Vb? same as Vbb?

[m_charles]

Are these both "bias voltage"? meaning, connect all the points? or is there a difference?

thanks!

C

[The Tone God]

Most of the time I would say but check the schematic to see if Vb* ties to a circuit piece that looks like a bias point.

Andrew

[Mark Hammer]

Ditto.  There have been assorted postings here over the years regarding the nomenclature of the various less-than-supply-max voltages.  One of the reasons that I have some reluctance in simply saying that Vb = Vbb is because there are a number of tube-circuit voltages that also have letter designations, and I wouldn't want you to confuse those.

[m_charles]

thanks guys!

[markm]

Good point.
While we're on this subject, what is the real difference between V- and Ground?
My thoughts are it has to do with Voltage Swing in a circuit but alas, I am unsure.
The Trem Face schem of R.G.'s comes to mind, lots of stuff tied to V- rather than ground.

[rockgardenlove]

Well, in our stompboxes, V- is ground.  I suppose in a bipolar PS setup it would be difference?

[markm]

Well, in our stompboxes, V- is ground.  I suppose in a bipolar PS setup it would be difference?

Agreed.
But there IS a difference.
I was looking over the Trem Face schem at GEO and RG has a ground and V- referenced.

[Meanderthal]

 Took me a while to find the trem face... I see whatcha mean. Clearly not bipolar(sure dosen't look that way anyhow), but some grounds are mared V-... really, only 2 have the triangle symbol for ground. 

I'm thinkin' typo...

[markm]

I was originally thing "just ground" but, don't know if RG did it for a different reason?
Strange though, ain't it? 

[rockgardenlove]

Yeah...no clue.

[markm]

Here's a link to R.G.'s project if anyone else would like to take a look or chime in perhaps?
http://www.geofex.com/Article_Folders/trem_face/tremface.htm

[Alex C]

I've looked at the TremFace schematics, and I can't figure out what's going on either.
I think it is a positive ground circuit, and R.G. is using "V-" to denote the point of the most negative potential.

R.G. says this in regards to the first rough schematic:
"the battery as shown is connected with its positive to ground - the wrong polarity for the NPN BC184C to work."
- http://geofex.com/Article_Folders/trem_face/tremface.htm
But this was shown incorrectly on the diagram.

He says about the second, corrected schematic:
"Here's the corrected circuit. The BC184C circuit is a perfectly workable phase shift oscillator if the battery terminals are reversed, making the emitter the most negative terminal."
- http://geofex.com/Article_Folders/trem_face/tremface2.htm
This still looks like "postive ground" to me.  It looks like the positive terminal of the battery is being connected to ground through the switching input jack, if we're calling "ground" the common between the sleeves of the jacks.
In these two layouts, the positive battery terminal is connected to the sleeve of the input jack.

So I guess this common point is still 0V, and the others are just more negative.  We're used to ground being the most negative, but in this case V- is most negative.  There's still a difference of 9V.  (This doesn't really help, does it?)

I'm still not sure if I'm thinking about it right, though.

R.G. also says this:
"It's worth noting that the JFET is a p-channel. I chose that because (a) it keeps the signal referenced to ground instead of the floating negative power supply as would have happened with an N-channel JFET"
- http://geofex.com/Article_Folders/trem_face/tremface4.htm
and I don't know what to think about that.

[markm]

Yes, that's the answer, it's positive ground which I did not notice until R.G. pointed that out to me..... We all have "those" days right?