What is it? I wanted to create a box that got a good Marshall 1959 (Plexi) sound - that's what the Plexizer does.
I built this a few months ago after a lot of experiments with a few JFET projects based on a bunch of Marshall designs and the Dr Boogey and it's really become one of my favorite distortions. The ThunderChief and Dr Boogey have a bit meaner/edgier sound, and I wanted someting with that really warm/smooth distortion that you get from the Marshall 1959 circuit. What I ended up with is a really nice sounding box that I can plug a strat into and get an early Hendrix sound, put in front of some delay/reverb and get an early Eric Johnson sound, or plug in a Gibson and get an early Clapton sound.
I want to thank Bucksears for his help with putting this together and his great layouts - Buck has a layout for this one as well, which he will post later and wampcat1 who helped with advice he posted on the the LPF on the end of this circuit - which works great. I also wanted to thank all of those who contributed to related designs and those that contributed to the Dr Boogie threads, here, especially Bucksears, PaulC, RDV and many others.
(http://www.mojotronics.com/images/plexizer/Plexizer_s.JPG)
Bigger images at:
http://www.mojotronics.com/images/plexizer/Plexizer_sc.JPG (http://www.mojotronics.com/images/plexizer/Plexizer_sc.JPG) - 20% bigger
http://www.mojotronics.com/images/plexizer/Plexizer_sch.JPG (http://www.mojotronics.com/images/plexizer/Plexizer_sch.JPG) - 50% bigger
Notes:
R11 controls Treble
R13 controls Bass
R14 controls Mids
R18 controls Presence -
Note: You can play with the value of C19 - use bigger values (up to 1uF) to get more presence - 100uF is what I use.
Output Pot: I use a 100kA because I think it sounds better, but this circuit has a lot of gain and you could use a 50kA or 25kA if you wanted a bit more granularity on the output control.
On my pedal board, this is a really great compliment to the ThunderChief, Dr Boogey, a Fat Boostered and my Vibin' Champ pedals - covering the entire range of overdrive/distortion for what I need.
I know that some people will not like my statements about God in this schematic. I'll just say this and leave it at that: I know how you feel, I once did not believe in God, I was not one who you would have thought would ever come to know God, and I thought stuff like this was kind of annoying and silly: despite a lot of misinformation floating around out there about God, my only motivation for making these statements is to try to let people know Jesus Christ is real, holds the meaning of life, and will give anyone a true peace in their life that comes from knowing God. I'm not recruiting for any church or want anyone to feel guilty, obligated or to think that somehow I am a better person than anyone else - believe me - that is not the case. There's no financial motivation to this what so ever either. If you would like to talk about it my email address is developerlinux@hotmail.com.
Aha, that reminds me of Hank Wangford's set closer - Joggin' with Jesus! Or Big G, better than a smoke or a cup of tea.
Thanks for the schematic, bet the pedal sounds great - will have to try it out. I could've done with the preaching at the end though.
:icon_twisted:
Holy shit!! Thank you for sharing!!!
Looks great Mike , final vol pot say's just "R" ?? 100k perhaps ?
Many thanks :D
Marty.
Looks great mang! I was in the studio a couple weeks ago with Zac Maloy and he had a 71 plexi that was out of this world... THE sound... might as well stompbox it :) and FWIW, put what you want on your schematics, you took the trouble to make it, if someone doesn't like it, just like TV, they can change the channel, or in this case click over to another thread. Rock on, 'Tron
-Nate
Quote from: MartyMart on October 07, 2006, 08:01:53 PM
Looks great Mike , final vol pot say's just "R" ?? 100k perhaps ?
Many thanks :D
Marty.
Thanks - this is sort of a 'refactor' the the ThunderChief (with tone stack) - adding in a few changes from the 1959 design, as well as taking out one stage, and doning some tweaking to get the gain/sound just right... The sound is a lot like the sound clips of Indyguitarist's PlexiDrive... I'll post some clips later.
Right, I like 100kA, because this sounds better to me, but I think 50kA or 25kA would work great for those that want a more granular volume adjustment.
Bucksears has a layout that he's going to post for this.
Thanks mojotron for sharing. Since you made this, you can put whatever you want in your file, those who don´t like it, don´t look!! :icon_mrgreen:
Soundclips when, you say?? :icon_wink:
Morocotopo
Aye, Got sound clip?
I thought jesus was gods son tho! (and that he died?)
Another to add to the list! Thanks once again Mojo, Great job.
Thanks a lot for share it. Soundclips???
Just a suggestion to clean the schematic a little, in the preferences there's an option to hide the grid, it will make it more cleaner.
yeaah!!!that's cool!!!we are all waiting for samples and the layout!!!
I'll add to this too,
Nice work 8) and when can we see a Layout??
I'll have the layout up sometime very soon; today, if I can get a few minutes.
The presence has been modified since this version, I think, so I want to update my PCB and layout as well.
From what I've heard from Mojotron on this circuit, I'm chomping at the bit to build it.
- Buck
Quote from: RaceDriver205 on October 07, 2006, 09:48:45 PM
Aye, Got sound clip?
Sound clips for the Plexizer:
All recorded using VAMP w/small combo setting w/1x12 cab sim and reverb into a computer sound card
Note: I hit the strings very hard sometimes - I'm really a rock player - so your level of distortion may vary - mine is always quite high as I beat my guitar to death. If I really restrain myself, I can get a lot of different tones out of this box by changing my pick angle/attack and location of my picking. I didn't really bring this out very well in the below clips, but I think the below clips cover the Plexizer's sound fairly well.
Set1:Guitar: Ibanez S470 w/Gibson Classic '57/'57+ pickups
Set1 Clip1:
http://mojotronics.com/smf/p_demo_brown.mp3 (http://mojotronics.com/smf/p_demo_brown.mp3)
- Gain = 50%
- B/M = 100%
-T = 50%
-P = 0
Set1 Clip2:
http://mojotronics.com/smf/p_demo_brown_2.mp3 (http://mojotronics.com/smf/p_demo_brown_2.mp3) (settings same as above)
Set1 Clip3:
http://mojotronics.com/smf/p_demo_mid_control.mp3 (http://mojotronics.com/smf/p_demo_mid_control.mp3)
Settings: everything at 50%
Set1 Clip4:
http://mojotronics.com/smf/p_demo_full_control.mp3 (http://mojotronics.com/smf/p_demo_full_control.mp3)
Settings: everything at 100%
Set2: Guitar: Warmoth Strat w/Fender Fat '50's(n/m), HS2(br)
Set2 Clip1:
http://mojotronics.com/smf/p_demo_brown_strat.mp3 (http://mojotronics.com/smf/p_demo_brown_strat.mp3)
Using all of the different pickup combos and tone knob here and there
- Gain = 100%
- B/M = 100%
-T = 50%
-P = 0
Set2 Clip2:
Settings same as Set2 Clip1, using just the br pickup
http://mojotronics.com/smf/p_demo_brown_strat_br.mp3 (http://mojotronics.com/smf/p_demo_brown_strat_br.mp3)
Set2 Clip3:
http://mojotronics.com/smf/p_demo_full_control_strat_br.mp3 (http://mojotronics.com/smf/p_demo_full_control_strat_br.mp3)
Settings: everything at 100%
My apologies, I should have put these together before I posted the schematic. I recorded these at 6am in the morning (trying not to wake everyone in the house up..); I just slapped 'em down - sorry if my playing is a little erratic - there's a lot of rough playing in there :icon_redface:
Quote from: RaceDriver205 on October 07, 2006, 09:48:45 PM
I thought jesus was gods son tho! (and that he died?)
This is really layed out in the first chapter of the book of John (who Jesus is) - God the Father, Jesus - God the Son, and the Holy Spirit are God. Jesus rose from the dead (last few chapters of the Book of John) - this is what easter is all about.
Wooh - Mike , that sounds absolutely fabulous !! :D
It's just jumped position to my very next build :D ( small 1.8watt valve amp to finish first )
Great clips,
Marty.
2xpost...
Quote from: RaceDriver205 on October 07, 2006, 09:48:45 PM
I thought jesus was gods son tho! (and that he died?)
(http://img.photobucket.com/albums/v515/TheToneGod/found_jesus_couch.jpg)
Nice work Mojotron.
Andrew
Quote from: The Tone God on October 08, 2006, 01:28:18 PM
(http://img.photobucket.com/albums/v515/TheToneGod/found_jesus_couch.jpg)
that is one of the funniest things i've ever seen.
Oh boy! Here we go!
This is why religion or politics does not belong here. We all know and love building effects, that's why were are here..everything runs smooth and fine. Enter politics and religion and everyone gets uptight and gets on their soap box. Please spare us!!!!!
The schematic looks cool thanks!
John
Quote from: Bucksears on October 08, 2006, 01:00:04 PM
I'll have the layout up sometime very soon; today, if I can get a few minutes.
The presence has been modified since this version, I think, so I want to update my PCB and layout as well.
From what I've heard from Mojotron on this circuit, I'm chomping at the bit to build it.
- Buck
Sorry for the last minute changes Buck, thanks for making the layout for this.
I had been trying to make the presence circuit on this a bit more like the Marshall 1959, all of the changes I tried were very subtle; the implementation I left in there on this version is the best I had tried. You can use .1uF to 1uF for the bypass cap across the presence control. I use 1uF for C19 in my sound clips (the difference is pretty slight over using .1uF for C19) - this control as it is gives you a little more chimey high end while not changing the low-end.
If you notice, I use a 4.7k resistor for R17 (in stead of 10k in the 1959 design), and this allows the presence to have a more affect on the sound, as well as providing a little more gain without changing the sound over the original circuits value for what is R17 in the Plexizer.
Mods:
1) If you have a high wattage amp and a 2x12 or 4x12 cab, you could try 10k for R17 if you want a less 'beefy' (slightly less gain/thinner) sound.
2) Use 1uF caps for C10 and C3 - this will fatten up the sound a bit - I like the values with either the .68uF and 1uF caps - .68uF is a bit more 'vintage' sounding. For a strat, I recommend the 1uF caps - unless you want to sound exactly like early Jimi.
3) If you think the sound is a bit too dark, every rig is a bit different, you can remove C20 or C21 - and/or just put these on a dpdt switch to make it switchable.
Thanks everyone! If you build one of these, let me know what you think.
No problemo.
Well, here it is. The PCB and parts layout files for the Plexizer can be found here:
http://www.4thlevelmedia.com/stompboxes.html
If anyone sees any mistakes or anything, please let me know. I advise saving the files to your computer and printing them out from something other than Internet Explorer; IE has been known to resize pics when opened within IE.
The two parts that were removed from the schematic are removed from the parts layout, but the pads still remain on the PCB. It's ok, you don't need to populate those two parts. They are marked with red dashed lines on the Parts Layout.
Please post if you build this so we can get some feedback.
Enjoy!!
Buck
Ahh yes, I've been waiting for something like this! But now I have to send puma some more money to make me the board LOL!
QuoteJesus rose from the dead (last few chapters of the Book of John) - this is what easter is all about.
Awesome, I love easter!
QuoteEnter politics and religion and everyone gets uptight and gets on their soap box.
Lol, true dat. Everyone gets annoyed at how silly everone else is. RD205 4 governor! :D
Sounds like it works pretty good, this Plexizer. I think I have enough distortions tho, I have a hard time telling if any new ones I find will sound different to ones I have. Might build it in the end anyway, just to be sure.
Quotechimey high end
Someone add 'chimey' to the stompbox dictionary ;D
Holy cow !!!!!
Thanks for the contribution Mojo !!!!!!
When I have the time I'll work on the perf layout
My Dr. Boogey is not boogeying, so I might use this circuit instead.
Quote from: bluesdevil on October 07, 2006, 07:17:37 PM
Holy shit!! Thank you for sharing!!!
I'm a very devoted Christian myself but I just about fell out of my chair laughing at this one... :icon_mrgreen:
Mojo, those clips sound GREAT! :)
bw
Hi
Cool design.
Obviously a lot of work went into it.
I'll give it a build when there's a layout. Might be a good front end for a dual Ruby.
cheers
PS
QuoteI know that some people will not like my statements about God
So why upset people (e.g. me)? There are plenty of other sites for that stuff. Please use them.
QuoteSo why upset people (e.g. me)?
Funnily enough, if we were talking about the great alL@h, no one would dare joke!
At that I say religon talk should end.
I'm not offended in any way at all, however, I think that we should do what the
folks at www.18watt.com do , dont allow ANY religious or political chit chat at all
After all , this is an FX forum .... right mods ??
.... not even in the OT section !!
peace ,
Marty.
Ah crap, here we go again.
Re: Religion.
Have you guys thought about acting like adults by just ignoring the statements instead of making a silly little fuzz about it ? I would think around here we should not berate somebody for harmless statements but instead focus on thanking them for contributing hoping they will contribute more in the future.
Andrew
Quote from: wampcat1 on October 09, 2006, 07:59:53 AM
Quote from: bluesdevil on October 07, 2006, 07:17:37 PM
Holy shit!! Thank you for sharing!!!
I'm a very devoted Christian myself but I just about fell out of my chair laughing at this one... :icon_mrgreen:
Me too..
Quote from: wampcat1 on October 09, 2006, 07:59:53 AM
Mojo, those clips sound GREAT! :)
...
Thanks Brian, your clips for one of you pedals really inspired me to put something together that would do something like that - smooth Marshall-ish crunch - your advice on the LPF in another thread made a big difference in the authenticity of the sound - at least with my TubeWorks amp and 2x12 H&K cab.
I have a hard time reconciling the need to put 6 knobs on this, but I use them all and they add a bit of versatility. I have tried a number of tone circuits and none of them really hit the right sound. And, the Marshall tone stack just sounds right on this. Anyone have any thoughts on that?
Xavier - if you want to re-cycle your Dr. B board - you can build this on top of a Dr. B layout with some creative use of the back-side of the board. For my prototypes I used Buck's ThunderChief w/Tone Stack layout (with some rather ugly mods) just so I would not have to make an initial layout when I got started with this.
my 6505+ with my Burn Unit/Hellatone 30's/75's sounds SOOOO close to a plexi. but everytime i hear about some new distortion build, i want to build it!
but this time around, i think i for sure am going to build this, as a backup for my rig.
good stuff!
Quote from: The Tone God on October 09, 2006, 02:07:42 PM
Ah crap, here we go again.
Re: Religion.
Have you guys thought about acting like adults by just ignoring the statements instead of making a silly little fuzz about it ? I would think around here we should not berate somebody for harmless statements but instead focus on thanking them for contributing hoping they will contribute more in the future.
Andrew
Andrew, as I clearly stated, I personally dont mind a bit, but the immediate "taking the piss" etc is a bit out
of order from some members.
So my suggestion is just to remove any chace of "all that rubbish happening" by keeping it off here totally.
That was all :D
MM..
Quote from: MartyMart on October 09, 2006, 04:09:38 PM
Andrew, as I clearly stated, I personally dont mind a bit, but the immediate "taking the piss" etc is a bit out
of order from some members.
So my suggestion is just to remove any chace of "all that rubbish happening" by keeping it off here totally.
That was all :D
The statements I made was not directly to anyone in particular. If an all out flame war came about I would agree but that hasn't happen, and quite frankly I doubt it will, so I was just encouraging others to look past it if it bothered them so things would not get to the point of having to put furthur restrictions on the forum. I do not want to see a contributer driven away is all.
Its all cool. :)
Andrew
Quote from: The Furious One on October 08, 2006, 11:01:16 PM
Ahh yes, I've been waiting for something like this! But now I have to send puma some more money to make me the board LOL!
:icon_mrgreen:
Mike, built and working on stripboard :D
Question re voltages :
Q1/Q2/Q4 sitting at 4.5v Q3 at 9v but I;m having problems with Q5 !
Seems to move around and only works properly at about 6v , however
this causes the circuit to have quite a lot of hiss !
I'll keep persuing it, I've built and designed a number of these jfet amp sims
so should be able to solve it , just wondering what your voltages are like ?
Cheers,
Marty
BTW - It's sounding quite like your clips :D
OK, solved it , tuned the trimmer at Q5 by "ear" to remove the hiss
and this works great now :D
Happens to be 7.1v !!
Sounding great now, many thanks Mike.
Marty.
Jeez marty, you don't waist any time at all, do you? Soundclips? (jab, jab...)
John
Quote from: Basicaudio on October 10, 2006, 11:40:27 AM
Jeez marty, you don't waist any time at all, do you? Soundclips? (jab, jab...)
John
Well, I'm a sucker for a nice marshall tone !! :icon_lol:
MM
So (getting a second opinion), does it do a nice early Marshall tone or what?
Quote from: MartyMart on October 10, 2006, 10:15:47 AM
OK, solved it , tuned the trimmer at Q5 by "ear" to remove the hiss
and this works great now :D
Happens to be 7.1v !!
Sounding great now, many thanks Mike.
Marty.
That's GREAT! I'm really glad you like it :icon_biggrin: - 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 :icon_redface: :icon_rolleyes: :icon_redface:) 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?
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 :D
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.
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.
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?
:icon_redface: :icon_redface: :icon_redface:
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.
thanks guru!
Is there a vero layout for thi sproject or is someone working on it?
Quote from: hilbi on October 11, 2006, 07:23:20 AM
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 ?? :icon_wink:
MM.
Quote from: MartyMart on October 11, 2006, 07:58:10 AM
Quote from: hilbi on October 11, 2006, 07:23:20 AM
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 ?? :icon_wink:
MM.
I know, I have done a lot of vero layouts already, not all published.
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
Quote-Friedrich Nietzsche
Thanks
For what? Mojo sharing the circuit freely? Or an opportunity for you to vent?
Quote from: britt-stinker on October 11, 2006, 09:19:47 AM
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
? ? ?
Quote"God id dead"
-Friedrich Nietzsche
how about Nietzsche himself?
(btw: a relative...)
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
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?
Quote from: britt-stinker on October 11, 2006, 09:19:47 AM
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.
Quote from: Mark Hammer on October 11, 2006, 02:22:08 PM
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.
Thanks Andrew for saying it.
QuoteOr an opportunity for you to vent?
Please, no more vent-ers! :icon_lol: :icon_lol: :icon_lol:
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.
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... :icon_lol:
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 !
Please keep this thread re: pedal info.
Yes Boss ;D
btw this circuit just reminds me of a Doug H's take on trainwreck :icon_rolleyes:
Quote from: mojotron on October 07, 2006, 06:14:35 PM
What is it? I wanted to create a box that got a good Marshall 1959 (Plexi) sound - that's what the Plexizer does.
So the Thunderchief isn't a "good Marshall 1959 (Plexi) sound"?
Seriously though, nice work, mojotron.
I have spent the last several years studying Marshall amp circuits and have found many things. "Plexi" can mean many things. There was the Plexi JTM45 with KT66 tubes, which is a slightly modified Fender Tweed Bassman, or 5F6-A circuit right down to the shared cathodes of V1. There was the "Plexi" Bass and Super Bass. There was the "Plexi" Lead and Super Lead, the Tremolo, the Super PA, Organ and so on. Each of these circuits varied wildly from batch to batch, even within the same year or month of production. Marshall would often substitute parts and significantly different values.
It was not out of the ordinary to see three amps with sequential serial numbers that had different OTs, different cathode configurations, etc. This is the root of the old "a good Marshall" story. There are the ones that sound good stock, and there are the ones that you need to tweak a little to get them to sound as good. This is how the whole clique of "Marshall blueprinters" have become popular. They are trying to match their amps to the "magic Marshall" recipe.
My point is, "Plexi" means different things to different people.
BTW, your circuit, like the TC, is based on the popular circa 1969 schematic. Atleast, the "standard" amp schematic.
Again, nice work. I'm looking forward to hearing the sound files.
Impressive design/schematic, to say the least :icon_eek:
cool that you worked a v-amp into the chain too. Congratulations on what looks to have been a lot of hard work.
Quote from: Gary on October 13, 2006, 09:11:25 AM
Quote from: mojotron on October 07, 2006, 06:14:35 PM
What is it? I wanted to create a box that got a good Marshall 1959 (Plexi) sound - that's what the Plexizer does.
So the Thunderchief isn't a "good Marshall 1959 (Plexi) sound"?
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My point is, "Plexi" means different things to different people.
BTW, your circuit, like the TC, is based on the popular circa 1969 schematic. Atleast, the "standard" amp schematic.
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I'm looking forward to hearing the sound files.
Very good point! On top of there not being a 'Plexi' model... I tried a lot of different Marshall designs from a lot of different schematics to shoot for the JTM100 Super Lead sound comparing it to several I had played through (and sadly - never owned :'() the years - my favorite was/is a SL Tremolo (T1959). I think I really got interested in these from the first time I got the chance to play one loud enough to feel it - at that point I was hooked. The TC got me pretty close to that sound, I started modding things, added in the tone stack, as well as the caps C2, C8 and C17 (based on the info in the Fetzer Valve design - the ROG site ROCKS btw!!!), then I came up with these subtle changes from this 'Marshall 1959' (which I do believe is circa late '60's/early '70's) schematic http://www.mojotronics.com/smf/1959.gif (http://www.mojotronics.com/smf/1959.gif) that I think recreate the sound I have in
my head - everyone else's head will differ I'm sure - I was shooting for a very specific tone I know well. Finally, I swapped out a 4.7k for the 10k resistor I was using in R17 because I really liked that extra kick that it gives you on the TC - and bingo I finally had that sound I was looking for. Of, course the louder you play with this thing, the better it sounds - as anyone within a square mile of my house will tell you!!
I would agree that this project has a rather presumptive title - but I think it's a cool name for a project.
I posted a bunch of sound samples earlier in this thread. One of these days I'm going to get some more sane clips on the mojotronics site - but the one's above are fairly representative.
Quote from: idlechatterbox on October 13, 2006, 09:51:56 AM
Impressive design/schematic, to say the least :icon_eek:
cool that you worked a v-amp into the chain too. Congratulations on what looks to have been a lot of hard work.
Thanks, I REALLY need to get a new SM57 - but the VAMP does a good job for a 'generic amp' sound for stuff like sound clips using the line outs on the back.
The v-amp Pro even has a digital-out line in the back :icon_cool:.
Quote from: mojotron on October 13, 2006, 02:15:01 PM
I tried a lot of different Marshall designs from a lot of different schematics to shoot for the JTM100 Super Lead...
You mean just a Super Lead.
The JTM100, sometimes called a JTM45/100 was identifiable by the chrome "100" on the upper left corner of the cabs. That amp was a 100W version of the JTM45. I think they had four KT66s, similar to 6L6s, in the power amp and a shared cathode on the first preamp tube. They also typically had a 220-330uF cathode bypass cap. Those amps were the fathers of the Super Lead/Lead amps.
Quote from: mojotron on October 13, 2006, 02:15:01 PM
http://www.mojotronics.com/smf/1959.gif (http://www.mojotronics.com/smf/1959.gif)
Yes, that's a schematic from the days when I think Unicord was making Jim Marshall's amps. After that contract ran out, he opened his own factory and launched the JMP amps. The schematics from before this time are very hard to find and are often not accurate, due to the changes that happened in production.
Quote from: mojotron on October 13, 2006, 02:15:01 PM
I would agree that this project has a rather presumptive title - but I think it's a cool name for a project.
Calling this a Plexi is as justified as anything else. I hope you didn't take what I said as aggressive. I wanted to point out that there are many things that are called Plexi, right or wrong. For that matter, the circuit you built from was the same basic schematic that was used for the metal panel amps.
Quote from: mojotron on October 13, 2006, 02:15:01 PM
I posted a bunch of sound samples earlier in this thread.
I've D/Led the files. I will listen to them when I get home from work. I'm really looking forward to it.
As someone else said, the JFET as amp-sim thing all started with Doug H's Meteor. We spoke with Doug after the Meteor came out and asked if we could explore this further. Doug said it was cool, so off we went. I still have that e-mail printed out somewhere.
About 4 years ago, RoG posted the original "Grace" circuit. That was the first attempt at series CS JFET stages we tried. That was in April 2002. Doug's Meteor showed us how to refine that first idea into something much cooler.
Again, nice job. See the RoG FAQ for something very similar.
Quote from: Gary on October 13, 2006, 05:50:51 PM
You mean just a Super Lead.
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Hmmmmm, :icon_question: you are probably correct about that.
Quote from: Gary on October 13, 2006, 05:50:51 PM
Yes, that's a schematic from the days when I think Unicord was making Jim Marshall's amps. After that contract ran out, he opened his own factory and launched the JMP amps. The schematics from before this time are very hard to find and are often not accurate, due to the changes that happened in production.
This is about the only schematic I could find that was from the right period, that would explain a few things.
Quote from: Gary on October 13, 2006, 05:50:51 PM
Quote from: mojotron on October 13, 2006, 02:15:01 PM
I would agree that this project has a rather presumptive title - but I think it's a cool name for a project.
Calling this a Plexi is as justified as anything else. I hope you didn't take what I said as aggressive. I wanted to point out that there are many things that are called Plexi, right or wrong. For that matter, the circuit you built from was the same basic schematic that was used for the metal panel amps.
Thanks for the clarifications, I appreciate the info! Correct me if I'm wrong, during that period in time didn't they mix the panels depending on what they had?
Quote from: Gary on October 13, 2006, 05:50:51 PM
As someone else said, the JFET as amp-sim thing all started with Doug H's Meteor. We spoke with Doug after the Meteor came out and asked if we could explore this further. Doug said it was cool, so off we went. I still have that e-mail printed out somewhere.
About 4 years ago, RoG posted the original "Grace" circuit. That was the first attempt at series CS JFET stages we tried. That was in April 2002. Doug's Meteor showed us how to refine that first idea into something much cooler.
Again, nice job. See the RoG FAQ for something very similar.
Yes, quite similar, it's obvious this and the TC were shooting for the same Marshall 1959 design. I don't have a schematic of the Medeor - but I know this sort of thing all started with Doug and we owe him a lot.
I did not very too much from the 1959 schematic, on this project, as I really liked the sound. The only exceptions were the presence circuit and where I put R17, 10k sounded kind of weak - I noticed that this was half that on the TC and Electric's JCM emu - and that sounds great. I'm still working to perfect the presence circuit using yet another stage, however I'm coming across diminishing returns on my last few ideas.... The simple 100n bypass works pretty well I think.
The early metal panels were, for the most part, identical to the schematic you used. By mid to late '69, the basic design had gelled into what you see on the Unicord schematic. There were deviations from that in production, as that appeared to be the Marshall philosophy. Their attitude seemed to be to use whatever they had on hand when they ran out of a certain part.
Something else I've noticed on your schematic:
The second stage cathode (source) bypass cap. This only appeared on a few amps that I've seen. Those were mostly from the earlier '68 period, which was when they began to transition to the values on the Unicord schematic you worked from. Coincidentally, we used the Unicord schematic for the TC. The new HW 1959s use this same schematic, despite the marketing line of being based on a pre-July '69 schematic.
I have spent many years trying to unravel the Marshall history. The "History of Marshall" is a good starting place to learn more, but even that book will not prepare you for all the variations in production you will see in real-world analysis of the amps. 90% of the vintage amps you'll see are from the Unicord schematic. The earlier ones are sometimes very different. Another good source for Marshall information is from Velvet George at Metroamps.com. Unfortunately, they have taken their board down, but you may be able to contact them directly for information. they have a nice CD of schematics that comes with their amp kits. It has som pretty good information that details many variations of Lead and Super Lead amps from around '67 on up.
On your presence control, look at the Full TC schematic on the RoG FAQ. See the 4k7 on the tail of the PI stage? Change that to a 5kL pot and tie the 100n to the pot's lug 2. Lug 3 will go where the top of the 4k7 was. Lug 1 goes to ground, of course. There you go. That's how the amp was wired. It will work here, too. Most classic use of the 1959 was "dime all the controls and let her rip." That's why the TC omitted the tone stack and wired the presence pot wide open. Besides, the Marshall tone stack doesn't have a wide range of adjustment.
Hope this helps.
BTW, I listened to your clips. They sound nice. I like that Yngwie-esque scale up you do.
Do you find the Vamp speaker sim adds a lot of bass back to the sound? You used the analog one, right? You bypassed everything and took the signal out from the XLR connectors?
Quote from: Gary on October 15, 2006, 10:21:25 AM
The early metal panels were, for the most part, identical to the schematic you used. By mid to late '69, the basic design had gelled into what you see on the Unicord schematic. There were deviations from that in production, as that appeared to be the Marshall philosophy. Their attitude seemed to be to use whatever they had on hand when they ran out of a certain part.
Something else I've noticed on your schematic:
The second stage cathode (source) bypass cap. This only appeared on a few amps that I've seen. Those were mostly from the earlier '68 period, which was when they began to transition to the values on the Unicord schematic you worked from. Coincidentally, we used the Unicord schematic for the TC. The new HW 1959s use this same schematic, despite the marketing line of being based on a pre-July '69 schematic.
I have spent many years trying to unravel the Marshall history. The "History of Marshall" is a good starting place to learn more, but even that book will not prepare you for all the variations in production you will see in real-world analysis of the amps. 90% of the vintage amps you'll see are from the Unicord schematic. The earlier ones are sometimes very different. Another good source for Marshall information is from Velvet George at Metroamps.com. Unfortunately, they have taken their board down, but you may be able to contact them directly for information. they have a nice CD of schematics that comes with their amp kits. It has som pretty good information that details many variations of Lead and Super Lead amps from around '67 on up.
That's awesome! Gary - I appreciate it - thanks for the info! I have a lot of homework to do.
Quote from: Gary on October 15, 2006, 10:21:25 AM
On your presence control, look at the Full TC schematic on the RoG FAQ. See the 4k7 on the tail of the PI stage? Change that to a 5kL pot and tie the 100n to the pot's lug 2. Lug 3 will go where the top of the 4k7 was. Lug 1 goes to ground, of course. There you go. That's how the amp was wired. It will work here, too. Most classic use of the 1959 was "dime all the controls and let her rip." That's why the TC omitted the tone stack and wired the presence pot wide open. Besides, the Marshall tone stack doesn't have a wide range of adjustment.
Hope this helps.
That's pretty close to the presence control I have on there - minus the 2.2nF/100k feedback - and I do like that. As I remember that presence control was not all that significant on the actual amp - infact, IMO the Marshall tone stack is not really that affective for controlling 'tone', but rather significant to getting the right tone for anything that was not a 'dimed' tone. I think the Miller caps C2 and C8 really make the tonestack work - at least to my ears.
The caps C6, C9 and C17, I just put them in there to see if I liked the sound any better: I think the circuit retains just a bit more bite with C6 (came from the 1959 sch) and C9 in there and C17 cut some of the shrill of my Strat when I used a booster in front of it. C9 and C17 were actually mistakes, putting them on the wrong Qs at 2am (happens...), but I liked the subtle changes so I left them on there. I found that C6, with the treble and presence rolled back - T@50% P@0% and roll the mids back to about 80-90% - gave me a great early Eric Johnson sound - add a little FF and TubeDriver in front of the plexizer with a generous amount of delay in the loop and you get the right EJ tone when going pentatonic at light speed - IMO. This is all very subjective, but there is an upper mid emphasis with these 3 caps in there that I really like. I spared you guys my attempts at 'Cliffs of Dover' on the clips :icon_redface:, but getting a dimed sound as well as that Ah Via/Venus EJ sound (with the right supporting boxes) was what I was shooting for - equally. People can leave off C9/17 if they want to save 5 cents, or experiment and put C17 from gate to ground which is where it was supposed to go initially.
Quote from: Gary on October 15, 2006, 10:21:25 AM
BTW, I listened to your clips. They sound nice. I like that Yngwie-esque scale up you do.
Do you find the Vamp speaker sim adds a lot of bass back to the sound? You used the analog one, right? You bypassed everything and took the signal out from the XLR connectors?
Thanks - I like Yngwie's playing on 'Fire and Ice' a lot - I'm not sure if I think I'm a big fan of some of his stuff, but he's the godfather of that sort of thing.
I think the VAMP does adds some bass, but I can dial it out on it's 1x12 speaker sim. I never really look at that box as a 'dead-on' set of sims, rather not a purist, I lower my expectations to just getting about the same tone as my TubeWorks gear - and it does that well for testing effects. I just plug into the font, use a small combo sim with it's 1x12 cab sim then take the line outs off of the back and run them into my computer. It works, usually my biggest problem is overloading the front end of the VAMP, but I have been using a Morley volume pedal to adjust for that and it works for what I need it for.
Using the VAMP I still wake up my kids a night when I scream "Thankyou Peoria!!" at the end of a session :icon_biggrin:
I think the Presence control on the amp is pretty effective, although I have not had the chance to play one with the more rare 0.68uF cap. My experiences have always been with ones that used a 0.1 cap.
My point was, with the negative feedback, the Presence control has a more dramatic effect.
I have a Vamp Pro. I use it fairly regularly, although I do not like the Brit Classic setting.