Clean Boost Diode ??

[petemoore]

Phillip Bryant's Clean Boost schematic calls for 1n914 diodes.
 I believe that's what I'm using, they measure .624 or .635 thereabouts on the DMM diode setting. They are small, glass, red with black stripe.
 Sounds real good lol with a Mosfet stage driving it, nice smooth very subtle distortion, I don't even know that I need to get it working... :lol:
 Anyway the transistors Drain is on a 10k trimpot and has the classic bias fades at either end [depending on the transistor] of the pots travel, that makes me think I'm biasing it, plus I'm getting 1/2v at the drain.
 I should have posted more measurements but I'll ask:
 Would putting a 100k volpot in place of the 100k fixed resistor change the output level...it goes to about unity...
 I used a 10k V/R for the gain pot...it increases/decreases output to 0.
 Basically the output seems low, I think there's an error in my circuit, whech has a few 'undecided' parts...the diodes, the subbed output pot, and the 10k gaiin pot...I don't suspect the latter two, but included them in the thread.

[phillip]

Pete, how hard does it boost?

The diodes that you describe sound like the 1N914...maybe 1N4148s.

You could replace the two 1N914 diodes with a single 1N4739A 9.1V Zener across the Gate-Source...it'll reduce the parts count and simplify things a little

Phillip

[petemoore]

Well Phillip, at this stage, no boost at all, possibly just below unity.
 I'm pretty sure those Are 1n914's as I have tested numerous ones, they're all close, and probably all from the numerous 20 packs of them I'd gotten from RS.
 Seems like it aught to be a boosting, I'll recheck...probably some simple thing....
 I've tried also quite a few different 2N7000's, some Jfets, and a SK161, just for fun, and whatever the SK161 is, it came from the NTE guy.

[petemoore]

I'm sorry, a revision of earlier readings revealed that I'm not getting bias on Mosfets, It must have been one of those Jfets I stuck in there that was showing about 1/2 V.
 I found a bad 10M resistor, as fate would have it on the same day I posted about consistancy on Resistor values...lol.
 So they both got swapped for 4m7's, that didn't seem to change the drain bias.
 I've had trouble similar to this with using Mosfets before, perhaps that is coincidence.
 The battery is at 8.94v, and the drain measures 8.94v at one end of the 10k trimpot travel [drain bias trimpot] and 8.76v with the pot turned all the way the other way.
 Gain pot measures between 0k and 10k like it should from one end to the other of it's travel, has no effect tho on the mosfet.

[phillip]

Do you have the pinout of the MOSFETs right?  The BS170 is S-G-D, and the 2N7000 is D-G-S (top lead to bottom lead, looking at the top of the transistor, with the flat face pointing right).

Phillip

[petemoore]

The Transistor pinout, when corrected, made all the difference...dohh
  ...N/P at all now with the sound, or getting 4.5V at drain!
 10k pot tapers up the volume as it's turned till about '8'. After that it starts causing the transistor to cutoff I think. I'll have to get a 5k on there or tag a 10k resistor on the 10k pots ears.
 Thank you for a nice, easy, Mosfet build Phillip ! ! !...I think I'll have another [now that I re-figured out the 7000's pinout!]...it does sound good with another Mosfet stage driving it or not!!!
 Whacky  :idea:  ??/ ..use one 10k gain pot for both stages, by connecting the wiper to ground, and both sources: one to each outer lug, thereby turning one gain up as the other goes down...nohh...might work kool if tapered extensively, I'll stick with the ~5k pot per Mosfet.

[petemoore]

Stage 2 [the other Clean M.Boost], came off without a hitch, very nice sounding well, boost, but, almost like a slight hint of OD tone.
 I still have a grab bag of at least 8 x 2N7000's and may even try a third stage...I'll post any results I get.
 I don't know how necessary having trimpots for drain are, I just put them there out of habit I guess, or like for tuning in bias...this is a straightforeward build, not complicated, and [as I figured], fires right up when wired right !!!
 Great sounding Clean Mosfet Boost, with EZ to find parts...the second ones diodes came from a computer monitor board. Great build!

[phillip]

Glad to hear that it's working, Pete.  

I'm also glad to hear that the 2N7000 will work in place of the BS170.  I checked their individual data sheets, and they were almost identical in the critical parameters.  I have a bag of 9 of them that I can use...I did have 10 but I accidentally fried one in a Fuzz Face experiment once...oops

Phillip

[petemoore]

Overconfidence before the bout is a sure sign that failure may be imminent  :evil:
 Sounded just great, but the box really beat tar out of it.
 First it grabbed the transistor I had in there.
 This is a RACO by the way, not my prefferred new design with great bottom board access and EZ installs.
 Then trying to bias the 'other transistors for Q1, I got burned good a couple times, pulling the transistor out instead of the battery connection, frying a good portion of the mosfets, and probably melting of the bias pot...it's no longer adjustable.
 Frick  :evil:,  and Frack :twisted:,  were in the box with a Small Mosfet Boost board, a couple Jacks a  pot and a switch. They sprung on me these problems, one after the other, just near the bout's completion and beat down any efforts to defeat them...They were so good at it I thought it bears mentioning! ...
 Daft...I'll work on those two later...fortunately I still have 1 Mosfet in with F and F, and still working...them mosffets REALLY HEat Up, and not so slow either...

[BDuguay]

Fella's
Which Phillip Bryant schematic are you discussing here?
B.

[phillip]

It's the one that our "ethics police" got canned because it was pretty much the same as a famous boutique boost pedal, which was unknown to me before I posted the schematic.

EDIT:  Here's the URL to the schematic on the site where I originally found it:

http://www.kilback.net/homebrewtweaks/pedals/cleanboost.htm

Phillip

[Jered]

You shouldn't need trimpots for the drain resistors on this circuit. In a final build of a circuit trimpots usually add noise, especially dist/hi gain circuits.
Jered