RnFR- MasterBlaster

RnFR · Post by **RnFR** » 28 Jan 2009, 07:58

well here's my latest to throw in the pot. this one started out as my entry into the AC30 race, but turned into much more. it could even get tossed in with the Honey Bee pile as well as you are able to go from a cleanish boost to a light OD, to a fuzz, depending on how you set it.

there are 2 gain controls ala SoulSonic's Hunny Bunny pedal, except mine is built around a 3 tranny germanium platform using some low leakage soviet ge's with a gain range of around 40-60. the Blaster pot is the main Gain control and the Master control is kind of like SS's Hunny control except it does more of a mid/hi boost in gain. the Blaster pot is set up a bit like the AC30, but there is also the HI/LO switch which basically allows you to go from something like the AC's Top Boost channel or to the Normal channel. in the HI position this thing does a great treble booster impersonation with a real glassy, sparkling, top end and can get up to a very tight focused fuzz sound. in the LO position the tone gets filled out a bit and you have another octave on the low end. turn up the Master and Blaster control and you end up with something like an AC30 crossed with a germanium fuzz. finally there is the Gas control which is your basic starve pot. i found that this thing can survive on extremely low voltage(i ended up using a 350K pot) as there is still plenty of boost to bring the volume up. with the Gas down, the tone gets thicker and crunchier. very cool with your tone rolled off on the guitar as well for a super nasty thick fingerpicking or slide blues fuzz. very lofi! there really are a lot of options with this thing- boost, OD, or fuzz, and it's got tons of hi-mids. it'll cut through a mix for damn sure. i might end up doing a high end roll off pot or switch at the end of the circuit as well, but that's kind of an afterthought.

attached is the schematic and PCB layout(unverified- all my shit is packed for the move this weekend). also just so there is no confusion- the layout is made for some larger size components that i wanted to use. hopefully i'll get some sound samples done soon and post em up. cheers.

RnFR · Post by **RnFR** » 28 Jan 2009, 11:55

oops, i did it again!

there was a small mistake on the Blaster pot. lugs 1 and 2 shouldn't be connected. here's the correct item.

briggs · Post by **briggs** » 28 Jan 2009, 14:33

That looks cool RnFR. Pity I have no germanium at the moment. I really need to order some!

RnFR · Post by **RnFR** » 29 Jan 2009, 00:27

a lot of people seem to think that if ge's are in the perfect fuzzface gain range that they are unusable. hopefully this design will give them something to put them in.

soulsonic · Post by **soulsonic** » 31 Jan 2009, 04:34

I'm going to try breadboarding an NPN version with these 104NU71s I got... they're all low gain-ish.

RnFR · Post by **RnFR** » 31 Jan 2009, 09:06

cool. i've found now that using it with a guitar with hotter pickups that the bias needs to be tweaked a little. you can get away with using the starve knob though. also i've been putting a basic tone knob at the end of the circuit- it get's kinda bright with some guitars. i'll probably do version 2 sometime soon.

RnFR · Post by **RnFR** » 04 Feb 2009, 06:16

just a note-

i biased the first two trannies to 4.5V on the collectors with the 33K resistors, but they sound over biased. try 68K-100K. didn't notice this until i plugged in my guitar with a P90 in it. usually i'll swap out guitars to see how the circuit reacts, but i guess i was a little too enamored with my airline to put it down.

i'll update this one with the values soon, but as it is it still sounds fine with an adjustment of the voltage starve pot.

also, a 2200pF cap to Gr with a 100K pot before the volume pot rounds the tone out nicely.

RnFR · Post by **RnFR** » 30 Apr 2009, 02:26

i revisited this circuit and built it up last night. it sounds really good, and is much higher gain than i remember with a high output guitar. all those "glassy clean tones" were coming from a guitar with very low output pickups so keep that in mind. i made a couple of adjustments-

-the collector resistors stayed at 33K, it seemed fine.
-input cap was upped to .1uF. more gain, and a bigger difference when switched.
-the Blaster pot(gain) was lowered to 100K(250 might be better). i didn't like what was going on when the gain was too low.
-the Master pot(hi freq gain) was lowered to 20K for better sweep. use 25K if you don't have a 20K.
-the Gas pot(voltage) was lowered to 250K.

i'll post a new schematic shortly.

RnFR · Post by **RnFR** » 30 Apr 2009, 03:21

i also already have a pcb layout, but it uses some large axial caps that i bought from the russian dudes. if anyone wants a copy, just let me know.
here's the latest schematic.

RnFR · Post by **RnFR** » 30 Apr 2009, 19:50

here's the new layout.

steelplayer · Post by **steelplayer** » 30 Apr 2009, 22:45

Heya RnFR,
Thx for posting an update to this. I have some of the Russian GE's on the way, and I'm really looking forward to playing around with this and the "Dirty Boots" Cool stuff!

May I ask specifically what transistor(s) you're using here?

Thx man!

RnFR · Post by **RnFR** » 01 May 2009, 01:15

for this one, i used mp14s. the gains were around 40-50, low leakage. another forumite is going to give GT308s a try, and i think they should work as well. let me know how it goes!

steelplayer · Post by **steelplayer** » 02 May 2009, 00:22

Thanks man, I appreciate the info!

Over the next couple of weeks I'll be breadboarding these circuits with a selection of the Russian GEs. I'll keep you posted as to how it goes. Gonna take me a while to sort through it all I'm sure.....still a noob with a lot of this stuff. First order of business will be to study up on testing leakage and gain.

Again, thx for the inspiration.

RnFR · Post by **RnFR** » 02 May 2009, 00:50

no problem! and good luck. you have any questions feel free to ask. the cool thing about making circuits with these soviet trannies is that usually they are extremely consistent gain wise, and usually very low leakage, so once you get an idea of the gain of a certian make, you can usually just pop them in without having to do things like using trimpots for biasing, or measuring gain and leakage every time you make a circuit. i used to just test a batch for duds to make sure they are all ok, and then go from there. now that i have a peak analyser, it makes it a lot easier.

steelplayer · Post by **steelplayer** » 02 May 2009, 12:13

Whoa....hold the phone....I just looked up some info on the Peak analyzer.

Am I understanding this correctly, the Peak DCA255 will identify npn\pnp, measure gain AND leakage? Yikes, that imho would be $70 well spent! Would that be the one you'd recommend?

RnFR, did you buy it direct or get it here in the States.

Again, thanks......Learn something new every day around here!

JJ Gabor · Post by **JJ Gabor** » 06 May 2009, 08:40

This looks interesting, have tonnes of Russian low gain germs kicking around. Might try it with the 308Bs and the 313s.

RnFR · Post by **RnFR** » 06 May 2009, 08:58

steelplayer wrote:Whoa....hold the phone....I just looked up some info on the Peak analyzer.

Am I understanding this correctly, the Peak DCA255 will identify npn\pnp, measure gain AND leakage? Yikes, that imho would be $70 well spent! Would that be the one you'd recommend?

RnFR, did you buy it direct or get it here in the States.

Again, thanks......Learn something new every day around here!

i bought it direct. really cool box!

JJ Gabor wrote:This looks interesting, have tonnes of Russian low gain germs kicking around. Might try it with the 308Bs and the 313s.

then check out the thundertone as well. it's a Ge model of the Supro Thunderbolt amp. it's a nice sounding circuit with a cool tone control.