http://diystompboxes.com/sboxforum/viewtopic.php?t=19321&highlight=unidrive
The schem is in this post above.
This rivals the "Jordan Bosstone" ... I'm totally blown away with this little
circuit, it's a 10/10 :D
I didn't find much posted about this one, odd looking setup but here's
what I changed/discovered :
Ditched that whole "reistors/multi pot" front end - after all, I don't need to
connect to "a piano/hammond/trumpet/cassette tape" etc etc ...
Just went straight in via 1M to ground instead of the 220k to ground, no
pot needed as there's one on every gtr !
The back end looks like volume, but is a "gain/drive" pot coming off the
8k2 link from Q1.
The point of the 10k pot going to ground via the wiper of a 2k pot is lost
on me, so that went, I just used a 50k pot as "normal" wiper to jack and
lug 1 to ground.
Transistors:
My guess is any "medium/high" gain NPN's will work, I went straight to
a pair of 2N5089's Q1/Q2 and an MPSA18 for Q3.
Resistors:
There are two "odd" ones, the 7.55K and the 4K emitter resistors, I used
a 6k8 and a 3k9 for these, also used a 20k trim pot for Q2 from 9v.
Every other value was preserved for resistors/caps
All the 10uf's are 50v electro's and the "50uf" is a 47uf/50volt electro
SOUND:
With the 50k gain pot low, nice almost clean drive - not like a "fuzz" at
all - more like a low gain TS-9 sound.
At higher settings this thing comes alive, sound is a mix between a Jordan Bosstone and a "Blackfire" !! HUGE !! and bright and full :D
SUMMARY:
GO BUILD THIS RIGHT NOW !!!
Try my small changes, you WILL NOT be dissappointed
:twisted:
( I hope this doesn't come over like a bad "Harmony-Central" review, I'm
just VERY excited by this one, it really is THAT GOOD :D )
Marty.
you submit a new fuzz build report every three days....how many fuzz pedals does one man need?
sounds good though, well worth a look, I only have MPSA13 so I will give them a go....
I actually have a vintage Uni-Drive around the shop somewhere, and it's a truly killer pedal. The only thing that's kept it off the pedalboard until now is that large foot pedal enclosure!
The 10k / 2k resistor combo is part of the rocker pedal setup. The 2k pot lets you "preset" the heel down volume, and you get full volume with toe down. No reaosn not to use a 10k pot by itself there if you want to.
And the back end _is_ a volume control. The 8k2 resistor is for feedback to the first transistor, probably to keep it from oscillating.
Matt Farrow
Quote from: nelsonyou submit a new fuzz build report every three days....how many fuzz pedals does one man need?
sounds good though, well worth a look, I only have MPSA13 so I will give them a go....
NOT TRUE !!! :D
I've been away for a week, and was working flat out for 8 days before
that ....... !
I guess I'm just getting quick, it only took 1&1/2 hrs to build it !
Totally worth building, though mine is not a "fuzz" sound at all :D
Perhaps my 50k out pot has changed things, but it doesn't do much of a
"volume" increase, only the last 10%, the whole range seems like "gain"
to me ??
Marty.
Glad you're excited about it... now, where is that schematic exactly? There's a link to the Fuzz Guts page which has a few Univox pedals but no Unidrive. Am I missing something? It's early and I haven't had enough coffee.
AL
http://diystompboxes.com/sboxforum/viewtopic.php?t=19321&highlight=unidrive
SORRY !!
Here's the correct link, I'll put it up top also :D
Marty.
Ahhhhh !!!! Thank you
AL
I see a "FF". Third transistor and two feedback loops...definitely interesting topology there...
The front end is for sales to those who couldn't swap input caps/ use with different guitars/bass I think. one, or a selection of two cap values there'd do me.
Marty,
Did you just use a 50k pot or a pedal with a 50k pot?
Thanks!
Arn C.
Quote from: Arn C.Marty,
Did you just use a 50k pot or a pedal with a 50k pot?
Thanks!
Arn C.
For now, it's just a 50k pot I do have a "crappy" wah which I might use
the case for this, but it works well "set" like a normal OD pedal and will
"clean up" quite well rolling back the gtr vol pot so ........ ?
Pete :
I't's more akin to the "coloursound OD" than any type of "Fuzz" - unless
you put in some NPN germaniums of course :wink:
It is a "Unidrive" after all !!
Don't get the use of all those input resistors, just "level" control ??
A BMP tonestack/Superfuzz notch would make it even more "fun"
Definate "keeper" and will be on the pedal board quite a lot I think :D
Marty.
hey, post a simple sound clip if you have a chance... I'm curious on how it sounds...
Thanks Marty!!!! 8)
Arn C.
Hello Hello---
Jeez Marty, I was just thinking that you don't build ENOUGH fuzzes!
This is interesting......I've had this schematic for years and never built it.
Is the MPS 18 higher gain then the 5089?? [Just wondering if the "higher gain in Q3" relationship needs to be observed for this circuit.]
Brian.
the MPSA18 is a darlington NPN, V high gain.
good for ampeg scrambler clones...
Quote from: brian wenzHello Hello---
Jeez Marty, I was just thinking that you don't build ENOUGH fuzzes!
This is interesting......I've had this schematic for years and never built it.
Is the MPS 18 higher gain then the 5089?? [Just wondering if the "higher gain in Q3" relationship needs to be observed for this circuit.]
Brian.
The MPSA18 is probably overkill ! It's a VERY hot output !!
I'm busy 'til monday, but I'll get a sound clip done then and also try some
less "gainy" transistors, at the moment it's breaking up my amps a bit
which is adding to the "crunch" some what !!! :shock:
BC549's or 2N3904's/2N5088's may be a better bet.
If someone has time over the weekend, please build one and tell me how
you like it ?
Marty.
It really doesn't matter what the last transistor is, with regard to hFe. It's used here as an emitter follower and doesn't provide voltage gain, only current gain and a low-impedance output. If you want higher gain from this circuit, use your MPSA18 for Q2. Q3 could be a 2N3904 or 2N2222 with no real effect on the sound or response.
The sound of the vintage unit I have is NOT fuzzy at all - it's a fairly clean boost with some hints of transistor overdrive. It's really designed to pummel the preamp of a tube amplifier into submission, and it does a great job at that.
For folks who'd like to clone this in a non-rocker pedal format, I'd say:
Ditch the rotary switch up front, change the 220K to a 1M, change the input cap to a 1uf NP (if you can't get a 1uf NP, then a .1 film or poly cap would work, don't use an electro on this one.)
The 7.5K resistor can be replaced with a 20k and a 12k in parallel.
Ditch the 2K pot, just run the 10k pot's 3rd lug to ground.
One knob, no waiting. A super-loud boost that sounds great and will crunch up your amp with no complaints.
Matt Farrow
Thanks Matt, that's about what I have, I guess that using 2x2N5089's is
giving me that extra "crunch" to the circuit - which I like BTW :D
I'll ditch the first electro on monday and use a 1uf NP poly cap.
I can't detect any "noise" though at present, its very quiet !
It does "blast" my valve amps in a VERY nice way !!
Could a "Fuzz" pot be added, a bit like a FuzzFace arrangement ?
That would give some nice control around Q1/Q2 ?
Marty.
soundclip soundclip soundclip!!!
Thanks for the heads up Marty!
I just built the Unidrive using Matts suggested substitutes and 2N5089 trannys. This is a ballsy booster! Very nice bite and definition to the notes, scary amount of boost. No fuzz to speak of.
I am testing it out on my Boss VF-1 modeling preamp tonight but hopefully will get to crank it up with an amp tomorrow. I am certain the preamp tubes will get a surprise.
A very cool circuit ... thanks Marty and Matt!
For the caps marked 10v, I'd use 16v or 25v....
The input and output caps at 10uf are quite large, and should pass bass guitar source inputs N/p.
Have you Tried smaller ones for less bass ?
That whole input thing is like a big ol volume [input gain] pot made from fixed resistors. It looks like a rotory switch would be used, I'd replace that with a 'rotory' pot, or eliminate it...maybe just insert series resistance there.
Looking at the input section of the UniDrive, it seems that it was designed to accommodate a variety of different inputs (keyboard / bass / guitar, etc.) and thus the stepped attenuator. The coupling caps are also large because some of those sources have very low impedance inputs, and the lower the impedance, the bigger your coupling caps have to be in order to pass the same low frequencies.
For guitar and other high-impedance sources, smaller caps are OK. 10uf is WAY overkill, I'd suggest 1uf at most. 0.1uf would work just as well, but I'd stay away from polarized electros on the input stage because IME they can be "farty" sounding. An 0.1uf film or poly cap would be a great choice.
As for voltage ratings, the easiest way to determine it is to figure out what voltage should be applied to each end of the cap and then add some safety margin. In this case, one end is at somewhat less than 1V (transistor base,) and the other end is floating (but we can assume no DC potential.) So 1V across the cap, you'd be okay with a 6.3 or 5V cap. Since most caps you're likely to meet are higher-rated than that, 10V or 16V is probably easier to obtain. Anything would work for this purpose.
For power supply caps, it's the same story, just figure out the voltage difference across the cap (for a battery powered circuit, it's typically 9V and a bit,) and add some safety margin. I use 25V caps for most of my pedals, but some of my stock is still 16V caps. I allow a 20% safety margin ALWAYS, and more is better if you can fit it on the board.
Matt Farrow
Quoteyou submit a new fuzz build report every three days....how many fuzz pedals does one man need?
What?? :shock:
There can
never be enough fuzz/distortion pedals....
:roll:
All of them. Until he finds the few he really is going to use, then the rest for 'diversity'...lol, that' IMCase means like 20.
Between buying [earli in my 'career'] and building [once I started] I must have tried 100+ fuzzes., OD's...
Quote from: petemooreAll of them. Until he finds the few he really is going to use, then the rest for 'diversity'...lol, that' IMCase means like 20.
It is so important in this day & age that we maintain an atmosphere of multi-fuzzal diversity.
Doug
Quote from: Doug_HQuote from: petemooreAll of them. Until he finds the few he really is going to use, then the rest for 'diversity'...lol, that' IMCase means like 20.
It is so important in this day & age that we maintain an atmosphere of multi-fuzzal diversity.
Doug
:D :D
It also gives me great pleasure to "build" something that makes a good
useful/musical noise .... WITH MINE OWN HAND !!
.... Plus I DO make my living from music .......
and I love building a "classic" that sounds like "POO" then watching as
someone pays £500 on Ebay for the same thing ... minus the "tweaks"!!!
:shock: :shock:
M
I ran some bias and TRANsient sims on the stock circuit and (regardless of models) it showed onset of clipping with just under 30mV of input voltage swing and no input resistance to the circuit ...
Quote
Univox Unidrive -- Headroom Test without Input-Source Resistance
Vcc 99 0 9
Vin 11 0 0 sin(0 0.03 1e3) ac 1
Rin 11 0 220k
Cin 11 1 10u
Rb1 1 0 150k
Rc1 99 2 100k
Re1a 3 33 7.5k
Ce1a 3 33 50u
Re1b 33 0 100
q1 2 1 3 2N5089
Cbe1 1 3 .001u
Rc2 99 4 10k
Re2 5 0 4.1k
Ce3 5 0 0.2u
q2 4 2 5 2N5089
Cbc2 2 4 40p
Rf1 1 5 100k
Re1 6 0 3.3k
q3 99 4 6 2N5089
Co1 6 44 10u
Rf2 44 3 8.2k
Co2 44 55 10u
Ro 55 0 10k
.model 2N5089 NPN(Is=5.911f Xti=3 Eg=1.11 Vaf=62.37 Bf=1.434K Ne=1.421
+ Ise=5.911f Ikf=15.4m Xtb=1.5 Br=1.262 Nc=2 Isc=0 Ikr=0 Rc=1.61
+ Cjc=4.017p Mjc=.3174 Vjc=.75 Fc=.5 Cje=4.973p Mje=.4146 Vje=.75
+ Tr=4.671n Tf=822.3p Itf=.35 Vtf=4 Xtf=7 Rb=10)
.model 2N5210 NPN(Is=5.911f Xti=3 Eg=1.11 Vaf=62.37 Bf=809.9 Ne=1.358
+ Ise=5.911f Ikf=14.26m Xtb=1.5 Br=1.287 Nc=2 Isc=0 Ikr=0 Rc=1.61
+ Cjc=4.017p Mjc=.3174 Vjc=.75 Fc=.5 Cje=4.973p Mje=.4146 Vje=.75
+ Tr=4.68n Tf=820.9p Itf=.35 Vtf=4 Xtf=7 Rb=10)
.model Q2N2222 NPN(Is=3.108f Xti=3 Eg=1.11 Vaf=131.5 Bf=217.5 Ne=1.541
+ Ise=190.7f Ikf=1.296 Xtb=1.5 Br=6.18 Nc=2 Isc=0 Ikr=0 Rc=1
+ Cjc=14.57p Vjc=.75 Mjc=.3333 Fc=.5 Cje=26.08p Vje=.75
+ Mje=.3333 Tr=51.35n Tf=451p Itf=.1 Vtf=10 Xtf=2)
.MODEL 2N3904 NPN(Is=6.734f Xti=3 Eg=1.11 Vaf=74.03 Bf=416.4 Ne=1.259
+ Ise=6.734f Ikf=66.78m Xtb=1.5 Br=.7371 Nc=2 Isc=0 Ikr=0 Rc=1
+ Cjc=3.638p Mjc=.3085 Vjc=.75 Fc=.5 Cje=4.493p Mje=.2593 Vje=.75
+ Tr=239.5n Tf=301.2p Itf=.4 Vtf=4 Xtf=2 Rb=10)
Here's some changes I did to run it smoother and with a higher clipping threshold:
(i) 10k (PAD) pot in series with input
(ii) replace 100 ohm in first stage emitter circuit by 1k (GAIN) pot
(iii) all caps replaced by metal film caps - no electrolytics :
input cap replaced by 0.033 poly
47u aross 7k5 replaced by 0.66u (0.22 x3)
10u across 4k replaced by 0.22u
10u output caps replaced by 0.22u each
I think some input resistance helps make the circuit feel less hyper and the idea of using smaller non-electro caps a real good idea - the 47u electro sucked ... also, as I drop the 1k GAIN pot (increasing gain) I get slightly enhanced brightness - so there's some sort of pocket thing happening there ... great circuit for getting edgy/squeaky sound with tube amps ... thx!
~jc
JC that's great !!
Thanks for the input, I'll build a version tomorrow with that setup and
see how it sounds :D
marty.