(un)Worthy Mods

[Dominic.]

yeah it's a horrible clashy sound. Take it it's not meant to be like that? Unless I'm playing octaves or fifths it sounds absolute gash and unlistenable. I always presumed that's what it was meant to be

[james90]

Nope it's not supposed to be like that. I wonder if it had something to do with that noise issue? Did that guy you sent it to change anything?

 

Should sound more or less like this

 

http://www.youtube.com/watch?v=7xxk4QjjNYQ

 

The fat setting on the mini toggle is much more useful than the bright setting. MOAR MIDS

[Dominic.]

The guy I sent it to said it was fine and no problems. I've used it with good power supply, cheap one and battery, same sound. I can try take some gut pics to show you guys if there's anything that looks dodgy?

[james90]

I don't think the pictures would show much to be honest. I wouldn't be surprised if it was some sort of interference problem - is it sort of a harsh white noise type of sound that you hear on certain chords but not others?

 

 

Also, can someone point me in the direction of some NKT275s? Or whatever's closest to those.

 

Idea is to build a reproduction of the 1966 fuzz face, possibly with the Hendrix mods...

 

 

 

 

So far I've got the film cap (Philips/Mullard thing, but I'm also going to try a tropical fish because those look nice), the electrolytic caps, and PCB (which may or may not be good quality)

 

I found some NKT275s on ebay which are EXACTLY like those, and supposedly tested for fuzz pedals... but they cost $100 for a pair.

[Dominic.]

Ill record it when I get back to uni

[Jaicen]

NKT275's? Fuggeddaboudit. There's too much MOJOBULLSHIT attached to get them at a cost that is at all reasonable. Do yourself a favour and contact Steve at Smallbear. He will hook you up with some NOS Russion Ge trannies that will sound great in a Fuzz Face.

Then forget about 'the Hendrix mods' and build it stock, with a trimmer to bias Q2.

 

Once you have it working, put in some difference caps for C1 (the input cap), that will make a huge difference to the tone, smaller caps take away a lot of the flabby bottom end, so unless you're running a 4x12 it can be a godsend.

[james90]

haha fair enough

 

Do you know what type of transistor I should be asking for? I don't see any ones like you mention listed on his website.

 

What would you recommend for C1? something like 1.5uf? 2.2uf is stock

[Don'tPostThePear]

Just do a search on ebay for "russian germanium transistor"

they are cheap and most of the time better than the european and american Ge stuff (lower leakage etc.) (hopefully they wont make a geiger counter go crazy)

 

btw building a stock or hendrix or any other FF with Ge trannies will probably sound like shit most of the time (with Si trannies they suck even more)

 

Biasing the second transistor to half supply voltage (-4.5V) is the key for good sound, you should get a PCB which allows a trimpot for that feature or it might be a good idea to put that pot on the pedal like in the Analogman Sunface (in this case it will be harder to measure the voltage on that transistor)

 

(edit: for C1 use something like an 1uF film then change it according to your taste)

[james90]

Just do a search on ebay for "russian germanium transistor"

they are cheap and most of the time better than the european and american Ge stuff (lower leakage etc.) (hopefully they wont make a geiger counter go crazy)

 

btw building a stock or hendrix or any other FF with Ge trannies will probably sound like shit most of the time (with Si trannies they suck even more)

 

Biasing the second transistor to half supply voltage (-4.5V) is the key for good sound, you should get a PCB which allows a trimpot for that feature or it might be a good idea to put that pot on the pedal like in the Analogman Sunface (in this case it will be harder to measure the voltage on that transistor)

 

(edit: for C1 use something like an 1uF film then change it according to your taste)

 

so will any russian germanium transistor work?

 

the PCB I have is a clone of the original, so I don't think it will allow a trim pot. What about using a fixed resistor?

[Jaicen]

Seriously, email Steve at small bear. He wil sort you out. Tell him I sent you

[Crowella]

Seriously, email Steve at small bear. He wil sort you out. Tell him I sent you

 

+1 on this and the Fuzz Face build.

 

Just saw the site again. Changed a bit since I last used it. Nice to have the pictures up. Will be good when looking for things such as knobs now.

[Don'tPostThePear]

so will any russian germanium transistor work?

 

the PCB I have is a clone of the original, so I don't think it will allow a trim pot. What about using a fixed resistor?

 

there is no reason to clone the original shitty layout, (only for the looks and maybe for the extra noise if there are groundloops, unnecessary long paths etc.) get a proper one from Madbean (or from any other place which allows bias setting of Q2)

 

I think any low leakage transistor should be good though DIYers found out ages ago that the optimum gain is around 70-90hFe for the first transistor and 110-130 for the second.

 

Tha later value gets rarer and rarer everytime, when i started out (and it wasnt long ago) you could buy single selected AC128 trannies of this gain but nowadays not really but i havent looked at it in more than a year.

 

You can probably get optimal pairs in pricy matched sets (like at smallbear or maybe musikding etc.)

 

You can use a fixed resistor, i think you should build one with a fixed resistor on your pcb and if it will suck then try a new pcb with the bias trimmer.

[Neil.]

as far as fuzz faces go, I was always a big fan of the Peppermint Fuzz series. That shit is tasty.

[Neil.]

Considering the common size of peddle boxes, ie, type a/type b/type d, fitting a normal size twin triode into those boxes is not easy. I'm talking about a 12AX7 in one of those boxes. If you go for the transformer to get real voltages too, than you're really fucked. UNLESS you mount them outside, but i'm not considering that.

 

Now, as some of you will have seen, there's pedals out there that use mini tubes, with similar characteristics to a a lot of twin triodes, with MU's of 80-100, as per 12AX7s etc. These are relevant to my interests. I know FrequencyCentral has done some work with 9111's, which seem very interesting, although there's a lot of other options out there too.

 

But what about the powersupply I hear you say? well a nixie smps seems the way to go. I've breadboarded them before, and they're good, provided you stick rigidly to the voltage limitations, ie, 9V in = max of 90V (that's +/- 20V depending on what inductor you go for), and with 12V, you can basically double that to ~180V.

 

What is all this for, well I think I'm going to get back to making pedals, but I'm going to go for some pretty elaborate designs, and I'm going to test out a few different ways of populating boards, including something that combines 3d printing with turretboards. To get back into the swing of things, I'm going to make some boosts and fuzzes first, but I'm planning for some pretty elaborate tube designs in the near future too.

 

SO, in conclusion, suggestions for mini tubes?

[Crowella]

Dat feel when you wire a pedlol and it works first go.

 

@NeilDOT, I can't actually think of any other mini tubes that will suit your use although I do want to hear about what you find out. I might try making a tube pedlol in the future.

[Neil.]

I had a little look about on d'ebays and it turns out there's a lot of old russian dual-triodes in sub-mini form factors. To make it more interesting, they seem to run at much lower voltages; 6-12V for the heaters, and as low as 50V for the anode. I'd be sceptical about the level of gain that a mere 50V would give, but it makes it interesting.

 

If you look at some vintage amps, for example, silvertone stuff, they take 100-200V, so I wonder if you made a tube pedal running 50V on one of those subminis, could you get something that sounds like a silvertone. In anycase, there's tonnes of other ideas I'd have for something that small, like a variation on the Vibracaster.

 

If you're thinking of making a tube pedal, I'd deffinitely recommend the nixie SMPS for a power supply. It's a tiny little power circuit, maybe 10-15 components, and takes a normal 9V DC power supply, but it will output anything from 9V-200V. It's a pretty delicate circuit though. You need to know where the limitations are voltage wise or you'll easily burn out the inductor. Your best bet is to start at it outputting 9V and adjust the 5k trimmer till you hit a voltage that you're happy with, but well below the max.

 

 

That's the schematic I use.

 

The plan is to adapt that into a more authentic version of those amp-sim effects that use a JFET (eg, J201) to simulate a triode. What's great about those is that you can use 1 or 2 jfets, to get the tone you're after, and then just adjust the gain with things like smaller resistors after each gain stage. For example, if you look at an amp schematic and see that the amp uses a 200k-470k resistor after each gain stage and they're using 4, you could probably drop that to 2 gain stages, with the first resistor replaced by a 100k pot (I'd also put a 4.7k resistor between the pot and ground) for your gain control, and then after the second gain stage, maybe something between 10k and 100k. You'd have to test it out, but you'd certainly get a good tone out of it.

 

It's on the todo list anyway. I've a MASSIVE list of pedals I'd like to build. Some would be ones already out there, like some devi ever ones, maybe a TS808, a filter sample/hold, and perhaps something like a ring mod or an mxr bluebox, but then I've a tonne of original ones, like a 90 degree tremolo (like a really choppy one), a bucket-brigade chip delay, a full tube boost/od/preamp, and a fuzz that allows you to select between sin/tri/square/shmitt waves.

 

My big ambitious project in all this is a full tube analog spring reverb. I know that sounds crazy, and yeah, the first thing that came to mind was fender's reverb unit which is about the size of a decent amp head, but actually, I'm thinking much smaller. Like, pedal sized. Allow me to explain.

 

So as you may know, VanAmps make what is widely known as the best analog spring reverb, this one: http://vanamps.com/products/sole-mate/

And yes, that would be fairly plausable to make something similar to it. I wouldn't be surprised if the schematic is floating about on the interweb, and it's just a MOD tank they use. BUT, it's still using things like opamps as drivers. Not great, I know. The difficulty is, if you want tubes, it has to be bigger, right? WRONG/BIGYELLOWTEXT.

 

1. http://www.tubesandmore.com/products/P-RAMC2BF3

2. http://www.musikding.de/BoxType-DD

 

Granted, a box that measures 187x118x38mm is pretty big, but it's still smaller than the vanamps reverbmate, more durable, and it's not a million miles off the size of my other favorite reverb, ehx's cathedral.

 

What's the plan for all this? Well, sub-mini triodes as drivers, a full sized spring reverb tank, and a selection of controls: Drive, Dwell, Blend, Feedback, Muffler (a filter of some sort) and Level.

 

Yes, this is all massively ambitious, and I can only imagine how cramped that box would be, but it's possible, and if it worked, mother of reverb....

[Don'tPostThePear]

I designed a tube OD a while back, it uses a small russian tube i've seen in a modular synth circuit. It can run on 30V. Now i don't know how much gain it can make on 30V but it is not important because i drive it with an opamp. I run the opamp on 30V too so luckily the tube starts distorting much sooner than the opamp.

 

The tube is called 1j24b and it is cheap and cute.

 

I made a pic to show you how small it is:

(that is a guitar patch cable next to it)

 

[Neil.]

do you have the schematic for that? I'd love to see how much gain you got out of that.

 

edit:

1j24b is a pentode. that's like 100 times the gain of a triode lol!

[Don'tPostThePear]

do you have the schematic for that? I'd love to see how much gain you got out of that.

 

edit:

1j24b is a pentode. that's like 100 times the gain of a triode lol!

 

i just swapped parts on the breadboard till it was good

 

it is basically just an opamp with gain around 20 into the tube and then an unity gain opamp and a vol pot at the end

 

it was based on this but i omitted the CV stuff and remade the cathode biasing

 

http://www.cgs.synth.net/modules/cgs65_vca.html

[Don'tPostThePear]

btw i don't think that you should expect all your gainz from the tube, it is better to get as much as clean gain as you can get from a better opamp and amplify that with a tube. a good opamp will make clean gain heaps better than any tube could. distortion is a different story.

[Neil.]

what would you run as signal in to that?

[Don'tPostThePear]

what would you run as signal in to that?

 

Anything. If you run a guitar into it you should raise the gain of the input opamp.

 

On the schem it is an inverting unity gain summer or mixer but if you plug a single guitar into it i would convert it into a non/inverting opamp to get rid of the 100k resistor on the input. (that could create a lowpass filter with shitty direct guitar signals and guitar cable capacitances)

 

Also since most of synth oscillators are outputting a -5V +5V signal (10V p2p) and guitar signals are much weaker i would set the gain of the opamp at 10 for a start and mod stuff till it sounds good. (you have to mess with both tube gain and opamp gain till its good)

 

The output opamp can stay at unity gain with a volume pot after it for guitar use.

 

There is a lot of variation in this circuit, i had to make more mods to it to make it more useful than your average guitar pedal boutique company does to a fuzz face before it gets marketed as the next big thing.

 

Also pin 5 is a problematic thing since we does not have CV in guitar pedals, i just connected 5V to the CV input when i breadboarded it for guitar but you can probably leave the whole CV section out and just connect a fixed voltage to pin5 of the tube.

[Lexical_Whale]

This just came up in my Facebook feed:

http://phys.org/news/2013-05-pens-pots-creatives.html?fb_action_ids=10151459828981615&fb_action_types=og.likes

 

Could be put to some pretty interesting use in DIY projects.

[Jaicen]

Maplin have been selling conductive paint since the dawn of time. It's nothing new or exciting, though I guess it's the application that's become fashionable.

[Neil.]

resurrect an old thread day? resurrect an old thread day

 

so I just discovered that there's now a conductive material I can buy for my 3d printer. The benefit of that is that I could essentially print circuit boards. But it gets better than that. It's essentially just printing the copper part of the circuit board. It's actually a type of plastic that it prints, but it's like just printing the copper part of the circuit. Imagine opening up an amp or a pedal and it's just the components and the copper, no green part of the board.

 

only problem is, you can't solder onto it as far as I know. So I'm trying to find out a way of doing that. could make for some SERIOUSLY interesting builds in the future.

 

ideas/opinions on a way to do this? Maybe some sort of eyelet that I could push into it? or what about that conductive copper paint or something similar? The plastic itself is heat resistant up to ~230C though. I'm not sure how hot soldering irons go to, and i've no experience with other methods like those new cold-solder guns (wtf, further evil?)