Messages

Thank you Culturjam.

If you and MadBean are right - which i guess you are - then my earlier assumption about ESD-safety was wrong. I was pretty sure i have read it somewhere (Craig Andertons DIY for guitarists) but i guess i mixed it up with series resistor in the signal path (input). Learnin stuff is a good thing.

Cheers

Thank you gentlemen for some clearifying answers!

I don't really know the answers to all of your questions, but here's an interesting article that probably explains Question 2:

http://www.maxim-ic.com/app-notes/index.mvp/id/1957

Perfect link, explained it all! May i passs it forward as a brief summary: To avoid noise from an unused stage of an OP-amp, its in- and outputs have to be correctly terminated. There are some different ways to do this, some "right", some "wrong". On the mentioned circuit - Mysterioso - its done the right way:)

I've always assumed that those low value resistors (in this case the 120R R18) were a current-draw failsafe in case there was a short on the board.

If i have read my books right (correct me if i am wrong here!): Failsafe yes, but not for board-shorts in the first place, rather for protecting the circuit for ESD-damage.  Anyway, it is a "security" resistor, which still makes it a little confusing that Blackstone design a circuit and let a fairly sensitive device as TL072 not take advantage of it... Maybe Madbean just gave us the answer though;

1) Separate supply rails is a pretty common way to reduce noise in a circuit.

Sounds reasonable.

1) Separate supply rails is a pretty common way to reduce noise in a circuit. Given that this is a high gain overdrive, my guess is the inverter is supplied this way for that reason. Note that the voltage drop is very very small across a tiny resistor, so it's not so much a matter of different voltages, but unique supply lines, I think.

2) There is probably no difference between tying the unused pins to ground or virtual ground. It is not buffering the VB supply in this case.

3) Check FSB for a thread on the Red Llama re-issue which discusses this very topic.

Hmm, ive done my search, and im not sure i find the right thread? Do you mind linking me right?
... it seems a bit like common sence though, that "nothing" shall be left floating, and when it comes to inverters they shall "rest" with a high input. It's their natural passive state.

Cheers and thanx again!

Hi folks.

I am playing around (breadboard, simulation...) with the 4049UBE circuit, i have a Red Lama ready to box, and i guess i will build something like the Mysterioso.

As i read the Mysterioso schematic i have a question that i guess is fairly basic, but i dont understand why:

The "9V" input meets "the usual" reversed diod and cap to gnd, and is divided in half for "VB". Also, "9V" connects to a serie resistor to "VR".

Question 1: To me it makes sence/is obvious that the 4049 IC is powerred by "VR". BUT, why is the TL072 IC not fed with the same "VR"? It is powerred by "9V". I dont get the point, even though i guess there is one.

Question 2: The unused half of TL072 (pin 5, 6, 7) has VB connected to its positive input, and then a negative feedback loop. Does this design help to stabilize VB? Or is it just there to not leave the pins unconnected?

Question 3: The unused inputs of the 4049 IC (pin 9, 11, 14) is connected to "VR", and their associated outputs (pin 10, 12, 15) are left unconnected. This is the same design that we find in Red Llama. Is there a reason for this? To me it would be more logical to connect unused inputs to ground, but maybe the circuit feels better if it can "rest in high position" as the (inverted) output will be low?

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I would really appreciate if someone has the time to answer this!

Cheers in advance
/Bengt

yup, I've done that before on a face plate.  welcome to the short bus.

Glad we are two!

...On the other hand, shit happens on a fairly regular basis in different fields. At least over here. And as this one nether killed or hurted me, i really had a good laugh when peeling off the paper... like... wtf...

You spelled "awesome" wrong.

Ok, new try: Awesöme

FWIW, if I had the skills, I'd have done it that way on purpose - for my money, it's great.

Now dont you dare to steal my idea !

Etch it dude.

Just make sure to use a mirror whenever you plugin it in.

I love it!  Happy accident

Call it the "Mirror Image Drive", pretend like you did it on purpose because it does such a great job retaining the overall tone of your rig, and then market the hell out of it.  

Hehe... You know, now when i read your posts, i beleive i really should have gone with it as it... was.

That was the accident that could have made me the millionaire. Now i am grieving myself for announce it here as a mistake!  DAMM

Too late. the magic backward etch mask is gone. Back to ordinary boxing!

Hehe, thought i could share this. Or maybe entertain you... What is the english word? Faux pah? Slip? Fuckup? Goof?

Well... i just peeled off the well prepaired, well ironed photo paper off my enclosure... next step should be etching... but... well...

Ehh
Hmm
Ehhmmm... How... ehh.. something...is... wrong...ehh..hm.

Well... just to start it over i guess... or take a break

Cheers folks

Red Llama (two pots) with a buffer (switch)?

... i have just etched a Llama board... its really the first OD/Dist/Fuzz that makes my crappy small practising amp sound good. Nice and simple build. But you maybe have one allready?

Cheers

Hi again. I solved it and can go on:)... If anyone is interested, i hope its ok to link to my thread on DIYstompboxes:

http://www.diystompboxes.com/smfforum/index.php?topic=98583.0

...where the solution is written down.

Cheers

Thank you and thank you again:) I feel honoured to receive so much positive comments among all you talented folks! Really inspiring.

Thanks once more! And cheers!

Hi folks. I just posted a similar thread at DIYstompboxes. I try here too:)

I am fairly new at circuit simulation... and i tend to do all things simultanously... last week i bought a drill for my first home-etched circuit boards as well as finnishing some huge project, and now i am in the middle of simulation...

I have tried out (or given a look at) LTspice (i dont like it), Pspice, 5spice (which i like, but the free version is verrrrry limited) and TINA-TI. I think i have decided to go on with TINA-TI, which seems to be fairly user-friendly and "unlimited"(?)... (even though, when i browse around DIY-forums, LTspice seems to be the most common platform for simulation?)

Anyway; I want to simulate circuits around the cd4049ube chip (as used in red llama and others...). Does anyone of you have a clue how to get this circuit/model up and running in TINA-TI? Anyone has a model? On the TINA-TI download page it sais that "any spice model is fine for TINA-TI", which i read as i should be able to use a model from LT- or Pspice as well.

And - this makes me confused (almost annoyed...) in the "Component help" for TINA-TI, the 4049 circuit is listed. But i cant find how to load it... Maybe this is one limitation for the "free version", that i cant load some circuits that are coverred in the help.

Anyone?



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And: Would it be a good idea to have a "Simulation" sub-forum on this forum, Madbean? Just a thought:)

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Cheers
/Bengt

I like the Bi Technology pots. They're made of conductive plastic instead of carbon, rated for 100,000 cycles instead of Alpha's 15,000.

This is good news. BI costs about a third of the price for ALPHA on mouser.

Thanx guys:)

Maybe this subject has been up for discussion before on this forum? I did a short search though.

One of the defacto standard products (?) in DIY-boxing seems to be ALPHA (16 mm) pots. I use them myself as well as other things i got recommended from reading here and on other forums.

But; Are they the "only" alternative? They are rather expensive, and if you search Mouser they have 12000+ (!) different pots. Some of them should be comparable in quality (and of course functionality) and less pricey? Or?

Just to try, with my last mouser order orderred one pot branded BI Technologies ( http://se.mouser.com/Search/ProductDetail.aspx?R=P160KN2-4QC20B10Kvirtualkey57700000virtualkey858-P160KN24QC20B10K ), and to me it works fine, even though it doesnt feel exactly as good as the ALPHA dito (you know the feeling when u tighten the nut).

Any of you with any opinions on this subject? Anyone using pots that are not ALPHA?

Thanx folks:) I am happily reading your cheerioos!