills]

Capacitors are open circuits to DC. They make absolutely no difference whatsoever in DC conditions as long as they are not defective.

I thought that capacitors blocked DC voltages, hence their use in input/output locations. How does that translate into an open circuit to DC?

[DiscoVlad]

Capacitors are open circuits to DC. They make absolutely no difference whatsoever in DC conditions as long as they are not defective.

I thought that capacitors blocked DC voltages, hence their use in input/output locations. How does that translate into an open circuit to DC?

An Open circuit is essentially two conductors with some insulating material between them.  Where no current (Amps) can flow through from one conductor to the other.
However, you can have any (up to infinity Volts!) Voltage _across_ these two points, and no current will flow.
From Ohm's law, this means that you have an effectively infinite resistance.

The dual of this, the Short circuit has a conductor with a resistance of zero Ohms, this means the voltage across any two points on the conductor is 0V, but the current through can be very large (infinite Amps for the ideal case).

Now, back to the point, a Capacitor is constructed from two conducting plates, with an insulator (e.g. air, paper, plastic, glass, oil, metal oxide, etc.) between them... which sounds suspiciously similar to... An open circuit. This means they behave similarly.

[StereoKills]

Thanks! That makes so much more sense.

[PRR]

"Open" in electronics confuses people.

If the garden fence gate is open, you can walk right through.

So why is an "open circuit" a no-flow condition?

Think like a squirrel walking along the top of the fence. You come to the gate. If the gate is closed you stroll right along. If the gate is open (to people), then there is nothing to walk on (if you are a squirrel). While a squirrel can climb down and walk across the ground then climb up to the fence on the other side of the gate, that's more work. In a good switch or cap, the "walk around" path is nearly infinitely difficult.