Tubescreamer clone advice

aord43

So I have built a TS808 clone based on the compact version here (http://tagboardeffects.blogspot.co.uk/2012/02/ibanez-ts808.html) but with a few mods from the General Guitar Gadgets site (http://www.generalguitargadgets.com/effects-projects/distortion/tube-screamer/).
It's the first time I have made or even used an overdrive pedal so I have some questions coming out of my testing - it's currently unboxed and wired up without the footswitch.  I would appreciate people's opinion of the following points.

 - Initially I used a 4558 op amp as per the spec, but it was really noisy, I mean a loud constant white noise.  I wonder if it's because I got them off ebay!  I went to Maplin and bought an NE5532 which was hugely better, and also tried a TL072, which sounded a bit better still to my ears so I will stick with that.
 - I am trying different diode pairs for the clipping, and I find that, even with no diodes, I still get some distortion - is this to be expected?
 - 1N4148 diodes reduce the volume quite a bit, which surprised me because they are the supposedly standard ones
 - Small red LEDs sound better, they don't reduce the volume much.  I can't tell the difference between those and all the other diodes I have tried including Zeners and a MOSFET transistor clipping circuit.
 - The Gain control also reduces the volume down to pretty much nothing. I thought it would just reduce the amount of distortion.  Is this normal?  there clearly is also a volume control.
 - The tone control makes a tiny difference, almost undetectable.  This isn't right, is it?

What I would really like is to fix the tone control so it has more of an effect, and if appropriate, the gain control
What do the experts think?

Danny1969

If you have copied the standard circuit then I think you've got a fault, maybe a bad joint or microscopic short somewhere

Without the diodes the circuit will essentially function as a clean boost so somethings wrong there

The tone control is very noticeable normally, so again somethings wrong etc

Do you have  a meter capable of measuring volts ... is so remove the opamp if in a holder before you start. Power on and measure between pins 8 and 4, you should have half the supply volts, so maybe 4.5V  .... is that's good then move on to next point 

In the negative FB loop you should have a 51K resistor and the gain pot value so with gain down there should be 51K between pins 1 and 2 

What schematic did you copy ?

aord43

I didn't copy a schematic, I used the tagboardeffects layout.  I did refer to the schematic on GGG for reference though, and one I found somewhere else (I forget where).
I just found a couple of sites with very detailed analysis of the circuit, very interesting and informative.
But you must be right. I will double check and measure the voltages and resistance as you suggest.

rroberts

You could still see some clipping, even without the diodes, depending on the supply voltage and the gain of the drive section, with a strong enough signal from the guitar, the output signal could be clattering into the supply rails.
Does it only clip with the gain pot turned up?

Agree with Danny on checking the voltage and the tone control.

Cheers - Rab.

Kalimna

You might also consider posting over on the tagboardeffects forum - they are generally very helpful with these sort of things.

As well as the advice above, it might be that your circuit is particularly noisy because it hasn't been boxed yet. Whilst that won't really affect the working of the tone/volume issues, the metal enclosure acts as a shield to interference.

I have built a few circuits from there, and whilst no Tubescreamer, I have had success with some of the more complex circuits. I would advise either trying the Way Huge Red Llama or Lovepedal Woodrow as simple circuits that sound good.

Adam

Danny1969

Ah tagboard is veroboard, never heard it called tagboard before .... it used to be called stripboard

Most mistakes people make on veroboard circuits are either caused by not cutting tracks properly or accidentally shorting adjacent tracks when soldering 
Running a sharp knife up between adjacent tracks will get rid of any tiny shorts
Make sure all cuts are complete and not still bridging slightly, few spins of a sharp drill bit will do the trick
Make sure any polarised caps are round the right way, circuits will show the orientation of the positive side of the cap but it's the negative side that is actually marked on the cap it's self 

Kalimna

Out of interest, I think the tagboardeffects site was originaly based around actual tagboard layouts, only after a year or so did nearly all of their layouts come out on stripboard/veroboard. They just didn't change the name. They have something like 4-500 layouts (I think) now, although never host circuit diagrams due to copyright reasons.

Adam

aord43

Hey @Danny1969, I think the distortion is OK.  The circuit without the diodes is not completely clean but that might be the boost resulting in a little distortion.
I am still concerned that the tone control doesn't have a great effect.
Looking at the schematic here http://www.muzique.com/lab/tstone.htm I have measured the resistances and it looks OK - my pot is 25K (rather than 20 specified but I can't see that making a significant difference), the 220R is OK, and the 1K between pins 6 and 7 measures OK.

jpfamps

Diodes limit the signal, so you will get a drop in volume cf no diodes.

Red LEDs have higher threshold voltage than 1N4148, so will give more volume.

There is enough gain in the first stage to clip the output of an op-amp without any diodes. 

The TL072 with invert the output when the negative half of the signal clips (around 5.7 Vp-p in that circuit), as does some of the reissue 4558s I tested.

The 4558 should not be obviously noisy, so I suspect you have a duff chip. 

My experience with buying ICs off eBay is not great; there are plenty of fakes out there.

aord43

jpfamps said:

Diodes limit the signal, so you will get a drop in volume cf no diodes.

Red LEDs have higher threshold voltage than 1N4148, so will give more volume.

There is enough gain in the first stage to clip the output of an op-amp without any diodes. 

The TL072 with invert the output when the negative half of the signal clips (around 5.7 Vp-p in that circuit), as does some of the reissue 4558s I tested.

The 4558 should not be obviously noisy, so I suspect you have a duff chip. 

My experience with buying ICs off eBay is not great; there are plenty of fakes out there.

Thanks @jpfamps  I am most concerned about the tone control, maybe I just don't know what to expect.  In online demos of OD units you don't tend to see people demoing how it sounds when you change ONLY the tone.
I have rewired to try one "Tone 1" on http://www.muzique.com/lab/tstone.htm and I am boxing up now.  I am getting a lot of hum but will try to address that too.