New Distortion Project - The Plexizer

[mojotron]

OK, solved it , tuned the trimmer at Q5 by "ear" to remove the hiss
and this works great now
Happens to be 7.1v !!
Sounding great now, many thanks Mike.

Marty.

That's GREAT! I'm really glad you like it - that's a great suggestion to also give the drain voltages on the FETs - I will do that tonight when I get home. For those that might not know though, JFETs, especially J201s, have differing gains - more so than Si transistors in a lot of cases - and someone else's voltages may vary from what I use. This circuit is one of my quieter ones due to all of the Miller emu caps, hissing is not one of the things I had encountered while adjusting the trimmers - I will see if mine does the same thing.

What do you guys think of this procedure below? It's what I started doing after building (re-building       ) a bunch of these JFET distortion circuits: I do the following to get the voltages just right:

1) set up the drains on the FETs to 1/2 the supply voltage - this should make the circuit pass a sound

2) starting with the last FET before the output, the last FET in the circuit, tune by ear for the loudest output. In the case of the Plexizer, tune Q5 to be the loudest possible

3) then, repeat #2 for Q4, then Q3 then Q2, then Q1

Now, #4 and #5 are the tough part as it's really subtle - but IMO really makes the sound of a circuit like this (or the Dr B, ThunderChief...) more authentic

4) then, crank the gain up to max with all of the tone stack maxed, volume slightly higher than unity - 3db should do - hit an open d string on the guitar and tune Q4 until you hear the first harmonic come out a bit better about 1-3 sec after you hit the note - I warn you this is a tough tweak with a single turn 100k trimmer, but after some practice...

5) repeat step #4 for Q5 - Q5 seems to have the more dominate affect - now the 1st harmonic should be pretty easy to hear mid-neck on the middle strings and pinch harmonics should be fairly easy.

I think it would also be interesting to see what others think of all of these 'cousin marshall-ish' circuits when used on the same pedal board (not at the same time..)? I think this one, Electric's JCM 800 Emulation, the ThunderChief, and the Dr Boogey (respectively) cover that whole spectrum - what you could want from a distortion box - very well: Keeping in mind - for overdrive there is another world of circuits, and for sonic destruction there is another world of circuits in the realm of rats/fuzzes. I'm thinking with some carefull CD40XX switching one could put them all on the same board utilizing all of the common bits of these circuits; this might require dual-ganged pots for the tone stack and some really good debouncing - thoughts?

[MartyMart]

As has been discussed before, these Jfet circuits can be a bit of a bugger to get "just right" !
Jfet's are all over the place ( gain wise ) so tone/voltage at drain will vary a LOT .
It is sounding very good, lots of tones on tap and it has that "vintage" kind of warm sound
to it
Mine Doesn't really clean up well, until you lower the gtr vol a bit though !

Just out of interest, here's my final "best sound" Drain voltages :

Battery - 9.1v
Q1 - 4.5v
Q2 - 4.6v
Q3 - 9.1v
Q4 - 4.75v
Q5 - 7.1v  ( tried three J201's here to find best tone )

Subs or all I had :
Bypass caps ( C3/10 ) 1uf poly
R3 - 2k2
R9 - 8k2
R20 - 1k2
R22/23 - 12k
C20/C21 - 1n ( for a bit less roll off at the end )
C5 - 390p
C2/8/9/15/17 - 100p
R11 - 220k lin
R14 - 25k lin

Additions :
1M pull down r at front of circuit
extra 100n filter cap next to C7 ( 100uf )
D1 1N4001

MM.

[mojotron]

I experimented a bit with caps and I got my 'best sound' voltages - using the method I described in my last post. Here's what I came up with.

For C3/10 - I really like 1uf AVX Multi-Layer Film Capacitors - a bit fatter/even-smoother tone IMO over the film .68uF and electo 1uF caps I tried.

My 'best sound' voltages:
Source: 8.98v
Q1 - 4.14v
Q2 - 3.46v
Q3 - 8.98v
Q4 - 4.02
Q5 - 4.1v

I did not try different JFETs - though that's something worth trying - but after tonight I like what I have too much to mess with anymore. I might build another one to try some other changes.

[uan]

i am very sorry if this sounds really stupid but honestly but i need to know, how do you measure voltage from your JFET? what to set to the Multimeter, which part of the number on the multimeter do account?

   

[aron]

Set your multimeter on DC, put the black probe on ground and then put the red probe on the legs of the transistor you want to measure.

[uan]

thanks guru!

[hilbi]

Is there a vero layout for thi sproject or is someone working on it?

[MartyMart]

Is there a vero layout for this project or is someone working on it?

I built mine on vero , but not drawn up .... YOU could learn a lot by doing one
.... what do you say ??   

MM.

[hilbi]

Is there a vero layout for this project or is someone working on it?

I built mine on vero , but not drawn up .... YOU could learn a lot by doing one
.... what do you say ??   

MM.

I know, I have done a lot of vero layouts already, not all published.

[britt-stinker]

I think it's distasteful to post something about god inhere.
I can't see what other reason that shit about god and jesus christ has to do with anything, other than to recruite people to your church.

"God id dead"
-Friedrich Nietzsche

Thanks

[tungngruv]

-Friedrich Nietzsche

Thanks

For what? Mojo sharing the circuit freely? Or an opportunity for you to vent?

[puretube]

I think it's distasteful to post something about god inhere.
I can't see what other reason that shit about god and jesus christ has to do with anything, other than to recruite people to your church.

"God id dead"
-Friedrich Nietzsche

Thanks

? ? ?

"God id dead"
-Friedrich Nietzsche

how about Nietzsche himself?

(btw: a relative...)

[The Tone God]

To all: I would ask to keep to the technical discussion at hand.

britt-stinker: If you have a problem with the poster take it up privately please.

Andrew

[uan]

I strongly believe the answer whether is there god or who is god will be revealed after we die. Meanwhile its better to have some respect on other's belief..

now lets just continue about plexizer..

Question: what need i do if i want to swap the 1st JFEt to the real 12ax tube?

[Mark Hammer]

I think it's distasteful to post something about god inhere.
I can't see what other reason that shit about god and jesus christ has to do with anything, other than to recruite people to your church.

"God id dead"
-Friedrich Nietzsche

Thanks

While the "Jesus thing" is not my cup of tea, people do an awful lot of nice things for other people because they are inspired to for religious reasons, and this is no exception.  The schems could stand to be a little subtler in their presentation of that content, but if it bugs you, you can always edit the religious content out and save the schem minus that stuff.  Just make sure to save all the IP information.

I think Andrew's suggestion to address this "policy disagreement" off-line is entirely appropriate.  Some folks here can let their enthusiasm for some things get the better of them now and then, whether that be of a religious or philosophical nature, or a commercial interest, and a friendly word here and there often yields remarkable results and much fence-mending.

[Jay Doyle]

While the "Jesus thing" is not my cup of tea...

Thanks for the laugh Mark, that has me chuckling.

I think it is distateful to complain about someone contributing freely.

[aron]

Thanks Andrew for saying it.

[RaceDriver205]

Or an opportunity for you to vent?

Please, no more vent-ers! 

[mojotron]

I did ask for a bunch of opinions on technical things... tone stack, mods... When people have a few built I would love to hear their views on those things.

[goosonique]

Nice build ...thanks !!

i am here able to do what i am doin is because of JESUS ....when no person or idea or entity bothered to give me a hand !!
He is my cup of life !! and i do love tea too ....we Asians know more abt tea than you fellas...
I do get annoyed with organized religion and i do at times feel thrusting my fist up their.....  but NOTHING will rob me from getting connected with my Jesus....period !