Sweet 16 (stupid) question - working on a new PCB....

[Bucksears]

I'm working out a PCB for Doug Hammond's Sweet 16 (shown here)
http://aronnelson.com/gallery/WGTP/Sweet_16?full=1

My question is this: in the schematic above, is the 100uF/10k/1M/10k junction supposed to connect to the 1M resistor in the top/center of the schem? Just above the 100uF cap in the upper left, it reads '1/2v' and to the left of the 1M resistor in the center of the schem it reads the same thing. I may have to jumper something across to make the connection, but I wanted to be sure first.
Also, I've worked out a new PCB for Doug's VoxEXP (dubbing it the 'VoxEXP II' as a not-so-distant cousin to Ed G's popular circuit); the main difference is, I've subbed out the two 15k resistors (above J1 and J2) for 100k trimpots. It still has the Minibooster at the end, but I wanted a way to bias those two transistors for maximum clarity/definition. I'd like to see if it would be possible to scale down the tonestack some a la Gaussmarkov's Dr. Boogey revision, but if not that's ok.
I'll post these on my site when done, unless anyone has any objections.

- Buck

[Barcode80]

My question is this: in the schematic above, is the 100uF/10k/1M/10k junction supposed to connect to the 1M resistor in the top/center of the schem?
[/quote]
that't the way i would read it, but maybe i'm missing something too. anyone else?

[Shakal]

Good question...

A lot of circuits have the Vb, I think it's Bias Voltage, and maybe it is the same thing on your circuit. If I'm right, u just have to connect the two 1/2V together.

Again with my assumptions:

This 1/2v means Half of the Input Voltage, and 10K/10K/100uF make an auto-biasing circuit, so you can get a half of the voltage in the middle of the resistor association. The capacitor meaning is to make the "noiseless biasing" that is write on description.

Well, as I said, they're all assumptions but makes totally sense to me.

Sorry about any bad English. I did a Spell Check...

Regards.

[markm]

Yes.
Because that is the Bias Voltage.
It will connect to the junction of the 2 10K/ 100uF cap.

[WGTP]

Whoops, I didn't think about that.  The "noiseless biasing" is the only thing I changed from Dougs original schematic, so if you are using the PCB that surfaced after I posted it, something will need to change.  The original used 2 -1M resistors on each Mu-Amp for bias, 1 going to V+ and the other going to Ground, as you will see some of the Mu-Amps using.  That would match the PCB.  Because of all the gain, mine was a little noisey, so I added the noiseless biasing to the schematic.  I probably need to add a note now that the PCB has been resurected.  Hope that doesn't mess you up any.  Be sure and report your findings.   

[Bucksears]

WGTP,
This is actually new 'from scratch' PCB that I made up. I'll see about posting it tomorrow night; I have done too much tonight and have to get some other things done.
I'd like another pair of eyes (or three) to check it over.

Thanks,
- Buck

[WGTP]

Glad it didn't mess you up.  I don't know how much quieter the noiseless biasing is, but R.G. seems to think it helps, so it probably does.  The noise from mine isn't horrible or anything and it is probably more attributable to my messy built.  Once you done, you may want to tweak the tone control.  I think I added a little more treble to mine because of my dark amp.  I don't think you will be disappointed if you like a big scooped mid-range monster.   

[Bucksears]

Glad it didn't mess you up.  I don't know how much quieter the noiseless biasing is, but R.G. seems to think it helps, so it probably does.  The noise from mine isn't horrible or anything and it is probably more attributable to my messy built.  Once you done, you may want to tweak the tone control.  I think I added a little more treble to mine because of my dark amp.  I don't think you will be disappointed if you like a big scooped mid-range monster.   

No problem. I had the original Sweet Thing years ago, but noise issues got in the way, so I scrapped it. 9 times out of 10, I'll recreate a PCB in Illustrator (even if it's exactly the same, no changes) just so I can have that clarity from an original layout rather than a scan of an image. I PNP blue'd a copper board last night with the Sweet 16, VoxEXP II & others, and it came out without any flaws, so I'll be etching tonight.
What cap/part adjusts the treble response of this circuit? I see the cap that you adjust for bass.

- Buck

[WGTP]

I bought a PCB from Frank Clarke who used to hang around here, but not sure what happended to him.  Anyway, I think I doubled the 330pf cap.  I'm still not sure how that tone control works, but I think it lowered the roll off point of the high frequencies adding some lower treble and reduced the depth of the notch somewhat.  I added a switch to by-pass it just to see what it sounded like.  The cap across the gain control is pretty significant, unless the gain is maxed out.  I think I used a 220pf, but a 100pf or 150pf might work better, depending on how you set it.   

[mydementia]

WGTP - Is this the 'resurfaced' board/layout you are referring to?
http://168.144.51.162/PCB_layouts/Layouts/sthart.pdf
Looks like it's from RG circa 2001...

Was there anything wrong with it?  Looks pretty clean to me.... and it includes a 'treb cut' cap (could make it switchable...).

Mike

[WGTP]

Yes, that's it.  There is no problem, it has the original biasing method rather than the noiseless version.  That is the one I actually have sitting here.