Random Number Generator - Bad Gain Problem

[niggez]

Sorry, I remembered wrong. I read about it in your thread! So its the Diode Mod by Matt! http://www.diystompboxes.com/smfforum/index.php?topic=63001.0

[birt]

The name is Bert, but you can call me Matt if you want :p

see the first post of that thread, i found that diode trick



edit: for once i found something cool, i was proud ok? :p

[niggez]

Yep Bert! As soon as i get my RNG to modulate I will reattach the diode to actually find out what it sounds like with/without...but right now its back to the original schematic to get ot modulating...
No success....i'm pretty sure theres something wrong with my transistors, maybe i have to swap q1. When i just finished building it, and it was too loud (but worked) i had a different transistor in q1 (which broke) so i replaced it. Its the same model, but...i guess it might have made a difference...
Its the worst thing, trying to fix something and breaking something else in the process 

[niggez]

I have double checked all the connections, solder points, offboard wiring, resistor values...Everything is according to the original schematic, and still it wont work. I'm almost certain its a problem with my Q1, I will go buy some other transistors to test in this stage tomorrow.
My Transistor voltages now read:
         E       B      C
Q1    0     0.61   2.78
Q2    0     0.54   0.88
Q3    0     0.49   0.75
Q4    0     0.76   1.88

Question: Is the base voltage on Q3 too low? It's close to 0.5 which i thought was the minimum...

[birt]

i never took any voltage readings, i just picked some medium gain transistors (4 different ones) and used those. and i kept on trying things with feedback (neg and pos) and other stuff and kept on modding. to me it doesn't even sound anymore like the original. it's a fun circuit to play around with.

[niggez]

Couldnt go buy transistors today, but definately need some to play around with. What other transistors would you suggest? I will mount sockets so i can test a hole bunch. Ill try the ones suggested in the schematic, any others? I.e. what did you use?

[birt]

i have no clue what i used. i took a bag full of old transitors and measured Hfe. alle of them were between 60 and 150.

[niggez]

allright. Thats what ill do then.

[runmikeyrun]

slightly OT but will any 2nXXXX series work?  I have 2n2222s and 2n5088s.  Always wanted to try this thing but never had the right trannies, esp. the 1st one.

[Dragonfly]

I was bored, so I did a "quickie layout" for this on PCB...untested, but should be ok. I did it with the "trim pot mod". Let me know if you spot any errors...

[ambulancevoice]

yep, its all good andy
just went over it with the schematics

[Dragonfly]

yep, its all good andy
just went over it with the schematics

Thanks..I usually do a good job on them, but having a second set of "eyes" look at it is ALWAYS a good thing !

[andrew_k]

So...umm.... what's this thing do? Fuzz? Quasi-bit crusher of sorts? With a name like that I assume it makes noise...


EDIT: n/m, found out

[niggez]

It adds fuzz, but also has this harmonic modulation thing going. With decreasing signal, it adds mostly octaves up and down which can be heard clearly, which means you play one note, and the thing makes a "melody out of it".
Check soundsample at http://www.midfielectronics.com/

[birt]

i just found out that the more volume you take away (with eather the volume control or a fixed resistor to ground) the more bass you lose. that's a bad thing so i'd like to find a solution for that

especially because i doubled teh value of the input and output caps to have more bass. volume increased so i had to cut more volume and ended up with less bass and the sound isn't as good as it was.

[niggez]

i still havent got mine working...i went to the electronics store to buy some low gain transistors, i wanted to try some bc107a, so the guy sais yeah we got those. He packs me bc107b. Great. Of course i only noticed this at home.
I tried some other 2n2222 in Q1, also 2n3904 but no success. Still no modulation.

[doug deeper]

the modulation all happens in the second stage, make sure the 100k resistor from the last transistors collector, to the second transistors collector is in the right spot.