Author Topic: Please help with new build distortion.  (Read 3875 times)

ChrisMcC

Please help with new build distortion.
« on: August 15, 2017, 01:06:17 PM »
Hi,
I am trying to build the most basic of distortion circuits using perfboard.
I am following a PDF guide, but it is very similar to many basic circuits shared online.
My issue is that it doesn't distort.
I wonder if my choice of components is off.  I used some scavenged parts, so this may be the case, but what elements could be at fault?
I have attached images of the front and rear.
Thanks,
Chris








suryabeep

Re: Please help with new build distortion.
« Reply #1 on: August 15, 2017, 01:12:05 PM »
Can you attach the schematic or pdf from which you are building the circuit?
Still in the process of learning, so bear with me if I ask dumb questions :P

ChrisMcC

Re: Please help with new build distortion.
« Reply #2 on: August 15, 2017, 05:36:32 PM »
Yes, one is a screenshot from the PDF, and the other one is from an instructable.
I don't have the exact components from either, but understand that you can mess with these.





Thanks,
Chris

Cozybuilder

Re: Please help with new build distortion.
« Reply #3 on: August 15, 2017, 06:46:44 PM »
It looks like you placed 1K for R1 and 100K for R2. Try swapping those, and it might work.
Some people drink from the fountain of knowledge, others just gargle.

Hatredman

Re: Please help with new build distortion.
« Reply #4 on: August 15, 2017, 09:10:58 PM »
It looks like you placed 1K for R1 and 100K for R2. Try swapping those, and it might work.
A one-transistor distortion?


--
Scarlett Johansson uses a Burst Box with her Telecaster.

Kirk Hammet invented the Burst Box.

suryabeep

Re: Please help with new build distortion.
« Reply #5 on: August 15, 2017, 09:21:11 PM »
A one-transistor distortion?
[/quote]

looks like a plain vanilla common emitter amplifier to me. Seems like it'll be more fuzz than distortion
Still in the process of learning, so bear with me if I ask dumb questions :P

ChrisMcC

Re: Please help with new build distortion.
« Reply #6 on: August 16, 2017, 04:59:36 AM »
Thanks Cosybuilder! That was spot on.
I think I reversed them after my last failed attempt.   ;D
The effect is a slight overdrive, the type that kicks in with full chords and lower strings, but doesn't touch lightly played or single notes.
This should probably go on another post, and I'm going to research more, now I have a working concept, but which elements could I change to get more gain? Maybe with a pot rather than a resistor?
Thanks,
Chris

duck_arse

Re: Please help with new build distortion.
« Reply #7 on: August 16, 2017, 10:56:05 AM »
the easiest way to get more gain is an "emitter bypass cap". look on the fuzzface circuits for the general idea, the fuzz pot in particular.

and - welcome to the forum.
"I think we're done here."

"rule #1 - don't paraphrase."

'redundant legs don't grease the skids'

Cozybuilder

Re: Please help with new build distortion.
« Reply #8 on: August 16, 2017, 02:16:04 PM »
If you want to increase the volume, these will help:
  1. the 100K bias / feedback resistor (R1)  should be increased substantially, say anywhere from 1 M to 4.7 M
  2. Adjust the collector resistor (R2) to a value that yields about 5 volts on the collector.
  3. Use additional clipping diodes in series, or use LEDs as clippers instead.
« Last Edit: August 16, 2017, 02:42:17 PM by Cozybuilder »
Some people drink from the fountain of knowledge, others just gargle.

thenewguy

  • Guest
Re: Please help with new build distortion.
« Reply #9 on: August 18, 2017, 11:17:23 PM »
A one-transistor distortion?

looks like a plain vanilla common emitter amplifier to me. Seems like it'll be more fuzz than distortion
[/quote]

The schematic doesn't show the clipping diodes.  I built an LPB-1 last year and added switchable clipping diodes on the output just to see what it sounded like.  Not much distortion.

ChrisMcC

Re: Please help with new build distortion.
« Reply #10 on: August 24, 2017, 07:37:06 AM »
Thanks again Cosybuilder!
I now have a breadboard, so will mess around with these values and see how it goes.

ChrisMcC

Re: Please help with new build distortion.
« Reply #11 on: August 25, 2017, 07:10:32 AM »
Progress!
I built a test circuit with all sockets.


Measured voltage at the 3 legs of the transistor:






Does this look like correct readings? I tried changing resistors, and I found changing the one that I have connected in series, does make for a much stronger effect, but changing the other resistor doesn't seem to change anything.

Also, these resistors in these 2 places have different terms do they? What do I call them?

Thanks,
Chris

Cozybuilder

Re: Please help with new build distortion.
« Reply #12 on: August 25, 2017, 08:59:03 AM »
The emitter should be at 0V. Are you measuring the voltages in reference to ground?

Your caps are definitely nowhere near 10uF and 100uF as shown in the schematic- you could use 100nF input and anything larger than that for the output cap. Those look like they are in the high pF to low nF range, and won't give the full range your are looking for. Try a couple of poly film caps at least 100nF in value.
Some people drink from the fountain of knowledge, others just gargle.

duck_arse

Re: Please help with new build distortion.
« Reply #13 on: August 25, 2017, 11:04:00 AM »
plug your black lead into the black meter socket, and the red lead to the red (or +) socket. then connect your black lead to ground (always, we always measure against ground) and poke about with your red probe. in this way, this circuit, all your voltage readings will be positive. please also give your battery voltage measure.

the emitter has a resistor, the collector has a resistor. sometimes the base has two resistors. sometimes there is a collector-base resistor, you could call it a bias resistor, as it provides the base (with its) bias. and sometimes there is no emitter resistor at all, the emitter is instead grounded, for maxx gain.
"I think we're done here."

"rule #1 - don't paraphrase."

'redundant legs don't grease the skids'

ChrisMcC

Re: Please help with new build distortion.
« Reply #14 on: August 25, 2017, 03:43:08 PM »
Oh!

Readings are now:
1.45
0.56
0

Does that make more sense?

ChrisMcC

Re: Please help with new build distortion.
« Reply #15 on: August 25, 2017, 03:45:13 PM »
Battery should be 9v, but is 7.69
Maybe time for a new one    :icon_smile:

Cozybuilder

Re: Please help with new build distortion.
« Reply #16 on: August 26, 2017, 12:01:47 AM »
Yeah, new battery will help. Once you have that, I'd play with the collector resistor and try to get the collector voltage up to about 5V. The easy way is to sub a 100K pot in there, and adjust until you get the right voltage, then measure the resistance required and sub in the nearest value resistor. I suspect it will be about 10K.

Some people drink from the fountain of knowledge, others just gargle.